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Sample records for bursting pacemaker neurons

  1. Regulation of Excitability, Pacemaking, and Bursting: Insights from Dopamine Neuron Electrophysiology

    OpenAIRE

    Drion, Guillaume

    2013-01-01

    The present thesis attempts to extract the dynamical mechanisms underlying neuronal excitability and its regulation, through the use of experimental and mathematical techniques. In particular, tools of dynamical system theory are used to extract physiologically relevant key players in the firing activity of various neuron types. The main contribution of the thesis highlights the role of voltage-gated calcium-permeable channels in neuron excitability and fi ring patterns. Calcium chann...

  2. Synchronization of Coupled Neurons Controlled by a Pacemaker

    International Nuclear Information System (INIS)

    We investigate synchronization of Hindmarsh—Rose neurons with gap junctions under the control of a pacemaker. In a ring Hindmarsh—Rose neuronal network, the coupled neurons with the pacemaker can occur in synchronization more easily than those without the pacemaker. Furthermore, the pacemaker can induce phase synchronization or nearly-complete synchronization of nonidentical neurons. This synchronization can occur more easily when time delay is considered. Theses results can be helpful to understand the activities of the real neuronal system. (general)

  3. Neuronal Coding of pacemaker neurons - A random dynamical systems approach

    OpenAIRE

    de Jaeger, T

    2009-01-01

    The behaviour of neurons under the influence of periodic external input has been modelled very successfully by circle maps. The aim of this note is to extend certain aspects of this analysis to a much more general class of forcing processes. We apply results on the fibred rotation number of randomly forced circle maps to show the uniqueness of the asymptotic firing frequency of ergodically forced pacemaker neurons. The details of the analysis are carried out for the forced leaky integrate-and...

  4. "Caged calcium" in Aplysia pacemaker neurons. Characterization of calcium-activated potassium and nonspecific cation currents

    OpenAIRE

    1989-01-01

    We have studied calcium-activated potassium current, IK(Ca), and calcium-activated nonspecific cation current, INS(Ca), in Aplysia bursting pacemaker neurons, using photolysis of a calcium chelator (nitr-5 or nitr-7) to release "caged calcium" intracellularly. A computer model of nitr photolysis, multiple buffer equilibration, and active calcium extrusion was developed to predict volume-average and front-surface calcium concentration transients. Changes in arsenazo III absorbance were used to...

  5. Firing Patterns and Transitions in Coupled Neurons Controlled by a Pacemaker

    Institute of Scientific and Technical Information of China (English)

    LI Mei-Sheng; LU Qi-Shao; DUAN Li-Xia; WANG Qing-Yun

    2008-01-01

    @@ To reveal the dynamics of neuronal networks with pacemakers, the firing patterns and their transitions are investigated in a ring HR neuronal network with gap junctions under the control of a pacemaker. Compared with the situation without pacemaker, the neurons in the network can exhibit various firing patterns as the external current is applied or the coupling strength of pacemaker varies. The results are beneficial for understanding the complex cooperative behaviour of large neural assemblies with pacemaker control.

  6. Pacemaker potentials for the periodic burst discharge in the heart ganglion of a stomatopod, Squilla oratoria.

    Science.gov (United States)

    Watanabe, A; Obara, S; Akiyama, T

    1967-03-01

    From somata of the pacemaker neurons in the Squilla heart ganglion, pacemaker potentials for the spontaneous periodic burst discharge are recorded with intracellular electrodes. The electrical activity is composed of slow potentials and superimposed spikes, and is divided into four types, which are: (a) "mammalian heart" type, (b) "slow generator" type, (c) "slow grower" type, and (d) "slow deficient" type. Since axons which are far from the somata do not produce slow potentials, the soma and dendrites must be where the slow potentials are generated. Hyperpolarization impedes generation of the slow potential, showing that it is an electrically excitable response. Membrane impedance increases on depolarization. Brief hyperpolarizing current can abolish the plateau but brief tetanic inhibitory fiber stimulation is more effective for the abolition. A single stimulus to the axon evokes the slow potential when the stimulus is applied some time after a previous burst. Repetitive stimuli to the axon are more effective in eliciting the slow potential, but the depolarization is not maintained on continuous stimulation. Synchronization of the slow potential among neurons is achieved by: (a) the electrotonic connections, with periodic change in resistance of the soma membrane, (b) active spread of the slow potential, and (c) synchronization through spikes. PMID:6034506

  7. Disinhibition Bursting of Dopaminergic Neurons

    Directory of Open Access Journals (Sweden)

    Collin J Lobb

    2011-05-01

    Full Text Available Substantia nigra pars compacta (SNpc dopaminergic neurons receive strong tonic inputs from GABAergic neurons in the substantia nigra pars reticulata (SNpr and globus pallidus (GP, and glutamatergic neurons in the subthalamic nucleus. The presence of these tonic inputs raises the possibility that phasic disinhibition may trigger phasic bursts in dopaminergic neurons. We first applied constant NMDA and GABAA conductances onto a two-compartment single cell model of the dopaminergic neuron (Kuznetsov et al., 2006. The model exhibited disinhibition bursting upon stepwise removal of inhibition. A further bifurcation analysis suggests that disinhibition may be more robust than excitation alone in that for most levels of NMDA conductance, the cell remains capable of bursting even after a complete removal of inhibition, whereas too much excitatory input will drive the cell into depolarization block. To investigate the network dynamics of disinhibition, we used a modified version of an integrate-and-fire based model of the basal ganglia (Humphries et al., 2006. Synaptic activity generated in the network was delivered to the two-compartment single cell dopaminergic neuron. Phasic activation of the D1-expressing medium spiny neurons in the striatum (D1STR produced disinhibition bursts in dopaminergic neurons through the direct pathway (D1STR to SNpr to SNpc. Anatomical studies have shown that D1STR neurons have collaterals that terminate in GP. Adding these collaterals to the model, we found that striatal activation increased the intra-burst firing frequency of the disinhibition burst as the weight of this connection was increased. Our studies suggest that striatal activation is a robust means by which disinhibition bursts can be generated by SNpc dopaminergic neurons, and that recruitment of the indirect pathway via collaterals may enhance disinhibition bursting.

  8. Persistently Active, Pacemaker-Like Neurons in Neocortex

    OpenAIRE

    Le Bon-Jego, Morgane; Yuste, Rafael

    2007-01-01

    The neocortex is spontaneously active, however, the origin of this self-generated, patterned activity remains unknown. To detect potential “pacemaker cells,” we use calcium imaging to directly identify neurons that discharge action potentials in the absence of synaptic transmissionin slices from juvenile mouse visual cortex. We characterize 60 of these neurons electrophysiologically and morphologically, finding that they belong to two classes of cells: one class composed of pyramidal neurons ...

  9. Persistently active, pacemaker-like neurons in neocortex

    OpenAIRE

    Morgane Le Bon-Jego; Rafael Yuste

    2007-01-01

    The neocortex is spontaneously active, however, the origin of this self-generated, patterned activity remains unknown. To detect potential pacemaker cells, we use calcium imaging to directly identify neurons that discharge action potentials in the absence of synaptic transmissionin slices from juvenile mouse visual cortex. We characterize 60 of these neurons electrophysiologically and morphologically, finding that they belong to two classes of cells: one class composed of pyramidal neurons...

  10. Chimera states in bursting neurons

    OpenAIRE

    Bera, Bidesh K.; Ghosh, Dibakar; Lakshmanan, M.

    2015-01-01

    We study the existence of chimera states in pulse-coupled networks of bursting Hindmarsh-Rose neurons with nonlocal, global and local (nearest neighbor) couplings. Through a linear stability analysis, we discuss the behavior of stability function in the incoherent (i.e. disorder), coherent, chimera and multi-chimera states. Surprisingly, we find that chimera and multi-chimera states occur even using local nearest neighbor interaction in a network of identical bursting neurons alone. This is i...

  11. SYNCHRONIZATION OF TWO COUPLED HINDMARSH-ROSE NEURONS BY A PACEMAKER

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    This paper considers the synchronization of two coupled Hindmarsh-Rose neurons by a pacemaker.Based on the stability theory of differential equations,the complete synchronization of this pacemaker neuron model is reached.Moreover,we also show that pacemaker can enhance or induce synchronization.Numerical simulations are given to illustrate the main results.

  12. Chimera states in bursting neurons

    Science.gov (United States)

    Bera, Bidesh K.; Ghosh, Dibakar; Lakshmanan, M.

    2016-01-01

    We study the existence of chimera states in pulse-coupled networks of bursting Hindmarsh-Rose neurons with nonlocal, global, and local (nearest neighbor) couplings. Through a linear stability analysis, we discuss the behavior of the stability function in the incoherent (i.e., disorder), coherent, chimera, and multichimera states. Surprisingly, we find that chimera and multichimera states occur even using local nearest neighbor interaction in a network of identical bursting neurons alone. This is in contrast with the existence of chimera states in populations of nonlocally or globally coupled oscillators. A chemical synaptic coupling function is used which plays a key role in the emergence of chimera states in bursting neurons. The existence of chimera, multichimera, coherent, and disordered states is confirmed by means of the recently introduced statistical measures and mean phase velocity.

  13. Rhythm dynamics of complex neuronal networks with mixed bursting neurons

    International Nuclear Information System (INIS)

    The spatiotemporal order and rhythm dynamics of a complex neuronal network with mixed bursting neurons are studied in this paper. A quantitative characteristic, the width factor, is introduced to describe the rhythm dynamics of an individual neuron, and the average width factor is used to characterize the rhythm dynamics of a neuronal network. An r parameter is introduced to denote the ratio of the short bursting neurons in the network. Then we investigate the effect of the ratio on the rhythm dynamics of the neuronal network. The critical value of r is derived, and the neurons in the network always remain short bursting when the r ratio is larger than the critical value. (general)

  14. Rhythm dynamics of complex neuronal networks with mixed bursting neurons

    Institute of Scientific and Technical Information of China (English)

    Lü Yong-Bing; Shi Xia; Zheng Yan-Hong

    2013-01-01

    The spatiotemporal order and rhythm dynamics of a complex neuronal network with mixed bursting neurons are studied in this paper.A quantitative characteristic,the width factor,is introduced to describe the rhythm dynamics of an individual neuron,and the average width factor is used to characterize the rhythm dynamics of a neuronal network.An r parameter is introduced to denote the ratio of the short bursting neurons in the network.Then we investigate the effect of the ratio on the rhythm dynamics of the neuronal network.The critical value of r is derived,and the neurons in the network always remain short bursting when the r ratio is larger than the critical value.

  15. Pacemaker neuron and network oscillations depend on a neuromodulator-regulated linear current

    Directory of Open Access Journals (Sweden)

    Shunbing Zhao

    2010-05-01

    Full Text Available Linear leak currents have been implicated in the regulation of neuronal excitability, generation of neuronal and network oscillations, and network state transitions. Yet, few studies have directly tested the dependence of network oscillations on leak currents or explored the role of leak currents on network activity. In the oscillatory pyloric network of decapod crustaceans neuromodulatory inputs are necessary for pacemaker activity. A large subset of neuromodulators is known to activate a single voltage-gated inward current IMI, which has been shown to regulate the rhythmic activity of the network and its pacemaker neurons. Using the dynamic clamp technique, we show that the crucial component of IMI for the generation of oscillatory activity is only a close-to-linear portion of the current-voltage relationship. The nature of this conductance is such that the presence or the absence of neuromodulators effectively regulates the amount of leak current and the input resistance in the pacemaker neurons. When deprived of neuromodulatory inputs, pyloric oscillations are disrupted; yet, a linear reduction of the total conductance in a single neuron within the pacemaker group recovers not only the pacemaker activity in that neuron, but also leads to a recovery of oscillations in the entire pyloric network. The recovered activity produces proper frequency and phasing that is similar to that induced by neuromodulators. These results show that the passive properties of pacemaker neurons can significantly affect their capacity to generate and regulate the oscillatory activity of an entire network, and that this feature is exploited by neuromodulatory inputs.

  16. Bursting neurons and ultrasound avoidance in crickets

    Directory of Open Access Journals (Sweden)

    Gary eMarsat

    2012-07-01

    Full Text Available Decision making in invertebrates often relies on simple neural circuits composed of only a few identified neurons. The relative simplicity of these circuits makes it possible to identify the key computation and neural properties underlying decisions. In this review, we summarize recent research on the neural basis of ultrasound avoidance in crickets, a response that allows escape from echolocating bats. The key neural property shaping behavioral output is high-frequency bursting of an identified interneuron, AN2, which carries information about ultrasound stimuli from receptor neurons to the brain. AN2's spike train consists of clusters of spikes –bursts– that may be interspersed with isolated, non-burst spikes. AN2 firing is necessary and sufficient to trigger avoidance steering but only high-rate firing, such as occurs in bursts, evokes this response. AN2 bursts are therefore at the core of the computation involved in deciding whether or not to steer away from ultrasound. Bursts in AN2 are triggered by synaptic input from nearly synchronous bursts in ultrasound receptors. Thus the population response at the very first stage of sensory processing –the auditory receptor- already differentiates the features of the stimulus that will trigger a behavioral response from those that will not. Adaptation, both intrinsic to AN2 and within ultrasound receptors, scales the burst-generating features according to the stimulus statistics, thus filtering out background noise and ensuring that bursts occur selectively in response to salient peaks in ultrasound intensity. Furthermore AN2’s sensitivity to ultrasound varies adaptively with predation pressure, through both developmental and evolutionary mechanisms. We discuss how this key relationship between bursting and the triggering of avoidance behavior is also observed in other invertebrate systems such as the avoidance of looming visual stimuli in locusts or heat avoidance in beetles.

  17. Autaptic pacemaker mediated propagation of weak rhythmic activity across small-world neuronal networks

    Science.gov (United States)

    Yilmaz, Ergin; Baysal, Veli; Ozer, Mahmut; Perc, Matjaž

    2016-02-01

    We study the effects of an autapse, which is mathematically described as a self-feedback loop, on the propagation of weak, localized pacemaker activity across a Newman-Watts small-world network consisting of stochastic Hodgkin-Huxley neurons. We consider that only the pacemaker neuron, which is stimulated by a subthreshold periodic signal, has an electrical autapse that is characterized by a coupling strength and a delay time. We focus on the impact of the coupling strength, the network structure, the properties of the weak periodic stimulus, and the properties of the autapse on the transmission of localized pacemaker activity. Obtained results indicate the existence of optimal channel noise intensity for the propagation of the localized rhythm. Under optimal conditions, the autapse can significantly improve the propagation of pacemaker activity, but only for a specific range of the autaptic coupling strength. Moreover, the autaptic delay time has to be equal to the intrinsic oscillation period of the Hodgkin-Huxley neuron or its integer multiples. We analyze the inter-spike interval histogram and show that the autapse enhances or suppresses the propagation of the localized rhythm by increasing or decreasing the phase locking between the spiking of the pacemaker neuron and the weak periodic signal. In particular, when the autaptic delay time is equal to the intrinsic period of oscillations an optimal phase locking takes place, resulting in a dominant time scale of the spiking activity. We also investigate the effects of the network structure and the coupling strength on the propagation of pacemaker activity. We find that there exist an optimal coupling strength and an optimal network structure that together warrant an optimal propagation of the localized rhythm.

  18. Sexual interactions influence the molecular oscillations in DN1 pacemaker neurons in Drosophila melanogaster.

    Science.gov (United States)

    Hanafusa, Shiho; Kawaguchi, Tomoaki; Umezaki, Yujiro; Tomioka, Kenji; Yoshii, Taishi

    2013-01-01

    Circadian rhythms can synchronize to environmental time cues, such as light, temperature, humidity, and food availability. Previous studies have suggested that these rhythms can also be entrained by social interactions. Here, we used Drosophila melanogaster as a model to study the influence of socio-sexual interactions on the circadian clock in behavior and pacemaker neurons. If two flies of opposite sex were paired and kept in a small space, the daily activity patterns of the two flies were clearly different from the sum of the activity of single male and female flies. Compared with single flies, paired flies were more active in the night and morning, were more active during females' active phase, and were less active during males' active phase. These behavioral phenotypes are related to courtship behavior, but not to the circadian clock. Nevertheless, in male-female pairs of flies with clocks at different speeds (wild-type and per (S) flies), clock protein cycling in the DN1 pacemaker neurons in the male brain were slightly influenced by their partners. These results suggest that sexual interactions between male-female couples can serve as a weak zeitgeber for the DN1 pacemaker neurons, but the effect is not sufficient to alter rhythms of behavioral activity. PMID:24367668

  19. Emergent synchronous bursting of oxytocin neuronal network.

    Directory of Open Access Journals (Sweden)

    Enrico Rossoni

    Full Text Available When young suckle, they are rewarded intermittently with a let-down of milk that results from reflex secretion of the hormone oxytocin; without oxytocin, newly born young will die unless they are fostered. Oxytocin is made by magnocellular hypothalamic neurons, and is secreted from their nerve endings in the pituitary in response to action potentials (spikes that are generated in the cell bodies and which are propagated down their axons to the nerve endings. Normally, oxytocin cells discharge asynchronously at 1-3 spikes/s, but during suckling, every 5 min or so, each discharges a brief, intense burst of spikes that release a pulse of oxytocin into the circulation. This reflex was the first, and is perhaps the best, example of a physiological role for peptide-mediated communication within the brain: it is coordinated by the release of oxytocin from the dendrites of oxytocin cells; it can be facilitated by injection of tiny amounts of oxytocin into the hypothalamus, and it can be blocked by injection of tiny amounts of oxytocin antagonist. Here we show how synchronized bursting can arise in a neuronal network model that incorporates basic observations of the physiology of oxytocin cells. In our model, bursting is an emergent behaviour of a complex system, involving both positive and negative feedbacks, between many sparsely connected cells. The oxytocin cells are regulated by independent afferent inputs, but they interact by local release of oxytocin and endocannabinoids. Oxytocin released from the dendrites of these cells has a positive-feedback effect, while endocannabinoids have an inhibitory effect by suppressing the afferent input to the cells.

  20. Modelling Feedback Excitation, Pacemaker Properties and Sensory Switching of Electrically Coupled Brainstem Neurons Controlling Rhythmic Activity.

    Science.gov (United States)

    Hull, Michael J; Soffe, Stephen R; Willshaw, David J; Roberts, Alan

    2016-01-01

    What cellular and network properties allow reliable neuronal rhythm generation or firing that can be started and stopped by brief synaptic inputs? We investigate rhythmic activity in an electrically-coupled population of brainstem neurons driving swimming locomotion in young frog tadpoles, and how activity is switched on and off by brief sensory stimulation. We build a computational model of 30 electrically-coupled conditional pacemaker neurons on one side of the tadpole hindbrain and spinal cord. Based on experimental estimates for neuron properties, population sizes, synapse strengths and connections, we show that: long-lasting, mutual, glutamatergic excitation between the neurons allows the network to sustain rhythmic pacemaker firing at swimming frequencies following brief synaptic excitation; activity persists but rhythm breaks down without electrical coupling; NMDA voltage-dependency doubles the range of synaptic feedback strengths generating sustained rhythm. The network can be switched on and off at short latency by brief synaptic excitation and inhibition. We demonstrate that a population of generic Hodgkin-Huxley type neurons coupled by glutamatergic excitatory feedback can generate sustained asynchronous firing switched on and off synaptically. We conclude that networks of neurons with NMDAR mediated feedback excitation can generate self-sustained activity following brief synaptic excitation. The frequency of activity is limited by the kinetics of the neuron membrane channels and can be stopped by brief inhibitory input. Network activity can be rhythmic at lower frequencies if the neurons are electrically coupled. Our key finding is that excitatory synaptic feedback within a population of neurons can produce switchable, stable, sustained firing without synaptic inhibition. PMID:26824331

  1. Lmo mutants reveal a novel role for circadian pacemaker neurons in cocaine-induced behaviors.

    Directory of Open Access Journals (Sweden)

    Linus T-Y Tsai

    2004-12-01

    Full Text Available Drosophila has been developed recently as a model system to investigate the molecular and neural mechanisms underlying responses to drugs of abuse. Genetic screens for mutants with altered drug-induced behaviors thus provide an unbiased approach to define novel molecules involved in the process. We identified mutations in the Drosophila LIM-only (LMO gene, encoding a regulator of LIM-homeodomain proteins, in a genetic screen for mutants with altered cocaine sensitivity. Reduced Lmo function increases behavioral responses to cocaine, while Lmo overexpression causes the opposite effect, reduced cocaine responsiveness. Expression of Lmo in the principal Drosophila circadian pacemaker cells, the PDF-expressing ventral lateral neurons (LN(vs, is sufficient to confer normal cocaine sensitivity. Consistent with a role for Lmo in LN(vfunction,Lmomutants also show defects in circadian rhythms of behavior. However, the role for LN(vs in modulating cocaine responses is separable from their role as pacemaker neurons: ablation or functional silencing of the LN(vs reduces cocaine sensitivity, while loss of the principal circadian neurotransmitter PDF has no effect. Together, these results reveal a novel role for Lmo in modulating acute cocaine sensitivity and circadian locomotor rhythmicity, and add to growing evidence that these behaviors are regulated by shared molecular mechanisms. The finding that the degree of cocaine responsiveness is controlled by the Drosophila pacemaker neurons provides a neuroanatomical basis for this overlap. We propose that Lmo controls the responsiveness of LN(vs to cocaine, which in turn regulate the flies' behavioral sensitivity to the drug.

  2. Dissecting the Phase Response of a Model Bursting Neuron

    CERN Document Server

    Sherwood, William Erik

    2009-01-01

    We investigate the phase response properties of the Hindmarsh-Rose model of neuronal bursting using burst phase response curves (BPRCs) computed with an infinitesimal perturbation approximation and by direct simulation of synaptic input. The resulting BPRCs have a significantly more complicated structure than the usual Type I and Type II PRCs of spiking neuronal models, and they exhibit highly timing-sensitive changes in the number of spikes per burst that lead to large magnitude phase responses. We use fast-slow dissection and isochron calculations to analyze the phase response dynamics in both weak and strong perturbation regimes.

  3. Strong attachment of circadian pacemaker neurons on modified ultrananocrystalline diamond surfaces.

    Science.gov (United States)

    Voss, Alexandra; Wei, HongYing; Zhang, Yi; Turner, Stuart; Ceccone, Giacomo; Reithmaier, Johann Peter; Stengl, Monika; Popov, Cyril

    2016-07-01

    Diamond is a promising material for a number of bio-applications, including the fabrication of platforms for attachment and investigation of neurons and of neuroprostheses, such as retinal implants. In the current work ultrananocrystalline diamond (UNCD) films were deposited by microwave plasma chemical vapor deposition, modified by UV/O3 treatment or NH3 plasma, and comprehensively characterized with respect to their bulk and surface properties, such as crystallinity, topography, composition and chemical bonding nature. The interactions of insect circadian pacemaker neurons with UNCD surfaces with H-, O- and NH2-terminations were investigated with respect to cell density and viability. The fast and strong attachment achieved without application of adhesion proteins allowed for advantageous modification of dispersion protocols for the preparation of primary cell cultures. Centrifugation steps, which are employed for pelletizing dispersed cells to separate them from dispersing enzymes, easily damage neurons. Now centrifugation can be avoided since dispersed neurons quickly and strongly attach to the UNCD surfaces. Enzyme solutions can be easily washed off without losing many of the dispersed cells. No adverse effects on the cell viability and physiological responses were observed as revealed by calcium imaging. Furthermore, the enhanced attachment of the neurons, especially on the modified UNCD surfaces, was especially advantageous for the immunocytochemical procedures with the cell cultures. The cell losses during washing steps were significantly reduced by one order of magnitude in comparison to controls. In addition, the integration of a titanium grid structure under the UNCD films allowed for individual assignment of physiologically characterized neurons to immunocytochemically stained cells. Thus, employing UNCD surfaces free of foreign proteins improves cell culture protocols and immunocytochemistry with cultured cells. The fast and strong attachment of

  4. Phase resetting of the mammalian circadian clock relies on a rapid shift of a small population of pacemaker neurons.

    Directory of Open Access Journals (Sweden)

    Jos H T Rohling

    Full Text Available The circadian pacemaker of the suprachiasmatic nuclei (SCN contains a major pacemaker for 24 h rhythms that is synchronized to the external light-dark cycle. In response to a shift in the external cycle, neurons of the SCN resynchronize with different pace. We performed electrical activity recordings of the SCN of rats in vitro following a 6 hour delay of the light-dark cycle and observed a bimodal electrical activity pattern with a shifted and an unshifted component. The shifted component was relatively narrow as compared to the unshifted component (2.2 h and 5.7 h, respectively. Curve fitting and simulations predicted that less than 30% of the neurons contribute to the shifted component and that their phase distribution is small. This prediction was confirmed by electrophysiological recordings of neuronal subpopulations. Only 25% of the neurons exhibited an immediate shift in the phase of the electrical activity rhythms, and the phases of the shifted subpopulations appeared significantly more synchronized as compared to the phases of the unshifted subpopulations (p<0.05. We also performed electrical activity recordings of the SCN following a 9 hour advance of the light-dark cycle. The phase advances induced a large desynchrony among the neurons, but consistent with the delays, only 19% of the neurons peaked at the mid of the new light phase. The data suggest that resetting of the central circadian pacemaker to both delays and advances is brought about by an initial shift of a relatively small group of neurons that becomes highly synchronized following a shift in the external cycle. The high degree of synchronization of the shifted neurons may add to the ability of this group to reset the pacemaker. The large desynchronization observed following advances may contribute to the relative difficulty of the circadian system to respond to advanced light cycles.

  5. Bursting in a model with delay for networks of neurons

    OpenAIRE

    Gail, Annette

    2004-01-01

    It is the intention of this thesis to analyse the mechanisms that lead to bursting in a neuron model. The neuron model used within the thesis describes the membrane potentials as well as the postsynaptic potentials of neurons. The neuron is modelled by a coupled nonlinear system of three differential equations with delay. It consists of a FitzHugh-Nagumo oscillator that is to be considered as an oscillation generator at the axon hillock of the neuron. Further, the model consists of a network ...

  6. PreBötzinger complex and pacemaker neurons: hypothesized site and kernel for respiratory rhythm generation

    DEFF Research Database (Denmark)

    Rekling, J C; Feldman, J L

    1998-01-01

    , progress has been made In particular, a site in the ventrolateral medulla, the preBötzinger Complex, is hypothesized to contain neuronal circuits generating respiratory rhythm. Lesions or disruption of synaptic transmission within the preBötzinger Complex, either in vivo or in vitro, can abolish...... respiratory activity. Furthermore, the persistence of respiratory rhythm following interference with postsynaptic inhibition and the subsequent discovery of neurons with endogenous bursting properties within the preBötzinger Complex have led to the hypothesis that rhythmogenesis results from synchronized...

  7. Different types of bursting in Chay neuronal model

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Based on actual neuronal firing activities, bursting in the Chay neuronal model is considered, in which VK, reversal potentials for K+, VC, reversal potentials for Ca2+, time kinetic constant λn and an additional depolarized current I are considered as dynamical parameters. According to the number of the Hopf bifurcation points on the upper branch of the bifurcation curve of fast subsystem, which is associated with the stable limit cycle corresponding to spiking states, different types of bursting and their respective dynamical behavior are surveyed by means of fast-slow dynamical bifurcation analysis.

  8. Different types of bursting in Chay neuronal model

    Institute of Scientific and Technical Information of China (English)

    YANG ZhuoQin; LU QiShao

    2008-01-01

    Based on actual neuronal firing activities,bursting in the Chay neuronal model is considered,in which Vk,reversal potentials for K+,Vc,reversal potentials for Ca2+,time kinetic constant λn and an additional depolarized current I are considered as dynamical parameters,According to the number of the Hopf bifurcation points on the upper branch of the bifurcation curve of fast subsystem,which is associated with the stable limit cycle corresponding to spiking states,different types of bursting and their respective dynamical behavior are surveyed by means of fast-slow dynamical bifurcation analysis.

  9. Synchronization and rhythm dynamics of a neuronal network consisting of mixed bursting neurons with hybrid synapses

    Science.gov (United States)

    Shi, Xia; Xi, Wenqi

    2016-05-01

    In this paper, burst synchronization and rhythm dynamics of a small-world neuronal network consisting of mixed bursting types of neurons coupled via inhibitory-excitatory chemical synapses are explored. Two quantities, the synchronization parameter and average width factor, are used to characterize the synchronization degree and rhythm dynamics of the neuronal network. Numerical results show that the percentage of the inhibitory synapses in the network is the major factor for we get a similarly bell-shaped dependence of synchronization on it, and the decrease of the average width factor of the network. We also find that not only the value of the coupling strength can promote the synchronization degree, but the probability of random edges adding to the small-world network also can. The ratio of the long bursting neurons has little effect on the burst synchronization and rhythm dynamics of the network.

  10. Bursting oscillations, bifurcation and synchronization in neuronal systems

    International Nuclear Information System (INIS)

    Highlights: → We investigate bursting oscillations and related bifurcation in the modified Morris-Lecar neuron. → Two types of fast-slow bursters are analyzed in detail. → We show the properties of some crucial bifurcation points. → Synchronization transition and the neural excitability are explored in the coupled bursters. - Abstract: This paper investigates bursting oscillations and related bifurcation in the modified Morris-Lecar neuron. It is shown that for some appropriate parameters, the modified Morris-Lecar neuron can exhibit two types of fast-slow bursters, that is 'circle/fold cycle' bursting and 'subHopf/homoclinic' bursting with class 1 and class 2 neural excitability, which have different neuro-computational properties. By means of the analysis of fast-slow dynamics and phase plane, we explore bifurcation mechanisms associated with the two types of bursters. Furthermore, the properties of some crucial bifurcation points, which can determine the type of the burster, are studied by the stability and bifurcation theory. In addition, we investigate the influence of the coupling strength on synchronization transition and the neural excitability in two electrically coupled bursters with the same bursting type. More interestingly, the multi-time-scale synchronization transition phenomenon is found as the coupling strength varies.

  11. Neuromedin s-producing neurons act as essential pacemakers in the suprachiasmatic nucleus to couple clock neurons and dictate circadian rhythms.

    Science.gov (United States)

    Lee, Ivan T; Chang, Alexander S; Manandhar, Manabu; Shan, Yongli; Fan, Junmei; Izumo, Mariko; Ikeda, Yuichi; Motoike, Toshiyuki; Dixon, Shelley; Seinfeld, Jeffrey E; Takahashi, Joseph S; Yanagisawa, Masashi

    2015-03-01

    Circadian behavior in mammals is orchestrated by neurons within the suprachiasmatic nucleus (SCN), yet the neuronal population necessary for the generation of timekeeping remains unknown. We show that a subset of SCN neurons expressing the neuropeptide neuromedin S (NMS) plays an essential role in the generation of daily rhythms in behavior. We demonstrate that lengthening period within Nms neurons is sufficient to lengthen period of the SCN and behavioral circadian rhythms. Conversely, mice without a functional molecular clock within Nms neurons lack synchronous molecular oscillations and coherent behavioral daily rhythms. Interestingly, we found that mice lacking Nms and its closely related paralog, Nmu, do not lose in vivo circadian rhythms. However, blocking vesicular transmission from Nms neurons with intact cell-autonomous clocks disrupts the timing mechanisms of the SCN, revealing that Nms neurons define a subpopulation of pacemakers that control SCN network synchrony and in vivo circadian rhythms through intercellular synaptic transmission. PMID:25741729

  12. Pacemaker-neuron-dependent disturbance of the molecular clockwork by a Drosophila CLOCK mutant homologous to the mouse Clock mutation.

    Science.gov (United States)

    Lee, Euna; Cho, Eunjoo; Kang, Doo Hyun; Jeong, Eun Hee; Chen, Zheng; Yoo, Seung-Hee; Kim, Eun Young

    2016-08-16

    Circadian clocks are composed of transcriptional/translational feedback loops (TTFLs) at the cellular level. In Drosophila TTFLs, the transcription factor dCLOCK (dCLK)/CYCLE (CYC) activates clock target gene expression, which is repressed by the physical interaction with PERIOD (PER). Here, we show that amino acids (AA) 657-707 of dCLK, a region that is homologous to the mouse Clock exon 19-encoded region, is crucial for PER binding and E-box-dependent transactivation in S2 cells. Consistently, in transgenic flies expressing dCLK with an AA657-707 deletion in the Clock (Clk(out)) genetic background (p{dClk-Δ};Clk(out)), oscillation of core clock genes' mRNAs displayed diminished amplitude compared with control flies, and the highly abundant dCLKΔ657-707 showed significantly decreased binding to PER. Behaviorally, the p{dClk-Δ};Clk(out) flies exhibited arrhythmic locomotor behavior in the photic entrainment condition but showed anticipatory activities of temperature transition and improved free-running rhythms in the temperature entrainment condition. Surprisingly, p{dClk-Δ};Clk(out) flies showed pacemaker-neuron-dependent alterations in molecular rhythms; the abundance of dCLK target clock proteins was reduced in ventral lateral neurons (LNvs) but not in dorsal neurons (DNs) in both entrainment conditions. In p{dClk-Δ};Clk(out) flies, however, strong but delayed molecular oscillations in temperature cycle-sensitive pacemaker neurons, such as DN1s and DN2s, were correlated with delayed anticipatory activities of temperature transition. Taken together, our study reveals that the LNv molecular clockwork is more sensitive than the clockwork of DNs to dysregulation of dCLK by AA657-707 deletion. Therefore, we propose that the dCLK/CYC-controlled TTFL operates differently in subsets of pacemaker neurons, which may contribute to their specific functions. PMID:27489346

  13. Design of bursting in a two-dimensional discrete-time neuron model

    International Nuclear Information System (INIS)

    Alternating a quiescent state and a spiking one in a neuron is called bursting, which is one of important neuron activities. In this Letter, we will propose a simple design method for a bursting neuron model with a specified period and duty ratio of the bursting based on bifurcation theory. The neuron model has been proposed by the author et al. based on Aihara's chaotic neuron model. Mechanism of generating the bursting in the neuron model is a quasi-periodic oscillation with respect to internal states, which is caused from a Hopf bifurcation for a pair of two-periodic points. We also show an example derived by the proposed design method

  14. Adaptation to visual stimulation modifies the burst firing property of V1 neurons%Adaptation to visual stimulation modifies the burst firing property of V1neurons

    Institute of Scientific and Technical Information of China (English)

    Rui-Long LIU; Ke WANG; Jian-Jun MENG; Tian-Miao HUA; Zhen LIANG; Min-Min XI

    2013-01-01

    The mean firing rate of visual cortical neurons is reduced after prolonged visual stimulation,but the underlying process by which this occurs as well as the biological significance of this phenomenon remains unknown.Computational neuroscience studies indicate that high-frequency bursts in stimulus-driven responses can be transmitted across synapses more reliably than isolated spikes,and thus may carry accurate stimulus-related information.Our research examined whether or not adaptation affects the burst firing property of visual cortical neurons by examining changes in the burst firing changes of V1 neurons during adaptation to the preferred visual stimulus.The results show that adaptation to prolonged visual stimulation significantly decreased burst frequency (bursts/s) and burst length (spikes/burst),but increased burst duration and the interspike interval within bursts.These results suggest that the adaptation of V1 neurons to visual stimulation may result in a decrease of feedforward response gain but an increase of functional activities from lateral and/or feedback connections,which could lead to a reduction in the effectiveness of adapted neurons in transmitting information to its driven neurons.

  15. Leader neurons in population bursts of 2D living neural networks

    International Nuclear Information System (INIS)

    Eytan and Marom (2006 J. Neurosci. 26 8465-76) recently showed that the spontaneous bursting activity of rat neuron cultures includes 'first-to-fire' cells that consistently fire earlier than others. Here, we analyze the behavior of these neurons in long-term recordings of spontaneous activity of rat hippocampal and rat cortical neuron cultures from three different laboratories. We identify precursor events that may either subside ('aborted bursts') or can lead to a full-blown burst ('pre-bursts'). We find that the activation in the pre-burst typically has a first neuron ('leader'), followed by a localized response in its neighborhood. Locality is diminished in the bursts themselves. The long-term dynamics of the leaders is relatively robust, evolving with a half-life of 23-34 h. Stimulation of the culture alters the leader distribution, but the distribution stabilizes within about 1 h. We show that the leaders carry information about the identity of the burst, as measured by the signature of the number of spikes per neuron in a burst. The number of spikes from leaders in the first few spikes of a precursor event is furthermore shown to be predictive with regard to the transition into a burst (pre-burst versus aborted burst). We conclude that the leaders play a role in the development of the bursts and conjecture that they are part of an underlying sub-network that is excited first and then acts as a nucleation center for the burst

  16. Strange Nonchaotic Bursting in A Quasiperiodially-Forced Hindmarsh-Rose Neuron

    CERN Document Server

    Lim, Woochang; 10.3938/jkps57.1356

    2011-01-01

    We study the transition from a silent state to a bursting state by varying the dc stimulus in the Hindmarsh-Rose neuron under quasiperiodic stimulation. For this quasiperiodically forced case, a new type of strange nonchaotic (SN) bursting state is found to occur between the silent state and the chaotic bursting state. This is in contrast to the periodically forced case where the silent state transforms directly to a chaotic bursting state. Using a rational approximation to the quasiperiodic forcing, the mechanism for the appearance of such an SN bursting state is investigated. Thus, a smooth torus (corresponding to a silent state) is found to transform to an SN bursting attractor through a phase-dependent subcritical period-doubling bifurcation. These SN bursting states, together with chaotic bursting states, are characterized in terms of the interburst interval, the bursting length, and the number of spikes in each burst. Both bursting states are found to be aperiodic complex ones. Consequently, aperiodic c...

  17. Phase-locked cluster oscillations in periodically forced integrate-and-fire-or-burst neuronal populations

    Science.gov (United States)

    Langdon, Angela J.; Breakspear, Michael; Coombes, Stephen

    2012-12-01

    The minimal integrate-and-fire-or-burst neuron model succinctly describes both tonic firing and postinhibitory rebound bursting of thalamocortical cells in the sensory relay. Networks of integrate-and-fire-or-burst (IFB) neurons with slow inhibitory synaptic interactions have been shown to support stable rhythmic states, including globally synchronous and cluster oscillations, in which network-mediated inhibition cyclically generates bursting in coherent subgroups of neurons. In this paper, we introduce a reduced IFB neuronal population model to study synchronization of inhibition-mediated oscillatory bursting states to periodic excitatory input. Using numeric methods, we demonstrate the existence and stability of 1:1 phase-locked bursting oscillations in the sinusoidally forced IFB neuronal population model. Phase locking is shown to arise when periodic excitation is sufficient to pace the onset of bursting in an IFB cluster without counteracting the inhibitory interactions necessary for burst generation. Phase-locked bursting states are thus found to destabilize when periodic excitation increases in strength or frequency. Further study of the IFB neuronal population model with pulse-like periodic excitatory input illustrates that this synchronization mechanism generalizes to a broad range of n:m phase-locked bursting states across both globally synchronous and clustered oscillatory regimes.

  18. Thermodynamic order parameters and statistical-mechanical measures for characterization of the burst and spike synchronizations of bursting neurons

    Science.gov (United States)

    Kim, Sang-Yoon; Lim, Woochang

    2015-11-01

    We are interested in characterization of population synchronization of bursting neurons which exhibit both the slow bursting and the fast spiking timescales, in contrast to spiking neurons. Population synchronization may be well visualized in the raster plot of neural spikes which can be obtained in experiments. The instantaneous population firing rate (IPFR) R(t) , which may be directly obtained from the raster plot of spikes, is often used as a realistic collective quantity describing population behaviors in both the computational and the experimental neuroscience. For the case of spiking neurons, realistic thermodynamic order parameter and statistical-mechanical spiking measure, based on R(t) , were introduced in our recent work to make practical characterization of spike synchronization. Here, we separate the slow bursting and the fast spiking timescales via frequency filtering, and extend the thermodynamic order parameter and the statistical-mechanical measure to the case of bursting neurons. Consequently, it is shown in explicit examples that both the order parameters and the statistical-mechanical measures may be effectively used to characterize the burst and spike synchronizations of bursting neurons.

  19. Synchronization of the minimal models of bursting neurons coupled by delayed chemical or electrical synapses

    Institute of Scientific and Technical Information of China (English)

    Neboj?a Vasovi; Nikola Buri; Kristina Todorovi; Ines Grozdanovi

    2012-01-01

    The minimal two-dimensional model of bursting neuronal dynamics is used to study the influence of time-delay on the properties of synchronization of bursting neurons.Generic properties of bursting and dependence of the stability of synchronization on the time-lag and the strength of coupling are described,and compared with the two common types of synaptical coupling,i.e.,time-delayed chemical and electrical synapses.

  20. Thalamic neuron models encode stimulus information by burst-size modulation

    Directory of Open Access Journals (Sweden)

    Daniel Henry Elijah

    2015-09-01

    Full Text Available Thalamic neurons have been long assumed to fire in tonic mode during perceptive states, and in burst mode during sleep and unconsciousness. However, recent evidence suggests that bursts may also be relevant in the encoding of sensory information. Here we explore the neural code of such thalamic bursts. In order to assess whether the burst code is generic or whether it depends on the detailed properties of each bursting neuron, we analyzed two neuron models incorporating different levels of biological detail. One of the models contained no information of the biophysical processes entailed in spike generation, and described neuron activity at a phenomenological level. The second model represented the evolution of the individual ionic conductances involved in spiking and bursting, and required a large number of parameters. We analyzed the models' input selectivity using reverse correlation methods and information theory. We found that n-spike bursts from both models transmit information by modulating their spike count in response to changes to instantaneous input features, such as slope, phase, amplitude, etc. The stimulus feature that is most efficiently encoded by bursts, however, need not coincide with one of such classical features. We therefore searched for the optimal feature among all those that could be expressed as a linear transformation of the time-dependent input current. We found that bursting neurons transmitted 6 times more information about such more general features. The relevant events in the stimulus were located in a time window spanning ~100 ms before and ~20 ms after burst onset. Most importantly, the neural code employed by the simple and the biologically realistic models was largely the same, implying that the simple thalamic neuron model contains the essential ingredients that account for the computational properties of the thalamic burst code. Thus, our results suggest the n-spike burst code is a general property of

  1. Burst analysis tool for developing neuronal networks exhibiting highly varying action potential dynamics

    Directory of Open Access Journals (Sweden)

    Fikret Emre eKapucu

    2012-06-01

    Full Text Available In this paper we propose a firing statistics based neuronal network burst detection algorithm for neuronal networks exhibiting highly variable action potential dynamics. Electrical activity of neuronal networks is generally analyzed by the occurrences of spikes and bursts both in time and space. Commonly accepted analysis tools employ burst detection algorithms based on predefined criteria. However, maturing neuronal networks, such as those originating from human embryonic stem cells (hESC, exhibit highly variable network structure and time-varying dynamics. To explore the developing burst/spike activities of such networks, we propose a burst detection algorithm which utilizes the firing statistics based on interspike interval (ISI histograms. Moreover, the algorithm calculates interspike interval thresholds for burst spikes as well as for pre-burst spikes and burst tails by evaluating the cumulative moving average and skewness of the ISI histogram. Because of the adaptive nature of the proposed algorithm, its analysis power is not limited by the type of neuronal cell network at hand. We demonstrate the functionality of our algorithm with two different types of microelectrode array (MEA data recorded from spontaneously active hESC-derived neuronal cell networks. The same data was also analyzed by two commonly employed burst detection algorithms and the differences in burst detection results are illustrated. The results demonstrate that our method is both adaptive to the firing statistics of the network and yields successful burst detection from the data. In conclusion, the proposed method is a potential tool for analyzing of hESC-derived neuronal cell networks and thus can be utilized in studies aiming to understand the development and functioning of human neuronal networks and as an analysis tool for in vitro drug screening and neurotoxicity assays.

  2. Circadian- and Light-Dependent Regulation of Resting Membrane Potential and Spontaneous Action Potential Firing of Drosophila Circadian Pacemaker Neurons

    OpenAIRE

    Sheeba, Vasu; Gu, Huaiyu; Sharma, Vijay K.; O'Dowd, Diane K.; Holmes, Todd C.

    2007-01-01

    The ventral lateral neurons (LNvs) of adult Drosophila brain express oscillating clock proteins and regulate circadian behavior. Whole cell current-clamp recordings of large LNvs in freshly dissected Drosophila whole brain preparations reveal two spontaneous activity patterns that correlate with two underlying patterns of oscillating membrane potential: tonic and burst firing of sodium-dependent action potentials. Resting membrane potential and spontaneous action potential firing are rapidly ...

  3. Intermittent synchronization in a network of bursting neurons

    Science.gov (United States)

    Park, Choongseok; Rubchinsky, Leonid L.

    2011-09-01

    Synchronized oscillations in networks of inhibitory and excitatory coupled bursting neurons are common in a variety of neural systems from central pattern generators to human brain circuits. One example of the latter is the subcortical network of the basal ganglia, formed by excitatory and inhibitory bursters of the subthalamic nucleus and globus pallidus, involved in motor control and affected in Parkinson's disease. Recent experiments have demonstrated the intermittent nature of the phase-locking of neural activity in this network. Here, we explore one potential mechanism to explain the intermittent phase-locking in a network. We simplify the network to obtain a model of two inhibitory coupled elements and explore its dynamics. We used geometric analysis and singular perturbation methods for dynamical systems to reduce the full model to a simpler set of equations. Mathematical analysis was completed using three slow variables with two different time scales. Intermittently, synchronous oscillations are generated by overlapped spiking which crucially depends on the geometry of the slow phase plane and the interplay between slow variables as well as the strength of synapses. Two slow variables are responsible for the generation of activity patterns with overlapped spiking, and the other slower variable enhances the robustness of an irregular and intermittent activity pattern. While the analyzed network and the explored mechanism of intermittent synchrony appear to be quite generic, the results of this analysis can be used to trace particular values of biophysical parameters (synaptic strength and parameters of calcium dynamics), which are known to be impacted in Parkinson's disease.

  4. Cardiac Pacemakers

    International Nuclear Information System (INIS)

    A complete survey of physiological biophysical,clinical and engineering aspects of cardiac facing,including the history and an assessment of possible future developments.Among the topics studied are: pacemakers, energy search, heart stimulating with pacemakers ,mathematical aspects of the electric cardio stimulation chronic, pacemaker implants,proceeding,treatment and control

  5. Food Restriction Increases Glutamate Receptor-Mediated Burst Firing of Dopamine Neurons

    OpenAIRE

    Branch, Sarah Y.; Goertz, R. Brandon; Sharpe, Amanda L.; Pierce, Janie; Roy, Sudip; Ko, Daijin; Paladini, Carlos A; Beckstead, Michael J.

    2013-01-01

    Restriction of food intake increases the acquisition of drug abuse behavior and enhances the reinforcing efficacy of those drugs. However, the neurophysiological mechanisms responsible for the interactions between feeding state and drug use are largely unknown. Here we show that chronic mild food restriction increases the burst firing of dopamine neurons in the substantia nigra. Dopamine neurons from food-restricted mice exhibited increased burst firing in vivo, an effect that was enhanced by...

  6. Detection of bursts in neuronal spike trains by the mean inter-spike interval method

    Institute of Scientific and Technical Information of China (English)

    Lin Chen; Yong Deng; Weihua Luo; Zhen Wang; Shaoqun Zeng

    2009-01-01

    Bursts are electrical spikes firing with a high frequency, which are the most important property in synaptic plasticity and information processing in the central nervous system. However, bursts are difficult to identify because bursting activities or patterns vary with phys-iological conditions or external stimuli. In this paper, a simple method automatically to detect bursts in spike trains is described. This method auto-adaptively sets a parameter (mean inter-spike interval) according to intrinsic properties of the detected burst spike trains, without any arbitrary choices or any operator judgrnent. When the mean value of several successive inter-spike intervals is not larger than the parameter, a burst is identified. By this method, bursts can be automatically extracted from different bursting patterns of cultured neurons on multi-electrode arrays, as accurately as by visual inspection. Furthermore, significant changes of burst variables caused by electrical stimulus have been found in spontaneous activity of neuronal network. These suggest that the mean inter-spike interval method is robust for detecting changes in burst patterns and characteristics induced by environmental alterations.

  7. A unified model for two modes of bursting in GnRH neurons.

    Science.gov (United States)

    Moran, Spencer; Moenter, Suzanne M; Khadra, Anmar

    2016-06-01

    Gonadotropin-releasing hormone (GnRH) neurons exhibit at least two intrinsic modes of action potential burst firing, referred to as parabolic and irregular bursting. Parabolic bursting is characterized by a slow wave in membrane potential that can underlie periodic clusters of action potentials with increased interspike interval at the beginning and at the end of each cluster. Irregular bursting is characterized by clusters of action potentials that are separated by varying durations of interburst intervals and a relatively stable baseline potential. Based on recent studies of isolated ionic currents, a stochastic Hodgkin-Huxley (HH)-like model for the GnRH neuron is developed to reproduce each mode of burst firing with an appropriate set of conductances. Model outcomes for bursting are in agreement with the experimental recordings in terms of interburst interval, interspike interval, active phase duration, and other quantitative properties specific to each mode of bursting. The model also shows similar outcomes in membrane potential to those seen experimentally when tetrodotoxin (TTX) is used to block action potentials during bursting, and when estradiol transitions cells exhibiting slow oscillations to irregular bursting mode in vitro. Based on the parameter values used to reproduce each mode of bursting, the model suggests that GnRH neurons can switch between the two through changes in the maximum conductance of certain ionic currents, notably the slow inward Ca(2+) current I s, and the Ca(2+) -activated K(+) current I KCa. Bifurcation analysis of the model shows that both modes of bursting are similar from a dynamical systems perspective despite differences in burst characteristics. PMID:26975615

  8. Interaction of NMDA receptor and pacemaking mechanisms in the midbrain dopaminergic neuron.

    Directory of Open Access Journals (Sweden)

    Joon Ha

    Full Text Available Dopamine neurotransmission has been found to play a role in addictive behavior and is altered in psychiatric disorders. Dopaminergic (DA neurons display two functionally distinct modes of electrophysiological activity: low- and high-frequency firing. A puzzling feature of the DA neuron is the following combination of its responses: N-methyl-D-aspartate receptor (NMDAR activation evokes high-frequency firing, whereas other tonic excitatory stimuli (α-amino-3-hydroxyl-5-methyl-4-isoxazolepropionate receptor (AMPAR activation or applied depolarization block firing instead. We suggest a new computational model that reproduces this combination of responses and explains recent experimental data. Namely, somatic NMDAR stimulation evokes high-frequency firing and is more effective than distal dendritic stimulation. We further reduce the model to a single compartment and analyze the mechanism of the distinct high-frequency response to NMDAR activation vs. other stimuli. Standard nullcline analysis shows that the mechanism is based on a decrease in the amplitude of calcium oscillations. The analysis confirms that the nonlinear voltage dependence provided by the magnesium block of the NMDAR determine its capacity to elevate the firing frequency. We further predict that the moderate slope of the voltage dependence plays the central role in the frequency elevation. Additionally, we suggest a repolarizing current that sustains calcium-independent firing or firing in the absence of calcium-dependent repolarizing currents. We predict that the ether-a-go-go current (ERG, which has been observed in the DA neuron, is the best fit for this critical role. We show that a calcium-dependent and a calcium-independent oscillatory mechanisms form a structure of interlocked negative feedback loops in the DA neuron. The structure connects research of DA neuron firing with circadian biology and determines common minimal models for investigation of robustness of oscillations

  9. Chaotic Phase Synchronization in Bursting-neuron Models Driven by a Weak Periodic Force

    OpenAIRE

    Ando, Hiroyasu; Suetani, Hiromichi; Kurths, Juergen; Aihara, Kazuyuki

    2012-01-01

    We investigate the entrainment of a neuron model exhibiting a chaotic spiking-bursting behavior in response to a weak periodic force. This model exhibits two types of oscillations with different characteristic time scales, namely, long and short time scales. Several types of phase synchronization are observed, such as 1 : 1 phase locking between a single spike and one period of the force and 1 : l phase locking between the period of slow oscillation underlying bursts and l periods of the forc...

  10. Bursting of Morris-Lecar neuronal model with current-feedback control

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The Morris-Lecar (ML) neuronal model with current-feedback control is considered as a typical fast-slow dynamical system to study the combined influences of the reversal potential VCa of Ca2+ and the feedback current I on the generation and transition of different bursting oscillations. Two-parameter bifurcation analysis of the fast subsystem is performed in the parameter (I, VCa)-plane at first. Three important codimension-2 bifurcation points and some codimension-1 bifurcation curves are obtained which enable one to determine the parameter regions for different types of bursting. Next, we further divide the control parameter (V0, VCa)-plane into five different bursting regions, namely, the "fold/fold" bursting region R1, the "fold/Hopf" bursting region R2, the "fold/homoclinic" bursting region R3, the "subHopf/homoclinic" bursting region R4 and the "subHopf/subHopf" bursting region R5, as well as a silence region R6. Codimension-1 and -2 bifurcations are responsible for explanation of transition mechanisms between different types of bursting. The results are instructive for further understanding the dynamical behavior and mechanisms of complex firing activities and information processing in biological nervous systems.

  11. Bursting of Morris-Lecar neuronal model with current-feedback control

    Institute of Scientific and Technical Information of China (English)

    DUAN LiXia; LU QiShao; CHENG DaiZhan

    2009-01-01

    The Morris-Lecar (ML) neuronal model with current-feedback control is considered as a typical fast-slow dynamical system to study the combined influences of the reversal potential Vca of Ca2+ and the feedback current I on the generation and transition of different bursting oscillations. Two-parameter bifurcation analysis of the fast subsystem is performed in the parameter (I, Vca)-plane at first. Three important codimension-2 bifurcation points and some codimension-1 bifurcation curves are obtained which enable one to determine the parameter regions for different types of bursting. Next, we further divide the control parameter (Vo, Vca)-plane into five different bursting regions, namely, the "fold/fold" bursting region R1, the "fold/Hopf" bursting region R2, the "fold/homoclinic" bursting region R3, the "subHopf/homoclinic" bursting region R4 and the "subHopf/subHopf" bursting region R5, as well as a silence region R6. Codimension-1 and-2 bifurcations are responsible for explanation of transition mechanisms between different types of bursting. The results are instructive for further understanding the dynamical behavior and mechanisms of complex firing activities and information processing in biological nervous systems.

  12. Effect of network architecture on burst and spike synchronization in a scale-free network of bursting neurons.

    Science.gov (United States)

    Kim, Sang-Yoon; Lim, Woochang

    2016-07-01

    We investigate the effect of network architecture on burst and spike synchronization in a directed scale-free network (SFN) of bursting neurons, evolved via two independent α- and β-processes. The α-process corresponds to a directed version of the Barabási-Albert SFN model with growth and preferential attachment, while for the β-process only preferential attachments between pre-existing nodes are made without addition of new nodes. We first consider the "pure" α-process of symmetric preferential attachment (with the same in- and out-degrees), and study emergence of burst and spike synchronization by varying the coupling strength J and the noise intensity D for a fixed attachment degree. Characterizations of burst and spike synchronization are also made by employing realistic order parameters and statistical-mechanical measures. Next, we choose appropriate values of J and D where only burst synchronization occurs, and investigate the effect of the scale-free connectivity on the burst synchronization by varying (1) the symmetric attachment degree and (2) the asymmetry parameter (representing deviation from the symmetric case) in the α-process, and (3) the occurrence probability of the β-process. In all these three cases, changes in the type and the degree of population synchronization are studied in connection with the network topology such as the degree distribution, the average path length Lp, and the betweenness centralization Bc. It is thus found that just taking into consideration Lp and Bc (affecting global communication between nodes) is not sufficient to understand emergence of population synchronization in SFNs, but in addition to them, the in-degree distribution (affecting individual dynamics) must also be considered to fully understand for the effective population synchronization. PMID:27131467

  13. VTA dopamine neuron bursting is altered in an animal model of depression and corrected by desipramine.

    Science.gov (United States)

    Friedman, Alexander; Friedman, Yaakov; Dremencov, Eliyahu; Yadid, Gal

    2008-03-01

    Ventral tegmental area (VTA) neuronal activity plays an important role in reward-related learning and motivation. Tracing the bursting signal is important for understanding neural state and understanding communication between individual neurons. The dopaminergic system, which projects from the VTA to other regions in the mesolimbic system, is involved in hedonia and motivation. However, the role of this system in the pathophysiology of depression and its manipulation for treatment of depression has received little attention. Inter-spike interval time series were recorded from the VTA of control Sprague-Dawley and Flinders sensitive line (FSL) rats with or without 14 days of desipramine (5 mg/kg) treatment. Comparison of the firing modes of control and desipramine-treated FSL rats reveals dissimilar patterns. Desipramine treatment normalized depressive-like behavior and elevated the dopaminergic mesolimbic activity, although not to control levels. Mesolimbic neuronal activity is known to occur either in burst or in single-spike firing mode. Herein, we suggest a third mode that is characterized as a "cluster" formed from burst and post-burst activity. A significant reduction in the activity of both bursts and cluster was detected in FSL rats, which was restored by desipramine treatment. PMID:18197479

  14. Chemosensory burst coding by mouse vomeronasal sensory neurons

    OpenAIRE

    Arnson, Hannah A.; Holy, Timothy E.

    2011-01-01

    The capabilities of any sensory system are ultimately constrained by the properties of the sensory neurons: the ability to detect and represent stimuli is limited by noise due to spontaneous activity, and optimal decoding in downstream circuitry must be matched to the nature of the encoding performed at the input. Here, we investigated the firing properties of sensory neurons in the accessory olfactory system, a distinct sensory system specialized for detection of socially relevant odors. Usi...

  15. Calcium-activated potassium channels in insect pacemaker neurons as unexpected target site for the novel fumigant dimethyl disulfide.

    Science.gov (United States)

    Gautier, Hélène; Auger, Jacques; Legros, Christian; Lapied, Bruno

    2008-01-01

    Dimethyl disulfide (DMDS), a plant-derived insecticide, is a promising fumigant as a substitute for methyl bromide. To further understand the mode of action of DMDS, we examined its effect on cockroach octopaminergic neurosecretory cells, called dorsal unpaired median (DUM) neurons, using whole-cell patch-clamp technique, calcium imaging and antisense oligonucleotide strategy. At low concentration (1 microM), DMDS modified spontaneous regular spike discharge into clear bursting activity associated with a decrease of the amplitude of the afterhyperpolarization. This effect led us to suspect alterations of calcium-activated potassium currents (IKCa) and [Ca(2+)](i) changes. We showed that DMDS reduced amplitudes of both peak transient and sustained components of the total potassium current. IKCa was confirmed as a target of DMDS by using iberiotoxin, cadmium chloride, and pSlo antisense oligonucleotide. In addition, we showed that DMDS induced [Ca(2+)](i) rise in Fura-2-loaded DUM neurons. Using calcium-free solution, and (R,S)-(3,4-dihydro-6,7-dimethoxy-isoquinoline-1-yl)-2-phenyl-N,N-di-[2-(2,3,4-trimethoxy-phenyl)ethyl]-acetamide (LOE 908) [an inhibitor of transient receptor potential (TRP)gamma], we demonstrated that TRPgamma initiated calcium influx. By contrast, omega-conotoxin GVIA (an inhibitor of N-type high-voltage-activated calcium channels), did not affect the DMDS-induced [Ca(2+)](i) rise. Finally, the participation of the calcium-induced calcium release mechanism was investigated using thapsigargin, caffeine, and ryanodine. Our study revealed that DMDS-induced elevation in [Ca(2+)](i) modulated IKCa in an unexpected bell-shaped manner via intracellular calcium. In conclusion, DMDS affects multiple targets, which could be an effective way to improve pest control efficacy of fumigation. PMID:17942746

  16. Synaptic Mechanisms Underlying Functional Dichotomy between Intrinsic-Bursting and Regular-Spiking Neurons in Auditory Cortical Layer 5

    OpenAIRE

    Sun, Yujiao J.; Kim, Young-Joo; Ibrahim, Leena A.; Tao, Huizhong W.; Zhang, Li I.

    2013-01-01

    Corticofugal projections from the primary auditory cortex (A1) have been shown to play a role in modulating subcortical processing. However, functional properties of the corticofugal neurons and their synaptic circuitry mechanisms remain unclear. In this study, we performed in vivo whole-cell recordings from layer 5 (L5) pyramidal neurons in the rat A1 and found two distinct neuronal classes according to their functional properties. Intrinsic-bursting (IB) neurons, the L5 corticofugal neurons...

  17. Different levels of Ih determine distinct temporal integration in bursting and regular-spiking neurons in rat subiculum.

    NARCIS (Netherlands)

    I. van Welie; M.W.H. Remme; J.A. van Hooft; W.J. Wadman

    2006-01-01

    Pyramidal neurons in the subiculum typically display either bursting or regular-spiking behaviour. Although this classification into two neuronal classes is well described, it is unknown how these two classes of neurons contribute to the integration of input to the subiculum. Here, we report that bu

  18. Desynchronization in an ensemble of globally coupled chaotic bursting neuronal oscillators by dynamic delayed feedback control

    Science.gov (United States)

    Che, Yanqiu; Yang, Tingting; Li, Ruixue; Li, Huiyan; Han, Chunxiao; Wang, Jiang; Wei, Xile

    2015-09-01

    In this paper, we propose a dynamic delayed feedback control approach or desynchronization of chaotic-bursting synchronous activities in an ensemble of globally coupled neuronal oscillators. We demonstrate that the difference signal between an ensemble's mean field and its time delayed state, filtered and fed back to the ensemble, can suppress the self-synchronization in the ensemble. These individual units are decoupled and stabilized at the desired desynchronized states while the stimulation signal reduces to the noise level. The effectiveness of the method is illustrated by examples of two different populations of globally coupled chaotic-bursting neurons. The proposed method has potential for mild, effective and demand-controlled therapy of neurological diseases characterized by pathological synchronization.

  19. Desynchronization in an ensemble of globally coupled chaotic bursting neuronal oscillators by dynamic delayed feedback control

    CERN Document Server

    Che, Yanqiu; Li, Ruixue; Li, Huiyan; Han, Chunxiao; Wang, Jiang; Wei, Xile

    2014-01-01

    In this paper, we propose a dynamic delayed feedback control approach for desynchronization of chaotic-bursting synchronous activities in an ensemble of globally coupled neuronal oscillators. We demonstrate that the difference signal between an ensemble's mean field and its time delayed state, filtered and fed back to the ensemble, can suppress the self-synchronization in the ensemble. These individual units are decoupled and stabilized at the desired desynchronized states while the stimulation signal reduces to the noise level. The effectiveness of the method is illustrated by examples of two different populations of globally coupled chaotic-bursting neurons. The proposed method has potential for mild, effective and demand-controlled therapy of neurological diseases characterized by pathological synchronization.

  20. Decreased Neuronal Bursting and Phase Synchrony in the Hippocampus of Streptozotocin Diabetic Rats

    Directory of Open Access Journals (Sweden)

    Zhimei Qiao

    2014-01-01

    Full Text Available Diabetic encephalopathy is one of the complications of diabetes. Cognitive dysfunction is the main consequence. Previous findings from neuroanatomical and in vitro electrophysiological studies showed that the structure and function of the hippocampus is impaired in diabetes, which may underlie the cognitive dysfunction induced by diabetes. However the study of electrophysiological abnormality of hippocampal neurons in intact networks is sparse. In the current study, we recorded the spontaneous firing of neurons in hippocampal CA1 area in anesthetized streptozotozin (STZ-diabetic and age-matched control rats. Profound reduction in burst activity was found in diabetic rats. Compared to control rats, the intra-burst inter-spike intervals were prolonged significantly in diabetic rats, while the burst ratio and the mean number of spikes within a burst decreased significantly. Treatment with APP 17-mer peptide retarded the effects of diabetes on these parameters. In addition, the average PLV of diabetic rats was lower than that of control rats. These findings provide in vivo electrophysiological evidence for the impairment of hippocampal function in STZ-diabetic rats, and may have some implications in the mechanisms associated with cognitive deficits in diabetes.

  1. TARGET-SPECIFIC OUTPUT PATTERNS CAN BE PREDICTED BY THE DISTRIBUTION OF REGULAR-SPIKING AND BURSTING PYRAMIDAL NEURONS IN THE SUBICULUM

    OpenAIRE

    Kim, Yujin; Spruston, Nelson

    2011-01-01

    Pyramidal neurons in the subiculum project to a variety of cortical and subcortical areas in the brain to convey information processed in hippocampus. Previous studies have shown that two groups of subicular pyramidal neurons – regular-spiking and bursting neurons – are distributed in an organized fashion along the proximal-distal axis, with more regular-spiking neurons close to CA1 (proximal) and more bursting neurons close to presubiculum (distal). Anatomically, neurons projecting to some t...

  2. A codimension-2 bifurcation controlling endogenous bursting activity and pulse-triggered responses of a neuron model.

    Directory of Open Access Journals (Sweden)

    William H Barnett

    Full Text Available The dynamics of individual neurons are crucial for producing functional activity in neuronal networks. An open question is how temporal characteristics can be controlled in bursting activity and in transient neuronal responses to synaptic input. Bifurcation theory provides a framework to discover generic mechanisms addressing this question. We present a family of mechanisms organized around a global codimension-2 bifurcation. The cornerstone bifurcation is located at the intersection of the border between bursting and spiking and the border between bursting and silence. These borders correspond to the blue sky catastrophe bifurcation and the saddle-node bifurcation on an invariant circle (SNIC curves, respectively. The cornerstone bifurcation satisfies the conditions for both the blue sky catastrophe and SNIC. The burst duration and interburst interval increase as the inverse of the square root of the difference between the corresponding bifurcation parameter and its bifurcation value. For a given set of burst duration and interburst interval, one can find the parameter values supporting these temporal characteristics. The cornerstone bifurcation also determines the responses of silent and spiking neurons. In a silent neuron with parameters close to the SNIC, a pulse of current triggers a single burst. In a spiking neuron with parameters close to the blue sky catastrophe, a pulse of current temporarily silences the neuron. These responses are stereotypical: the durations of the transient intervals-the duration of the burst and the duration of latency to spiking-are governed by the inverse-square-root laws. The mechanisms described here could be used to coordinate neuromuscular control in central pattern generators. As proof of principle, we construct small networks that control metachronal-wave motor pattern exhibited in locomotion. This pattern is determined by the phase relations of bursting neurons in a simple central pattern generator

  3. Structure-dynamics relationships in bursting neuronal networks revealed using a prediction framework.

    Directory of Open Access Journals (Sweden)

    Tuomo Mäki-Marttunen

    Full Text Available The question of how the structure of a neuronal network affects its functionality has gained a lot of attention in neuroscience. However, the vast majority of the studies on structure-dynamics relationships consider few types of network structures and assess limited numbers of structural measures. In this in silico study, we employ a wide diversity of network topologies and search among many possibilities the aspects of structure that have the greatest effect on the network excitability. The network activity is simulated using two point-neuron models, where the neurons are activated by noisy fluctuation of the membrane potential and their connections are described by chemical synapse models, and statistics on the number and quality of the emergent network bursts are collected for each network type. We apply a prediction framework to the obtained data in order to find out the most relevant aspects of network structure. In this framework, predictors that use different sets of graph-theoretic measures are trained to estimate the activity properties, such as burst count or burst length, of the networks. The performances of these predictors are compared with each other. We show that the best performance in prediction of activity properties for networks with sharp in-degree distribution is obtained when the prediction is based on clustering coefficient. By contrast, for networks with broad in-degree distribution, the maximum eigenvalue of the connectivity graph gives the most accurate prediction. The results shown for small ([Formula: see text] networks hold with few exceptions when different neuron models, different choices of neuron population and different average degrees are applied. We confirm our conclusions using larger ([Formula: see text] networks as well. Our findings reveal the relevance of different aspects of network structure from the viewpoint of network excitability, and our integrative method could serve as a general framework for

  4. Structure-dynamics relationships in bursting neuronal networks revealed using a prediction framework.

    Science.gov (United States)

    Mäki-Marttunen, Tuomo; Aćimović, Jugoslava; Ruohonen, Keijo; Linne, Marja-Leena

    2013-01-01

    The question of how the structure of a neuronal network affects its functionality has gained a lot of attention in neuroscience. However, the vast majority of the studies on structure-dynamics relationships consider few types of network structures and assess limited numbers of structural measures. In this in silico study, we employ a wide diversity of network topologies and search among many possibilities the aspects of structure that have the greatest effect on the network excitability. The network activity is simulated using two point-neuron models, where the neurons are activated by noisy fluctuation of the membrane potential and their connections are described by chemical synapse models, and statistics on the number and quality of the emergent network bursts are collected for each network type. We apply a prediction framework to the obtained data in order to find out the most relevant aspects of network structure. In this framework, predictors that use different sets of graph-theoretic measures are trained to estimate the activity properties, such as burst count or burst length, of the networks. The performances of these predictors are compared with each other. We show that the best performance in prediction of activity properties for networks with sharp in-degree distribution is obtained when the prediction is based on clustering coefficient. By contrast, for networks with broad in-degree distribution, the maximum eigenvalue of the connectivity graph gives the most accurate prediction. The results shown for small ([Formula: see text]) networks hold with few exceptions when different neuron models, different choices of neuron population and different average degrees are applied. We confirm our conclusions using larger ([Formula: see text]) networks as well. Our findings reveal the relevance of different aspects of network structure from the viewpoint of network excitability, and our integrative method could serve as a general framework for structure

  5. Spinal neurons bursting in phase with fictive scratching are not related to spontaneous cord dorsum potentials.

    Science.gov (United States)

    Cuellar, C A; Trejo, A; Linares, P; Delgado-Lezama, R; Jiménez-Estrada, I; Abyazova, L M; Baltina, T V; Manjarrez, E

    2014-04-25

    Spontaneous cord dorsum potentials (spontaneous CDPs) are produced by the activation of dorsal horn neurons distributed along the L4 to S1 spinal cord segments, in Rexed's laminae III-VI, in the same region in which there are interneurons rhythmically bursting during fictive scratching in cats. An interesting observation is that spontaneous CDPs are not rhythmically superimposed on the sinusoidal CDPs generated during fictive scratching episodes, thus suggesting that the interneurons producing both types of CDPs belong to different spinal circuits. In order to provide experimental data to support this hypothesis, we recorded unitary activity of neurons in the L6 spinal cord segment. We found that the neurons firing rhythmically during the sinusoidal CDPs associated with the extensor, flexor or intermediate phases of scratching were not synchronized with the spontaneous CDPs. Moreover, we found that the neurons firing during the spontaneous CDPs were not synchronized with the sinusoidal CDPs. These results suggest that the neurons involved in the occurrence of spontaneous CDPs are not part of the spinal cord central pattern generators (CPGs). This study will be relevant for understanding the relationships between the spinal cord neuronal populations firing spontaneously and the CPGs, in the intact and injured spinal cord. PMID:24530658

  6. Specific T-type calcium channel isoforms are associated with distinct burst phenotypes in deep cerebellar nuclear neurons

    OpenAIRE

    Molineux, Michael L.; McRory, John E.; McKay, Bruce E.; Hamid, Jawed; Mehaffey, W. Hamish; Rehak, Renata; Snutch, Terrance P; Gerald W Zamponi; Turner, Ray W

    2006-01-01

    T-type calcium channels are thought to transform neuronal output to a burst mode by generating low voltage-activated (LVA) calcium currents and rebound burst discharge. In this study we assess the expression pattern of the three different T-type channel isoforms (Cav3.1, Cav3.2, and Cav3.3) in cerebellar neurons and focus on their potential role in generating LVA spikes and rebound discharge in deep cerebellar nuclear (DCN) neurons. We detected expression of one or more Cav3 channel isoforms ...

  7. Synchronous bursts on scale-free neuronal networks with attractive and repulsive coupling.

    Directory of Open Access Journals (Sweden)

    Qingyun Wang

    Full Text Available This paper investigates the dependence of synchronization transitions of bursting oscillations on the information transmission delay over scale-free neuronal networks with attractive and repulsive coupling. It is shown that for both types of coupling, the delay always plays a subtle role in either promoting or impairing synchronization. In particular, depending on the inherent oscillation period of individual neurons, regions of irregular and regular propagating excitatory fronts appear intermittently as the delay increases. These delay-induced synchronization transitions are manifested as well-expressed minima in the measure for spatiotemporal synchrony. For attractive coupling, the minima appear at every integer multiple of the average oscillation period, while for the repulsive coupling, they appear at every odd multiple of the half of the average oscillation period. The obtained results are robust to the variations of the dynamics of individual neurons, the system size, and the neuronal firing type. Hence, they can be used to characterize attractively or repulsively coupled scale-free neuronal networks with delays.

  8. Prominent burst firing of dopaminergic neurons in the ventral tegmental area during paradoxical sleep.

    Science.gov (United States)

    Dahan, Lionel; Astier, Bernadette; Vautrelle, Nicolas; Urbain, Nadia; Kocsis, Bernat; Chouvet, Guy

    2007-06-01

    Dopamine is involved in motivation, memory, and reward processing. However, it is not clear whether the activity of dopamine neurons is related or not to vigilance states. Using unit recordings in unanesthetized head restrained rats we measured the firing pattern of dopamine neurons of the ventral tegmental area across the sleep-wake cycle. We found these cells were activated during paradoxical sleep (PS) via a clear switch to a prominent bursting pattern, which is known to induce large synaptic dopamine release. This activation during PS was similar to the activity measured during the consumption of palatable food. Thus, as it does during waking in response to novelty and reward, dopamine could modulate brain plasticity and thus participate in memory consolidation during PS. By challenging the traditional view that dopamine is the only aminergic group not involved in sleep physiology, this study provides an alternative perspective that may be crucial for understanding the physiological function of PS and dream mentation. PMID:17151599

  9. Antagonism of NMDA receptors but not AMPA/kainate receptors blocks bursting in dopaminergic neurons induced by electrical stimulation of the prefrontal cortex.

    Science.gov (United States)

    Tong, Z Y; Overton, P G; Clark, D

    1996-01-01

    Evidence suggests that the prefrontal cortex (PFC) plays an important role in the burst activity of midbrain dopaminergic (DA) neurons. In particular, electrical stimulation of the PFC elicits patterns of activity in DA neurons, closely time-locked to the stimulation, which resemble natural bursts. Given that natural bursts are produced by the activity of excitatory amino acid (EAA)-ergic afferents, if PFC-induced time-locked bursts are homologues of natural bursts, EAA antagonists should attenuate them. Hence, the NMDA (N-methyl-D-aspartate) antagonist CPP (3-((+/-)-2-carboxypiperazin-4-yl)propyl-1-phosphonic acid) and the AMPA (D,L-alpha-amino-3-hydroxy-5-methyl-4-isoxalone propionic acid)/kainate antagonist CNQX (6-cyano-7-nitroquinoxaline-2,3-dione) were applied by iontophoresis to DA neurons exhibiting time-locked bursts during PFC stimulation. CPP produced a significant reduction in time-locked bursting. In contrast, CNQX (at currents which antagonised AMPA responses) did not. These effects of CPP and CNQX on time-locked bursting mirror the effects previously reported for these drugs on natural bursting. Since natural bursting and bursting induced by PFC stimulation are both blocked selectively by CPP, the present results increase the degree of analogy between the two burst phenomena, thereby adding extra support to the contention that the cortex is involved in producing the natural bursting in DA neurons. PMID:9013383

  10. Pacemakers and Implantable Defibrillators

    Science.gov (United States)

    ... need a cardiac pacemaker or an implantable cardioverter defibrillator (ICD). They are devices that are implanted in ... can act as both a pacemaker and a defibrillator. Many ICDs also record the heart's electrical patterns ...

  11. Altered intrinsic properties and bursting activities of neurons in layer IV of somatosensory cortex from Fmr-1 knockout mice.

    Science.gov (United States)

    Zhang, Linming; Liang, Zhanrong; Zhu, Pingping; Li, Meng; Yi, Yong-Hong; Liao, Wei-Ping; Su, Tao

    2016-06-01

    Neuroadaptations and alterations in neuronal excitability are critical in brain maturation and many neurological diseases. Fragile X syndrome (FXS) is a pervasive neurodevelopmental disorder characterized by extensive synaptic and circuit dysfunction. It is still unclear about the alterations in intrinsic excitability of individual neurons and their link to hyperexcitable circuitry. In this study, whole cell patch-clamp recordings were employed to characterize the membrane and firing properties of layer IV cells in slices of the somatosensory cortex of Fmr-1 knockout (KO) mice. These cells generally exhibited a regular spiking (RS) pattern, while there were significant increases in the number of cells that adopted intrinsic bursting (IB) compared with age-matched wild type (WT) cells. The cells subgrouped according to their firing patterns and maturation differed significantly in membrane and discharge properties between KO and WT. The changes in the intrinsic properties were consistent with highly facilitated discharges in KO cells induced by current injection. Spontaneous activities of RS neurons driven by local network were also increased in the KO cells, especially in neonate groups. Under an epileptiform condition mimicked by omission of Mg(2+) in extracellular solution, these RS neurons from KO mice were more likely to switch to burst discharges. Analysis on bursts revealed that the KO cells tended to form burst discharges and even severe events manifested as seizure-like ictal discharges. These results suggest that alterations in intrinsic properties in individual neurons are involved in the abnormal excitability of cortical circuitry and possibly account for the pathogenesis of epilepsy in FXS. PMID:27048919

  12. Pacemakers handshake synchronization mechanism of mammalian respiratory rhythmogenesis

    OpenAIRE

    Wittmeier, Steffen; Song, Gang; Duffin, James; Poon, Chi-Sang

    2008-01-01

    Inspiratory and expiratory rhythms in mammals are thought to be generated by pacemaker-like neurons in 2 discrete brainstem regions: pre-Bötzinger complex (preBötC) and parafacial respiratory group (pFRG). How these putative pacemakers or pacemaker networks may interact to set the overall respiratory rhythm in synchrony remains unclear. Here, we show that a pacemakers 2-way “handshake” process comprising pFRG excitation of the preBötC, followed by reverse inhibition and postinhibitory rebound...

  13. How Does a Pacemaker Work?

    Science.gov (United States)

    ... the NHLBI on Twitter. How Does a Pacemaker Work? A pacemaker consists of a battery, a computerized ... these recordings to adjust your pacemaker so it works better for you. Your doctor can program the ...

  14. The Drosophila melanogaster circadian pacemaker circuit

    Indian Academy of Sciences (India)

    Vasu Sheeba

    2008-12-01

    As an experimental model system, the fruit fly Drosophila melanogaster has been seminal in shaping our understanding of the circadian clockwork. The wealth of genetic tools at our disposal over the past four decades has enabled discovery of the genetic and molecular bases of circadian rhythmicity. More recently, detailed investigation leading to the anatomical, neurochemical and electrophysiological characterization of the various neuronal subgroups that comprise the circadian machinery has revealed pathways through which these neurons come together to act as a neuronal circuit. Thus the D. melanogaster circadian pacemaker circuit presents a relatively simple and attractive model for the study of neuronal circuits and their functions.

  15. A migrating pacemaker

    OpenAIRE

    Gale, C.; Mulley, G.

    2005-01-01

    A deceased 79 year old man with a permanent cardiac pacemaker was due to be cremated, but the pacemaker generator was not detectable by palpation. A hand held metal detector to locate the device so that it could be extracted before cremation.

  16. Participation of a persistent sodium current and calcium-activated nonspecific cationic current to burst generation in trigeminal principal sensory neurons.

    Science.gov (United States)

    Tsuruyama, Kentaro; Hsiao, Chie-Fang; Chandler, Scott H

    2013-10-01

    The properties of neurons participating in masticatory rhythmogenesis are not clearly understood. Neurons within the dorsal trigeminal principal sensory nucleus (dPrV) are potential candidates as components of the masticatory central pattern generator (CPG). The present study examines in detail the ionic mechanisms controlling burst generation in dPrV neurons in rat (postnatal day 8-12) brain stem slices using whole cell and perforated patch-clamp methods. Nominal extracellular Ca(2+) concentration transformed tonic discharge in response to a maintained step pulse of current into rhythmical bursting in 38% of nonbursting neurons. This change in discharge mode was suppressed by riluzole, a persistent Na(+) current (INaP) antagonist. Veratridine, which suppresses the Na(+) channel inactivation mechanism, induced rhythmical bursting in nonbursting neurons in normal artificial cerebrospinal fluid, suggesting that INaP contributes to burst generation. Nominal extracellular Ca(2+) exposed a prominent afterdepolarizing potential (ADP) following a single spike induced by a 3-ms current pulse, which was suppressed, but not completely blocked, by riluzole. Application of BAPTA, a Ca(2+) chelator, intracellularly, or flufenamic acid, a Ca(2+)-activated nonspecific cationic channel (ICAN) antagonist, extracellularly to the bath, suppressed rhythmical bursting and the postspike ADP. Application of drugs to alter Ca(2+) release from endoplasmic reticulum also suppressed bursting. Finally, voltage-clamp methods demonstrated that nominal Ca(2+) facilitated INaP and induced ICAN. These data demonstrate for the first time that the previously observed induction in dPrV neurons of rhythmical bursting in nominal Ca(2+) is mediated by enhancement of INaP and onset of ICAN, which are dependent on intracellular Ca(2+). PMID:23883859

  17. Effects of cooling on the response of the snail bursting neuron to acetylcholine.

    Science.gov (United States)

    Nedeljković, Miodrag; Kartelija, Gordana; Radenović, Lidija

    2005-06-01

    The Br-type neuron of the snail Helix pomatia, involved in neuronal regulation of various homeostatic and adaptive mechanisms, represents an interesting model for studying effects of temperature change on neuronal activity of poikilotherms. Acetylcholine induces a transient, inward dose-dependent current in the identified Br neuron. In the work presented, we analyzed the effects of cooling on the acetylcholine-induced inward current. The amplitude of acetylcholine-induced inward current was markedly decreased after cooling, and the speed of the decay of acetylcholine response was decreased. PMID:16154950

  18. Regional distribution of calcium influx into bursting neurons detected with arsenazo III.

    OpenAIRE

    Graubard, K; Ross, W N

    1985-01-01

    Absorbance changes of the metallochromic indicator arsenazo III were used in conjunction with an array of 100 photodiodes to measure changes in intracellular calcium concentration at many positions simultaneously in identified neurons of the crab stomatogastric ganglion. When stimulated with intrasomatically injected current, several of these neurons showed calcium changes all over the cell, indicating that calcium channels were distributed widely in the neuropil and on the soma. When the mem...

  19. The possible roles of hyperpolarization-activated cyclic nucleotide channels in regulating pacemaker activity in colonic interstitial cells of Cajal

    OpenAIRE

    Shahi, Pawan Kumar; Choi, Seok; Zuo, Dong Chuan; Kim, Man Yoo; Park, Chan Guk; Kim, Young Dae; Lee, Jun; Park, Kyu Joo; So, Insuk; Jun, Jae Yeoul

    2013-01-01

    Background Hyperpolarization-activated cyclic nucleotide (HCN) channels are pacemaker channels that regulate heart rate and neuronal rhythm in spontaneously active cardiac and neuronal cells. Interstitial cells of Cajal (ICCs) are also spontaneously active pacemaker cells in the gastrointestinal tract. Here, we investigated the existence of HCN channel and its role on pacemaker activity in colonic ICCs. Methods We performed whole-cell patch clamp, RT-PCR, and Ca2+-imaging in cultured ICCs fro...

  20. Dependence of synchronized bursting activity on medium stirring and the perfusion rate in a cultured network of neurons

    Science.gov (United States)

    Heo, Ryoun; Kim, Hyun; Lee, Kyoung J.

    2016-05-01

    A cultured network of neurons coupled with a multi-electrode-array (MEA) recording system has been a useful platform for investigating various issues in neuroscience and engineering. The neural activity supported by the system can be sensitive to environmental fluctuations, for example, in the medium's nutrient composition, ph, and temperature, and to mechanical disturbances, yet this issue has not been the subject. Especially, a normal practice in maintaining neuronal cell cultures involves an intermittent sequence of medium exchanges, typically at a time interval of a few days, and one such sudden medium exchange is unavoidably accompanied by many unintended disturbances. Here, based on a quantitative time-series analysis of synchronized bursting events, we explicitly demonstrate that such a medium exchange can, indeed, bring a huge change in the existing neural activity. Subsequently, we develop a medium perfusion-stirring system and an ideal protocol that can be used in conjunction with a MEA recording system, providing long-term stability. Specifically, we systematically evaluate the effects of medium stirring and perfusion rates. Unexpectedly, even some vigorous mechanical agitations do not have any impacts on neural activity. On the other hand, too much replenishment ( e.g., 1.8 ml/day for a 1.8-ml dish) of neurobasal medium results in an excitotoxicity.

  1. Modulation of spike and burst rate in a minimal neuronal circuit with feed-forward inhibition

    NARCIS (Netherlands)

    F. Zeldenrust; W.J. Wadman

    2013-01-01

    Pyramidal cells perform computations on their inputs within the context of the local network. The present computational study investigates the consequences of feed-forward inhibition for the firing rate and reliability of a typical hippocampal pyramidal neuron that can respond with single spikes as

  2. Cardiac pacemaker power sources

    International Nuclear Information System (INIS)

    A review of chemical and radioisotope batteries used in cardiac pacemakers is presented. The battery systems are examined in terms of longevity, reliability, cost, size and shape, energy density, weight, internal resistance versus time, end-of-life voltage, chemical compatibility, and potential failure mechanisms

  3. Network bursting dynamics in excitatory cortical neuron cultures results from the combination of different adaptive mechanisms.

    Directory of Open Access Journals (Sweden)

    Timothée Masquelier

    Full Text Available In the brain, synchronization among cells of an assembly is a common phenomenon, and thought to be functionally relevant. Here we used an in vitro experimental model of cell assemblies, cortical cultures, combined with numerical simulations of a spiking neural network (SNN to investigate how and why spontaneous synchronization occurs. In order to deal with excitation only, we pharmacologically blocked GABAAergic transmission using bicuculline. Synchronous events in cortical cultures tend to involve almost every cell and to display relatively constant durations. We have thus named these "network spikes" (NS. The inter-NS-intervals (INSIs proved to be a more interesting phenomenon. In most cortical cultures NSs typically come in series or bursts ("bursts of NSs", BNS, with short (~1 s INSIs and separated by long silent intervals (tens of s, which leads to bimodal INSI distributions. This suggests that a facilitating mechanism is at work, presumably short-term synaptic facilitation, as well as two fatigue mechanisms: one with a short timescale, presumably short-term synaptic depression, and another one with a longer timescale, presumably cellular adaptation. We thus incorporated these three mechanisms into the SNN, which, indeed, produced realistic BNSs. Next, we systematically varied the recurrent excitation for various adaptation timescales. Strong excitability led to frequent, quasi-periodic BNSs (CV~0, and weak excitability led to rare BNSs, approaching a Poisson process (CV~1. Experimental cultures appear to operate within an intermediate weakly-synchronized regime (CV~0.5, with an adaptation timescale in the 2-8 s range, and well described by a Poisson-with-refractory-period model. Taken together, our results demonstrate that the INSI statistics are indeed informative: they allowed us to infer the mechanisms at work, and many parameters that we cannot access experimentally.

  4. Burst-generating neurones in the dorsal horn in an in vitro preparation of the turtle spinal cord

    DEFF Research Database (Denmark)

    Russo, R E; Hounsgaard, J

    1996-01-01

    these cells the burst following a hyperpolarizing current pulse, applied from the resting membrane potential, facilitated the activation of the plateau potential. Wind-up of the plateau potential was produced when the hyperpolarizing pulse generating the burst was repeated at 0.1-0.3 Hz or faster. 5...... horn, was distinguished by the ability to generate a burst response following a hyperpolarization from rest or during a depolarization from a hyperpolarized holding potential. The burst response was inactivated at the resting membrane potential. 3. The burst response was mediated by a low threshold Ca2....... The burst response and the underlying low threshold Ca2+ spike were activated synaptically by primary afferent stimuli in a voltage range hyperpolarized from the resting membrane potential. 6. Cells with bursts were morphologically distinguishable from cells with bursts and plateau properties. 7. Our...

  5. Macro- and micro-chaotic structures in the Hindmarsh-Rose model of bursting neurons

    Energy Technology Data Exchange (ETDEWEB)

    Barrio, Roberto, E-mail: rbarrio@unizar.es; Serrano, Sergio [Computational Dynamics Group, Departamento de Matemática Aplicada, GME and IUMA, Universidad de Zaragoza, E-50009 Zaragoza (Spain); Angeles Martínez, M. [Computational Dynamics Group, GME, Universidad de Zaragoza, E-50009 Zaragoza (Spain); Shilnikov, Andrey [Neuroscience Institute and Department of Mathematics and Statistics, Georgia State University, Atlanta, Georgia 30078 (United States); Department of Computational Mathematics and Cybernetics, Lobachevsky State University of Nizhni Novgorod, 603950 Nizhni Novgorod (Russian Federation)

    2014-06-01

    We study a plethora of chaotic phenomena in the Hindmarsh-Rose neuron model with the use of several computational techniques including the bifurcation parameter continuation, spike-quantification, and evaluation of Lyapunov exponents in bi-parameter diagrams. Such an aggregated approach allows for detecting regions of simple and chaotic dynamics, and demarcating borderlines—exact bifurcation curves. We demonstrate how the organizing centers—points corresponding to codimension-two homoclinic bifurcations—along with fold and period-doubling bifurcation curves structure the biparametric plane, thus forming macro-chaotic regions of onion bulb shapes and revealing spike-adding cascades that generate micro-chaotic structures due to the hysteresis.

  6. Experimental evidence of a chaotic region in a neural pacemaker

    International Nuclear Information System (INIS)

    In this Letter, we report the finding of period-adding scenarios with chaos in firing patterns, observed in biological experiments on a neural pacemaker, with fixed extra-cellular potassium concentration at different levels and taken extra-cellular calcium concentration as the bifurcation parameter. The experimental bifurcations in the two-dimensional parameter space demonstrate the existence of a chaotic region interwoven with the periodic region thereby forming a period-adding sequence with chaos. The behavior of the pacemaker in this region is qualitatively similar to that of the Hindmarsh–Rose neuron model in a well-known comb-shaped chaotic region in two-dimensional parameter spaces.

  7. Trends in Cardiac Pacemaker Batteries

    Directory of Open Access Journals (Sweden)

    Venkateswara Sarma Mallela

    2004-10-01

    Full Text Available Batteries used in Implantable cardiac pacemakers-present unique challenges to their developers and manufacturers in terms of high levels of safety and reliability. In addition, the batteries must have longevity to avoid frequent replacements. Technological advances in leads/electrodes have reduced energy requirements by two orders of magnitude. Micro-electronics advances sharply reduce internal current drain concurrently decreasing size and increasing functionality, reliability, and longevity. It is reported that about 600,000 pacemakers are implanted each year worldwide and the total number of people with various types of implanted pacemaker has already crossed 3 million. A cardiac pacemaker uses half of its battery power for cardiac stimulation and the other half for housekeeping tasks such as monitoring and data logging. The first implanted cardiac pacemaker used nickel-cadmium rechargeable battery, later on zinc-mercury battery was developed and used which lasted for over 2 years. Lithium iodine battery invented and used by Wilson Greatbatch and his team in 1972 made the real impact to implantable cardiac pacemakers. This battery lasts for about 10 years and even today is the power source for many manufacturers of cardiac pacemakers. This paper briefly reviews various developments of battery technologies since the inception of cardiac pacemaker and presents the alternative to lithium iodine battery for the near future.

  8. Cardiac pacemakers and nuclear batteries

    International Nuclear Information System (INIS)

    Following the introduction giving the indications for cardiac pacemaker therapy with special regard to the use of pacemakers powered by nuclear batteries, reference is made to the resulting radiation exposure of the patient. The activities of the Federal Health Office in this field such as recommendations and surveys including the entire Federal Republic are outlined. (orig.)

  9. Defibrillator/monitor/pacemakers.

    Science.gov (United States)

    2003-05-01

    Defibrillator/monitors allow operators to assess and monitor a patient's ECG and, when necessary, deliver a defibrillating shock to the heart. When integral noninvasive pacing is added, the device is called a defibrillator/monitor/pacemaker. In this Evaluation, we present our findings for two newly evaluated models, the Welch Allyn PIC 50 and the Zoll M Series CCT, and we summarize our findings for the previously evaluated models that are still on the market. We rate the models for the following applications: general crash-cart use, in-hospital transport use, and emergency medical service (EMS) use. PMID:12827940

  10. Glutamatergic synaptic currents of nigral dopaminergic neurons follow a postnatal developmental sequence

    Directory of Open Access Journals (Sweden)

    Edouard ePearlstein

    2015-05-01

    Full Text Available The spontaneous activity pattern of adult dopaminergic (DA neurons of the substantia nigra pars compacta (SNc results from interactions between intrinsic membrane conductances and afferent inputs. In adult SNc DA neurons, low-frequency tonic background activity is generated by intrinsic pacemaker mechanisms, whereas burst generation depends on intact synaptic inputs in particular the glutamatergic ones. Tonic DA release in the striatum during pacemaking is required to maintain motor activity, and burst firing evokes phasic DA release, necessary for cue-dependent learning tasks. However, it is still unknown how the firing properties of SNc DA neurons mature during postnatal development before reaching the adult state. We studied the postnatal developmental profile of spontaneous and evoked AMPA and NMDA receptor-mediated excitatory postsynaptic currents (EPSCs in SNc DA neurons in brain slices from immature (postnatal days P4-10 and young adult (P30-50 tyrosine hydroxylase (TH-GFP mice. We found that somato-dendritic fields of SNc DA neurons are already mature at P4-10. In contrast, spontaneous glutamatergic EPSCs show a developmental sequence. Spontaneous NMDA EPSCs in particular are larger and more frequent in immature SNc DA neurons than in young adult ones and have a bursty pattern. They are mediated by GluN2B and GluN2D subunit-containing NMDA receptors. The latter generate long-lasting, DQP1105-sensitive, spontaneous EPSCs, which are transiently recorded during this early period. Due to high NMDA activity, immature SNc DA neurons generate large and long lasting NMDA receptor-dependent (APV-sensitive bursts in response to the stimulation of the subthalamic nucleus. We conclude that the transient high NMDA activity allows calcium influx into the dendrites of developing SNc DA neurons.

  11. Functiogenesis of cardiac pacemaker activity.

    Science.gov (United States)

    Sakai, Tetsuro; Kamino, Kohtaro

    2016-07-01

    Throughout our investigations on the ontogenesis of the electrophysiological events in early embryonic chick hearts, using optical techniques to record membrane potential probed with voltage-sensitive dyes, we have introduced a novel concept of "functiogenesis" corresponding to "morphogenesis". This article gives an account of the framework of "functiogenesis", focusing on the cardiac pacemaker function and the functional organization of the pacemaking area. PMID:26719289

  12. Modern pacemaker therapy

    Directory of Open Access Journals (Sweden)

    Mijatov Milan

    2010-01-01

    Full Text Available Introduction. Pacemakers are devices that modern medicine and cardiology cannot be imagined without. The technique of implantation comes to surgical procedure where all principles of asepsis and antisepsis have to be respected. Although some complications do happen, they are rather rare. Results. After the implantation of the device, the patient is not handicapped (unless the heart was additionally damaged. On the contrary, the patient returns to his work and functions normally within his family in most of the cases. The first medical appointment is scheduled a month after the implantation and the following are three and six months after. Types of devices. Today there are „new types of electrostimulation”- implantable cardioverter defibrillators and multisite electrostimulators. The former is implanted in patients at high risk of sudden cardiac death and the latter in patients with heart failure and left bundle branch block. Owing to these devices, the sudden cardiac death can be prevented successfully and the quality of a patient’s life is improved.

  13. Devices That May Interfere with Pacemakers

    Science.gov (United States)

    ... group of cellphone companies is studying that possibility. Bluetooth® headsets do not appear to interfere with pacemakers. ... group of cellphone companies is studying that possibility. Bluetooth® headsets do not appear to interfere with pacemakers. ...

  14. Bursting response to current-evoked depolarization in rat CA1 pyramidal neurons is correlated with lucifer yellow dye coupling but not with the presence of calbindin-D28k

    International Nuclear Information System (INIS)

    Calbindin-D28k (CaBP) immunohistochemistry has been combined with electrophysiological recording and Lucifer Yellow (LY) cell identification in the CA1 region of the rat hippocampal formation. CaBP is shown to be contained within a distinct sub-population of CA1 pyramidal cells which is equivalent to the superficial layer described by Lorente de No (1934). The neurogenesis of these CaBP-positive neurons occurs 1-2 days later than the CaBP-negative neurons in the deep pyramidal cell layer, as shown by 3H-thymidine autoradiography. No correlation could be found between the presence or absence of CaBP and the type of electrophysiological response to current-evoked depolarizing pulses. The latter could be separated into bursting or non-bursting types, and the bursting-type response was nearly always found to be associated with the presence of LY dye coupling. Furthermore, when dye coupling involved three neurons, a characteristic pattern was observed which may represent the coupling of phenotypically identical neurons into distinct functional units within the CA1 pyramidal cell layer. In this particular case the three neurons were all likely to be CaBP-positive

  15. Bursting response to current-evoked depolarization in rat CA1 pyramidal neurons is correlated with lucifer yellow dye coupling but not with the presence of calbindin-D28k

    Energy Technology Data Exchange (ETDEWEB)

    Baimbridge, K.G.; Peet, M.J.; McLennan, H.; Church, J. (Department of Physiology, University of British Columbia, Vancouver (Canada))

    1991-04-01

    Calbindin-D28k (CaBP) immunohistochemistry has been combined with electrophysiological recording and Lucifer Yellow (LY) cell identification in the CA1 region of the rat hippocampal formation. CaBP is shown to be contained within a distinct sub-population of CA1 pyramidal cells which is equivalent to the superficial layer described by Lorente de No (1934). The neurogenesis of these CaBP-positive neurons occurs 1-2 days later than the CaBP-negative neurons in the deep pyramidal cell layer, as shown by 3H-thymidine autoradiography. No correlation could be found between the presence or absence of CaBP and the type of electrophysiological response to current-evoked depolarizing pulses. The latter could be separated into bursting or non-bursting types, and the bursting-type response was nearly always found to be associated with the presence of LY dye coupling. Furthermore, when dye coupling involved three neurons, a characteristic pattern was observed which may represent the coupling of phenotypically identical neurons into distinct functional units within the CA1 pyramidal cell layer. In this particular case the three neurons were all likely to be CaBP-positive.

  16. [Future cardiac pacemakers – technical visions].

    Science.gov (United States)

    Haeberlin, Andreas; Zurbuchen, Adrian; Pfenniger, Aloïs; Fuhrer, Jürg; Vogel, Rolf

    2015-08-01

    Cardiac pacemakers are routinely used for the treatment of bradyarrhythmias. Contemporary pacemakers are reliable and allow for a patient specific programming. However, pacemaker replacements due to battery depletion are common (~25 % of all implantation procedures) and bear the risk of complications. Batteryless pacemakers may allow overcoming this limitation. To power a batteryless pacemaker, a mechanism for intracorporeal energy harvesting is required. Such a generator may consist out of subcutaneously implanted solar cells, transforming the small amount of transcutaneously available light into electrical energy. Alternatively, intravascular turbines may harvest energy from the blood flow. Energy may also be harvested from the ventricular wall motion by a dedicated mechanical clockwork converting motion into electrical energy. All these approaches have successfully been tested in vivo. Pacemaker leads constitute another Achilles heel of contemporary pacemakers. Thus, leadless devices are desired. Miniaturized pacemaker circuits and suitable energy harvesting mechanisms (incorporated in a single device) may allow catheter-based implantation of the pacemaker in the heart. Such miniaturized battery- and leadless pacemakers would combine the advantages of both approaches and overcome major limitations of today’s systems. PMID:26227982

  17. Involvement of Na+-leak Channel in Substance P-induced Depolarization of Pacemaking Activity in Interstitial Cells of Cajal

    OpenAIRE

    Kim, Byung Joo; Chang, In Youb; Choi, Seok; Jun, Jae Yeoul; Jeon, Ju-Hong; Xu, Wen-Xie; Kwon, Young Kyu; Ren, Dejian; So, Insuk

    2012-01-01

    Interstitial cells of Cajal (ICCs) are the pacemaking cells in the gastrointestinal muscles that generate the rhythmic oscillations in membrane potential known as slow waves. ICCs also mediate or transduce inputs from the enteric nervous system. Substance P (SubP) is a member of the family of mammalian tachykinin peptides that are predominantly released by enteric neurons. This study assessed the relationship of Na+-leak channel (NALCN) in the SubP-induced depolarization in pacemaking activit...

  18. Pacemakers and implantable cardioverter defibrillators.

    Science.gov (United States)

    Allen, M

    2006-09-01

    An increasing number of patients are now treated cardiac pacemakers and implantable cardioverter defibrillators and the technology of these is constantly changing. It is vital to have a good understanding of how they function and what the real risks are. Understanding how the device should work when functioning normally, and the possible effects of electromagnetic interference, is paramount to their safe management in the peri-operative period. Knowing when a device should be disabled or reprogrammed requires careful consideration. Information from the patient's pacemaker clinic should be sought whenever possible and can be invaluable. In addition, the Medicines Healthcare products Regulatory Agency have published the first set of UK guidelines on the management of implantable devices in the presence of surgical diathermy and this will undoubtedly provide a firm foundation on which anaesthetists can base much of their practice. PMID:16922756

  19. Circadian Pacemaker – Temperature Compensation

    OpenAIRE

    Gerkema, Menno P.; Binder, Marc D.; Hirokawa, Nobutaka; Windhorst, Uwe

    2009-01-01

    One of the defining characteristics of circadian pacemakers and indicates the independence of the speed of circadian clock processes of environmental temperature. Mechanisms involved, so far not elucidated in full detail, entail at least two processes that are similarly affected by temperature changes, but with an opposing and counterbalancing effect on the periodicity of the clock system. As a result of temperature compensation, the increase in reaction velocity for every 10° rise in tempera...

  20. Low atrial septum pacing in pacemaker patients

    OpenAIRE

    Voogt, Willem Gijsbert de

    2006-01-01

    In patients with an indication for anti bradycardia pacing, atrial fibrillation (AF) is a common arrhythmia (30-50%) even in the absence of atrial tachy arrhythmias before pacemaker implantation. Pace prevention and pace intervention for atrial tachy arrhythmias could be an interesting adjuvant treatment in the prevention of the arrhythmia related complications. These treatment modalities when available in pacemaker systems could come at a relative low cost as the indication for pacemaker imp...

  1. L-type calcium channels in adrenal chromaffin cells: role in pace-making and secretion.

    Science.gov (United States)

    Marcantoni, A; Baldelli, P; Hernandez-Guijo, J M; Comunanza, V; Carabelli, V; Carbone, E

    2007-01-01

    Voltage-gated L-type (Cav1.2 and Cav1.3) channels are widely expressed in cardiovascular tissues and represent the critical drug-target for the treatment of several cardiovascular diseases. The two isoforms are also abundantly expressed in neuronal and neuroendocrine tissues. In the brain, Cav1.2 and Cav1.3 channels control synaptic plasticity, somatic activity, neuronal differentiation and brain aging. In neuroendocrine cells, they are involved in the genesis of action potential generation, bursting activity and hormone secretion. Recent studies have shown that Cav1.2 and Cav1.3 are also expressed in chromaffin cells but their functional role has not yet been identified despite that L-type channels possess interesting characteristics, which confer them an important role in the control of catecholamine secretion during action potentials stimulation. In intact rat adrenal glands L-type channels are responsible for adrenaline and noradrenaline release following splanchnic nerve stimulation or nicotinic receptor activation. L-type channels can be either up- or down-modulated by membrane autoreceptors following distinct second messenger pathways. L-type channels are tightly coupled to BK channels and activate at relatively low-voltages. In this way they contribute to the action potential hyperpolarization and to the pace-maker current controlling action potential firings. L-type channels are shown also to regulate the fast secretion of the immediate readily releasable pool of vesicles with the same Ca(2+)-efficiency of other voltage-gated Ca(2+) channels. In mouse adrenal slices, repeated action potential-like stimulations drive L-type channels to a state of enhanced stimulus-secretion efficiency regulated by beta-adrenergic receptors. Here we will review all these novel findings and discuss the possible implication for a specific role of L-type channels in the control of chromaffin cells activity. PMID:17561252

  2. Ionizing radiation effects on implanted pacemakers

    International Nuclear Information System (INIS)

    Fourteen multi-programmable pacemakers and 2 intercardial defibrillators were exposed to 60Co radiation, to 9 MeV electrons and to 6 MV and 10 MV photon radiation. The pacemakers were placed into a water phantom. The following parameters were examined: telemetry, battery, pulse frequency, pulse amplitude, and period at accumulated doses from 2 Gy to 100 Gy. It is concluded that pacemakers in CMOS/Bipolar technology and in 8μ CMOS technology should not be exposed to an absorbed dose exceeding 5 Gy, the latest generation of pacemakers in the 3μm technology will perform satisfactorily up to 70 Gy. (P.A.)

  3. Autaptic Connections Shift Network Excitability and Bursting

    OpenAIRE

    Wiles, Laura; Gu, Shi; Pasqualetti, Fabio; Bassett, Danielle S.; Meaney, David F.

    2016-01-01

    Network architecture forms a critical constraint on neuronal function. Here we examine the role of structural autapses, when a neuron synapses onto itself, in driving network-wide bursting behavior. Using a simple spiking model of neuronal activity, we study how autaptic connections affect activity patterns, and evaluate if neuronal degree or controllability are significant factors that affect changes in bursting from these autaptic connections. We observed that adding increasing numbers of a...

  4. Pacemaker interactions induce reentrant wave dynamics in engineered cardiac culture

    Science.gov (United States)

    Borek, Bartłomiej; Shajahan, T. K.; Gabriels, James; Hodge, Alex; Glass, Leon; Shrier, Alvin

    2012-09-01

    Pacemaker interactions can lead to complex wave dynamics seen in certain types of cardiac arrhythmias. We use experimental and mathematical models of pacemakers in heterogeneous excitable media to investigate how pacemaker interactions can be a mechanism for wave break and reentrant wave dynamics. Embryonic chick ventricular cells are cultured invitro so as to create a dominant central pacemaker site that entrains other pacemakers in the medium. Exposure of those cultures to a potassium channel blocker, E-4031, leads to emergence of peripheral pacemakers that compete with each other and with the central pacemaker. Waves emitted by faster pacemakers break up over the slower pacemaker to form reentrant waves. Similar dynamics are observed in a modified FitzHugh-Nagumo model of heterogeneous excitable media with two distinct sites of pacemaking. These findings elucidate a mechanism of pacemaker-induced reentry in excitable media.

  5. Pacemaker lead design masquerading as lead fracture

    OpenAIRE

    Madhu Gangadhara; Charles Peebles; James Gnanapragasam

    2015-01-01

    Performing chest X-ray is an important annual investigation to check pacemaker lead integrity during follow-up of patients with pacemakers. Understanding lead design is vital to the correct interpretation of X-rays to prevent inappropriate interventions for patients as highlighted in this case.

  6. Pacemakers charging using body energy

    Directory of Open Access Journals (Sweden)

    Dinesh Bhatia

    2010-01-01

    Full Text Available Life-saving medical implants like pacemakers and defibrillators face a big drawback that their batteries eventually run out and patients require frequent surgery to have these batteries replaced. With the advent of technology, alternatives can be provided for such surgeries. To power these devices, body energy harvesting techniques may be employed. Some of the power sources are patient′s heartbeat, blood flow inside the vessels, movement of the body parts, and the body temperature (heat. Different types of sensors are employed, such as for sensing the energy from the heartbeat the piezoelectric and semiconducting coupled nanowires are used that convert the mechanical energy into electricity. Similarly, for sensing the blood flow energy, nanogenerators driven by ultrasonic waves are used that have the ability to directly convert the hydraulic energy in human body to electrical energy. Another consideration is to use body heat employing biothermal battery to generate electricity using multiple arrays of thermoelectric generators built into an implantable chip. These generators exploit the well-known thermocouple effect. For the biothermal device to work, it needs a 2°C temperature difference across it. But there are many parts of the body where a temperature difference of 5°C exists - typically in the few millimeters just below the skin, where it is planned to place this device. This study focuses on using body heat as an alternative energy source to recharge pacemaker batteries and other medical devices and prevent the possibility of life-risk during repeated surgery.

  7. DsRNA as a stimulator of cell pacemaker activity

    International Nuclear Information System (INIS)

    The authors study the action of double-stranded RNAs (dsRNA) on the characteristics of neuron pacemaker activity which permits prediction of the character of action of dsRNA on the pacemaker activity of cells and organs, and takes the investigators closer to an understanding of the membrane mechanisms underlying the action of dsRNA on the cell. The methods for isolating and fractionating dsRNA from yeasts and the intracellular recording of the electrical activity of the snail giant neuron have been described by the authors earlier. The authors determined the dependence of Ca2+ entry upon dsRNA concentration using the isotope 45Ca. Preweighed ganglia were incubated five each for an hour in 2 ml Ringer's solution containing dsRNA and 5 microliters 45CaCl2 of 12.5 mCi activity. After incubation, the ganglia were rinsed three times for 8 min each time in normal Ringers solution. The washed ganglia were dissolved for one day in KOH. The amount of isotope entering was counted using Brav's scintillator and an RGT counter tuned to the 45Ca isotope. The physiological saline used for the isolated ganglion contained 85 mmole NaCl, 4 mmole KCl, 8 mmole CaCl2, 10 mmole MgCl2, 10 mmole Tris-HCl, and 5 mmole glucose

  8. Pacemaker

    Science.gov (United States)

    ... travels, it causes the heart to contract and pump blood. Each electrical signal normally begins in a group ... the atria (AY-tree-uh), contract. This contraction pumps blood into the heart's two lower chambers, the ventricles ( ...

  9. Pacemaker failure associated with therapeutic radiation

    International Nuclear Information System (INIS)

    A 48-year-old white man with a multiprogrammable Intramedics 259-01 pacemaker was treated for inoperable lung cancer with a course of cobalt-60 radiotherapy (total 3500 rad). Several weeks subsequent to his last radiation treatment, the patient presented to the emergency department with chest and abdominal pain, shortness of breath, hypotension, and tachycardia. A paced tachycardia was noted, and application of a magnet over the pacemaker completely inhibited its function, allowing a normal sinus rhythm to ensue and the patient's symptoms to be relieved. Pacemaker failure probably was a complication of radiotherapy

  10. Leadless Cardiac Pacemakers: Back to the Future.

    Science.gov (United States)

    Miller, Marc A; Neuzil, Petr; Dukkipati, Srinivas R; Reddy, Vivek Y

    2015-09-01

    Despite significant advances in battery longevity, lead performance, and programming features since the first implanted permanent pacemaker was developed, the basic design of cardiac pacemakers has remained relatively unchanged over the past 50 years. Because of inherent limitations in their design, conventional (transvenous) pacemakers are prone to multiple potential short- and long-term complications. Accordingly, there has been intense interest in a system able to provide the symptomatic and potentially lifesaving therapies of cardiac pacemakers while mitigating many of the risks associated with their weakest link-the transvenous lead. Leadless cardiac pacing represents the future of cardiac pacing systems, similar to the transition that occurred from the use of epicardial pacing systems to the familiar transvenous systems of today. This review summarizes the current evidence and potential benefits of leadless pacing systems, which are either commercially available (in Europe) or under clinical investigation. PMID:26337997

  11. Measurement and analysis EMC parameters of implantable pacemaker

    OpenAIRE

    Penhaker, Marek; Hájovský, Radovan; Korpas, David

    2011-01-01

    This paper deals with problematic of Electromagnetic Compatibility of Implantable Pacemaker. The ambient electromagnetic field can negatively influence the pacemaker functionality and also the wireless communication between its programmer and device. Electromagnetic compatibility parameters are tested by direct induction of interference signal to the inputs of cardiac pacemaker according to technical specification. The experimental tests were also made by generating of interference radio freq...

  12. 21 CFR 870.1750 - External programmable pacemaker pulse generator.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false External programmable pacemaker pulse generator... External programmable pacemaker pulse generator. (a) Identification. An external programmable pacemaker pulse generators is a device that can be programmed to produce one or more pulses at...

  13. 21 CFR 870.3600 - External pacemaker pulse generator.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false External pacemaker pulse generator. 870.3600... pacemaker pulse generator. (a) Identification. An external pacemaker pulse generator is a device that has a power supply and electronic circuits that produce a periodic electrical pulse to stimulate the...

  14. 21 CFR 870.3610 - Implantable pacemaker pulse generator.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Implantable pacemaker pulse generator. 870.3610... pacemaker pulse generator. (a) Identification. An implantable pacemaker pulse generator is a device that has a power supply and electronic circuits that produce a periodic electrical pulse to stimulate...

  15. Uniform pacemaker and ICD information system in the Netherlands

    NARCIS (Netherlands)

    Hooijschuur, CAM; Dijk, WA; van der Velde, W; Sanon, B; Ammeraal, C; Dassen, WRM; Spruijt, HJ; Murray, A

    2002-01-01

    In the Netherlands the Central Pacemaker Patient Registry (CPPR) collects information of pacemaker and ICD (Implantable Cardio Defibrillator) patients from all 109 Dutch hospitals. Many pacemaker clinics are using a computer to store their implant and follow-up data in a database. Because the device

  16. Does bipolar pacemaker current activate blood platelets?

    DEFF Research Database (Denmark)

    Gjesdal, Grunde; Hansen, Annebirthe Bo; Brandes, Axel

    2009-01-01

    platelets and muscle cells contain actin and myosin filaments, and both cells are activated following calcium influx. Muscle cells open their calcium channels and contract when exposed to an electric current. Current through a bipolar pacemaker lead will expose a small volume of blood, including platelets......, to the depolarizing current. Platelet activation may ensue, resulting in aggregation, release reaction, and contraction. In contrast, a unipolar pacemaker system will not depolarize blood, but transmit current directly into the myocardium, and the current afterward passes through other tissues before...

  17. Nuclear-powered pacemaker fuel cladding study

    International Nuclear Information System (INIS)

    The fabrication of fuel capsules with refractory metal and alloy clads used in nuclear-powered cardiac pacemakers precludes the expedient dissolution of the clad in inorganic acid solutions. An experiment to measure penetration rates of acids on commonly used fuel pellet clads indicated that it is not impossible, but that it would be very difficult to dissolve the multiple cladding. This work was performed because of a suggestion that a 238PuO2-powered pacemaker could be transformed into a terrorism weapon

  18. Permanent transvenous pacemaker implantation in forty dogs

    International Nuclear Information System (INIS)

    Permanent transvenous cardiac pacemakers were implanted in 40 dogs. Electrocardiographic diagnoses included persistent atrial standstill (3 dogs), sick sinus syndrome (8 dogs), and high-grade second-degree or third-degree atrioventricular (AV) block (29 dogs). Thirteen dogs were alive and well 4 to 42 months after pacemaker implantation (mean, 16.9 months). The mean and median survival times of the 26 dogs that died or were euthanatized during the study were 17.9 months and 13 months, respectively. Most of these dogs succumbed to problems unrelated to the arrhythmia and pacemaker implant. One dog was lost to follow-up. Complications associated with permanent transvenous pacemaker implantation included lead dislodgement, infection, hematoma formation, skeletal muscle stimulation, ventricular arrhythmia, migration of the pulse generator, and skin erosion. Lead dislodgement was the most common complication, occurring in 7 of 9 dogs paced using untined electrode leads and in 6 of 30 dogs paced using tined leads. Lead dislodgement did not occur in the only dog paced using an actively fixed endocardial lead. It was concluded that permanent transvenous cardiac pacing is a feasible, less traumatic alternative to epimyocardial pacing in dogs, but that successful use of this technique requires careful implantation technique and anticipation of the potential complications

  19. Low atrial septum pacing in pacemaker patients

    NARCIS (Netherlands)

    Voogt, Willem Gijsbert de

    2006-01-01

    In patients with an indication for anti bradycardia pacing, atrial fibrillation (AF) is a common arrhythmia (30-50%) even in the absence of atrial tachy arrhythmias before pacemaker implantation. Pace prevention and pace intervention for atrial tachy arrhythmias could be an interesting adjuvant trea

  20. Gamma bursts

    International Nuclear Information System (INIS)

    The Vela satellite series has recently detected gamma bursts in the 0.2-1.5MeV energy range. These bursts last an average of from 0.1 to 10s and have a fine time structure, with pulses lasting less than several tens of milliseconds. With simultaneous observations from different satellites it has been possible to determine the spatial origin of some of the bursts. No correlation, however, has been made with known objects. In spite of the fragmentary character of the information received to date, several theories have already been proposed to account for these phenomena

  1. Burst firing is a neural code in an insect auditory system

    OpenAIRE

    Eyherabide, Hugo G.; Rokem, Ariel; Herz, Andreas V. M.; Samengo, Inés

    2008-01-01

    Various classes of neurons alternate between high-frequency discharges and silent intervals. This phenomenon is called burst firing. To analyze burst activity in an insect system, grasshopper auditory receptor neurons were recorded in vivo for several distinct stimulus types. The experimental data show that both burst probability and burst characteristics are strongly influenced by temporal modulations of the acoustic stimulus. The tendency to burst, hence, is not only determined by cell-intr...

  2. Generation of cardiac pacemaker cells by programming and differentiation.

    Science.gov (United States)

    Husse, Britta; Franz, Wolfgang-Michael

    2016-07-01

    A number of diseases are caused by faulty function of the cardiac pacemaker and described as "sick sinus syndrome". The medical treatment of sick sinus syndrome with electrical pacemaker implants in the diseased heart includes risks. These problems may be overcome via "biological pacemaker" derived from different adult cardiac cells or pluripotent stem cells. The generation of cardiac pacemaker cells requires the understanding of the pacing automaticity. Two characteristic phenomena the "membrane-clock" and the "Ca(2+)-clock" are responsible for the modulation of the pacemaker activity. Processes in the "membrane-clock" generating the spontaneous pacemaker firing are based on the voltage-sensitive membrane ion channel activity starting with slow diastolic depolarization and discharging in the action potential. The influence of the intracellular Ca(2+) modulating the pacemaker activity is characterized by the "Ca(2+)-clock". The generation of pacemaker cells started with the reprogramming of adult cardiac cells by targeted induction of one pacemaker function like HCN1-4 overexpression and enclosed in an activation of single pacemaker specific transcription factors. Reprogramming of adult cardiac cells with the transcription factor Tbx18 created cardiac cells with characteristic features of cardiac pacemaker cells. Another key transcription factor is Tbx3 specifically expressed in the cardiac conduction system including the sinoatrial node and sufficient for the induction of the cardiac pacemaker gene program. For a successful cell therapeutic practice, the generated cells should have all regulating mechanisms of cardiac pacemaker cells. Otherwise, the generated pacemaker cells serve only as investigating model for the fundamental research or as drug testing model for new antiarrhythmics. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel

  3. Spindle Bursts in Neonatal Rat Cerebral Cortex.

    Science.gov (United States)

    Yang, Jenq-Wei; Reyes-Puerta, Vicente; Kilb, Werner; Luhmann, Heiko J

    2016-01-01

    Spontaneous and sensory evoked spindle bursts represent a functional hallmark of the developing cerebral cortex in vitro and in vivo. They have been observed in various neocortical areas of numerous species, including newborn rodents and preterm human infants. Spindle bursts are generated in complex neocortical-subcortical circuits involving in many cases the participation of motor brain regions. Together with early gamma oscillations, spindle bursts synchronize the activity of a local neuronal network organized in a cortical column. Disturbances in spindle burst activity during corticogenesis may contribute to disorders in cortical architecture and in the activity-dependent control of programmed cell death. In this review we discuss (i) the functional properties of spindle bursts, (ii) the mechanisms underlying their generation, (iii) the synchronous patterns and cortical networks associated with spindle bursts, and (iv) the physiological and pathophysiological role of spindle bursts during early cortical development. PMID:27034844

  4. MRI-conditional pacemakers: current perspectives

    Directory of Open Access Journals (Sweden)

    Ferreira AM

    2014-05-01

    Full Text Available António M Ferreira,1,2 Francisco Costa,2 António Tralhão,2 Hugo Marques,3 Nuno Cardim,1 Pedro Adragão1,2 1Cardiology Department, Hospital da Luz, 2Cardiology Department, Hospital Santa Cruz- CHLO, 3Radiology Department, Hospital da Luz, Lisbon, Portugal Abstract: Use of both magnetic resonance imaging (MRI and pacing devices has undergone remarkable growth in recent years, and it is estimated that the majority of patients with pacemakers will need an MRI during their lifetime. These investigations will generally be denied due to the potentially dangerous interactions between cardiac devices and the magnetic fields and radiofrequency energy used in MRI. Despite the increasing reports of uneventful scanning in selected patients with conventional pacemakers under close surveillance, MRI is still contraindicated in those circumstances and cannot be considered a routine procedure. These limitations prompted a series of modifications in generator and lead engineering, designed to minimize interactions that could compromise device function and patient safety. The resulting MRI-conditional pacemakers were first introduced in 2008 and the clinical experience gathered so far supports their safety in the MRI environment if certain conditions are fulfilled. With this technology, new questions and controversies arise regarding patient selection, clinical impact, and cost-effectiveness. In this review, we discuss the potential risks of MRI in patients with electronic cardiac devices and present updated information regarding the features of MRI-conditional pacemakers and the clinical experience with currently available models. Finally, we provide some guidance on how to scan patients who have these devices and discuss future directions in the field. Keywords: pacemakers, magnetic resonance imaging, MRI, MRI-conditional devices, safety

  5. Measuring pacemaker dose: A clinical perspective

    Energy Technology Data Exchange (ETDEWEB)

    Studenski, Matthew T., E-mail: matthew.studenski@jeffersonhospital.org [Department of Radiation Oncology at the Jefferson Medical College and Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA (United States); Xiao Ying; Harrison, Amy S. [Department of Radiation Oncology at the Jefferson Medical College and Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA (United States)

    2012-07-01

    Recently in our clinic, we have seen an increased number of patients presenting with pacemakers and defibrillators. Precautions are taken to develop a treatment plan that minimizes the dose to the pacemaker because of the adverse effects of radiation on the electronics. Here we analyze different dosimeters to determine which is the most accurate in measuring pacemaker or defibrillator dose while at the same time not requiring a significant investment in time to maintain an efficient workflow in the clinic. The dosimeters analyzed here were ion chambers, diodes, metal-oxide-semiconductor field effect transistor (MOSFETs), and optically stimulated luminescence (OSL) dosimeters. A simple phantom was used to quantify the angular and energy dependence of each dosimeter. Next, 8 patients plans were delivered to a Rando phantom with all the dosimeters located where the pacemaker would be, and the measurements were compared with the predicted dose. A cone beam computed tomography (CBCT) image was obtained to determine the dosimeter response in the kilovoltage energy range. In terms of the angular and energy dependence of the dosimeters, the ion chamber and diode were the most stable. For the clinical cases, all the dosimeters match relatively well with the predicted dose, although the ideal dosimeter to use is case dependent. The dosimeters, especially the MOSFETS, tend to be less accurate for the plans, with many lateral beams. Because of their efficiency, we recommend using a MOSFET or a diode to measure the dose. If a discrepancy is observed between the measured and expected dose (especially when the pacemaker to field edge is <10 cm), we recommend analyzing the treatment plan to see whether there are many lateral beams. Follow-up with another dosimeter rather than repeating multiple times with the same type of dosimeter. All dosimeters should be placed after the CBCT has been acquired.

  6. Measuring pacemaker dose: A clinical perspective

    International Nuclear Information System (INIS)

    Recently in our clinic, we have seen an increased number of patients presenting with pacemakers and defibrillators. Precautions are taken to develop a treatment plan that minimizes the dose to the pacemaker because of the adverse effects of radiation on the electronics. Here we analyze different dosimeters to determine which is the most accurate in measuring pacemaker or defibrillator dose while at the same time not requiring a significant investment in time to maintain an efficient workflow in the clinic. The dosimeters analyzed here were ion chambers, diodes, metal-oxide-semiconductor field effect transistor (MOSFETs), and optically stimulated luminescence (OSL) dosimeters. A simple phantom was used to quantify the angular and energy dependence of each dosimeter. Next, 8 patients plans were delivered to a Rando phantom with all the dosimeters located where the pacemaker would be, and the measurements were compared with the predicted dose. A cone beam computed tomography (CBCT) image was obtained to determine the dosimeter response in the kilovoltage energy range. In terms of the angular and energy dependence of the dosimeters, the ion chamber and diode were the most stable. For the clinical cases, all the dosimeters match relatively well with the predicted dose, although the ideal dosimeter to use is case dependent. The dosimeters, especially the MOSFETS, tend to be less accurate for the plans, with many lateral beams. Because of their efficiency, we recommend using a MOSFET or a diode to measure the dose. If a discrepancy is observed between the measured and expected dose (especially when the pacemaker to field edge is <10 cm), we recommend analyzing the treatment plan to see whether there are many lateral beams. Follow-up with another dosimeter rather than repeating multiple times with the same type of dosimeter. All dosimeters should be placed after the CBCT has been acquired.

  7. Pacemakers and implantable cardioverter defibrillators - general and anesthetic considerations

    Directory of Open Access Journals (Sweden)

    Amy G. Rapsang

    2014-06-01

    Full Text Available A pacemaking system consists of an impulse generator and lead or leads to carry the electrical impulse to the patient's heart. Pacemaker and implantable cardioverter defibrillator codes were made to describe the type of pacemaker or implantable cardioverter defibrillator implanted. Indications for pacing and implantable cardioverter defibrillator implantation were given by the American College of Cardiologists. Certain pacemakers have magnet-operated reed switches incorporated; however, magnet application can have serious adverse effects; hence, devices should be considered programmable unless known otherwise. When a device patient undergoes any procedure (with or without anesthesia, special precautions have to be observed including a focused history/physical examination, interrogation of pacemaker before and after the procedure, emergency drugs/temporary pacing and defibrillation, reprogramming of pacemaker and disabling certain pacemaker functions if required, monitoring of electrolyte and metabolic disturbance and avoiding certain drugs and equipments that can interfere with pacemaker function. If unanticipated device interactions are found, consider discontinuation of the procedure until the source of interference can be eliminated or managed and all corrective measures should be taken to ensure proper pacemaker function should be done. Post procedure, the cardiac rate and rhythm should be monitored continuously and emergency drugs and equipments should be kept ready and consultation with a cardiologist or a pacemaker-implantable cardioverter defibrillator service may be necessary.

  8. Pacemaker patients’ perspective and experiences in a pacemaker outpatient clinic in relation to test intervals of the pacemaker

    DEFF Research Database (Denmark)

    Lauberg, Astrid; Hansen, Tina; Pedersen, Trine Pernille Dahl

    2014-01-01

    Aalborg University Hospital pacemakers are tested when implanted, 3 months later and then two years after the implantation. It is tested by a nurse specialist who also is interested in the patient’s general health status and well being. Patient expectations are unknown. Cheng et al (2002) have found an...... evident decline in quality of life regarding psychological and social aspects 6 month after the implantation in terms of cognitive function, work ability, and sexual activity. Mlynarski et al (2009) have found correlations between pacemaker implantation and anxiety and depression. Aim The aim of this...... man) before the 3 month visit and one (4 women, 1 man) after the 3 month visit. The interview was transcribed ad verbatim and analyzed inspired by Ricouers three text comprising levels: naïve reading, structural analysis and critical interpretation and discussion. Results Both interviews showed the...

  9. Pacemaker patients’ perspective and experiences in a pacemaker outpatient clinic in relation to test intervals of the pacemaker

    DEFF Research Database (Denmark)

    Lauberg, Astrid; Hansen, Tina; Pedersen, Trine Pernille Dahl

    Aalborg University Hospital pacemakers are tested when implanted, 3 months later and then two years after the implantation. It is tested by a nurse specialist who also is interested in the patient’s general health status and well being. Patient expectations are unknown. Cheng et al (2002) have found an...... evident decline in quality of life regarding psychological and social aspects 6 month after the implantation in terms of cognitive function, work ability, and sexual activity. Mlynarski et al (2009) have found correlations between pacemaker implantation and anxiety and depression. Aim The aim of this...... man) before the 3 month visit and one (4 women, 1 man) after the 3 month visit. The interview was transcribed ad verbatim and analyzed inspired by Ricouers three text comprising levels: naïve reading, structural analysis and critical interpretation and discussion. Results Both interviews showed the...

  10. Limit Cycle Oscillations in Pacemaker Cells

    CERN Document Server

    Endresen, L P; Endresen, Lars Petter; Skarland, Nils

    1999-01-01

    In recent decades, several mathematical models describing the pacemaker activity of the rabbit sinoatrial node have been developed. We demonstrate that it is not possible to establish the existence, uniqueness, and stability of a limit cycle oscillation in those models. Instead we observe an infinite number of limit cycles. We then display numerical results from a new model, with a limit cycle that can be reached from many different initial conditions.

  11. Protection of pacemaker wearers: effects on magnetic fields on the operation of implanted cardiac pacemakers

    International Nuclear Information System (INIS)

    The aim of this study was to assess the changes in the behavior of cardiac pacemakers exposed to 50 and 60 Hz magnetic fields generated by industrial current and 20 to 50 khz magnetic fields generated by a household in a booming period - the induction cook top - and to study the incidence of these changes in a population of subjects with implanted pacemakers. This will enabled to give patients advices about dealing with electric transport lines and facilities and with induction cook tops and to advise manufacturers about the risks involved

  12. Processing of sub- and supra-second intervals in the primate brain results from the calibration of neuronal oscillators via sensory, motor and feedback processes

    Directory of Open Access Journals (Sweden)

    Daya Shankar Gupta

    2014-08-01

    Full Text Available The processing of time intervals in the sub- to supra-second range by the brain is critical for the interaction of primates with their surroundings in activities, such as foraging and hunting. For an accurate processing of time intervals by the brain, representation of the physical time within neuronal circuits is necessary. I propose that time-dimension of the physical surrounding is represented in the brain by different types of neuronal oscillators, generating spikes or spike bursts at regular intervals. The proposed oscillators include the pacemaker neurons, tonic inputs and synchronized excitation and inhibition of inter-connected neurons. Oscillators, which are built inside various circuits of brain, help to form modular clocks, processing time intervals or other temporal characteristics specific to functions of a circuit. Relative or absolute duration is represented within neuronal oscillators by ‘neural temporal unit’, defined as the interval between regularly occurring spikes or spike bursts. Oscillator output is processed to produce changes in activities of neurons, named frequency modulator neuron, wired within a separate module, represented by the rate of change in frequency, and frequency of activities, proposed to encode time intervals. Inbuilt oscillators are calibrated by (a feedback processes (b input of time intervals resulting from rhythmic external sensory stimulation and (c synchronous effects of feedback processes and evoked sensory activity. A single active clock is proposed per circuit, which is calibrated by one or more mechanisms. Multiple calibration mechanisms, inbuilt oscillators and the presence of modular connections prevent a complete loss of interval timing functions of the brain.

  13. Memory-enhancing intra-basolateral amygdala clenbuterol infusion reduces post-burst afterhyperpolarizations in hippocampal CA1 pyramidal neurons following inhibitory avoidance learning.

    Science.gov (United States)

    Lovitz, E S; Thompson, L T

    2015-03-01

    Activation of the basolateral amygdala can modulate the strength of fear memories, including those in single-trial inhibitory avoidance (IA) tasks. Memory retention, measured by the latency to re-enter a dark-compartment paired 24h earlier with a footshock, varies with intensity of this aversive stimulus. When higher intensity footshocks were used, hippocampal CA1 pyramidal neurons exhibited reduced afterhyperpolarizations (AHPs) 24h post-trial, an effect blocked by immediate post-trial inactivation of the basolateral complex of the amygdala (BLA). Similar AHP reductions in CA1 have been observed in a number of learning tasks, with time courses appropriate to support memory consolidation. When less intense footshocks were used for IA training of Sprague-Dawley rats, immediate post-trial infusion of the β-adrenergic agonist clenbuterol into BLA was required to enhance hippocampal Arc protein expression 45 min later and to enhance memory retention tested 48 h later. Here, using Long-Evans rats and low-intensity footshocks, we confirmed that bilateral immediate post-trial infusion of 15 ng/0.5 μl of the β-adrenergic agonist clenbuterol into BLA significantly enhances memory for an IA task. Next, clenbuterol was infused into one BLA immediately post-training, with vehicle infused into the contralateral BLA, then hippocampal CA1 neuron AHPs were assessed 24 h later. Only CA1 neurons from hemispheres ipsilateral to post-trial clenbuterol infusion showed learning-dependent AHP reductions. Excitability of CA1 neurons from the same trained rats, but from the vehicle-infused hemispheres, was identical to that from untrained rats receiving unilateral clenbuterol or vehicle infusions. Peak AHPs, medium and slow AHPs, and accommodation were reduced only with the combination of IA training and unilateral BLA β-receptor activation. Similar to previous observations of BLA adrenergic memory-related enhancement of Arc protein expression in hippocampus, increased CA1 neuronal

  14. A NEW METHOD FOR DIAGRAMMING PACEMAKER/HEART INTERACTION

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Advancements in technology have enhanced the performance of pacemakers but made the interaction between the pacemaker and the heart becoming increasingly complex, and its is difficult to interpret the paced ECGs (PGCGs). This paper introduces a brief method to interpret PECGs, which illustrate the timing intervals graphically and avoid using symbols and strings.

  15. Runaway pacemaker: a still existing complication and therapeutic guidelines

    DEFF Research Database (Denmark)

    Mickley, H; Andersen, C; Nielsen, L H

    1989-01-01

    (rate 240-260 beats/min) was documented. One patient died. Runaway pacemakers must be exchanged as soon as possible. Until this can be accomplished, different emergency maneuvers should be tried. As documented in the cases presented, placing a magnet over the pacemaker may result in a lower, more...

  16. Design and Implementation of programmable Cardiac Pacemaker Using VHDL

    Directory of Open Access Journals (Sweden)

    Omkar Dwivedi

    2015-05-01

    Full Text Available Pacemaker design has evolved very rapidly over the last several years. There has been a great deal of work in enhancing the programmability of pacemakers, to enable them to be programmed to work with different selected operating parameters, and indeed to work in different modes. In Taiwan, about 70%of cardiac pacemakerpatients are paced only from the ventricle with some pacing parameter programmability. This paper goal is to design a cardiac pacemaker with various NBG modes. A state machine approach has been followed to achieve the desired purpose. The pacemaker system is divide into three main sections i.e. controlling unit, sensing unit and pulse generator. In this paper we mainly concentrate on controlling unit and pulse generator. It has been developed using VHDL coding and implemented in hardware using FPGA. In a simple pacemaker process i.e. single chamber or dual chamber pacemaker, first an input signal or an event is detected in heart through leads. When the input signal is detected a timer generates a delay for approximately 0.8 sec. It is the time between two consecutive heartbeats, thus giving us 72 heartbeats per minute. Once the generated delay expires, sensing unit again start detecting a new event. If any event is detected we repeat the process of detection and waiting. If no event is detected we need to provide an electrical pulse to the heart and then repeat the whole process of detection and waiting. The code has been optimized and modified for different pacemaker modes.

  17. Routine chest radiography after permanent pacemaker implantation: Is it necessary?

    Directory of Open Access Journals (Sweden)

    Edwards N

    2005-01-01

    Full Text Available Background and Aims: Chest radiographs (CXRs are performed routinely after permanent pacemaker implantation to identify pacemaker lead position and exclude pneumothorax. We assessed the clinical value and need for this procedure. Design: Retrospective analysis of pacemaker data and CXRs following permanent pacemaker insertion between December 2002 and February 2004. Materials and Methods: Post-procedural CXRs were available in 125/126 consecutive patients after either first endocardial pacemaker implantation or insertion of at least one new lead. Subclavian vein puncture was used for venous access in all cases. CXRs were examined to establish the incidence of pneumothorax and assess pacing lead positions. The clinical records were examined in all patients who had subsequent CXRs or a further pacemaker procedure to identify the indication for these and to establish whether CXR had influenced patient management. Results: In total, 192 post-procedural CXRs were performed, either postero-anterior (PA and/or lateral views. Ventricular and/or atrial pacing lead contour and electrode position was considered radiographically appropriate in 86% CXRs. Fourteen per cent of post-procedural radiographs were considered to have radiologically sub-optimal pacemaker lead positioning. None of the patients with these "abnormal" radiographs experienced subsequent pacemaker complications or had further radiographs recorded at a later date. Later repeat CXRs were performed in 16 patients (13% but only 3 patients (2% had pacing abnormalities as the primary indication. All three had satisfactory pacing lead position on initial post-implantation and later radiographs, but required further procedures for lead re-positioning. Iatrogenic pneumothorax occurred in one patient (incidence 0.8% in our series. CXR confirmed the clinical diagnosis and allowed an assessment of size to guide treatment. Conclusion: Routine CXR after permanent pacemaker insertion is not necessary in

  18. Of pacemakers and statistics: the actuarial method extended.

    Science.gov (United States)

    Dussel, J; Wolbarst, A B; Scott-Millar, R N; Obel, I W

    1980-01-01

    Pacemakers cease functioning because of either natural battery exhaustion (nbe) or component failure (cf). A study of four series of pacemakers shows that a simple extension of the actuarial method, so as to incorporate Normal statistics, makes possible a quantitative differentiation between the two modes of failure. This involves the separation of the overall failure probability density function PDF(t) into constituent parts pdfnbe(t) and pdfcf(t). The approach should allow a meaningful comparison of the characteristics of different pacemaker types. PMID:6160497

  19. Full System Bifurcation Analysis of Endocrine Bursting Models

    OpenAIRE

    Rieß, Thorsten; Sherman, Arthur; Tsaneva-Atanasova, KT; Osinga, HM

    2010-01-01

    Plateau bursting is typical of many electrically excitable cells, such as endocrine cells that secrete hormones and some types of neurons that secrete neurotransmitters. Although in many of these cell types the bursting patterns are regulated by the interplay between voltage-gated calcium channels and calcium-sensitive potassium channels, they can be very different. For example, in insulin-secreting pancreatic β-cells, plateau bursting is characterized by well-defined spikes during the depola...

  20. Sleep Apnea May Raise Heart Risks in People with Pacemakers

    Science.gov (United States)

    ... page: https://medlineplus.gov/news/fullstory_158688.html Sleep Apnea May Raise Heart Risks in People With ... 2016 (HealthDay News) -- People with heart pacemakers and sleep apnea are at much greater risk for a ...

  1. Sleep Apnea May Raise Heart Risks in People with Pacemakers

    Science.gov (United States)

    ... nlm.nih.gov/medlineplus/news/fullstory_158688.html Sleep Apnea May Raise Heart Risks in People With ... 2016 (HealthDay News) -- People with heart pacemakers and sleep apnea are at much greater risk for a ...

  2. Performance Analysis in Pacemaker Electrode and Study Effect Electric Resistance

    OpenAIRE

    S. Iman Zonoori , Elaheh Nikkhah Bahrami; Zahra Bahrami; Shahin Rezvani Abravani

    2014-01-01

    — In recent years, there has been an increasing use pacemaker electrode that is placed inside the heart and helps the patient’s heart to keep a normal rhythm. In this paper, performance of pacemaker electrode and electric resistance are investigated. These structures are modelled and numerically tested by using Finite Element Method (FEM) by using Comsol Multiphysics. The created virtual models using 3D simulation and computation software proved that used shiel...

  3. Delayed lead perforation: a rare cause of pacemaker dysfunction.

    Science.gov (United States)

    dos Santos, Luís Ferreira; Costa, Filipa; Correia, Emanuel; Rodrigues, Bruno; Moreira, Davide; Correia, Hugo; Nunes, Luís; Pipa, João; Costa, António; de Carvalho, Lopes; Cabral, Costa; Ribeiro, Nuno; de Olival, Ramos; Santos, Oliveira

    2011-06-01

    A 65-year-old woman with a dual-chamber pacemaker implanted in 2006 for symptomatic carotid sinus hypersensitivity was incidentally found to have loss of ventricular capture on routine pacemaker interrogation. A chest X-ray raised the suspicion of perforation and migration of the right ventricular lead, confirmed by three-dimensional echocardiogram and CT scan. On the basis of this case, we review myocardial lead perforation, including predisposing factors, pathophysiological mechanisms, diagnostic approach and therapeutic options. PMID:21874925

  4. Venous obstruction in permanent pacemaker patients: an isotopic study

    International Nuclear Information System (INIS)

    Isotope venography was used to study the venous circulation proximal to the superior vena cava in two groups of pacemaker patients, one with a single endocavitary electrode and the other with multiple pacing catheters. A control group of patients without pacemakers was also studied. Numerous abnormalities were found, especially in the group with multiple electrodes. These findings suggest that venous obstruction is a common complication of endocardial pacing

  5. Venous obstruction in permanent pacemaker patients: an isotopic study

    Energy Technology Data Exchange (ETDEWEB)

    Pauletti, M.; Di Ricco, G.; Solfanelli, S.; Marini, C.; Contini, C.; Giuntini, C.

    1981-01-01

    Isotope venography was used to study the venous circulation proximal to the superior vena cava in two groups of pacemaker patients, one with a single endocavitary electrode and the other with multiple pacing catheters. A control group of patients without pacemakers was also studied. Numerous abnormalities were found, especially in the group with multiple electrodes. These findings suggest that venous obstruction is a common complication of endocardial pacing.

  6. Cardiovascular magnetic resonance with an MR compatible pacemaker

    OpenAIRE

    Bhandiwad Anita R; Cummings Kristopher W; Crowley Michael; Woodard Pamela K

    2013-01-01

    Abstract Magnetic resonance imaging (MRI) within FDA guidelines for the MRI-conditional pacemaker precludes placing the heart at the center of the magnet’s bore. This in effect appears to preclude cardiovascular MR. In this manuscript, we describe a protocol for cardiovascular MR of patients with a Revo pacemaker system while operating within FDA guidelines, and the first US case of cardiovascular MR in a patient with a Revo MRI-conditional pacing system despite position constraints.

  7. Effects of irradiation on the components of implantable pacemakers

    International Nuclear Information System (INIS)

    The purpose of this study was to examine the effects of irradiation on implantable pacemaker components. The pacemaker was divided into three components: lead wire and electrode, battery, and electrical circuit, and each component was irradiated by X-ray and electron beams, respectively. The pacemaker parameters were measured by both telemetry data of the programmer and directly measured data from the output terminal. The following results were obtained. For the lead wire and electrode, there was no effect on the pacemaker function due to irradiation by X-ray and electron beams. In the case of battery irradiation, there was no change in battery voltage or current up to 236 Gy X-ray dose. In the electrical circuit, the pacemaker reverted to the regular beating rate (fixed-rate mode) immediately after the start of X-ray irradiation, and it continued in this mode during irradiation. In patients with their own heartbeat rhythm, changing to the fixed-rate mode may cause dangerous conditions such as ventricular fibrillation. When the accumulated irradiation dose is increased, another failure can be seen in the output voltage of the pacemaker. The pacing output voltage dropped rapidly by about 40% at 30-88 Gy. Decreasing the output voltage results in pacing disorders, and heart failure may occur. In the telemetry data of the programmer, no change in output voltage could be detected, highlighting the difference between telemetry data and actual pacing data. (author)

  8. Nonphotic entrainment of the human circadian pacemaker

    Science.gov (United States)

    Klerman, E. B.; Rimmer, D. W.; Dijk, D. J.; Kronauer, R. E.; Rizzo, J. F. 3rd; Czeisler, C. A.

    1998-01-01

    In organisms as diverse as single-celled algae and humans, light is the primary stimulus mediating entrainment of the circadian biological clock. Reports that some totally blind individuals appear entrained to the 24-h day have suggested that nonphotic stimuli may also be effective circadian synchronizers in humans, although the nonphotic stimuli are probably comparatively weak synchronizers, because the circadian rhythms of many totally blind individuals "free run" even when they maintain a 24-h activity-rest schedule. To investigate entrainment by nonphotic synchronizers, we studied the endogenous circadian melatonin and core body temperature rhythms of 15 totally blind subjects who lacked conscious light perception and exhibited no suppression of plasma melatonin in response to ocular bright-light exposure. Nine of these fifteen blind individuals were able to maintain synchronization to the 24-h day, albeit often at an atypical phase angle of entrainment. Nonphotic stimuli also synchronized the endogenous circadian rhythms of a totally blind individual to a non-24-h schedule while living in constant near darkness. We conclude that nonphotic stimuli can entrain the human circadian pacemaker in some individuals lacking ocular circadian photoreception.

  9. Rhythm Synchronization of Coupled Neurons with Temporal Coding Scheme

    Institute of Scientific and Technical Information of China (English)

    SHI Xia; LU Qi-Shao

    2007-01-01

    Encoding information by firing patterns is one of the basic neural functions, and synchronization is important collective behaviour of a group of coupled neurons. Taking account of two schemes for encoding information (that is, rate coding and temporal coding), rhythm synchronization of coupled neurons is studied. There are two types of rhythm synchronization of neurons: spike and burst synchronizations. Firstly, it is shown that the spike synchronization is equivalent to the phase synchronization for coupled neurons. Secondly, the similarity function of the slow variables of neurons, which have relevant to the bursting process, is proposed to judge the burst synchronization. It is also found that the burst synchronization can be achieved more easily than the spike synchronization, whatever the firing patterns of the neurons are. Hence the temporal encoding scheme, which is closely related to both the spike and burst synchronizations, is more comprehensive than the rate coding scheme in essence.

  10. Taming desynchronized bursting with delays in the Macaque cortical network

    Institute of Scientific and Technical Information of China (English)

    Wang Qing-Yun; Murks Aleksandra; Perc Matja(z); Lu Qi-Shao

    2011-01-01

    Inhibitory coupled bursting Hindmarsh-Rose neurons are considered as constitutive units of the Macaque cortical network. In the absence of information transmission delay the bursting activity is desynchronized, giving rise to spatiotemporally disordered dynamics. This paper shows that the introduction of finite delays can lead to the synchroization of bursting and thus to the emergence of coherent propagating fronts of excitation in the space-time domain.Moreover, it shows that the type of synchronous bursting is uniquely determined by the delay length, with the transitions from one type to the other occurring in a step-like manner depending on the delay. Interestingly, as the delay is tuned close to the transition points, the synchronization deteriorates, which implies the coexistence of different bursting attractors. These phenomena can be observed be different but fixed coupling strengths, thus indicating a new role for information transmission delays in realistic neuronal networks.

  11. Effects of irradiation on the components of implantable pacemakers

    CERN Document Server

    Kawamura, S; Kuga, N; Shiba, T; Hirose, T; Fujimoto, H; Toyoshima, T; Hyodo, K; Matoba, M

    2003-01-01

    The purpose of this study was to examine the effects of irradiation on implantable pacemaker components. The pacemaker was divided into three components: lead wire and electrode, battery, and electrical circuit, and each component was irradiated by X-ray and electron beams, respectively. The pacemaker parameters were measured by both telemetry data of the programmer and directly measured data from the output terminal. The following results were obtained. For the lead wire and electrode, there was no effect on the pacemaker function due to irradiation by X-ray and electron beams. In the case of battery irradiation, there was no change in battery voltage or current up to 236 Gy X-ray dose. In the electrical circuit, the pacemaker reverted to the regular beating rate (fixed-rate mode) immediately after the start of X-ray irradiation, and it continued in this mode during irradiation. In patients with their own heartbeat rhythm, changing to the fixed-rate mode may cause dangerous conditions such as ventricular fib...

  12. Surveillance and follow-up of patients with implanted cardiac pacemaker by telephone transmission.

    Science.gov (United States)

    Sakurai, T; Tokutsu, S; Nishimura, O; Tagami, Y; Takimoto, M; Ohta, H; Yamaoka, Y; Okada, K; Suzuki, Y; Yokoi, H; Enomoto, K; Okada, N; Tanaka, H; Murakami, K

    1978-11-01

    A follow-up study on pacemaker function in 15 patients with implanted cardiac pacemaker has been performed by telephone transmission. The transmitting set consisting of electrocardiograph, pacemaker pulse modulator and acoustic coupler was manipulated by the patients themselves. ECG, pacemaker pulse, and pulse rate were simultaneously transmitted through 1 channel to the receiver in our clinic. Of 56 patients with pacemaker, 15 patients were surveyed by telephone transmission. In these patients battery exhaustion was detected in 3, competition in 2, and lead fracture in 1. The fact that surveillance and follow-up of the patients with implanted cardiac pacemaker could be carried out by telephone transmission as well as by clinic visitation tells us that the telephone transmission is a useful method and plays an important role in a pacemaker clinic. Moreover our study established its further usefulness in the patient's preference due to difficulties in travelling to the pacemaker clinic and in reducing patient's anxiety. PMID:750667

  13. Discrete Pattern of Burst Stimulation in the Ventrobasal Thalamus for Anti-Nociception

    OpenAIRE

    Huh, Yeowool; Cho, Jeiwon

    2013-01-01

    The thalamus has been proposed to play a role in sensory modulation via switching between tonic and burst dual firing of individual neurons. Of the two firing modes, altered burst firing has been repeatedly implicated with pathological pain conditions, which suggests that maintaining a certain form of thalamic burst could be crucial for controlling pain. However, specific elements of burst firing that may contribute to pain control have not yet been actively investigated. Utilizing the deep b...

  14. Towards the Emulation of the Cardiac Conduction System for Pacemaker Testing

    OpenAIRE

    Yip, Eugene; Andalam, Sidharta; Roop, Partha S.; Malik, Avinash; Trew, Mark; Ai, Weiwei; Patel, Nitish

    2016-01-01

    The heart is a vital organ that relies on the orchestrated propagation of electrical stimuli to coordinate each heart beat. Abnormalities in the heart's electrical behaviour can be managed with a cardiac pacemaker. Recently, the closed-loop testing of pacemakers with an emulation (real-time simulation) of the heart has been proposed. An emulated heart would provide realistic reactions to the pacemaker as if it were a real heart. This enables developers to interrogate their pacemaker design wi...

  15. Surgical Removal of a Giant Vegetation on Permanent Endocavitary Pacemaker Wire and Lead

    Institute of Scientific and Technical Information of China (English)

    Guo-tao Ma; Qi Miao; Chao-ji Zhang; Li-hua Cao

    2011-01-01

    PACEMAKER lead infections are rare.There are only about 0.4%-1.1% of the patients who have been implanted permanent pacemakers suffering from serious infections which lead to endocarditis.1 Generally,removal of the infected pacemaker wire and lead,long-term anti-infection therapy,and implantation of a new pacemaker to another anatomic site are accepted approaches for these patients.

  16. Pacemaker patients' perception of unsafe activities: a survey

    Directory of Open Access Journals (Sweden)

    Shafquat Azam

    2008-11-01

    Full Text Available Abstract Background Cardiac pacing is a recognized and widely used treatment for patients presenting with bradycardia. Physicians expect patients to return to normal activities almost immediately post implantation. However, patients themselves may perceive interference to pacemaker function by various routine activities and devices, and hence continue to lead restricted, disabled lives. The aim of this study is to determine if routine activities are perceived by pacemaker patients to interfere with their device function. Methods A descriptive cross sectional survey was carried out on consecutive patients at the pacemaker clinic at a public hospital in Karachi, Pakistan. A 47-question tool was developed and tested. Patients' perceptions of safety of performing various routine activities, along with socio-demographic data were recorded. Results The final sample included 93 adult patients (45% males. 41% were illiterate. 77.4% recalled receiving counselling at implantation, predominantly from the implanting physician and house staff. A considerable proportion of patients considered many routine activities unsafe including driving automobiles (28%, passing through metal detectors (31%, bending over (37%, and sleeping on the side of the pacemaker (30%. Also considered unsafe were operation of household appliances- TV/VCR (television/video cassette recorders (53%, irons (55% and electrical wall switches (56%. For nearly all variables neither literacy nor history of counselling improved incorrect perceptions. Conclusion This study shows that our pacemaker patients perceive many routine activities as unsafe, potentially leading to disabling life style modifications. The tremendous investment in pacemaker technology to improve patient performance is not going to pay dividends if patients continue to remain disabled due to incorrect perceptions. Further studies are required to determine the reasons for these misperceptions, and to determine if these

  17. Permanent internal pacemaker safety in air medical transport.

    Science.gov (United States)

    Gordon, R S; O'Dell, K B

    1991-02-01

    Helicopter and fixed-wing air medical transportation provides an important role in the management of critically-ill patients. As the use of cardiac pacemakers continues to grow, knowledge of their expanding capabilities and sophistication is important. The environments of our "airborne intensive care units" are subject to many sources of electromagnetic and vibrational interference. Although pacemaker shielding mechanisms have become quite elaborate, further studies are needed to define their reliability in modern aircraft. Further, the possible effects of electromagnetic and vibrational interference upon inflight reprogramming require further study. PMID:10109075

  18. [Electromagnetic interference of electrical dental equipment with cardiac pacemakers].

    Science.gov (United States)

    Brand, H S; van der Hoeff, E V; Schrama, T A M; Entjes, M L; van Nieuw, Amerongen A

    2007-09-01

    Eight different electrical dental appliances were tested at different intervals for their ability to interfere with the function of a contemporary cardiac pacemaker. The normal atrial and ventricular pacing was inhibited by an ultrasonic bath cleaner at a distance of less than 15 cm. In contrast, a dental chair, an electrosurgical unit, an ultrasonic tooth scaler, 2 handpieces, and 2 amalgamators failed to produce electromagnetic interference at the minimum distance of 2.5 cm. In conclusion, the results suggest that normal clinical use of dental electrical equipment does not have any significant effect on the cardiac pacemaker tested. PMID:17937372

  19. Complex EPSCs Evoked in Substantia Nigra Reticulata Neurons are Disrupted by Repetitive Stimulation of the Subthalamic Nucleus

    OpenAIRE

    Shen, Ke-Zhong; Johnson, Steven W.

    2008-01-01

    Although substantia nigra reticulata (SNR) neurons fire bursts of action potentials during normal movement, excessive burst firing correlates with symptoms of Parkinson’s disease. A major excitatory output from the subthalamic nucleus (STN) to the SNR is thought to provide the synaptic impetus for burst firing in SNR neurons. Using patch pipettes to record from SNR neurons in rat brain slices, we found that a single electrical stimulus delivered to the STN evokes a burst of action potentials....

  20. Information Transmission in a Neuron-Astrocyte Coupled Model

    OpenAIRE

    Tang, Jun; Luo, Jin-Ming; Ma, Jun

    2013-01-01

    A coupled model containing two neurons and one astrocyte is constructed by integrating Hodgkin-Huxley neuronal model and Li-Rinzel calcium model. Based on this hybrid model, information transmission between neurons is studied numerically. Our results show that when the successive spikes are produced in neuron 1 (N1), the bursting-like spikes (BLSs) occur in two neurons simultaneously during the spikes being transferred to neuron 2 (N2). The existence of the astrocyte and a higher expression l...

  1. How Long does a Burst Burst?

    CERN Document Server

    Zhang, Bin-Bin; Murase, Kohta; Connaughton, Valerie; Briggs, Michael S

    2013-01-01

    Several gamma-ray bursts (GRBs) last much longer (~ hours) in gamma-rays than typical long GRBs (~ minutes), and recently it was proposed that these "ultra-long GRBs" may form a distinct population, probably with a different (e.g. blue supergiant) progenitor than typical GRBs. However, Swift observations have suggested that many GRBs have extended central engine activities manifested as flares and internal plateaus in X-rays. We perform a comprehensive study on a large sample of Swift GRBs with XRT observations to investigate GRB central engine activity duration and to check whether ultra-long GRBs are special. We define burst duration t_{burst} based on both gamma-ray and X-ray light curves rather than using gamma-ray observations only. We show that the distribution of t_{burst} peaks at ~ 320s for the entire sample, with 17.6% GRBs having t_{burst} > 10^3 s and 5.4% GRBs having t_{burst} > 10^4 s. The distribution shows a tail at the long t_{burst} end. The existence of a separate population is not ruled ou...

  2. Putative pacemakers in the eyestalk and brain of the crayfish Procambarus clarkii show circadian oscillations in levels of mRNA for crustacean hyperglycemic hormone.

    Directory of Open Access Journals (Sweden)

    Janikua Nelson-Mora

    Full Text Available Crustacean hyperglycemic hormone (CHH synthesizing cells in the optic lobe, one of the pacemakers of the circadian system, have been shown to be present in crayfish. However, the presence of CHH in the central brain, another putative pacemaker of the multi-oscillatory circadian system, of this decapod and its circadian transcription in the optic lobe and brain have yet to be explored. Therefore, using qualitative and quantitative PCR, we isolated and cloned a CHH mRNA fragment from two putative pacemakers of the multi-oscillatory circadian system of Procambarus clarkii, the optic lobe and the central brain. This CHH transcript synchronized to daily light-dark cycles and oscillated under dark, constant conditions demonstrating statistically significant daily and circadian rhythms in both structures. Furthermore, to investigate the presence of the peptide in the central brain of this decapod, we used immunohistochemical methods. Confocal microscopy revealed the presence of CHH-IR in fibers and cells of the protocerebral and tritocerebal clusters and neuropiles, particularly in some neurons located in clusters 6, 14, 15 and 17. The presence of CHH positive neurons in structures of P. clarkii where clock proteins have been reported suggests a relationship between the circadian clockwork and CHH. This work provides new insights into the circadian regulation of CHH, a pleiotropic hormone that regulates many physiological processes such as glucose metabolism and osmoregulatory responses to stress.

  3. Hardware-in-the-loop simulation and energy optimization of cardiac pacemakers.

    Science.gov (United States)

    Barker, Chris; Kwiatkowska, Marta; Mereacre, Alexandru; Paoletti, Nicola; Patane, Andrea

    2015-08-01

    Implantable cardiac pacemakers are medical devices that can monitor and correct abnormal heart rhythms. To provide the necessary safety assurance for pacemaker software, both testing and verification of the code, as well as testing the entire pacemaker hardware in the loop, is necessary. In this paper, we present a hardware testbed that enables detailed hardware-in-the-loop simulation and energy optimisation of pacemaker algorithms with respect to a heart model. Both the heart and the pacemaker models are encoded in Simulink/Stateflow™ and translated into executable code, with the pacemaker executed directly on the microcontroller. We evaluate the usefulness of the testbed by developing a parameter synthesis algorithm which optimises the timing parameters based on power measurements acquired in real-time. The experiments performed on real measurements successfully demonstrate that the testbed is capable of energy minimisation in real-time and obtains safe pacemaker timing parameters. PMID:26737950

  4. Pacemaker Related Infective Endocarditis from Staphylococcus Lugdunensis: A Case Report

    Directory of Open Access Journals (Sweden)

    Michael Ward

    2013-01-01

    Full Text Available Staphylococcus lugdunensis is a common skin flora not typically associated with infection. There are, however, several cases reported in the literature of Staphylococcus lugdunensis as a causative bacterium of various infections. This paper reports an additional case of pacemaker associated endocarditis with Staphylococcus lugdunensis as the causative bacterium.

  5. 238Pu sources for cardiac pacemakers. II. Control

    International Nuclear Information System (INIS)

    The method and the apparatus used for thermal (power) and radioactive control of radioisotopic sources for pacemakers are briefly described. The cybernetic system is also presented, which assumes almost automatically the monitoring of control, mechanical and electronic works, data processing, the measurements and computations, and the works related to quality control

  6. Synchronization transition in gap-junction-coupled leech neurons

    Science.gov (United States)

    Wang, Qingyun; Duan, Zhisheng; Feng, Zhaosheng; Chen, Guanrong; Lu, Qishao

    2008-07-01

    Real neurons can exhibit various types of firings including tonic spiking, bursting as well as silent state, which are frequently observed in neuronal electrophysiological experiments. More interestingly, it is found that neurons can demonstrate the co-existing mode of stable tonic spiking and bursting, which depends on initial conditions. In this paper, synchronization in gap-junction-coupled neurons with co-existing attractors of spiking and bursting firings is investigated as the coupling strength gets increased. Synchronization transitions can be identified by means of the bifurcation diagram and the correlation coefficient. It is illustrated that the coupled neurons can exhibit different types of synchronization transitions between spiking and bursting when the coupling strength increases. In the course of synchronization transitions, an intermittent synchronization can be observed. These results may be instructive to understand synchronization transitions in neuronal systems.

  7. How long does a burst burst?

    International Nuclear Information System (INIS)

    Several gamma-ray bursts (GRBs) last much longer (∼hours) in γ-rays than typical long GRBs (∼minutes), and it has recently been proposed that these 'ultra-long GRBs' may form a distinct population, probably with a different (e.g., blue supergiant) progenitor than typical GRBs. However, Swift observations suggest that many GRBs have extended central engine activities manifested as flares and internal plateaus in X-rays. We perform a comprehensive study on a large sample of Swift GRBs with X-Ray Telescope observations to investigate GRB central engine activity duration and to determine whether ultra-long GRBs are unusual events. We define burst duration t burst based on both γ-ray and X-ray light curves rather than using γ-ray observations alone. We find that t burst can be reliably measured in 343 GRBs. Within this 'good' sample, 21.9% GRBs have t burst ≳ 103 s and 11.5% GRBs have t burst ≳ 104 s. There is an apparent bimodal distribution of t burst in this sample. However, when we consider an 'undetermined' sample (304 GRBs) with t burst possibly falling in the gap between GRB duration T 90 and the first X-ray observational time, as well as a selection effect against t burst falling into the first Swift orbital 'dead zone' due to observation constraints, the intrinsic underlying t burst distribution is consistent with being a single component distribution. We found that the existing evidence for a separate ultra-long GRB population is inconclusive, and further multi-wavelength observations are needed to draw a firmer conclusion. We also discuss the theoretical implications of our results. In particular, the central engine activity duration of GRBs is generally much longer than the γ-ray T 90 duration and it does not even correlate with T 90. It would be premature to make a direct connection between T 90 and the size of the progenitor star.

  8. Design of the Pacemaker REmote Follow-up Evaluation and Review (PREFER trial to assess the clinical value of the remote pacemaker interrogation in the management of pacemaker patients

    Directory of Open Access Journals (Sweden)

    Johnson W Ben

    2008-04-01

    Full Text Available Abstract Background Although pacemakers are primarily used for the treatment of bradycardia, diagnostic data available in current pacemakers allow them to be also used as sophisticated, continuous monitoring devices. Easy access to these stored data may assist clinicians in making diagnostic and therapeutic decisions sooner, thus avoiding potential long-term sequelae due to untreated clinical disorders. Internet-based remote device interrogation systems provide clinicians with frequent and complete access to stored data in pacemakers. In addition to monitoring device function, remote monitors may be a helpful tool in assisting physicians in the management of common arrhythmia disorders. Methods The Pacemaker REmote Follow-up Evaluation and Review (PREFER trial is a prospective, randomized, parallel, unblinded, multicenter, open label clinical trial to determine the utility of remote pacemaker interrogation in the earlier diagnosis of clinically actionable events compared to the existing practice of transtelephonic monitoring. There have been 980 patients enrolled and randomized to receive pacemaker follow up with either remote interrogation using the Medtronic CareLink® Network (CareLink versus the conventional method of transtelephonic monitoring (TTM in addition to periodic in-person interrogation and programming evaluations. The purpose of this manuscript is to describe the design of the PREFER trial. The results, to be presented separately, will characterize the number of clinically actionable events as a result of pacemaker follow-up using remote interrogation instead of TTM. Trial registration ClinicalTrials.gov: NCT00294645.

  9. Temporary transvenous pacemaker placement in the Emergency Department.

    Science.gov (United States)

    Harrigan, Richard A; Chan, Theodore C; Moonblatt, Steven; Vilke, Gary M; Ufberg, Jacob W

    2007-01-01

    Emergency Department placement of a temporary transvenous cardiac pacemaker offers potential life-saving benefits, as the device can definitively control heart rate, ensure effective myocardial contractility, and provide adequate cardiac output in select circumstances. The procedure begins with establishment of central venous access, usually by a right internal jugular or left subclavian vein approach, although the femoral vein is an acceptable alternative, especially in patients who are more likely to bleed should vascular access become complicated. The indications for the procedure, as well as the equipment needed, are reviewed. Both blind and ECG-guided techniques of insertion are described. Methods of verification of pacemaker placement and function are discussed, as are the early complications of the procedure. PMID:17239740

  10. Transient apical dyskinesia with a pacemaker: Electrocardiographic features.

    Science.gov (United States)

    Núñez-Gil, Iván J; Feltes, Gisela I; Mejía-Rentería, Hernán D; Biagioni, Corina; De Agustín, J Alberto; Vivas, David; Fernández-Ortiz, Antonio

    2015-04-01

    Transient apical dyskinesia syndromes present features similar to acute coronary syndromes, but with normal coronary arteries and rapid complete resolution of wall motion alterations. We report the case of a 73-year-old woman who was admitted to hospital because of typical chest pain at rest after her brother's death. She had had a pacemaker implanted in 2001. Troponin levels were elevated and apical hypokinesia was shown by ventriculography and echocardiography, with normal coronary arteries. Evolving ECG alterations were observed in spite of the continued pacing rhythm. All these alterations were fully resolved after discharge. This case shows that, even in the presence of a pacemaker, evolving ECG alterations can be observed in Takotsubo syndrome. PMID:25840647

  11. Secure pacemaker fixation critical for prevention of Twiddler's syndrome.

    Science.gov (United States)

    Zimmerman, Sarah A; Bright, Janice M

    2004-05-01

    A two year old, female spayed border collie presented three weeks after permanent pacemaker implantation for weakness, lethargy and collapse. Electrocardiogram documented complete (3(rd) degree) atrioventricular (AV) block, the absence of pacing and a ventricular escape rhythm. Thoracic radiographs revealed retraction and dislodgement of the passive fixation lead from the right ventricular apex. During a procedure to reposition the lead, it was noted that lead retraction had resulted from rotation of the generator with twisting and entanglement of the lead on itself and around the generator, a complication recognized in human patients as "Twiddlers syndrome". The pacemaker lead was removed, a new lead securely placed at the right ventricular apex, and the generator was secured into a revised subcutaneous pocket. Pacing was re-established and the Twiddler's syndrome has not reoccurred. PMID:19083303

  12. Regulation of Irregular Neuronal Firing by Autaptic Transmission

    Science.gov (United States)

    Guo, Daqing; Wu, Shengdun; Chen, Mingming; Perc, Matjaž; Zhang, Yangsong; Ma, Jingling; Cui, Yan; Xu, Peng; Xia, Yang; Yao, Dezhong

    2016-05-01

    The importance of self-feedback autaptic transmission in modulating spike-time irregularity is still poorly understood. By using a biophysical model that incorporates autaptic coupling, we here show that self-innervation of neurons participates in the modulation of irregular neuronal firing, primarily by regulating the occurrence frequency of burst firing. In particular, we find that both excitatory and electrical autapses increase the occurrence of burst firing, thus reducing neuronal firing regularity. In contrast, inhibitory autapses suppress burst firing and therefore tend to improve the regularity of neuronal firing. Importantly, we show that these findings are independent of the firing properties of individual neurons, and as such can be observed for neurons operating in different modes. Our results provide an insightful mechanistic understanding of how different types of autapses shape irregular firing at the single-neuron level, and they highlight the functional importance of autaptic self-innervation in taming and modulating neurodynamics.

  13. Percutaneously Inject able Fetal Pacemaker: Electrodes, Mechanical Design and Implantation*

    OpenAIRE

    Zhou, Li; Chmait, Ramen; Bar-Cohen, Yaniv; Peck, Raymond A.; Gerald E. Loeb

    2012-01-01

    We are developing a self-contained cardiac pacemaker with a small, cylindrical shape (~3×20mm) that permits it to be implanted percutaneously into a fetus to treat complete heart block and consequent hydrops fetalis, which is otherwise fatal. The device uses off-the-shelf components including a rechargeable lithium cell and a highly efficient relaxation oscillator encapsulated in epoxy and glass. A corkscrew electrode made from activated iridium can be screwed into the myocardium, followed by...

  14. Clinicohemodynamic and roentgenologic correlations in patients with artificial pacemakers

    International Nuclear Information System (INIS)

    The clinical pattern, central hemodynamics and roentgenologic data are studied in 34 patients with artificial cardiac pacemaker (ACP) to solve the problem on adequate medicamental therapy of heart failure (HF). Heart sizes and the state of a pulmonary image are estimated roentgenologically. Two types of cardiac-vessel system reactions on physical load: adequate and nonadequate - are detected. Implantation of ACP in patients with the nonadequate reaction does not lead to total liquidation of HF

  15. Plethyzmography in assessment of hemodynamic results of pacemaker functions programming

    Science.gov (United States)

    Wojciechowski, Dariusz; Sionek, Piotr; Peczalski, Kazimierz; Janusek, Dariusz

    2011-01-01

    The paper presents potential role of plethyzmography in optimization of heart hemodynamic function during pacemaker programming. The assessment of optimal stroke volume in patients, with implanted dual chamber pacemaker (DDD), by plethyzmography was a goal of the study. The data were collected during pacing rhythm. 20 patients (8 female and 12 male, average 77.4+/-4.6 years) with dual chamber pacemaker (DDD) and with pacing rhythm during routine pacemaker control and study tests were incorporated in the study group. Hemodynamic parameters were assessed during modification of atrio-ventricular delay (AVD) for pacing rhythm of 70 bpm and 90 bpm. The time of atrioventricular was programmed with 20 ms steps within range 100-200 ms and data were recorded with two minutes delay between two consecutive measurements. Stroke volume (SV) and cardiac output (CO) were calculated from plethyzmographic signal by using Beatscope software (TNO Holand). Highest SV calculated for given pacing rhythm was named optimal stroke volume (OSV) and consequently highest cardiac output was named maximal cardiac output (MCO). The time of atrio-ventricular delay for OSV was named optimal atrioventricular delay (OAVD). The results have showed: mean values of OAVD for 70 bpm - 152+/-33 ms and for 90 bpm -149+/-35 ms, shortening of the mean OAVD time caused by increase of pacing rate from 70 bpm to 90 bpm what resulted in statistically significant decrease of OSV with not statistically significant increase of MCO. The analysis of consecutive patients revealed three types of response to increase of pacing rhythm: 1. typical-shortening of OAVD, 2. neutral-no change of OAVD and 3.atypical-lengthening of OAVD.

  16. Cardiac Output Measurement in Patients with an Implanted Pacemaker

    Czech Academy of Sciences Publication Activity Database

    Vondra, Vlastimil; Halámek, Josef; Viščor, Ivo; Jurák, Pavel; Novák, M.

    Danvers : Institute of Electrical and Electronics Engineers, Inc., 2007, s. 916-918. ISBN 978-1-4244-0787-3. ISSN 1557-170X. [Annual International Conference of the IEEE Engineering in Medicine and Biology Society /29./. Lyon (FR), 23.08.2007-26.08.2007] R&D Projects: GA ČR GA102/06/0136 Institutional research plan: CEZ:AV0Z20650511 Keywords : cardiac output measurement * implanted pacemaker Subject RIV: FA - Cardiovascular Diseases incl. Cardiotharic Surgery

  17. Thermonuclear burst oscillations

    CERN Document Server

    Watts, Anna L

    2012-01-01

    Burst oscillations, a phenomenon observed in a significant fraction of Type I (thermonuclear) X-ray bursts, involve the development of highly asymmetric brightness patches in the burning surface layers of accreting neutron stars. Intrinsically interesting as nuclear phenomena, they are also important as probes of dense matter physics and the strong gravity, high magnetic field environment of the neutron star surface. Burst oscillation frequency is also used to measure stellar spin, and doubles the sample of rapidly rotating (above 10 Hz) accreting neutron stars with known spins. Although the mechanism remains mysterious, burst oscillation models must take into account thermonuclear flame spread, nuclear processes, rapid rotation, and the dynamical role of the magnetic field. This review provides a comprehensive summary of the observational properties of burst oscillations, an assessment of the status of the theoretical models that are being developed to explain them, and an overview of how they can be used to...

  18. [When do you implant a pacemaker in myotonic dystrophy?].

    Science.gov (United States)

    Babuty, Dominique; Lallemand, Bénédicte; Laurent, Valérie; Clémenty, Nicolas; Pierre, Bertrand; Fauchier, Laurent; Raynaud, Martine; Pellieux, Sybille

    2011-01-01

    Myotonic dystrophy is the most frequent adult form of hereditary muscular dystrophy caused by a mutation on the DMPK gene. Myotonic dystrophy leads to multiple systemic complications related to weakness, respiratory failure, cardiac arrhythmias and cardiac conduction disturbances. Age of death is earlier in myotonic dystrophy patients than in general population with a high frequency of sudden death. Several mechanisms are involved in sudden death: atrio-ventricular block, severe ventricular arrhythmias or non-cardiac mechanism. The high degree of atrio-ventricular block is a well-recognized indication of pacemaker implantation but the prophylactic implantation of pacemaker should be considered to prevent sudden death in asymptomatic myotonic dystrophy patients. A careful clinical evaluation needs to be done for the identification of patients at high risk of sudden death. The resting ECG and SA ECG are non-invasive tools useful to select the patients who need an electrophysiologic study. In presence of prolonged HV interval more than or equal to 70 ms one can discuss the implantation of a prophylactic pacemaker. The choice of an implantable cardiac defibrillator is preferred in presence of spontaneous ventricular tachycardia or an alteration of the left ventricular ejection fraction. PMID:21549556

  19. Percutaneous Extraction of Transvenous Permanent Pacemaker/Defibrillator Leads

    Directory of Open Access Journals (Sweden)

    Stylianos Paraskevaidis

    2014-01-01

    Full Text Available Background. Widespread use of cardiovascular implantable electronic devices has inevitably increased the need for lead revision/replacement. We report our experience in percutaneous extraction of transvenous permanent pacemaker/defibrillator leads. Methods. Thirty-six patients admitted to our centre from September 2005 through October 2012 for percutaneous lead extraction were included. Lead removal was attempted using Spectranetics traction-type system (Spectranetics Corp., Colorado, CO, USA and VascoExtor countertraction-type system (Vascomed GmbH, Weil am Rhein, Germany. Results. Lead extraction was attempted in 59 leads from 36 patients (27 men, mean ± SD age 61±5 years, with permanent pacemaker (n=25, defibrillator (n=8, or cardiac resynchronisation therapy (n=3 with a mean ± SD implant duration of 50±23 months. The indications for lead removal included pocket infection (n=23, endocarditis (n=2, and ventricular (n=10 and atrial lead dysfunction (n=1. Traction device was used for 33 leads and countertraction device for 26 leads. Mean ± SD fluoroscopy time was 4±2 minutes/lead for leads implanted 48 months (n=21, P=0.03. Complete procedural success rate was 91.7% and clinical procedural success rate was 100%, while lead procedural success rate was 95%. Conclusions. In conclusion, percutaneous extraction of transvenous permanent pacemaker/defibrillator leads using dedicated removal tools is both feasible and safe.

  20. Permanent and temporary pacemaker implantation after orthotopic heart transplantation

    Directory of Open Access Journals (Sweden)

    Bacal Fernando

    2000-01-01

    Full Text Available PURPOSE:To determine the indication for and incidence and evolution of temporary and permanent pacemaker implantation in cardiac transplant recipients. METHODS: A retrospective review of 114 patients who underwent orthotopic heart transplantation InCor (Heart Institute USP BR between March 1985 and May 1993. We studied the incidence of and indication for temporary pacing, the relationship between pacing and rejection, the need for pemanent pacing and the clinical follow-up. RESULTS: Fourteen of 114 (12%heart transplant recipients required temporary pacing and 4 of 114 (3.5% patients required permanent pacing. The indication for temporary pacing was sinus node dysfunction in 11 patients (78.5% and atrioventricular (AV block in 3 patients (21.4%. The indication for permanent pacemaker implantation was sinus node dysfunction in 3 patients (75% and atrioventricular (AV block in 1 patient (25%. We observed rejection in 3 patients (21.4% who required temporary pacing and in 2 patients (50% who required permanent pacing. The previous use of amiodarone was observed in 10 patients (71.4% with temporary pacing. Seven of the 14 patients (50% died during follow-up. CONCLUSION: Sinus node dysfunction was the principal indication for temporary and permanent pacemaker implantation in cardiac transplant recipients. The need for pacing was related to worse prognosis after cardiac transplantation.

  1. Reuse of Occluded Veins During Permanent Pacemaker Lead Extraction: A New Indication for Femoral Lead Extraction

    OpenAIRE

    Staniforth, Andrew D; Schilling, Richard J

    2002-01-01

    Objectives: This study examined the utility of a novel technique for reuse of thrombosed veins when extracting permanent pacemaker leads via a femoral vein approach. Background: Although lead extraction permanent pacemaker using a femoral approach has advantages over the subclavian approach, it cannot be used to provide access for a new lead using currently employed techniques. This is important because up to 23% of patients have occluded veins after permanent pacemaker implantation. M...

  2. Effects of Lubiprostone on Pacemaker Activity of Interstitial Cells of Cajal from the Mouse Colon

    OpenAIRE

    Jiao, Han-Yi; Kim, Dong Hyun; Ki, Jung Suk; Ryu, Kwon Ho; Choi, Seok; Jun, Jae Yeoul

    2014-01-01

    Lubiprostone is a chloride (Cl-) channel activator derived from prostaglandin E1 and used for managing constipation. In addition, lubiprostone affects the activity of gastrointestinal smooth muscles. Interstitial cells of Cajal (ICCs) are pacemaker cells that generate slow-wave activity in smooth muscles. We studied the effects of lubiprostone on the pacemaker potentials of colonic ICCs. We used the whole-cell patch-clamp technique to determine the pacemaker activity in cultured colonic ICCs ...

  3. Cardiac magnetic resonance imaging of a patient with an magnetic resonance imaging conditional permanent pacemaker

    OpenAIRE

    Chris B. Pepper; Mohan Sivananthan; Artis, Nigel J.; Hogarth, Andrew J.

    2011-01-01

    Cardiac Magnetic Resonance Imaging (MRI) is increasingly used as the optimum modality for cardiac imaging. An aging population and rising numbers of patients with permanent pacemakers means many such individuals may require cardiac MRI scanning in the future. Whilst the presence of a permanent pacemaker is historically regarded as a contra-indication to MRI scanning, pacemaker systems have been developed to limit any associated risks. No reports have been published regarding the use of such d...

  4. Echocardiographic Improvements with Pacemaker Optimization in the Chronic Post Cardiac Resynchronization Therapy Setting

    OpenAIRE

    Alan J. Bank; Burns, Kevin V; Kelly, Aaron S.; Andrea M. Thelen; Kaufman, Christopher L.; Stuart W. Adler

    2008-01-01

    The current study assessed the acute effects of pacemaker optimization (PMO) on cardiac function using echocardiographic (ECHO) tissue Doppler imaging (TDI) in the post CRT setting. Data were analyzed from 50 consecutive patients clinically referred for PMO. Patients underwent a sequential ECHO/TDIguided PMO study to determine optimal pacemaker settings. In 34 of 50 patients a change in pacemaker settings was made because of an objective improvement in ECHO/TDI findings.Overall, significant i...

  5. Gold-coated pacemaker implantation for a patient with type IV allergy to titanium

    Science.gov (United States)

    Kypta, Alexander; Blessberger, Hermann; Lichtenauer, Michael; Lambert, Thomas; Kammler, Juergen; Steinwender, Clemens

    2016-01-01

    A 65-year-old man was scheduled for pacemaker implantation for symptomatic sick-sinus-syndrome (SSS). He suffered from multiple drug-allergies and allergies to several metals like quicksilver and titanium. Gold-coated pacemaker generators and polyurethane leads are effective in avoiding allergic reactions to pacing system components. Therefore, we decided to implant a custom-made gold-coated DDDR-pacemaker generator and polyurethane leads.

  6. Haemophilus parainfluenzae bacteremia associated with a pacemaker wire localized by gallium scan

    International Nuclear Information System (INIS)

    A young woman with a history of sick sinus syndrome and placement of a permanent pacemaker 6 months before admission had fever and Haemophilus parainfluenzae bacteremia. A gallium scan localized the infection to the site of the pacemaker wire. Echocardiograms were negative for any vegetations. The patient responded to cefotaxime and trimethoprim-sulfamethoxazole therapy. We believe that this is the first case of H. parainfluenzae bacteremia associated with a pacemaker wire and localized by gallium scan

  7. Interference of implanted cardiac pacemakers with TASER X26 dart mode application.

    Science.gov (United States)

    Leitgeb, Norbert; Niedermayr, Florian; Neubauer, Robert

    2012-06-01

    The prevalence of pacemaker patients among the general population and of conducted energy devices for law enforcement and self-defence is increasing. Consequently, the question on whether cardiac pacemaker patients are at particular risk becomes increasingly important, in particular, as the widespread use of such devices is planned in Europe. The risk of pacemaker patients has been investigated by numerical simulation at detailed anatomical models of patients with cardiac pacemakers implanted in left pectoral, right pectoral, and abdominal positions, with the monopolar electrode placed at the ventricular apex. The induced cardiac pacemaker interference voltages have been assessed for distant application of TASER X26 devices with dart electrodes propelled towards a subject. It could be shown that interference voltages are highest in abdominal pacemaker implantation, while they are about 20% lower in left or right pectoral sites. They remain below the immunity threshold level as defined by safety standards of implanted cardiac pacemakers and of implanted cardioverter defibrillators to prevent persisting malfunction or damage. However, induced voltages are high enough to be sensed by the pacemaker and to capture pacemaker function in case of hits at thorax and abdomen, frontal as well as dorsal. PMID:22691428

  8. Reuse Of Pacemakers In Ghana And Nigeria: Medical, Legal, Cultural And Ethical Perspectives.

    Science.gov (United States)

    Ochasi, Aloysius; Clark, Peter

    2015-12-01

    According to the World Health Organization (WHO) cardiovascular disease (CVD) is the leading cause of death globally. Over 80% of CVD deaths take place in low- and middle-income countries (LMICs). It is estimated that 1 million to 2 million people worldwide die each year due to lack of access to an implantable cardiac defibrillator (ICD) or a pacemaker. Despite the medical, legal, cultural and ethical controversies surrounding the pacemaker reutilization, studies done so far on the reuse of postmortem pacemakers show it to be safe and effective with an infection rate of 1.97% and device malfunction rate of 0.68%. Pacemaker reutilization can be effectively and safely done and does not pose significant additional risk to the recipient. Heart patients with reused pacemakers have an improved quality of life compared to those without pacemakers. The thesis of this paper is that pacemaker reutilization is a life-saving initiative in LMICs of Nigeria and Ghana. It is cost effective; consistent with the principles of beneficence, nonmaleficence, and justice with a commitment to stewardship of resources and the Common Good. Used pacemakers with adequate battery life can be properly sterilized for use by patients in LMICs who cannot afford the cost of a new pacemaker. PMID:24720369

  9. CaV1.3 as pacemaker channels in adrenal chromaffin cells: specific role on exo- and endocytosis?

    Science.gov (United States)

    Comunanza, Valentina; Marcantoni, Andrea; Vandael, David H; Mahapatra, Satyajit; Gavello, Daniela; Carabelli, Valentina; Carbone, Emilio

    2010-01-01

    Voltage-gated L-type calcium channels (LTCCs) are expressed in adrenal chromaffin cells. Besides shaping the action potential (AP), LTCCs are involved in the excitation-secretion coupling controlling catecholamine release and in Ca (2+) -dependent vesicle retrieval. Of the two LTCCs expressed in chromaffin cells (CaV1.2 and CaV1.3), CaV1.3 possesses the prerequisites for pacemaking spontaneously firing cells: low-threshold, steep voltage-dependence of activation and slow inactivation. By using CaV1 .3 (-/-) KO mice and the AP-clamp it has been possible to resolve the time course of CaV1.3 pacemaker currents, which is similar to that regulating substantia nigra dopaminergic neurons. In mouse chromaffin cells CaV1.3 is coupled to fast-inactivating BK channels within membrane nanodomains and controls AP repolarization. The ability to carry subthreshold Ca (2+) currents and activate BK channels confers to CaV1.3 the unique feature of driving Ca (2+) loading during long interspike intervals and, possibly, to control the Ca (2+) -dependent exocytosis and endocytosis processes that regulate catecholamine secretion and vesicle recycling. PMID:21084859

  10. Cannabinoid receptor activation reverses kainate-induced synchronized population burst firing in rat hippocampus

    OpenAIRE

    Rob Mason; Cheer, Joseph F

    2009-01-01

    Cannabinoids have been shown to possess anticonvulsant properties in whole animal models of epilepsy. The present investigation sought to examine the effects of cannabinoid receptor activation on kainic acid (KA)-induced epileptiform neuronal excitability. Under urethane anesthesia, acute KA treatment (10 mg/kg, i.p.) entrained the spiking mode of simultaneously recorded neurons from random firing to synchronous bursting (% change in burst rate). Injection of the high-affinity cannabinoid a...

  11. Cannabinoid Receptor Activation Reverses Kainate-Induced Synchronized Population Burst Firing in Rat Hippocampus

    OpenAIRE

    Mason, Rob; Cheer, Joseph F

    2009-01-01

    Cannabinoids have been shown to possess anticonvulsant properties in whole animal models of epilepsy. The present investigation sought to examine the effects of cannabinoid receptor activation on kainic acid (KA)-induced epileptiform neuronal excitability. Under urethane anesthesia, acute KA treatment (10 mg kg−1, i.p.) entrained the spiking mode of simultaneously recorded neurons from random firing to synchronous bursting (% change in burst rate). Injection of the high-affinity cannabinoid a...

  12. Modulation of Hippocampal Theta Oscillations and Spatial Memory by Relaxin-3 Neurons of the Nucleus Incertus

    Science.gov (United States)

    Ma, Sherie; Olucha-Bordonau, Francisco E.; Hossain, M. Akhter; Lin, Feng; Kuei, Chester; Liu, Changlu; Wade, John D.; Sutton, Steven W.; Nunez, Angel; Gundlach, Andrew L.

    2009-01-01

    Hippocampal theta rhythm is thought to underlie learning and memory, and it is well established that "pacemaker" neurons in medial septum (MS) modulate theta activity. Recent studies in the rat demonstrated that brainstem-generated theta rhythm occurs through a multisynaptic pathway via the nucleus incertus (NI), which is the primary source of the…

  13. GLAST's GBM Burst Trigger

    Science.gov (United States)

    Band, D.; Briggs, M.; Connaughton, V.; Kippen, M.; Preece, R.

    2003-01-01

    The GLAST Burst Monitor (GBM) will detect and localize bursts for the GLAST mission, and provide the spectral and temporal context in the traditional 10 keV to 25 MeV band for the high energy observations by the Large Area Telescope (LAT). The GBM will use traditional rate triggers in up to three energy bands, and on a variety of timescales between 16 ms and 16 s.

  14. Effects of Transient Receptor Potential Channel Blockers on Pacemaker Activity in Interstitial Cells of Cajal from Mouse Small Intestine

    OpenAIRE

    Kim, Byung Joo; Nam, Joo Hyun; Kim, Seon Jeong

    2011-01-01

    The interstitial cells of Cajal (ICCs) are pacemakers in the gastrointestinal tract and transient receptor potential melastatin type 7 (TRPM7) is a candidate for pacemaker channels. The effect of the 5-lipoxygenase (5-LOX) inhibitors NDGA, AA861, MK886 and zileuton on pacemaking activity of ICCs was examined using the whole cell patch clamp technique. NDGA and AA861 decreased the amplitude of pacemaker potentials in ICC clusters, but the resting membrane potentials displayed little change, re...

  15. Twiddler-syndrom er en årsag til pacemaker elektrode displacering

    DEFF Research Database (Denmark)

    Grønbech, Keea Treu; Hansen, Michael Gilså

    2013-01-01

    Twiddler's syndrome is a rare cause of pacemaker electrode displacement. The displacement is caused by the patient's manipulation with the pacemaker, so the electrode is retracted. We describe a case of a 79-year-old overweight woman with a known psychiatric anamnesis, who was admitted twice...

  16. Pacemaker and radiotherapy in breast cancer: is targeted intraoperative radiotherapy the answer in this setting?

    International Nuclear Information System (INIS)

    We present the case of an 83 year old woman with a cardiac pacemaker located close in distance to a subsequently diagnosed invasive ductal carcinoma of the left breast. Short range intraoperative radiotherapy was given following wide local excision and sentinel node biopsy. The challenges of using ionising radiation with pacemakers is also discussed

  17. Involvement of mitochondrial Na+–Ca2+ exchange in intestinal pacemaking activity

    OpenAIRE

    Kim, Byung Joo; Jun, Jae Yeoul; So, Insuk; Kim, Ki Whan

    2006-01-01

    AIM: Interstitial cells of Cajal (ICCs) are the pacemaker cells that generate slow waves in the gastrointestinal (GI) tract. We have aimed to investigate the involvement of mitochondrial Na+-Ca2+ exchange in intestinal pacemaking activity in cultured interstitial cells of Cajal.

  18. I-123 metaiodobenzylguanidine cardiac scintigraphy in patients with an implanted permanent pacemaker

    International Nuclear Information System (INIS)

    Tl scintigraphic abnormalities have been reported in patients with an implanted permanent pacemaker, but little is known about the MIBG scintigraphic findings in such patients. This study was performed to assess the MIBG scintigraphic findings in patients with an implanted permanent pacemaker, and to test the hypothesis that imaging characteristics of MIBG scintigraphy differ according to its mode. Twelve patients (4 men and 8 women, mean age: 72.4±9.5 years), who had undergone the implantation of a permanent pacemaker for bradyarrhythmias, underwent MIBG scintigraphy. The patients were divided into VVI pacemaker and DDD pacemaker groups. The tomograms were divided into nine segments and the MIBG defect in each segment scored on a scale ranging from 0 (normal uptake) to 3 (no uptake). Total MIBG defect scores were generated by summing the scores for the nine segments in each patient. MIBG scintigraphic abnormalities were found in ten of the twelve patients. The six patients with the VVI pacemaker manifested MIBG scintigraphic abnormalities. These MIBG scintigraphic abnormalities were observed in all segments, particularly in the posterior segments. The mean total defect score of the VVI group was higher than that of the DDD group (14.8±9.8 vs 3.0±3.5, respectively p<0.05). Therefore, we conclude that despite several limitations of the study, MIBG scintigraphic abnormalities occur in patients with implanted permanent pacemakers, and that such abnormalities are more prominent with the VVI than DDD pacemaker. (author)

  19. Electrical stimulation of primary neonatal rat ventricular cardiomyocytes using pacemakers.

    Science.gov (United States)

    Martherus, Ruben S R M; Zeijlemaker, Volkert A; Ayoubi, Torik A Y

    2010-01-01

    The study of gene regulation in cardiac myocytes requires a reliable in vitro model. However, monolayer cultures used for this purpose are typically not exposed to electrical stimulation, though this has been shown to strongly affect cardiomyocyte gene expression. Based on pacemakers for clinical use, we developed an easy-to-use portable system that allows the user to perform electro-stimulation of cardiomyocyte cultures in standard tissue incubators without the need for bulky equipment. In addition, we present a refined protocol for culturing high-purity cardiomyocyte cultures with excellent contractile properties for a wide variety of applications. PMID:20078430

  20. Pacemaker Created in Human Ventricle by Depressing Inward-Rectifier K(+) Current: A Simulation Study.

    Science.gov (United States)

    Zhang, Yue; Wang, Kuanquan; Li, Qince; Zhang, Henggui

    2016-01-01

    Cardiac conduction disorders are common diseases which cause slow heart rate and syncope. The best way to treat these diseases by now is to implant electronic pacemakers, which, yet, have many disadvantages, such as the limited battery life and infection. Biopacemaker has been expected to replace the electronic devices. Automatic ventricular myocytes (VMs) could show pacemaker activity, which was induced by depressing inward-rectifier K(+) current (I K1). In this study, a 2D model of human biopacemaker was created from the ventricular endocardial myocytes. We examined the stability of the created biopacemaker and investigated its driving capability by finding the suitable size and spatial distribution of the pacemaker for robust pacing and driving the surrounding quiescent cardiomyocytes. Our results suggest that the rhythm of the pacemaker is similar to that of the single cell at final stable state. The driving force of the biopacemaker is closely related to the pattern of spatial distribution of the pacemaker. PMID:26998484

  1. Identifying crucial parameter correlations maintaining bursting activity.

    Directory of Open Access Journals (Sweden)

    Anca Doloc-Mihu

    2014-06-01

    Full Text Available Recent experimental and computational studies suggest that linearly correlated sets of parameters (intrinsic and synaptic properties of neurons allow central pattern-generating networks to produce and maintain their rhythmic activity regardless of changing internal and external conditions. To determine the role of correlated conductances in the robust maintenance of functional bursting activity, we used our existing database of half-center oscillator (HCO model instances of the leech heartbeat CPG. From the database, we identified functional activity groups of burster (isolated neuron and half-center oscillator model instances and realistic subgroups of each that showed burst characteristics (principally period and spike frequency similar to the animal. To find linear correlations among the conductance parameters maintaining functional leech bursting activity, we applied Principal Component Analysis (PCA to each of these four groups. PCA identified a set of three maximal conductances (leak current, [Formula: see text]Leak; a persistent K current, [Formula: see text]K2; and of a persistent Na+ current, [Formula: see text]P that correlate linearly for the two groups of burster instances but not for the HCO groups. Visualizations of HCO instances in a reduced space suggested that there might be non-linear relationships between these parameters for these instances. Experimental studies have shown that period is a key attribute influenced by modulatory inputs and temperature variations in heart interneurons. Thus, we explored the sensitivity of period to changes in maximal conductances of [Formula: see text]Leak, [Formula: see text]K2, and [Formula: see text]P, and we found that for our realistic bursters the effect of these parameters on period could not be assessed because when varied individually bursting activity was not maintained.

  2. Vestibular Neuronitis

    Science.gov (United States)

    ... Prevent Painful Swimmer's Ear Additional Content Medical News Vestibular Neuronitis By Lawrence R. Lustig, MD NOTE: This ... Drugs Herpes Zoster Oticus Meniere Disease Purulent Labyrinthitis Vestibular Neuronitis Vestibular neuronitis is a disorder characterized by ...

  3. Full system bifurcation analysis of endocrine bursting models.

    Science.gov (United States)

    Tsaneva-Atanasova, Krasimira; Osinga, Hinke M; Riess, Thorsten; Sherman, Arthur

    2010-06-21

    Plateau bursting is typical of many electrically excitable cells, such as endocrine cells that secrete hormones and some types of neurons that secrete neurotransmitters. Although in many of these cell types the bursting patterns are regulated by the interplay between voltage-gated calcium channels and calcium-sensitive potassium channels, they can be very different. We investigate so-called square-wave and pseudo-plateau bursting patterns found in endocrine cell models that are characterized by a super- or subcritical Hopf bifurcation in the fast subsystem, respectively. By using the polynomial model of Hindmarsh and Rose (Proceedings of the Royal Society of London B 221 (1222) 87-102), which preserves the main properties of the biophysical class of models that we consider, we perform a detailed bifurcation analysis of the full fast-slow system for both bursting patterns. We find that both cases lead to the same possibility of two routes to bursting, that is, the criticality of the Hopf bifurcation is not relevant for characterizing the route to bursting. The actual route depends on the relative location of the full-system's fixed point with respect to a homoclinic bifurcation of the fast subsystem. Our full-system bifurcation analysis reveals properties of endocrine bursting that are not captured by the standard fast-slow analysis. PMID:20307553

  4. Effects of disinhibition on spatiotemporal pattern of neuronal first recruitment in neuronal networks

    Institute of Scientific and Technical Information of China (English)

    Liangbin Pan; Xindong Sing; Guangxin Xiang; Jing Zhu; Jing Cheng

    2009-01-01

    The propagation of neuronal activities is a key feature to understanding information processing in networks.The analysis based on first-spikes of bursts in turn plays an important role in the research of neuronal activity propagation.Our focus here is to investigate how spatiotemporal patterns of neuronal first-spikes are affected by disinhibition.Multi-electrode arrays were used to record stimulationevoked bursts of multiple neurons in randomly cultured neuronal networks.Both the precise timing of and the rank relationships between first-spikes were analyzed.Compared with evoked bursts in the network's native state,the precise first-spike latencies in its disinhibited state are more consistent and the propagation of its bursting activities is much faster.Additional points of interest are that disinhibited neuronal networks can be evoked to generate stable and distinguishable neuronal first recruitment spatiotemporal patterns specific to the stimulation site,and that the disinhibition may cause the original spatiotemporal patterns to change in a heterogeneous manner with regards to different propagation pathways.(C) 2009 National Natural Science Foundation of China and Chinese Academy of Sciences.Published by Elsevier Limited and Science inChina Press.All rights reserved.

  5. Interplanetary Type IV Bursts

    CERN Document Server

    Hillaris, Alexander; Nindos, Alexander

    2016-01-01

    In this work we study the characteristics of moving type IV radio bursts which extend to the hectometric wavelengths (interplanetary type IV or type IV IP bursts) and their relationship with energetic phenomena on the Sun. Our dataset comprised 48 Interplanetary type IV bursts observed by the Wind/WAVES in the 13.825 MHz?20 KHz frequency range. The dynamic spec tra of the RSTN, DAM, ARTEMIS-IV, CULGOORA, Hiraiso and IZMIRAN Radio-spectrographs were used to track the evolution of the events in the low corona; these were supplemented with SXR ?ux recordings from GOES and CME data from LASCO. Positional information for the coronal bursts were obtained by the Nan\\c{c}ay radioheliograph (NRH). We examined the relationship of the type IV events with coronal radio bursts, CMEs and SXR ?ares. The majority of the events (45) were characterized as compact; their duration was on average 106 min. This type of events were, mostly, associated with M and X class ?ares (40 out of 45) and fast CMEs; 32 of these events had CME...

  6. Excitation model of pacemaker cardiomyocytes of cardiac conduction system

    Science.gov (United States)

    Grigoriev, M.; Babich, L.

    2015-11-01

    Myocardium includes typical and atypical cardiomyocytes - pacemakers, which form the cardiac conduction system. Excitation from the atrioventricular node in normal conditions is possible only in one direction. Retrograde direction of pulses is impossible. The most important prerequisite for the work of cardiomyocytes is the anatomical integrity of the conduction system. Changes in contractile force of the cardiomyocytes, which appear periodically, are due to two mechanisms of self-regulation - heterometric and homeometric. Graphic course of the excitation pulse propagation along the heart muscle more accurately reveals the understanding of the arrhythmia mechanism. These models have the ability to visualize the essence of excitation dynamics. However, they do not have the proper forecasting function for result estimation. Integrative mathematical model enables further investigation of general laws of the myocardium active behavior, allows for determination of the violation mechanism of electrical and contractile function of cardiomyocytes. Currently, there is no full understanding of the topography of pacemakers and ionic mechanisms. There is a need for the development of direction of mathematical modeling and comparative studies of the electrophysiological arrangement of cells of atrioventricular connection and ventricular conduction system.

  7. Sensory-evoked and spontaneous gamma and spindle bursts in neonatal rat motor cortex.

    Science.gov (United States)

    An, Shuming; Kilb, Werner; Luhmann, Heiko J

    2014-08-13

    Self-generated neuronal activity originating from subcortical regions drives early spontaneous motor activity, which is a hallmark of the developing sensorimotor system. However, the neural activity patterns and role of primary motor cortex (M1) in these early movements are still unknown. Combining voltage-sensitive dye imaging (VSDI) with simultaneous extracellular multielectrode recordings in postnatal day 3 (P3)-P5 rat primary somatosensory cortex (S1) and M1 in vivo, we observed that tactile forepaw stimulation induced spindle bursts in S1 and gamma and spindle bursts in M1. Approximately 40% of the spontaneous gamma and spindle bursts in M1 were driven by early motor activity, whereas 23.7% of the M1 bursts triggered forepaw movements. Approximately 35% of the M1 bursts were uncorrelated to movements and these bursts had significantly fewer spikes and shorter burst duration. Focal electrical stimulation of layer V neurons in M1 mimicking physiologically relevant 40 Hz gamma or 10 Hz spindle burst activity reliably elicited forepaw movements. We conclude that M1 is already involved in somatosensory information processing during early development. M1 is mainly activated by tactile stimuli triggered by preceding spontaneous movements, which reach M1 via S1. Only a fraction of M1 activity transients trigger motor responses directly. We suggest that both spontaneously occurring and sensory-evoked gamma and spindle bursts in M1 contribute to the maturation of corticospinal and sensorimotor networks required for the refinement of sensorimotor coordination. PMID:25122889

  8. Interplanetary Type IV Bursts

    Science.gov (United States)

    Hillaris, A.; Bouratzis, C.; Nindos, A.

    2016-08-01

    We study the characteristics of moving type IV radio bursts that extend to hectometric wavelengths (interplanetary type IV or type {IV}_{{IP}} bursts) and their relationship with energetic phenomena on the Sun. Our dataset comprises 48 interplanetary type IV bursts observed with the Radio and Plasma Wave Investigation (WAVES) instrument onboard Wind in the 13.825 MHz - 20 kHz frequency range. The dynamic spectra of the Radio Solar Telescope Network (RSTN), the Nançay Decametric Array (DAM), the Appareil de Routine pour le Traitement et l' Enregistrement Magnetique de l' Information Spectral (ARTEMIS-IV), the Culgoora, Hiraso, and the Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN) Radio Spectrographs were used to track the evolution of the events in the low corona. These were supplemented with soft X-ray (SXR) flux-measurements from the Geostationary Operational Environmental Satellite (GOES) and coronal mass ejections (CME) data from the Large Angle and Spectroscopic Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO). Positional information of the coronal bursts was obtained by the Nançay Radioheliograph (NRH). We examined the relationship of the type IV events with coronal radio bursts, CMEs, and SXR flares. The majority of the events (45) were characterized as compact, their duration was on average 106 minutes. This type of events was, mostly, associated with M- and X-class flares (40 out of 45) and fast CMEs, 32 of these events had CMEs faster than 1000 km s^{-1}. Furthermore, in 43 compact events the CME was possibly subjected to reduced aerodynamic drag as it was propagating in the wake of a previous CME. A minority (three) of long-lived type {IV}_{{IP}} bursts was detected, with durations from 960 minutes to 115 hours. These events are referred to as extended or long duration and appear to replenish their energetic electron content, possibly from electrons escaping from the corresponding coronal

  9. A Repeating Fast Radio Burst

    CERN Document Server

    Spitler, L G; Hessels, J W T; Bogdanov, S; Brazier, A; Camilo, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J; Ferdman, R D; Freire, P C C; Kaspi, V M; Lazarus, P; Lynch, R; Madsen, E C; McLaughlin, M A; Patel, C; Ransom, S M; Seymour, A; Stairs, I H; Stappers, B W; van Leeuwen, J; Zhu, W W

    2016-01-01

    Fast Radio Bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measures (i.e. integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of the fast radio bursts has led several authors to hypothesise that they originate in cataclysmic astrophysical events. Here we report the detection of ten additional bursts from the direction of FRB121102, using the 305-m Arecibo telescope. These new bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and wh...

  10. False positive defects on exercise myocardial perfusion tomography in patients with a right ventricular pacemaker

    International Nuclear Information System (INIS)

    It is known that the specificity of exercise perfusion scintigraphy is decrease in patients with a left bundle block. Patients with a permanent ventricular pacemaker have a similar conduction abnormality that may also potentially result in similar false positive perfusion defects. Aim: To identify the presence or absence of abnormalities on myocardial perfusion in patients with permanent ventricular pacemaker during the exercise and without coronary artery disease. Material and Methods: We include twelve patients (mean age +/- SD: 73 +/- 12 year) in prospective form with ventricular pacemaker indication. All had a narrow QRS on the rest electrocardiogram and none had history of typical chest pain or myocardial infarction. All the patients had an exercise myocardial perfusion tomography with technetium 99m methoxyisonitrile, before the pacemaker placing. Ten with normal stress perfusion were subject to another exercise SPECT after a week, at least. They had the same load and heart rate up to the maximum exercise as in the previous study, but with pacemaker rhythm during the maximum exercise, The different studies before and after pacemaker placing were compared by semiquantitative analysis. Results: Seven out of ten normal patients before pacemaker placing had perfusion defects (70%) on the second study after pacemaker placing. The location of the defects were: two apical (28%), one inferior (14%), and four apical and inferior (57%). Conclusion: In patients without coronary artery disease the continuous pacemaker during the exercise has a high incidence of false positive perfusion defects in single photon emission computed tomography. Most of false positive defects were localized to the apical and inferior territories

  11. Mixed Burst Error Correcting Codes

    OpenAIRE

    Sethi, Amita

    2015-01-01

    In this paper, we construct codes which are an improvement on the previously known block wise burst error correcting codes in terms of their error correcting capabilities. Along with different bursts in different sub-blocks, the given codes also correct overlapping bursts of a given length in two consecutive sub-blocks of a code word. Such codes are called mixed burst correcting (mbc) codes.

  12. Sphingosine and FTY720 Modulate Pacemaking Activity in Interstitial Cells of Cajal from Mouse Small Intestine

    OpenAIRE

    Nam, Joo Hyun; Kim, Woo Kyung; Kim, Byung Joo

    2013-01-01

    Interstitial cells of Cajal (ICCs) are the pacemakers of the gastrointestinal tract, and transient receptor potential melastatin type 7 (TRPM7) and Ca2+ activated Cl− channels (ANO1) are candidate the generators of pacemaker potentials in ICCs. The effects of D-erythro-sphingosine (SPH) and structural analogues of SPH, that is, N,N-dimethyl-Derythro-sphingosine (N,N-DMS), FTY720, and FTY720-P on the pacemaking activities of ICCs were examined using the whole cell patch clamp technique. SPH, N...

  13. Ventricular oversensing of atrial electrical activity that inhibits VVI pacemaker and causes syncope

    Directory of Open Access Journals (Sweden)

    Elibet Chávez González

    2015-10-01

    Full Text Available Far-field oversensing of atrial electrical activity caused by a VVI pacemaker is a rare phenomenon; however, it may have serious clinical consequences. It has several causes and its timely identification may avoid a possible ventricular asystole. This article reports the case of a 72-year-old male who had a Biotronik Axios SR pacemaker implanted, in VVIR mode, six years ago, due to blocked atrial fibrillation. He suffered syncope due to pacemaker inhibition caused by ventricular oversensing of atrial electrical activity.

  14. New Canards Bursting and Canards Periodic-Chaotic Sequence

    Institute of Scientific and Technical Information of China (English)

    YOOER Chi-Feng; XU Jian-Xue; ZHANG Xin-Hua

    2009-01-01

    A trajectory following the repelling branch of an equilibrium or a periodic orbit is called a canards solution. Using a continuation method, we find a new type of canards bursting which manifests itself in an alternation between the oscillation phase following attracting the limit cycle branch and resting phase following a repelling fixed point branch in a reduced leech neuron model. Via periodic-chaotic alternating of infinite times, the number of windings within a canards bursting can approach infinity at a Gavrilov-Shilnikov homoclinic tangency bifurcation of a simple saddle limit cycle.

  15. Cumulative effect of 5 daily sessions of theta burst stimulation on corticospinal excitability in amyotrophic lateral sclerosis

    NARCIS (Netherlands)

    Munneke, Marten; Rongen, J.J.; Overeem, S.; Schelhaas, H.J.; Zwarts, M.J.; Stegeman, D.F.

    2013-01-01

    INTRODUCTION: Excitotoxicity plays an important role in the pathogenesis of the preferential motor neuron death observed in amyotrophic lateral sclerosis (ALS). Continuous theta burst stimulation (cTBS) by transcranial magnetic stimulation has an inhibitory effect on corticospinal excitability (CSE)

  16. Shaping Neuronal Network Activity by Presynaptic Mechanisms.

    Directory of Open Access Journals (Sweden)

    Ayal Lavi

    2015-09-01

    Full Text Available Neuronal microcircuits generate oscillatory activity, which has been linked to basic functions such as sleep, learning and sensorimotor gating. Although synaptic release processes are well known for their ability to shape the interaction between neurons in microcircuits, most computational models do not simulate the synaptic transmission process directly and hence cannot explain how changes in synaptic parameters alter neuronal network activity. In this paper, we present a novel neuronal network model that incorporates presynaptic release mechanisms, such as vesicle pool dynamics and calcium-dependent release probability, to model the spontaneous activity of neuronal networks. The model, which is based on modified leaky integrate-and-fire neurons, generates spontaneous network activity patterns, which are similar to experimental data and robust under changes in the model's primary gain parameters such as excitatory postsynaptic potential and connectivity ratio. Furthermore, it reliably recreates experimental findings and provides mechanistic explanations for data obtained from microelectrode array recordings, such as network burst termination and the effects of pharmacological and genetic manipulations. The model demonstrates how elevated asynchronous release, but not spontaneous release, synchronizes neuronal network activity and reveals that asynchronous release enhances utilization of the recycling vesicle pool to induce the network effect. The model further predicts a positive correlation between vesicle priming at the single-neuron level and burst frequency at the network level; this prediction is supported by experimental findings. Thus, the model is utilized to reveal how synaptic release processes at the neuronal level govern activity patterns and synchronization at the network level.

  17. A new acquisition method with pacemaker resetting of coronary multidetector-row computed tomography for reduction of radiation dose in patients with pacemaker

    International Nuclear Information System (INIS)

    We proposed a new acquisition method of coronary multidetector-row CT (MDCT) achieved by pacing rate resetting and/or propranolol or verapamil injection in patients with a pacemaker. Coronary MDCT was undertaken in 57 patients with a pacemaker (DDD: 51, VVI: 6) and in 2975 patients with sinus rhythm as control using Aquilion 64 (Toshiba). Pacing rate was reset to 60 beats per minute (bpm) in DDD, and spontaneous beats were suppressed by propranolol injection. Pacing rate was reset to 70 bpm in atrial fibrillation with VVI, and spontaneous beats were suppressed by verapamil injection. Coronary MDCT was undertaken using as high a beam pitch (BP) as possible. When spontaneous beats were not suppressed, we selected the optimal gantry speed and BP to get the highest temporal resolution. Image quality makes no significant difference between pacemaker and sinus rhythm. When spontaneous beats were completely suppressed (all pacing), mean radiation dose and acquisition time, respectively, decreased by 33.0% and 35.2% in DDD compared with the method recommended by Heart Navi (by Toshiba), and they decreased by 38.1% and 25.9%, respectively, in VVI compared with the method recommended by Heart Navi. We could not estimate coronary stenosis in the proximal right coronary artery by lead artifacts in 30% of DDD pacemakers. In conclusion, the new method is useful for not only reducing radiation dose and acquisition time, but also for maintaining image quality in patients with a pacemaker. (author)

  18. Synchronized Firing in Coupled Inhomogeneous Excitable Neurons

    Institute of Scientific and Technical Information of China (English)

    ZHENG Zhi-Gang; WANG Fu-Zhong

    2002-01-01

    We study the firing synchronization behavior of the inhomogeneous excitable media. Phase synchronizationof neuron firings is observed with increasing the coupling, while the phases of neurons are different (out-of-phase synchronization). We found the synchronization of bursts can be greatly enhanced by applying an external forcing (in-phasesynchronization). The external forcing can be either a periodic or just homogeneous thermal noise. The mechanismresponsible for this enhancement is discussed.PACS numbers: 05.45.-a, 87.10.+e

  19. A novel non invasive measurement of hemodynamic parameters: Comparison of single-chamber ventricular and dual-chamber pacemaker

    Directory of Open Access Journals (Sweden)

    Ingrid M. Pardede

    2008-03-01

    Full Text Available We carried out a cross sectional study to analyze hemodynamic parameters of single-chamber ventricular pacemaker compared with dual-chamber pacemaker by using thoracic electrical bioimpedance monitoring method (Physio Flow™ - a novel simple non-invasive measurement. A total of 48 consecutive outpatients comprised of 27 single chamber pacemaker and 21 dual chamber were analyzed. We measured cardiac parameters: heart rate, stroke volume index, cardiac output index, estimated ejection fraction, end diastolic volume, early diastolic function ratio, thoracic fluid index, and systemic parameters: left cardiac work index and systemic vascular resistance index. Baseline characteristic and pacemaker indication were similar in both groups. Cardiac parameters assessment revealed no significant difference between single-chamber pacemaker and dual-chamber pacemaker in heart rate, stroke volume index, cardiac index, estimated ejection fraction, end-diastolic volume, thoracic fluid index. There was significantly higher early diastolic function ratio in single-chamber pacemaker compared to dual-chamber pacemaker: 92% (10.2-187.7% vs. 100.6% (48.7-403.2%; p=0.006. Systemic parameters assessment revealed significantly higher left cardiac work index in single-chamber group than dual-chamber group 4.9 kg.m/m² (2.8-7.6 kg.m/m² vs. 4.3 kg.m/m² (2.9-7.2 kg.m/m²; p=0.004. There was no significant difference on systemic vascular resistance in single-chamber compared to dual-chamber pacemaker. Single-chamber ventricular pacemaker provides similar stroke volume, cardiac output and left cardiac work, compared to dual-chamber pacemaker. A non-invasive hemodynamic measurement using thoracic electrical bioimpedance is feasible for permanent pacemaker outpatients. (Med J Indones 2008; 17: 25-32Keywords: Permanent pacemaker, single chamber, dual chamber, thoracic electrical bioimpedance, hemodynamic parameter

  20. A repeating fast radio burst

    Science.gov (United States)

    Spitler, L. G.; Scholz, P.; Hessels, J. W. T.; Bogdanov, S.; Brazier, A.; Camilo, F.; Chatterjee, S.; Cordes, J. M.; Crawford, F.; Deneva, J.; Ferdman, R. D.; Freire, P. C. C.; Kaspi, V. M.; Lazarus, P.; Lynch, R.; Madsen, E. C.; McLaughlin, M. A.; Patel, C.; Ransom, S. M.; Seymour, A.; Stairs, I. H.; Stappers, B. W.; van Leeuwen, J.; Zhu, W. W.

    2016-03-01

    Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measure (that is, the integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of these bursts has led to the suggestion that they originate in cataclysmic events. Here we report observations of ten additional bursts from the direction of the fast radio burst FRB 121102. These bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB 121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB 121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and which vary on timescales of minutes or less. Although there may be multiple physical origins for the population of fast radio bursts, these repeat bursts with high dispersion measure and variable spectra specifically seen from the direction of FRB 121102 support an origin in a young, highly magnetized, extragalactic neutron star.

  1. A repeating fast radio burst.

    Science.gov (United States)

    Spitler, L G; Scholz, P; Hessels, J W T; Bogdanov, S; Brazier, A; Camilo, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J; Ferdman, R D; Freire, P C C; Kaspi, V M; Lazarus, P; Lynch, R; Madsen, E C; McLaughlin, M A; Patel, C; Ransom, S M; Seymour, A; Stairs, I H; Stappers, B W; van Leeuwen, J; Zhu, W W

    2016-03-10

    Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measure (that is, the integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of these bursts has led to the suggestion that they originate in cataclysmic events. Here we report observations of ten additional bursts from the direction of the fast radio burst FRB 121102. These bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB 121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB 121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and which vary on timescales of minutes or less. Although there may be multiple physical origins for the population of fast radio bursts, these repeat bursts with high dispersion measure and variable spectra specifically seen from the direction of FRB 121102 support an origin in a young, highly magnetized, extragalactic neutron star. PMID:26934226

  2. Influence of ionizing radiation on the probability of failure of long-term pacemakers

    Energy Technology Data Exchange (ETDEWEB)

    Eger, H.; Hesse, W.; Otte, K.B.; Rauh, G.; Salewski, D.; Stopp, G. (Zentralklinik fuer Herz- und Lungenkrankheiten, Bad Berka (German Democratic Republic); VEB Transformatoren- und Roentgenwerk ' Hermann Matern' Dresden (German Democratic Republic); Martin-Luther-Universitaet Halle-Wittenberg, Halle (German Democratic Republic). Radiologische Klinik; Staatliches Amt fuer Atomsicherheit und Strahlenschutz, Berlin (German Democratic Republic))

    1982-11-01

    The functional disturbances observed during the exposure of cardiac pacemakers with a CMOS switching circle U 115 are described qualitatively for different types of radiation. Based on the maximum sensitivity of the U 115 within the X-ray range, the correlation for this range between dose of exposure and parameter changes is established. As is demonstrated such changes is established. As is demonstrated such changes are not clinically relevant as long as the dose of 5,16 x 10/sup -2/ C/kg is not exceeded. Proceeding from the accumulated dose to which the U 115 is exposed during various diagnostic radiographic procedures it is shown that such procedures do not result in functional disturbances of the pacemaker. Recommendations are given for radiotherapeutic measures as to pacemaker patients, which should be realized in close co-operation between the pacemaker centre concerned and an authorized hospital.

  3. [Optimalization of rate adaptation using Holter functions in DDD/R pacemakers].

    Science.gov (United States)

    Novotný, T; Dvorák, R; Kozák, M; Vlasínová, J

    1998-06-01

    Introduction of the pacing rate adaptation according to the momentary metabolic needs added other programmable parametres which demand physician's attention during the initial postimplantation programmation and also in follow-up of pacemaker patients. The parametres setting is strictly individual with a need of feedback control. In some devices it is enabled by Holter functions as a part of pacemaker software. These methods were used to set the rate adaptive parametres in the group of 23 patients with implanted DDD/R pacemaker. The walking stress test was used. Model follow-up situations are presented in 3 case reports. Using Holter functions enables the physician to put patient's subjective complains in relation with actual heart rate--this is used to optimize the parametres of rate adaptation. The authors consider the Holter functions a necessary part of rate adaptive pacemaker software. PMID:9820057

  4. Magnetic Resonance Imaging in a Patient with a Dual Chamber Pacemaker

    Directory of Open Access Journals (Sweden)

    Lynne Martina Millar

    2010-01-01

    Full Text Available Having a pacemaker has been seen an absolute contraindication to having an MRI scan. This has become increasingly difficult in clinical practice as insertion of pacemakers and implantable cardiac defibrillators is at an all time high. Here we outline a case where a 71-year-old male patient with a permanent pacemaker needed to have an MRI scan to ascertain the aetiology of his condition and help guide further management. Given this clinical dilemma, an emergency clinical ethics consultation was arranged. As a result the patient underwent an MRI scan safely under controlled conditions with a consultant cardiologist and radiologist present. The results of the MRI scan were then able to tailor further treatment. This case highlights that in certain conditions an MRI can be performed in patients with permanent pacemakers and outlines the role of clinical ethics committees in complex medical decision making.

  5. A model of cardiac tissue as a conductive system with interacting pacemakers and refractory time

    OpenAIRE

    Loskutov, Alexander; Rybalko, Sergei; Zhuchkova, Ekaterina

    2002-01-01

    A model of the heart tissue as a conductive system with two interacting pacemakers and a refractory time, is proposed. In the parametric space of the model the phase locking areas are investigated in detail. Obtained results allow us to predict the behaviour of excitable systems with two pacemakers depending on the type and intensity of their interaction and the initial phase. Comparison of the described phenomena with intrinsic pathologies of cardiac rhythms is presented.

  6. Pacemaker Created in Human Ventricle by Depressing Inward-Rectifier K+ Current: A Simulation Study

    OpenAIRE

    Yue Zhang; Kuanquan Wang; Qince Li; Henggui Zhang

    2016-01-01

    Cardiac conduction disorders are common diseases which cause slow heart rate and syncope. The best way to treat these diseases by now is to implant electronic pacemakers, which, yet, have many disadvantages, such as the limited battery life and infection. Biopacemaker has been expected to replace the electronic devices. Automatic ventricular myocytes (VMs) could show pacemaker activity, which was induced by depressing inward-rectifier K+ current (IK1). In this study, a 2D model of human biopa...

  7. Sikkerhed af magnetisk resonans-skanning hos patienter med pacemaker og implanterbar defibrillator

    DEFF Research Database (Denmark)

    Al-Sabagh, Kifah Hekmat; Christensen, Britta Ege; Thøgersen, Anna Margrethe;

    2010-01-01

    INTRODUCTION: The presence of a cardiac implantable device is ICD considered an absolute contraindication to magnetic resonance imaging (MRI). The purpose of this study was to evaluate the safety of performing MRI in patients with cardiac pacemakers and ICDs that had a compelling clinical need fo...... pacemakers with an acceptable risk-benefit ratio, while MRI of patients with ICDs must still be considered an experimental procedure. Udgivelsesdato: 2010-Jun...

  8. Cardiovascular magnetic resonance in cardiac sarcoidosis with MR conditional pacemaker in situ

    OpenAIRE

    Hausenloy Derek; Harkness Allan; Plant Gordon T; Holdright Diana R; Quarta Giovanni; Hyare Harpreet; Moon James C

    2011-01-01

    Abstract Cardiovascular implantable electronic devices represent important limitations to magnetic resonance imaging (MRI). Recently, MRI-conditional dual chamber pacemakers and leads have become available. We describe a case of a patient with neuro-sarcoidosis presenting with diplopia and hydrocephalus requiring an MRI-conditional programmable ventriculo-peritoneal shunt, who developed complete heart block. In view of the ongoing need for neuro-imaging, MRI-conditional dual chamber pacemaker...

  9. Cancer patients with cardiac pacemakers needing radiation treatment: A systematic review

    OpenAIRE

    Anusheel Munshi; Jai Prakash Agarwal; Kailash Chander Pandey

    2013-01-01

    With improving average life expectancy of individuals in most countries, there has been increase in the incidence of cardiovascular diseases and cancers. Radiation oncologists therefore are likely to encounter an increasing number of cancer patients with in situ cardiac pacemaker devices needing radiation treatments. Pacemaker technology has advanced rapidly in recent years. As a result, the potential interactions of these devices with radiation therapy have changed since American Association...

  10. Designing a Computer-Assisted Clinic to Cope with the Evolution of Pacemaker Technology

    OpenAIRE

    Pfeil, Catherine N.; Keltz, Paul D.; Gertz, Edward W.; Okawachi, Melanie H.

    1983-01-01

    A computer-assisted program for follow-up monitoring of implanted cardiac pacemakers has been in operation at the San Francisco Veterans Administration Medical Center since 1977. It was originally created at a time when the technology of pacemakers was stable and only a few parameters could be measured or telemetered. Two recent developments have necessitated a major reassessment of this project as a well as redesign of the entire computer infrastructure: the advent of multi-programmable and ...

  11. Involvement of mitochondrial Na+-Ca2+ exchange in intestinal pacemaking activity

    Institute of Scientific and Technical Information of China (English)

    Byung Joo Kim; Jae Yeoul Jun; Insuk So; Ki Whan Kim

    2006-01-01

    AIM: Interstitial cells of Cajal (ICCs) are the pacemaker cells that generate slow waves in the gastrointestinal (GI) tract. We have aimed to investigate the involvement of mitochondrial Na+-Ca2+ exchange in intestinal pacemaking activity in cultured interstitial cells of Cajal.METHODS: Enzymatic digestions were used todissociate ICCs from the small intestine of a mouse. The whole-cell patch-clamp configuration was used to record membrane currents (voltage clamp) and potentials (current clamp) from cultured ICCs.RESULTS: Clonazepam and CGP37157 inhibited the pacemaking activity of ICCs in a dose-dependent manner.Clonazepam from 20 to 60 μmol/L and CGP37157 from 10 to 30 μmol/L effectively inhibited Ca2+ efflux from mitochondria in pacemaking activity of ICCs. The IC50S of clonazepam and CGP37157 were 37.1 and 18.2 μmol/L, respectively. The addition of 20 μmol/L NiCl2 to the internal solution caused a "wax and wane" phenomenon of pacemaking activity of ICCs.CONCLUSION: These results suggest that mitochondrial Na+-Ca2+ exchange has an important role in intestinal pacemaking activity.

  12. Phase synchronization of bursting neural networks with electrical and delayed dynamic chemical couplings

    Science.gov (United States)

    Megam Ngouonkadi, Elie B.; Nono, Martial Kabong; Tamba, Victor Kamdoum; Fotsin, Hilaire B.

    2015-11-01

    Diffusive electrical connections in neuronal networks are instantaneous, while excitatory or inhibitory couplings through chemical synapses contain a transmission time-delay. Moreover, chemical synapses are nonlinear dynamical systems whose behavior can be described by nonlinear differential equations. In this work, neuronal networks with diffusive electrical couplings and time-delayed dynamic chemical couplings are considered. We investigate the effects of distributed time delays on phase synchronization of bursting neurons. We observe that in both excitatory and Inhibitory chemical connections, the phase synchronization might be enhanced when time-delay is taken into account. This distributed time delay can induce a variety of phase-coherent dynamical behaviors. We also study the collective dynamics of network of bursting neurons. The network model presents the so-called Small-World property, encompassing neurons whose dynamics have two time scales (fast and slow time scales). The neuron parameters in such Small-World network, are supposed to be slightly different such that, there may be synchronization of the bursting (slow) activity if the coupling strengths are large enough. Bounds for the critical coupling strengths to obtain burst synchronization in terms of the network structure are given. Our studies show that the network synchronizability is improved, as its heterogeneity is reduced. The roles of synaptic parameters, more precisely those of the coupling strengths and the network size are also investigated.

  13. Inhibitory feedback promotes stability in an oscillatory network

    OpenAIRE

    F. Nadim; Zhao, S.; Zhou, L.; A Bose

    2011-01-01

    Reliability and variability of neuronal activity are both thought to be important for the proper function of neuronal networks. The crustacean pyloric rhythm (~1 Hz) is driven by a group of pacemaker neurons (AB/PD) which inhibit and burst out of phase with all follower pyloric neurons. The only known chemical synaptic feedback to the pacemakers is an inhibitory synapse from the follower LP neuron. Although this synapse has been extensively studied, its role in the generation and coordination...

  14. Use of an active fixation lead and a subpectoral pacemaker pocket may not avoid Twiddler′s syndrome

    Directory of Open Access Journals (Sweden)

    Floris E A Udink ten Cate

    2012-01-01

    Full Text Available Manipulation of a pacemaker with consequent malfunction of the device has been called Twiddler′s syndrome. Use of active-fixation leads and subpectoral pacemaker pockets has been considered to help in avoiding this problem. We describe a child in whom twiddling was not prevented despite implantation of a lumenless atrial lead and insertion of the pacemaker generator in a subpectoral pocket.

  15. Enhancement of Spontaneous Activity by HCN4 Overexpression in Mouse Embryonic Stem Cell-Derived Cardiomyocytes - A Possible Biological Pacemaker

    OpenAIRE

    Yukihiro Saito; Kazufumi Nakamura; Masashi Yoshida; Hiroki Sugiyama; Tohru Ohe; Junko Kurokawa; Tetsushi Furukawa; Makoto Takano; Satoshi Nagase; Hiroshi Morita; Kusano, Kengo F.; Hiroshi Ito

    2015-01-01

    Background Establishment of a biological pacemaker is expected to solve the persisting problems of a mechanical pacemaker including the problems of battery life and electromagnetic interference. Enhancement of the funny current (I f) flowing through hyperpolarization-activated cyclic nucleotide-gated (HCN) channels and attenuation of the inward rectifier K+ current (I K1) flowing through inward rectifier potassium (Kir) channels are essential for generation of a biological pacemaker. Therefor...

  16. Addition of a non-photic component to a light-based mathematical model of the human circadian pacemaker

    OpenAIRE

    St Hilaire, Melissa A.; Klerman, Elizabeth B.; Khalsa, Sat Bir; Wright, Kenneth P.; Czeisler, Charles A.; Kronauer, Richard E.

    2007-01-01

    Mathematical models have become vital to the study of many biological processes in humans due to the complexity of the physiological mechanisms underlying these processes and systems. While our current mathematical representation of the human circadian pacemaker has proven useful in many experimental situations, it uses as input only a direct effect of light on the circadian pacemaker. Although light (a photic stimulus) has been shown to be the primary synchronizer of the circadian pacemaker ...

  17. A novel non invasive measurement of hemodynamic parameters: Comparison of single-chamber ventricular and dual-chamber pacemaker

    OpenAIRE

    Ingrid M. Pardede; Yoga Yuniadi

    2008-01-01

    We carried out a cross sectional study to analyze hemodynamic parameters of single-chamber ventricular pacemaker compared with dual-chamber pacemaker by using thoracic electrical bioimpedance monitoring method (Physio Flow™) - a novel simple non-invasive measurement. A total of 48 consecutive outpatients comprised of 27 single chamber pacemaker and 21 dual chamber were analyzed. We measured cardiac parameters: heart rate, stroke volume index, cardiac output index, estimated ejection fraction,...

  18. Is metabolic rate a universal 'pacemaker' for biological processes?

    Science.gov (United States)

    Glazier, Douglas S

    2015-05-01

    A common, long-held belief is that metabolic rate drives the rates of various biological, ecological and evolutionary processes. Although this metabolic pacemaker view (as assumed by the recent, influential 'metabolic theory of ecology') may be true in at least some situations (e.g. those involving moderate temperature effects or physiological processes closely linked to metabolism, such as heartbeat and breathing rate), it suffers from several major limitations, including: (i) it is supported chiefly by indirect, correlational evidence (e.g. similarities between the body-size and temperature scaling of metabolic rate and that of other biological processes, which are not always observed) - direct, mechanistic or experimental support is scarce and much needed; (ii) it is contradicted by abundant evidence showing that various intrinsic and extrinsic factors (e.g. hormonal action and temperature changes) can dissociate the rates of metabolism, growth, development and other biological processes; (iii) there are many examples where metabolic rate appears to respond to, rather than drive the rates of various other biological processes (e.g. ontogenetic growth, food intake and locomotor activity); (iv) there are additional examples where metabolic rate appears to be unrelated to the rate of a biological process (e.g. ageing, circadian rhythms, and molecular evolution); and (v) the theoretical foundation for the metabolic pacemaker view focuses only on the energetic control of biological processes, while ignoring the importance of informational control, as mediated by various genetic, cellular, and neuroendocrine regulatory systems. I argue that a comprehensive understanding of the pace of life must include how biological activities depend on both energy and information and their environmentally sensitive interaction. This conclusion is supported by extensive evidence showing that hormones and other regulatory factors and signalling systems coordinate the processes of

  19. Mechanisms for multiple activity modes of VTA dopamine neurons

    Directory of Open Access Journals (Sweden)

    Andrew eOster

    2015-07-01

    Full Text Available Midbrain ventral segmental area (VTA dopaminergic neurons send numerous projections to cortical and sub-cortical areas, and diffusely release dopamine (DA to their targets. DA neurons display a range of activity modes that vary in frequency and degree of burst firing. Importantly, DA neuronal bursting is associated with a significantly greater degree of DA release than an equivalent tonic activity pattern. Here, we introduce a single compartmental, conductance-based computational model for DA cell activity that captures the behavior of DA neuronal dynamics and examine the multiple factors that underlie DA firing modes: the strength of the SK conductance, the amount of drive, and GABA inhibition. Our results suggest that neurons with low SK conductance fire in a fast firing mode, are correlated with burst firing, and require higher levels of applied current before undergoing depolarization block. We go on to consider the role of GABAergic inhibition on an ensemble of dynamical classes of DA neurons and find that strong GABA inhibition suppresses burst firing. Our studies suggest differences in the distribution of the SK conductance and GABA inhibition levels may indicate subclasses of DA neurons within the VTA. We further identify, that by considering alternate potassium dynamics, the dynamics display burst patterns that terminate via depolarization block, akin to those observed in vivo in VTA DA neurons and in substantia nigra pars compacta DA cell preparations under apamin application. In addition, we consider the generation of transient burst firing events that are NMDA-initiated or elicited by a sudden decrease of GABA inhibition, that is, disinhibition.

  20. Mixed-mode synchronization between two inhibitory neurons with post-inhibitory rebound

    Science.gov (United States)

    Nagornov, Roman; Osipov, Grigory; Komarov, Maxim; Pikovsky, Arkady; Shilnikov, Andrey

    2016-07-01

    We study an array of activity rhythms generated by a half-center oscillator (HCO), represented by a pair of reciprocally coupled neurons with post-inhibitory rebounds (PIR). Such coupling-induced bursting possesses two time scales, one for fast spiking and another for slow quiescent periods, is shown to exhibit an array of synchronization properties. We discuss several HCO configurations constituted by two endogenous bursters, by tonic-spiking and quiescent neurons, as well as mixed-mode configurations composed of neurons of different type. We demonstrate that burst synchronization can be accompanied by complex, often chaotic, interactions of fast spikes within synchronized bursts.

  1. Do tonic and burst TMS modulate the lemniscal and extralemniscal system differentially?

    Directory of Open Access Journals (Sweden)

    Dirk De Ridder, Elsa van der Loo, Karolien Van der Kelen, Tomas Menovsky, Paul van de Heyning, Aage Moller

    2007-01-01

    Full Text Available Introduction: Tinnitus is an auditory phantom percept related to tonic and burst hyperactivity of the auditory system. Two parallel pathways supply auditory information to the cerebral cortex: the tonotopically organised lemniscal system, and the non-tonotopic extralemniscal system, firing in tonic mode and burst mode respectively. Transcranial magnetic stimulation (TMS is a non-invasive method capable of modulating activity of the human cortex, by delivering tonic or burst stimuli. Burst stimulation is shown to be more powerful in activating the cerebral cortex than tonic stimulation and bursts may activate neurons that are not activated by tonic stimulations. Methods: The effect of both tonic and burst TMS in 14 placebo-negative patients presenting narrow band/white noise tinnitus were analysed. Results: Our TMS results show that narrow band/white noise tinnitus is better suppressed with burst TMS in comparison to tonic TMS, t(13=6.4, p=.000. For pure tone tinnitus no difference is found between burst or tonic TMS, t(13=.3, ns. Discussion: Based on the hypothesis that white noise is the result of hyperactivity in the non-tonotopic system and pure tone tinnitus of the tonotopic system, we suggest that burst stimulation modulates the extralemniscal system and lemniscal system and tonic stimulation only the lemniscal system.

  2. Introduction to Optical Burst Switching

    OpenAIRE

    KERNÁCS János; SZILÁGYI Szabolcs

    2010-01-01

    Optical Burst Switching (OBS) isconsidered a popular switching paradigm for therealization of all-optical networks due to the balance itoffers between the coarse-grained Optical CircuitSwitching (OSC) and fine-grained Optical PacketSwitching (OPS). Given that the data are switched allopticallyat the burst level, Optical Burst Switchingcombines the transparency of Optical CircuitSwitching with the benefits of statistical multiplexingin Optical Packet Switching.

  3. Sky Coverage and Burst Repetition

    OpenAIRE

    Band, David L.

    1996-01-01

    To investigate the repeater content of gamma ray burst samples I develop two models where sources burst at a constant average rate. I find that the sky coverage affects the number of repeaters in a sample predominantly through the detector livetime, and that the number of bursts in the sample is the primary parameter. Thus the repeater content of burst samples should be compared within the context of a repetition model; a direct comparison between two samples is possible only if the samples h...

  4. UWB dual burst transmit driver

    Science.gov (United States)

    Dallum, Gregory E.; Pratt, Garth C.; Haugen, Peter C.; Zumstein, James M.; Vigars, Mark L.; Romero, Carlos E.

    2012-04-17

    A dual burst transmitter for ultra-wideband (UWB) communication systems generates a pair of precisely spaced RF bursts from a single trigger event. An input trigger pulse produces two oscillator trigger pulses, an initial pulse and a delayed pulse, in a dual trigger generator. The two oscillator trigger pulses drive a gated RF burst (power output) oscillator. A bias driver circuit gates the RF output oscillator on and off and sets the RF burst packet width. The bias driver also level shifts the drive signal to the level that is required for the RF output device.

  5. Dynamics of Time Delay-Induced Multiple Synchronous Behaviors in Inhibitory Coupled Neurons

    Science.gov (United States)

    Gu, Huaguang; Zhao, Zhiguo

    2015-01-01

    The inhibitory synapse can induce synchronous behaviors different from the anti-phase synchronous behaviors, which have been reported in recent studies. In the present paper, synchronous behaviors are investigated in the motif model composed of reciprocal inhibitory coupled neurons with endogenous bursting and time delay. When coupling strength is weak, synchronous behavior appears at a single interval of time delay within a bursting period. When coupling strength is strong, multiple synchronous behaviors appear at different intervals of time delay within a bursting period. The different bursting patterns of synchronous behaviors, and time delays and coupling strengths that can induce the synchronous bursting patterns can be well interpreted by the dynamics of the endogenous bursting pattern of isolated neuron, which is acquired by the fast-slow dissection method, combined with the inhibitory coupling current. For an isolated neuron, when a negative impulsive current with suitable strength is applied at different phases of the bursting, multiple different bursting patterns can be induced. For a neuron in the motif, the inhibitory coupling current, of which the application time and strength is modulated by time delay and coupling strength, can cause single or multiple synchronous firing patterns like the negative impulsive current when time delay and coupling strength is suitable. The difference compared to the previously reported multiple synchronous behaviors that appear at time delays wider than a period of the endogenous firing is discussed. The results present novel examples of synchronous behaviors in the neuronal network with inhibitory synapses and provide a reasonable explanation. PMID:26394224

  6. Ectopic jejunal pacemakers and gastric emptying after Roux gastrectomy: Effect of intestinal pacing

    International Nuclear Information System (INIS)

    The aims of this study were to determine whether ectopic pacemakers are present after meals in the Roux limbs of dogs after vagotomy and Roux gastrectomy, whether these pacemakers slow gastric emptying of liquids or solids, and whether abolishing the pacemakers with electric pacing might speed any slow emptying that occurs. In six dogs that underwent vagotomy and Roux gastrectomy and in four dogs that underwent vagotomy and Billroth gastrectomy (controls), myoelectric activity of the Roux limb or duodenum was measured during gastric emptying of a 500 kcal mixed meal of 99mTc-labeled cooked egg and 111In-labeled milk. Roux dogs were tested with and without pacing of the Roux limb. Roux dogs showed ectopic pacemaker in the Roux limb that drove the pacesetter potentials of the limb in a reverse, or orad, direction during 57% of the postprandial recordings. Billroth dogs had no ectopic pacemakers (p less than 0.05). Liquids emptied more slowly in Roux dogs (half-life (t1/2) = 121 +/- 15 minutes) than in Billroth dogs (t1/2 = 43 +/- 9 minutes; p less than 0.05), but solids emptied similarly in both groups of dogs (t1/2 approximately 8 hours). Pacing the Roux limb abolished the ectopic pacemakers, restored the slow emptying of liquids to the more rapid rate found in the Billroth dogs (t1/2: paced Roux, 72 +/- 15 minutes; Billroth, 43 +/- 9 minutes; p greater than 0.05) and did not change emptying of solids. The conclusion was that ectopic pacemakers present in the Roux limb after vagotomy and Roux gastrectomy drove the limb in a reverse direction and slowed emptying of liquids after the operation. The defect was corrected by pacing the Roux limb in a forward direction

  7. NEW BURST ASSEMBLY AND SCHEDULING TECHNIQUE FOR OPTICAL BURST SWITCHING NETWORKS

    OpenAIRE

    V.KAVITHA; Palanisamy, V.

    2013-01-01

    The Optical Burst Switching is a new switching technology that efficiently utilizes the bandwidth in the optical layer. The key areas to be concentrated in Optical Burst Switching (OBS) networks are the burst assembly and burst scheduling i.e., assignment of wavelengths to the incoming bursts. This study presents a New Burst Assembly and Scheduling (NBAS) technique in a simultaneous multipath transmission for burst loss recovery in OBS networks. A Redundant Burst Segmentation (RBS) is used fo...

  8. Bursts generate a non-reducible spike-pattern code

    Directory of Open Access Journals (Sweden)

    Hugo G Eyherabide

    2009-05-01

    Full Text Available On the single-neuron level, precisely timed spikes can either constitute firing-rate codes or spike-pattern codes that utilize the relative timing between consecutive spikes. There has been little experimental support for the hypothesis that such temporal patterns contribute substantially to information transmission. Using grasshopper auditory receptors as a model system, we show that correlations between spikes can be used to represent behaviorally relevant stimuli. The correlations reflect the inner structure of the spike train: a succession of burst-like patterns. We demonstrate that bursts with different spike counts encode different stimulus features, such that about 20% of the transmitted information corresponds to discriminating between different features, and the remaining 80% is used to allocate these features in time. In this spike-pattern code, the "what" and the "when" of the stimuli are encoded in the duration of each burst and the time of burst onset, respectively. Given the ubiquity of burst firing, we expect similar findings also for other neural systems.

  9. Anticoagulation Management in Patients with Pacemaker-Detected Atrial Fibrillation

    Science.gov (United States)

    Poposka, Lidija; Boskov, Vladimir; Risteski, Dejan; Taleski, Jane; Georgievska-Ismail, Ljubica

    2016-01-01

    INTRODUCTION: In patients with an implanted pacemaker, asymptomatic atrial fibrillation (AF) is associated with an increased risk of thrombo-embolic complications. There is still no consensus which duration of episodes of atrial fibrillation should be taken as an indicator for inclusion of oral anticoagulation therapy (OAC). MATERIAL AND METHODS: A total of 104 patients who had no AF episodes in the past and have an indication for permanent pacing were included in the study. RESULTS: During an average follow-up of 18 months, 33 of the patients developed episodes of AF. Inclusion of OAC was performed in 17 patients, in whom AF was recorded, although in all patients CHA2DS2-VASc score was ≥ 1. The inclusion of OAC showed a statistically significant correlation with increasing duration of episodes of AF (r = 0.502, p = 0.003). During the follow-up period none of the patients developed thrombo-embolic complication. CONCLUSION: Considering that our group of patients had no thrombo-embolic events, we could conclude that dividing the AF episodes in less than 1% in 24 hours and longer than 1% within 24 hours could be an indicator for decision-making to include OAK if the CHA2DS2-VASc score is ≥ 1. PMID:27335594

  10. Gamma Ray Bursts

    Science.gov (United States)

    Gehrels, Neil; Meszaros, Peter

    2012-01-01

    Gamma-ray bursts (GRBs) are bright flashes of gamma-rays coming from the cosmos. They occur roughly once per day ,last typically lOs of seconds and are the most luminous events in the universe. More than three decades after their discovery, and after pioneering advances from space and ground experiments, they still remain mysterious. The launch of the Swift and Fermi satellites in 2004 and 2008 brought in a trove of qualitatively new data. In this review we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglows.

  11. Gamma-Ray Bursts

    Science.gov (United States)

    Gehrels, Neil; Mészáros, Péter

    2012-08-01

    Gamma-ray bursts (GRBs) are bright flashes of gamma rays coming from the cosmos. They occur roughly once per day, typically last for tens of seconds, and are the most luminous events in the universe. More than three decades after their discovery, and after pioneering advances from space and ground experiments, they still remain mysterious. The launch of the Swift and Fermi satellites in 2004 and 2008 brought in a trove of qualitatively new data. In this Review, we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglow.

  12. Gamma Ray Bursts

    CERN Document Server

    Gehrels, Neil; 10.1126/science.1216793

    2012-01-01

    Gamma-ray bursts (GRBs) are bright flashes of gamma-rays coming from the cosmos. They occur roughly once per day, last typically 10s of seconds and are the most luminous events in the universe. More than three decades after their discovery, and after pioneering advances from space and ground experiments, they still remain mysterious. The launch of the Swift and Fermi satellites in 2004 and 2008 brought in a trove of qualitatively new data. In this review we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglows.

  13. Dark Gamma Ray Bursts

    OpenAIRE

    Brdar, Vedran; Kopp, Joachim; Liu, Jia

    2016-01-01

    Many theories of dark matter (DM) predict that DM particles can be captured by stars via scattering on ordinary matter. They subsequently condense into a DM core close to the center of the star and eventually annihilate. In this work, we trace DM capture and annihilation rates throughout the life of a massive star and show that this evolution culminates in an intense annihilation burst coincident with the death of the star in a core collapse supernova. The reason is that, along with the stell...

  14. Dark Gamma Ray Bursts

    CERN Document Server

    Brdar, Vedran; Liu, Jia

    2016-01-01

    Many theories of dark matter (DM) predict that DM particles can be captured by stars via scattering on ordinary matter. They subsequently condense into a DM core close to the center of the star and eventually annihilate. In this work, we trace DM capture and annihilation rates throughout the life of a massive star and show that this evolution culminates in an intense annihilation burst coincident with the death of the star in a core collapse supernova. The reason is that, along with the stellar interior, also its DM core heats up and contracts, so that the DM density increases rapidly during the final stages of stellar evolution. We argue that, counterintuitively, the annihilation burst is more intense if DM annihilation is a p-wave process than for s-wave annihilation because in the former case, more DM particles survive until the supernova. If among the DM annihilation products are particles like dark photons that can escape the exploding star and decay to Standard Model particles later, the annihilation bu...

  15. Pre-ejection period by radial artery tonometry supplements echo doppler findings during biventricular pacemaker optimization

    Directory of Open Access Journals (Sweden)

    Qamruddin Salima

    2011-07-01

    Full Text Available Abstract Background Biventricular (Biv pacemaker echo optimization has been shown to improve cardiac output however is not routinely used due to its complexity. We investigated the role of a simple method involving computerized pre-ejection time (PEP assessment by radial artery tonometry in guiding Biv pacemaker optimization. Methods Blinded echo and radial artery tonometry were performed simultaneously in 37 patients, age 69.1 ± 12.8 years, left ventricular (LV ejection fraction (EF 33 ± 10%, during Biv pacemaker optimization. Effect of optimization on echo derived velocity time integral (VTI, ejection time (ET, myocardial performance index (MPI, radial artery tonometry derived PEP and echo-radial artery tonometry derived PEP/VTI and PEP/ET indices was evaluated. Results Significant improvement post optimization was achieved in LV ET (286.9 ± 37.3 to 299 ± 34.6 ms, p Conclusion An acute shortening of PEP by radial artery tonometry occurs post Biv pacemaker optimization and correlates with improvement in hemodynamics by echo Doppler and may provide a cost-efficient approach to assist with Biv pacemaker echo optimization.

  16. Echocardiography-guided Radiofrequency Catheter Ablation of Atrioventricular Node and VVI Pacemaker Implantation

    Directory of Open Access Journals (Sweden)

    T Guo

    2014-05-01

    Full Text Available Objective: This study is to evaluate the feasibility and safety of intracardiac radiofrequency catheter ablation (RFCA of the atrioventricular node (AVN and pacemaker implantation using transthoracic echocardiography. Methods: Eleven patients – six males and five females (mean age 66 years – with persistent or permanent atrial fibrillation/atrial flutter received RFCA of AVN and VVI pacemaker implantation (paces and senses the ventricle and is inhibited if it senses ventricular activity. Under transthoracic echocardiography, the electrode catheters were positioned intracardiac, and target ablation was performed, with the permanent pacemaking catheter in the left subclavian vein and the ablation catheter in the right femoral vein. The multi-view imaging and dynamic observation applied during the stable AV dissociation were successful. Results: Atrioventricular node ablation and permanent pacemaker implantation in 11 patients were completed successfully without X-ray exposure. The operation success rate was 100%. All patients recovered well within the follow-up period. Conclusions: Radiofrequency catheter ablation of AVN and VVI pacemaker implantation under transthoracic echocardiography guidance is a safe, easy and feasible approach. This procedure could be an important supplemental measure to catheter ablation of arrhythmia under routine X-ray fluoroscopy.

  17. Burst propagation in Texas Helimak

    Science.gov (United States)

    Pereira, F. A. C.; Toufen, D. L.; Guimarães-Filho, Z. O.; Caldas, I. L.; Gentle, K. W.

    2016-05-01

    We present investigations of extreme events (bursts) propagating in the Texas Helimak, a toroidal plasma device in which the radial electric field can be changed by application of bias. In the experiments analyzed, a large grid of Langmuir probes measuring ion saturation current fluctuations is used to study the burst propagation and its dependence on the applied bias voltage. We confirm previous results reported on the turbulence intermittency in the Texas Helimak, extending them to a larger radial interval with a density ranging from a uniform decay to an almost uniform value. For our analysis, we introduce an improved procedure, based on a multiprobe bidimensional conditional averaging method, to assure precise determination of burst statistical properties and their spatial profiles. We verify that intermittent bursts have properties that vary in the radial direction. The number of bursts depends on the radial position and on the applied bias voltage. On the other hand, the burst characteristic time and size do not depend on the applied bias voltage. The bias voltage modifies the vertical and radial burst velocity profiles differently. The burst velocity is smaller than the turbulence phase velocity in almost all the analyzed region.

  18. Short duration gamma ray bursts

    Indian Academy of Sciences (India)

    Patrick Das Gupta

    2004-10-01

    After a short review of gamma ray bursts (GRBs), we discuss the physical implications of strong statistical correlations seen among some of the parameters of short duration bursts (90 < 2 s). Finally, we conclude with a brief sketch of a new unified model for long and short GRBs.

  19. Burst Mode Transmission in GPON

    Institute of Scientific and Technical Information of China (English)

    LI Liang-chuan; ZHANG Yan-gan; LI Ling; XU Da-xiong

    2004-01-01

    In this paper, a newly approved standard G.984 for Gigabit-capable Passive Optical Networks (GPON) is introduced. Technical challenges about high-speed burst-mode data transmission in GPON are discussed and key issues such as Forward Error Correction (FEC), timing to uplink performance of burst mode are high-lighted.

  20. Scheduling start time in CDMA burst admission

    OpenAIRE

    Zhuge, L; Li, VOK

    2002-01-01

    Burst transmission protocols have been proposed in the next generation CDMA cellular systems to support short-time high-speed data communications. The existing burst admission algorithm considers only the current interference condition in the system. The burst transmission request will be rejected if the interference in the system will exceed the acceptable level with the burst admitted. In this paper we propose a new burst admission algorithm where a currently-unacceptable burst request can ...

  1. Burst Detector Sensitivity: Past, Present & Future

    OpenAIRE

    Band, David L.

    2006-01-01

    I compare the burst detection sensitivity of CGRO's BATSE, Swift's BAT, the GLAST Burst Monitor (GBM) and EXIST as a function of a burst's spectrum and duration. A detector's overall burst sensitivity depends on its energy sensitivity and set of accumulations times Delta t; these two factors shape the detected burst population. For example, relative to BATSE, the BAT's softer energy band decreases the detection rate of short, hard bursts, while the BAT's longer accumulation times increase the...

  2. Quantum key based burst confidentiality in optical burst switched networks.

    Science.gov (United States)

    Balamurugan, A M; Sivasubramanian, A

    2014-01-01

    The optical burst switching (OBS) is an emergent result to the technology concern that could achieve a feasible network in future. They are endowed with the ability to meet the bandwidth requirement of those applications that require intensive bandwidth. There are more domains opening up in the OBS that evidently shows their advantages and their capability to face the future network traffic. However, the concept of OBS is still far from perfection facing issues in case of security threat. The transfer of optical switching paradigm to optical burst switching faces serious downfall in the fields of burst aggregation, routing, authentication, dispute resolution, and quality of service (QoS). This paper deals with employing RC4 (stream cipher) to encrypt and decrypt bursts thereby ensuring the confidentiality of the burst. Although the use of AES algorithm has already been proposed for the same issue, by contrasting the two algorithms under the parameters of burst encryption and decryption time, end-to-end delay, it was found that RC4 provided better results. This paper looks to provide a better solution for the confidentiality of the burst in OBS networks. PMID:24578663

  3. Setups for in vitro assessment of RFID interference on pacemakers

    International Nuclear Information System (INIS)

    The aim of this study is to propose setups for in vitro assessment of RFID (radiofrequency identification) interference on pacemakers (PM). The voltage induced at the input stage of the PM by low-frequency (LF) and high-frequency (HF) RFID transmitters has been used to quantify the amount of the interference. A commercial PM was modified in order to measure the voltage at its input stage when exposed to a sinusoidal signal at 125 kHz and 13.56 MHz. At both frequencies, two antennas with different dimensions (diameter = 10 cm and 30 cm, respectively) were used to generate the interfering field, and the induced voltage was measured between the lead tip and the PM case (unipolar voltage), and between the tip and ring electrodes (bipolar voltage). The typical lead configurations adopted in similar studies or proposed by international standards, as well as lead paths closer to actual physiological implants were tested. At 125 kHz, the worst-case condition differs for the two antennas: the 10 cm antenna induced the highest voltage in the two-loop spiral configuration, whereas the 30 cm antenna in the 225 cm2 loop configuration. At 13.56 MHz, the highest voltage was observed for both the antennas in the 225 cm2 loop configuration. Bipolar voltages were found to be lower than the unipolar voltages induced in the same configurations, this difference being not as high as one could expect from theoretical considerations. The worst-case scenario, in terms of the induced voltage at the PM input stage, has been identified both for LF and HF readers, and for two sizes of transmitting antennas. These findings may provide the basis for the definition of a standard implant configuration and a lead path to test the EMI effects of LF and HF RFID transmitters on active implantable devices. (paper)

  4. NMDA spike/plateau potentials in dendrites of thalamocortical neurons.

    Science.gov (United States)

    Augustinaite, Sigita; Kuhn, Bernd; Helm, Paul Johannes; Heggelund, Paul

    2014-08-13

    Dendritic NMDA spike/plateau potentials, first discovered in cortical pyramidal neurons, provide supralinear integration of synaptic inputs on thin and distal dendrites, thereby increasing the impact of these inputs on the soma. The more specific functional role of these potentials has been difficult to clarify, partly due to the complex circuitry of cortical neurons. Thalamocortical (TC) neurons in the dorsal lateral geniculate nucleus participate in simpler circuits. They receive their primary afferent input from retina and send their output to visual cortex. Cortex, in turn, regulates this output through massive feedback to distal dendrites of the TC neurons. The TC neurons can operate in two modes related to behavioral states: burst mode prevailing during sleep, when T-type calcium bursts largely disrupt the transfer of signals from retina to cortex, and tonic mode, which provides reliable transfer of retinal signals to cortex during wakefulness. We studied dendritic potentials in TC neurons with combined two-photon calcium imaging and whole-cell recording of responses to local dendritic glutamate iontophoresis in acute brain slices from mice. We found that NMDA spike/plateaus can be elicited locally at distal dendrites of TC neurons. We suggest that these dendritic potentials have important functions in the cortical regulation of thalamocortical transmission. NMDA spike/plateaus can induce shifts in the functional mode from burst to tonic by blockade of T-type calcium conductances. Moreover, in tonic mode, they can facilitate the transfer of retinal signals to cortex by depolarization of TC neurons. PMID:25122891

  5. Subjective consequences of permanent pacemaker therapy in patients under the age of retirement

    DEFF Research Database (Denmark)

    Mickley, H; Petersen, J; Nielsen, B L

    1989-01-01

    During a 5-year period, 81 patients ages 20 to 60 years old had implantation of a permanent cardiac pacemaker at the University Hospital, Odense. At follow-up, during 1985, the 73 survivors received a semi-structured questionnaire regarding subjective consequences of pacemaker therapy, and 72...... people (98.6%) agreed to participate. The mean pacing period (range) was 33.8 (11-72) months. Surgical intervention was required in 14 patients (19.4%) during follow-up. Regarding all symptoms 67 patients (93.1%) perceived benefit from the pacemaker. The effectiveness of cardiac pacing was most...... pronounced in subjects suffering from syncope and/or dizziness. Eight patients (11.1%) perceived anxiety most frequently due to fear of pacing failure. Physical complaints were present in 17 patients (23.6%), and the discomfort was mainly due to the size of generator, pain/tenderness from the scar or a...

  6. [Verification of irradiation conditions of X-rays that influence implantable cardiac pacemakers].

    Science.gov (United States)

    Umezawa, Naoki; Hirose, Minoru; Shinbo, Toshihiro

    2008-07-20

    Originally, it was thought that X-rays did not influence implantable cardiac pacemakers. In general, radiological technologists did not take proper care of these devises at the time of X-Ray examinations. However, 11 cases in which pacemakers malfunctioned (for example partial electrical reset) during CT examinations have been reported in recent years. At the time, we tended to attribute such problems to the peculiarities of multi-detector CT (MDCT). However, on logical grounds this explanation seemed weak. To better explain the problem, we attempted various tests in which pacemakers were exposed to CT and X-ray photography equipment. We analyzed some ECG results to clarify the matter and took measurements to examine these problems. PMID:18719296

  7. Pacemaker reuse for patients in resource poor countries: is something always better than nothing?

    Science.gov (United States)

    VanArtsdalen, Jamie; Goold, Susan Dorr; Kirkpatrick, James N; Goldman, Ed; Eagle, Kim; Crawford, Thomas

    2012-01-01

    Cardiovascular disease is the most common cause of death across the globe. Large disparities in access to cardiovascular care exist in the world. An estimated one million people die each year due to lack of access to life saving pacemaker therapy. We discuss the concept of justice in health and health care as it relates to the use of refurbished pacemakers in patients in low- and middle- income countries, where financial circumstances severely limit access to brand new devices. Egalitarianism, utilitarianism, and justice as fairness are examined, as they relate to provision of re-processed pacemakers. This practice, since it holds promise to improve human functioning and capabilities, can be morally justified with some conditions: transparency, further research in is its safety and efficacy, and its impact on other needs and priorities in those countries. PMID:23217434

  8. Experimental Evaluation of SAR around an Implanted Cardiac Pacemaker Caused by Mobile Radio Terminal

    Science.gov (United States)

    Endo, Yuta; Saito, Kazuyuki; Watanabe, Soichi; Takahashi, Masaharu; Ito, Koichi

    Although the effect of electromagnetic interference on an implanted cardiac pacemaker due to a nearby mobile phone has been investigated, there have been few studies on the enhancement of the specific absorption rate (SAR) around an implanted cardiac pacemaker due to a nearby mobile phone. In this study, the SAR distribution around a pacemaker model embedded in a parallelepiped torso phantom when a mobile phone was nearby was numerically calculated and experimentally measured. The results of both investigations showed a characteristic SAR distribution. The system presented can be used to estimate the effects of electromagnetic interference on implanted electric circuits and thus could lead to the development of guidelines for the safe use of mobile radio terminals near people with medical implants.

  9. Reuse of Explanted Pacemakers: An Option for Economically Underprivileged Patients in Developing Countries

    Directory of Open Access Journals (Sweden)

    Johnson Francis

    2007-10-01

    Full Text Available Permanent pacemaker implantation is an established mode of life saving therapy for patients with symptomatic bradycardia. As the human population is aging world-over, the need for pacemakers are also increasing. Reviewing the results of the 2001 World Survey on Cardiac Pacing and Implantable Cardioverter Defibrillators (Table 1, it is evident that not all patients who require pacemakers are receiving them, particularly in the Asia-Pacific region. The largest implanting country per head of population is Germany, although the largest numbers implanted are in the United States of America. In contrast, the countries of Asia have much smaller numbers with Myanmar having less than one implant per million population per year1.

  10. High visual demand following theta burst stimulation modulates the effect on visual cortex excitability

    Directory of Open Access Journals (Sweden)

    Sabrina Brückner

    2015-10-01

    Full Text Available Modulatory effects of repetitive transcranial magnetic stimulation depend on the activity of the stimulated cortical area before, during, and even after application. In the present study we investigated the effects of theta burst stimulation on visual cortex excitability using phosphene thresholds. In a between-group design either continuous or intermittent theta burst stimulation was applied with 100% of individual phosphene threshold intensity. We varied visual demand following stimulation in form of high demand (acuity task or low demand (looking at the wall. No change of phosphene thresholds was observed directly after theta burst stimulation. We found increased phosphene thresholds only if subjects had high visual demand following continuous theta burst stimulation. With low visual demand following stimulation no change of phosphene threshold was observed. Intermittent theta burst stimulation had no effect on visual cortex excitability at all. Since other studies showed increased phosphene thresholds following continuous theta burst stimulation using subthreshold intensities, our results highlight the importance of stimulation intensity applying theta burst stimulation to the visual cortex. Furthermore, the state of the neurons in the stimulated cortex area not only before but also following theta burst stimulation has an important influence on the effects of stimulation, making it necessary to scrupulously control for activity during the whole experimental session in a study.

  11. Cerebral cortical neurons with activity linked to central neurogenic spontaneous and evoked elevations in cerebral blood flow

    Science.gov (United States)

    Golanov, E. V.; Reis, D. J.

    1996-01-01

    We recorded neurons in rat cerebral cortex with activity relating to the neurogenic elevations in regional cerebral blood flow (rCBF) coupled to stereotyped bursts of EEG activity, burst-cerebrovascular wave complexes, appearing spontaneously or evoked by electrical stimulation of rostral ventrolateral medulla (RVL) or fastigial nucleus (FN). Of 333 spontaneously active neurons only 15 (5%), in layers 5-6, consistently (P neurons in deep cortical laminae whose activity correlates with neurogenic elevations of rCBF. These neurons may function to transduce afferent neuronal signals into vasodilation.

  12. Concept for LEU Burst Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Steven Karl [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kimpland, Robert Herbert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-03-07

    Design and performance of a proposed LEU burst reactor are sketched. Salient conclusions reached are the following: size would be ~1,500 kg or greater, depending on the size of the central cavity; internal stresses during burst require split rings for relief; the reactor would likely require multiple control and safety rods for fine control; the energy spectrum would be comparable to that of HEU machines; and burst yields and steady-state power levels will be significantly greater in an LEU reactor.

  13. Concept for LEU Burst Reactor

    International Nuclear Information System (INIS)

    Design and performance of a proposed LEU burst reactor are sketched. Salient conclusions reached are the following: size would be ~1,500 kg or greater, depending on the size of the central cavity; internal stresses during burst require split rings for relief; the reactor would likely require multiple control and safety rods for fine control; the energy spectrum would be comparable to that of HEU machines; and burst yields and steady-state power levels will be significantly greater in an LEU reactor.

  14. Interference Resilience of Burst-by-burst Adaptive Modems

    OpenAIRE

    Torrance, J.M.; Hanzo, L.; Keller, T

    1997-01-01

    Adaptive modulation can achieve channel capacity gains by adapting t h e number of bits per transmission symbol on a burst-by-burst basis, in harmony with channel quality fluctuations. In this treatise their interference resilience is quantified and the modem mode switching levels are determined under interfered conditions. The associated performance curves are portrayed in Figures 6, 7 and 8 for target bit error rates of 1 and 0.01 %, respectively. The corresponding modem mode switching leve...

  15. Analysis of Burst Assembly Modeling for Optical Burst Switched Network

    Directory of Open Access Journals (Sweden)

    Bhumika Patel

    2013-11-01

    Full Text Available In this paper, we have study the current state of the technology, the Optical burst Switched (OBS network is the most practical in all-optical architecture. Here we define how Burst Assembly will carried out and also here in the network architecture each node is consist of Core router and Edge router. Moreover we define challenges faced at practical implementation of OBS and proposed its unique solution at the node as Delay model.

  16. FERMIGBRST - Fermi GBM Burst Catalog

    Data.gov (United States)

    National Aeronautics and Space Administration — This table lists all of the triggers observed by a subset of the 14 GBM detectors (12 NaI and 2 BGO) which have been classified as gamma-ray bursts (GRBs). Note...

  17. SWIFT and BATSE bursts' classification

    CERN Document Server

    Horvath, I; Balazs, L G; Tusnady, G; Veres, P

    2009-01-01

    Two classes of gamma-ray bursts were identified in the BATSE catalogs characterized by their durations. There were also some indications for the existence of a third type of gamma-ray bursts. Swift satellite detectors have different spectral sensitivity than pre-Swift ones for GRBs. Therefore in this paper we analyze the bursts' duration distribution and also the duration-hardness bivariate distribution, published in The First BAT Catalog. Similarly to the BATSE data, to explain the BAT GRBs' duration distribution three components are needed. Although, the relative frequencies of the groups are different than they were in the BATSE GRB sample, the difference in the instrument spectral sensitivities can explain this bias in a natural way. This means theoretical models may have to explain three different type of gamma-ray bursts.

  18. Bistability of bursting and silence regimes in a model of a leech heart interneuron

    Science.gov (United States)

    Malashchenko, Tatiana; Shilnikov, Andrey; Cymbalyuk, Gennady

    2011-10-01

    Bursting is one of the primary activity regimes of neurons. Our study is focused on determining a generic biophysical mechanism underlying the coexistence of the bursting and silent regimes observed in a neuron model. We show that the main ingredient for this mechanism is a saddle periodic orbit. The stable manifold of the orbit sets a threshold between the regimes of activity. Thus, the range of the controlling parameters, where the coexistence is observed, is limited by the bifurcations' values at which the saddle orbit appears and disappears. We show that it appears through the subcritical Andronov-Hopf bifurcation, where the equilibrium representing the silent regime loses stability, and disappears at the homoclinic bifurcation. Correspondingly, the bursting regime disappears in close proximity to the homoclinic bifurcation.

  19. Network and external perturbation induce burst synchronisation in cat cerebral cortex

    Science.gov (United States)

    Lameu, Ewandson L.; Borges, Fernando S.; Borges, Rafael R.; Batista, Antonio M.; Baptista, Murilo S.; Viana, Ricardo L.

    2016-05-01

    The brain of mammals are divided into different cortical areas that are anatomically connected forming larger networks which perform cognitive tasks. The cat cerebral cortex is composed of 65 areas organised into the visual, auditory, somatosensory-motor and frontolimbic cognitive regions. We have built a network of networks, in which networks are connected among themselves according to the connections observed in the cat cortical areas aiming to study how inputs drive the synchronous behaviour in this cat brain-like network. We show that without external perturbations it is possible to observe high level of bursting synchronisation between neurons within almost all areas, except for the auditory area. Bursting synchronisation appears between neurons in the auditory region when an external perturbation is applied in another cognitive area. This is a clear evidence that burst synchronisation and collective behaviour in the brain might be a process mediated by other brain areas under stimulation.

  20. Burst firing in a motion-sensitive neural pathway correlates with expansion properties of looming objects that evoke avoidance behaviours

    Directory of Open Access Journals (Sweden)

    Glyn Allan McMillan

    2015-12-01

    Full Text Available The locust visual system contains a well-defined motion-sensitive pathway that transfers visual input to motor centers involved in predator evasion and collision avoidance. One interneuron in this pathway, the descending contralateral movement detector (DCMD, is typically described as using rate coding; edge expansion of approaching objects causes an increased rate of neuronal firing that peaks after a certain retinal threshold angle is exceeded. However, evidence of intrinsic DCMD bursting properties combined with observable oscillations in mean firing rates and tight clustering of spikes in raw traces, suggest that bursting may be important for motion detection. Sensory neuron bursting provides important timing information about dynamic stimuli in many model systems, yet no studies have rigorously investigated if bursting occurs in the locust DCMD during object approach. We presented repetitions of 30 looming stimuli known to generate behavioural responses to each of 20 locusts in order to identify and quantify putative bursting activity in the DCMD. Overall, we found a bimodal distribution of inter-spike intervals (ISI with peaks of more frequent and shorter ISIs occurring from 1-8 ms and longer less frequent ISIs occurring from 40-50 ms. Subsequent analysis identified bursts and isolated single spikes from the responses. Bursting frequency increased in the latter phase of an approach and peaked at the time of collision, while isolated spiking was predominant during the beginning of stimulus approach. We also found that the majority of inter-burst intervals occurred at 40-50 ms (or 20-25 bursts/s. Bursting also occurred across varied stimulus parameters and suggests that burst timing may be a key component of looming detection. Our findings suggest that the DCMD uses two modes of coding to transmit information about looming stimuli and that these modes change dynamically with a changing stimulus at a behaviourally-relevant time.

  1. Burst Suppression: A Review and New Insights

    OpenAIRE

    Jonathan Dillon Kenny; M. Brandon Westover; ShiNung Ching; Brown, Emery N.; Ken Solt

    2014-01-01

    Burst suppression is a pattern of brain electrical activity characterized by alternating periods of high-amplitude bursts and electrical silence. Burst suppression can arise from several different pathological conditions, as well as from general anesthesia. Here we review current algorithms that are used to quantify burst suppression, its various etiologies, and possible underlying mechanisms. We then review clinical applications of anesthetic-induced burst suppression. Finally, we report the...

  2. Mining Gamma-Ray Burst Data

    OpenAIRE

    Hakkila, Jon; Roiger, Richard J.; Haglin, David J.; Mallozzi, Robert S.; Pendleton, Geoffrey N.; Meegan, Charles A.

    2000-01-01

    Gamma-ray bursts provide what is probably one of the messiest of all astrophysical data sets. Burst class properties are indistinct, as overlapping characteristics of individual bursts are convolved with effects of instrumental and sampling biases. Despite these complexities, data mining techniques have allowed new insights to be made about gamma-ray burst data. We demonstrate how data mining techniques have simultaneously allowed us to learn about gamma-ray burst detectors and data collectio...

  3. Reevaluation of the indications for permanent pacemaker implantation after transcatheter aortic valve implantation

    DEFF Research Database (Denmark)

    Bjerre Thygesen, Julie; Loh, Poay Huan; Cholteesupachai, Jiranut; Franzen, Olaf; Søndergård, Lars

    2014-01-01

    AIMS: Conduction abnormalities (CA) requiring permanent pacemaker (PPM) are a well-known complication after transcatheter aortic valve implantation (TAVI). This study aimed to determine the incidence of TAVI-related PPM and reevaluate the indications for PPM after the periprocedural period. METHO...

  4. Precise Estimation of Cellular Radio Electromagnetic Field in Elevators and EMI Impact on Implantable Cardiac Pacemakers

    Science.gov (United States)

    Harris, Louis-Ray; Hikage, Takashi; Nojima, Toshio

    The purpose of this paper is to investigate the possible impact of cellular phones' signals on implantable cardiac pacemakers in elevators. This is achieved by carrying out precise numerical simulations based on the Finite-Difference-Time-Domain method to examine the electromagnetic fields in elevator models. In order to examine the realistic and complicated situations where humans are present in the elevator, we apply the realistic homogeneous human phantom and cellular radios operating in the frequency bands 800MHz, 1.5GHz and 2GHz. These computed results of field strength inside the elevator are compared with a certain reference level determined from the experimentally obtained maximum interference distance of implantable cardiac pacemakers. This enables us to carry out a quantitative evaluation of the EMI risk to pacemakers by cellular radio transmission. The results show that for the case when up to 5 mobile radio users are present in the elevator model used, there is no likelihood of pacemaker malfunction for the frequency bands 800MHz, 1.5GHz and 2GHz.

  5. 76 FR 44872 - Effective Date of Requirement for Premarket Approval for an Implantable Pacemaker Pulse Generator

    Science.gov (United States)

    2011-07-27

    .... Improper Sensing Electromagnetic interference with pacemaker electronics, loose connections, or sensing... HUMAN SERVICES Food and Drug Administration 21 CFR Part 870 Effective Date of Requirement for Premarket... medical devices intended for human use. Section 513 of the FD&C Act (21 U.S.C. 360c) established...

  6. Influence of Continuous Nursing on the Psychological State and Coping Style of Patients Undergoing Pacemaker Implantation

    Directory of Open Access Journals (Sweden)

    Xin LIU

    2015-10-01

    Full Text Available Background: Patients undergoing pacemaker implantation often experience anxiety and fear. As such, studies have focused on the mechanisms that relieve the negative emotions caused by the intervention. Continuous nursing is a safe and effective nursing mode. In this study, continuous nursing intervention was provided for elderly patients undergo-ing pacemaker implantation and an empirical investigation was performed to determine the effects of their negative emotion and disease-coping ability.Methods: Overall, 114 (68 males and 46 females elderly patients who were undergoing pacemaker implantation from Harbin City (China, were enrolled in the study. The patients were divided into two groups, namely, the control group and the intervention group, based on different nursing methods. Routine nursing was applied to the control group; continuous nursing support was provided for the intervention group from January 2014 to January 2015. The nursing results of the two groups were compared. These results were also evaluated using self-rating depression scale, self-rating anxiety scale, and trait coping style questionnaire.Result: The effects of depression and anxiety intervention were significant in the intervention group (P<0.05. Com-pared with the control group, the intervention group did not significantly differ. The coping style of the intervention group elicited significant effects. Compared with the control group, the intervention group was significantly different (P < 0.05.Conclusion: Continuous nursing can relieve the negative emotion and improve the negative coping style of patients undergoing pacemaker implantation.

  7. Psychosocial aspects and mental health in children after permanent pacemaker implantation

    DEFF Research Database (Denmark)

    Andersen, C; Hørder, K; Kristensen, L;

    1994-01-01

    , and they were given a child-psychiatric evaluation consisting of a semi-structured and a child-psychiatric interview. The psychological interview used intelligence tests and the Draw-A-Person test as well as the Rorschach test. The patients had had their pacemakers during an average of 6.7 years...

  8. 76 FR 64223 - Cardiovascular Devices; Reclassification of External Pacemaker Pulse Generator Devices

    Science.gov (United States)

    2011-10-17

    ... premarket approval for external pacemaker pulse generator devices (52 FR 17732, May 11, 1987). In 2009, FDA... rule (44 FR 13284, March 9, 1979 and 44 FR 13372, March 9, 1979), the Cardiovascular Devices Panel..., 2009 (74 FR 16214, April 9, 2009). In response to that order, FDA received reclassification...

  9. Multiple photoreceptor systems control the swim pacemaker activity in box jellyfish

    DEFF Research Database (Denmark)

    Garm, Anders Lydik; Mori, S.

    2009-01-01

    Like all other cnidarian medusae, box jellyfish propel themselves through the water by contracting their bell-shaped body in discrete swim pulses. These pulses are controlled by a swim pacemaker system situated in their sensory structures, the rhopalia. Each medusa has four rhopalia each with a...

  10. Sikkerhed af magnetisk resonans-skanning hos patienter med pacemaker og implanterbar defibrillator

    DEFF Research Database (Denmark)

    Al-Sabagh, Kifah Hekmat; Christensen, Britta Ege; Thøgersen, Anna Margrethe;

    2010-01-01

    INTRODUCTION: The presence of a cardiac implantable device is ICD considered an absolute contraindication to magnetic resonance imaging (MRI). The purpose of this study was to evaluate the safety of performing MRI in patients with cardiac pacemakers and ICDs that had a compelling clinical need fo...

  11. Hyperpolarization-activated cation and T-type calcium ion channel expression in porcine and human renal pacemaker tissues.

    Science.gov (United States)

    Hurtado, Romulo; Smith, Carl S

    2016-05-01

    Renal pacemaker activity triggers peristaltic upper urinary tract contractions that propel waste from the kidney to the bladder, a process prone to congenital defects that are the leading cause of pediatric kidney failure. Recently, studies have discovered that hyperpolarization-activated cation (HCN) and T-type calcium (TTC) channel conductances underlie murine renal pacemaker activity, setting the origin and frequency and coordinating upper urinary tract peristalsis. Here, we determined whether this ion channel expression is conserved in the porcine and human urinary tracts, which share a distinct multicalyceal anatomy with multiple pacemaker sites. Double chromagenic immunohistochemistry revealed that HCN isoform 3 is highly expressed at the porcine minor calyces, the renal pacemaker tissues, whereas the kidney and urinary tract smooth muscle lacked this HCN expression. Immunofluorescent staining demonstrated that HCN(+) cells are integrated within the porcine calyx smooth muscle, and that they co-express TTC channel isoform Cav3.2. In humans, the anatomic structure of the minor calyx pacemaker was assayed via hematoxylin and eosin analyses, and enabled the visualization of the calyx smooth muscle surrounding adjacent papillae. Strikingly, immunofluorescence revealed that HCN3(+) /Cav3.2(+) cells are also localized to the human minor calyx smooth muscle. Collectively, these data have elucidated a conserved molecular signature of HCN and TTC channel expression in porcine and human calyx pacemaker tissues. These findings provide evidence for the mechanisms that can drive renal pacemaker activity in the multi-calyceal urinary tract, and potential causes of obstructive uropathies. PMID:26805464

  12. Environmental Impacts on Spiking Properties in Hodgkin–Huxley Neuron with Direct Current Stimulus

    International Nuclear Information System (INIS)

    Based on the well accepted Hodgkin–Huxley neuron model, the neuronal intrinsic excitability is studied when the neuron is subject to varying environmental temperatures, the typical impact for its regulating ways. With computer simulation, it is found that altering environmental temperature can improve or inhibit the neuronal intrinsic excitability so as to influence the neuronal spiking properties. The impacts from environmental factors can be understood that the neuronal spiking threshold is essentially influenced by the fluctuations in the environment. With the environmental temperature varying, burst spiking is realized for the neuronal membrane voltage because of the environment-dependent spiking threshold. This burst induced by changes in spiking threshold is different from that excited by input currents or other stimulus. (cross-disciplinary physics and related areas of science and technology)

  13. Environmental Impacts on Spiking Properties in Hodgkin-Huxley Neuron with Direct Current Stimulus

    Institute of Scientific and Technical Information of China (English)

    YUAN Chang-Qing; ZHAO Tong-Jun; ZHAN Yong; ZHANG Su-Hua; LIU Hui; ZHANG Yu-Hong

    2009-01-01

    Based on the well accepted Hodgkin-Huxley neuron model, the neuronal intrinsic excitability is studied when the neuron is subject to varying environmental temperatures, the typical impact for its regulating ways. With computer simulation, it is found that altering environmental temperature can improve or inhibit the neuronal intrinsic excitability so as to influence the neuronal spiking properties. The impacts from environmental factors can be understood that ,the neuronal spiking threshold is essentially influenced by the fluctuations in the environ-ment. With the environmental temperature varying, burst spiking is realized for the neuronal membrane voltage because of the environment-dependent spiking threshold. This burst induced by changes in spiking threshold is different from that excited by input currents or other stimulus.

  14. Correlation analysis of the relationship between B-type natriuretic peptide and selected echocardiographic parameters in patients with permanent pacemakers

    Directory of Open Access Journals (Sweden)

    Janusz Sielski

    2016-01-01

    Full Text Available Introduction: The present study was undertaken to evaluate the practical value of BNP measurements and echocardiographic left ventricular volume index in patients with permanent pacemakers because there are no such reports in the literature. Aim of the research: The aim of the study was to reveal multiple correlations between BNP levels and selected echocardiographic parameters of the left atrium in patients with permanent pacemakers. In the literature there are reports on the significance of BNP values and left atrial size in patients with permanent pacemakers. The results of the present study appear to be of value in the outpatient assessment of these patients. Material and methods: We analysed a group of 117 patients with permanent pacemakers (AAI/R 21 patients, DDD/R 59 patients, VVI/R 37 patients and 48 healthy volunteers serving as the control group. BNP measurements were performed on venous blood samples using Triage meters. The Simpson method and the ellipse method were used to assess the left atrium on echocardiography. Results: There was a significant correlation between BNP and maximum left atrial volume, minimum left atrial volume, and left atrial volume index in patients with AAI/R, DDD/R, and VVI/R pacemakers at 3 and 6 months after the implantation. Conclusions : In patients after implantation of permanent pacemakers there are correlations between BNP values and echocardiographic left atrial parameters, especially in patients with DDD/R pacemakers. Left atrial function improves in patients with DDD/R pacemakers. Pacemaker check-up should be extended to include BNP measurements and echocardiographic assessment of the left atrium.

  15. Cholecystokinin (CCK)-expressing neurons in the suprachiasmatic nucleus: innervation, light responsiveness and entrainment in CCK-deficient mice

    DEFF Research Database (Denmark)

    Hannibal, Jens; Hundahl, Christian; Fahrenkrug, Jan;

    2010-01-01

    FOS, and did not express the core clock protein PER1. Accordingly, CCK-deficient mice showed normal entrainment and had similar τ, light-induced phase shift and negative masking behaviour as wild-type animals. In conclusion, CCK signalling seems not to be involved directly in light-induced resetting of the......The suprachiasmatic nucleus (SCN) is the principal pacemaker driving circadian rhythms of physiology and behaviour. Neurons within the SCN express both classical and neuropeptide transmitters which regulate clock functions. Cholecyctokinin (CCK) is a potent neurotransmitter expressed in neurons of...... clock or in regulating core clock function. The expression of CCK in a subpopulation of neurons, which do not belonging to either the VIP or AVP cells but which have synaptic contacts to both cell types and reverse innervation of CCK neurons from VIP neurons, suggests that the CCK neurons may act in non...

  16. Cholecystokinin (CCK)-expressing neurons in the suprachiasmatic nucleus: innervation, light responsiveness and entrainment in CCK-deficient mice

    DEFF Research Database (Denmark)

    Hannibal, Jens; Hundahl, Christian; Fahrenkrug, Jan;

    2010-01-01

    FOS, and did not express the core clock protein PER1. Accordingly, CCK-deficient mice showed normal entrainment and had similar t, light-induced phase shift and negative masking behaviour as wild-type animals. In conclusion, CCK signalling seems not to be involved directly in light-induced resetting of the......The suprachiasmatic nucleus (SCN) is the principal pacemaker driving circadian rhythms of physiology and behaviour. Neurons within the SCN express both classical and neuropeptide transmitters which regulate clock functions. Cholecyctokinin (CCK) is a potent neurotransmitter expressed in neurons of...... clock or in regulating core clock function. The expression of CCK in a subpopulation of neurons, which do not belonging to either the VIP or AVP cells but which have synaptic contacts to both cell types and reverse innervation of CCK neurons from VIP neurons, suggests that the CCK neurons may act in non...

  17. Shengmaisan Regulates Pacemaker Potentials in Interstitial Cells of Cajal in Mice

    Directory of Open Access Journals (Sweden)

    Kim Byung Joo

    2013-12-01

    Full Text Available Objectives: Shengmaisan (SMS is a traditional Chinese medicine prescription widely used for the treatment of diverse organs in Korea. The interstitial cells of Cajal (ICCs are pacemaker cells that play an important role in the generation of coordinated gastrointestinal (GI motility. We have aimed to investigate the effects of SMS in the ICCs in the mouse small intestine. Methods: To dissociate the ICCs, we used enzymatic digestions from the small intestine in a mouse. After that, the ICCs were identified immunologically by using the anti-c-kit antibody. In the ICCs, the electrophysiological whole-cell patch-clamp configuration was used to record pacemaker potentials in the cultured ICCs. Results: The ICCs generated pacemaker potentials in the mouse small intestine. SMS produced membrane depolarization with concentration-dependent manners in the current clamp mode. Pretreatment with a Ca2+ free solution and thapsigargin, a Ca2+-ATPase inhibitor in the endoplasmic reticulum, stopped the generation of the pacemaker potentials. In the case of Ca2+-free solutions, SMS induced membrane depolarizations. However, when thapsigargin in a bath solution was applied, the membrane depolarization was not produced by SMS. The membrane depolarizations produced by SMS were inhibited by U-73122, an active phospholipase C (PLC inhibitors. Furthermore, chelerythrine and calphostin C, a protein kinase C (PKC inhibitors had no effects on SMS-induced membrane depolarizations. Conclusions: These results suggest that SMS might affect GI motility by modulating the pacemaker activity through an internal Ca2+- and PLC-dependent and PKC-independent pathway in the ICCs.

  18. Temporal correlations in neuronal avalanche occurrence

    Science.gov (United States)

    Lombardi, F.; Herrmann, H. J.; Plenz, D.; de Arcangelis, L.

    2016-04-01

    Ongoing cortical activity consists of sequences of synchronized bursts, named neuronal avalanches, whose size and duration are power law distributed. These features have been observed in a variety of systems and conditions, at all spatial scales, supporting scale invariance, universality and therefore criticality. However, the mechanisms leading to burst triggering, as well as the relationship between bursts and quiescence, are still unclear. The analysis of temporal correlations constitutes a major step towards a deeper understanding of burst dynamics. Here, we investigate the relation between avalanche sizes and quiet times, as well as between sizes of consecutive avalanches recorded in cortex slice cultures. We show that quiet times depend on the size of preceding avalanches and, at the same time, influence the size of the following one. Moreover we evidence that sizes of consecutive avalanches are correlated. In particular, we show that an avalanche tends to be larger or smaller than the following one for short or long time separation, respectively. Our analysis represents the first attempt to provide a quantitative estimate of correlations between activity and quiescence in the framework of neuronal avalanches and will help to enlighten the mechanisms underlying spontaneous activity.

  19. Hyperbolic Plykin attractor can exist in neuron models

    DEFF Research Database (Denmark)

    Belykh, V.; Belykh, I.; Mosekilde, Erik

    2005-01-01

    Strange hyperbolic attractors are hard to find in real physical systems. This paper provides the first example of a realistic system, a canonical three-dimensional (3D) model of bursting neurons, that is likely to have a strange hyperbolic attractor. Using a geometrical approach to the study of the...... neuron model, we derive a flow-defined Poincare map giving ail accurate account of the system's dynamics. In a parameter region where the neuron system undergoes bifurcations causing transitions between tonic spiking and bursting, this two-dimensional map becomes a map of a disk with several periodic...... holes. A particular case is the map of a disk with three holes, matching the Plykin example of a planar hyperbolic attractor. The corresponding attractor of the 3D neuron model appears to be hyperbolic (this property is not verified in the present paper) and arises as a result of a two-loop (secondary...

  20. The development of a system for the evaluation of electromagnetic interference with pacemaker function: hazards in the aircraft environment.

    Science.gov (United States)

    McDeller, A G; Toff, W D; Hobbs, R A; Robb, D J; Camm, A J

    1989-01-01

    It has been recognized for many years that the electromagnetic (EM) environment within aircraft presents a potential hazard to the subject with a pacemaker. Most of the information currently available is, however, several years old and may not be strictly relevant to modern pacemakers and the electromagnetic environment found in today's civil aircraft. In mid 1986 it was therefore decided to investigate the effect on a number of currently available unipolar pacemakers of typical levels of electromagnetic interference encountered in civil aircraft. PMID:2746623

  1. Infection and twiddler syndrome in a dog with addison's disease, complete heart block, and wandering artificial pacemakers

    International Nuclear Information System (INIS)

    Third degree heart block developed in an obese, 10-year-old Labrador retriever with adrenocortical failure. A permanent transthoracic pacemaker was fitted, but the pulse generator migrated 2 years later, to the ventral part of the flank, where an abscess formed. A new pacemaker was fitted, but also migrated and rotated and a syndrome analogous to Twiddler's syndrome in man developed. After a further 2 years the second pacemaker was located, encapsulated within the right pleural cavity. Culture of the brownish exudate around the pulse generator yielded Pseudomonas sp

  2. Bursting thalamic responses in awake monkey contribute to visual detection and are modulated by corticofugal feedback

    Directory of Open Access Journals (Sweden)

    Kenneth L Grieve

    2014-05-01

    Full Text Available The lateral geniculate nucleus is the gateway for visual information en route to the visual cortex. Neural activity is characterized by the existence of 2 firing modes: burst and tonic. Originally associated with sleep, bursts have now been postulated to be a part of the normal visual response, structured to increase the probability of cortical activation, able to act as a “wake-up” call to the cortex. We investigated a potential role for burst in the detection of novel stimuli by recording neuronal activity in the LGN of behaving monkeys during a visual detection task. Our results show that bursts are often the neuron’s first response, and are more numerous in the response to attended target stimuli than to unattended distractor stimuli. Bursts are indicators of the task novelty, as repetition decreased bursting. Because the primary visual cortex is the major modulatory input to the LGN, we compared the results obtained in control conditions with those observed when cortical activity was reduced by TMS. This cortical deactivation reduced visual response related bursting by 90%. These results highlight a novel role for the thalamus, able to code higher order image attributes as important as novelty early in the thalamo-cortical conversation.

  3. Evaluation of Burst Loss Rate of an Optical Burst Switching (OBS) Network with Wavelength Conversion Capability

    OpenAIRE

    Reza, Md. Shamim; Hossain, Md. Maruf; Majumder, Satya Prasad

    2010-01-01

    This paper presents a new analytical model for calculating burst loss rate (BLR) in a slotted optical burst switched network. The analytical result leads to a framework which provides guidelines for optical burst switched networks. Wavelength converter is used for burst contention resolution. The effect of several design parameters such as burst arrival probability, wavelength conversion capability, number of slots per burst and number of wavelengths is incorporated on the above performance m...

  4. Nonlinear Dynamics of Neuronal Excitability, Oscillations, and Coincidence Detection

    OpenAIRE

    Rinzel, John; Huguet, Gemma

    2013-01-01

    We review some widely studied models and firing dynamics for neuronal systems, both at the single cell and network level, and dynamical systems techniques to study them. In particular, we focus on two topics in mathematical neuroscience that have attracted the attention of mathematicians for decades: single-cell excitability and bursting. We review the mathematical framework for three types of excitability and onset of repetitive firing behavior in single-neuron models and their relation with...

  5. Design of Cortical Neuron Circuits With VLSI Design Approach

    OpenAIRE

    A.D.Tete; A. Y. Deshmukh

    2011-01-01

    A simple CMOS circuitry using very less number of MOSFETs reproduce most of the electrophysiologicalcortical neuron types and is capable of producing a variety of different behaviors with diversity similar tothat of real biological neuron cell. The firing pattern of basic cell classes like regular spiking (RS),chattering (CH), intrinsic bursting (IB) and fast spiking(FS) are obtained with a simple adjustment of onlyone biasing voltage makes circuit suitable for applications in reconfigurable ...

  6. Mathematical Modeling of Subthreshold Resonant Properties in Pyloric Dilator Neurons

    Science.gov (United States)

    Vazifehkhah Ghaffari, Babak; Kouhnavard, Mojgan; Aihara, Takeshi; Kitajima, Tatsuo

    2015-01-01

    Various types of neurons exhibit subthreshold resonance oscillation (preferred frequency response) to fluctuating sinusoidal input currents. This phenomenon is well known to influence the synaptic plasticity and frequency of neural network oscillation. This study evaluates the resonant properties of pacemaker pyloric dilator (PD) neurons in the central pattern generator network through mathematical modeling. From the pharmacological point of view, calcium currents cannot be blocked in PD neurons without removing the calcium-dependent potassium current. Thus, the effects of calcium (ICa) and calcium-dependent potassium (IKCa) currents on resonant properties remain unclear. By taking advantage of Hodgkin-Huxley-type model of neuron and its equivalent RLC circuit, we examine the effects of changing resting membrane potential and those ionic currents on the resonance. Results show that changing the resting membrane potential influences the amplitude and frequency of resonance so that the strength of resonance (Q-value) increases by both depolarization and hyperpolarization of the resting membrane potential. Moreover, hyperpolarization-activated inward current (Ih) and ICa (in association with IKCa) are dominant factors on resonant properties at hyperpolarized and depolarized potentials, respectively. Through mathematical analysis, results indicate that Ih and IKCa affect the resonant properties of PD neurons. However, ICa only has an amplifying effect on the resonance amplitude of these neurons. PMID:25960999

  7. Glutamate-induced glutamate release: A proposed mechanism for calcium bursting in astrocytes

    Science.gov (United States)

    Larter, Raima; Craig, Melissa Glendening

    2005-12-01

    Here we present a new model for the generation of complex calcium-bursting patterns in astrocytes, a type of brain cell recently implicated in a variety of neural functions including memory formation. The model involves two positive feedback processes, in which the key feedback species are calcium ion and glutamate. The latter is the most abundant excitatory neurotransmitter in the brain and has been shown to be involved in bidirectional communication between astrocytes and nearby neurons. The glutamate feedback process considered here is shown to be critical for the generation of complex bursting oscillations in the astrocytes and to, perhaps, code for information which may be passed from neuron to neuron via the astrocyte. These processes may be involved in memory storage and formation as well as in mechanisms which lead to dynamical diseases such as epilepsy.

  8. Signal transfer within a cultured asymmetric cortical neuron circuit

    Science.gov (United States)

    Isomura, Takuya; Shimba, Kenta; Takayama, Yuzo; Takeuchi, Akimasa; Kotani, Kiyoshi; Jimbo, Yasuhiko

    2015-12-01

    Objective. Simplified neuronal circuits are required for investigating information representation in nervous systems and for validating theoretical neural network models. Here, we developed patterned neuronal circuits using micro fabricated devices, comprising a micro-well array bonded to a microelectrode-array substrate. Approach. The micro-well array consisted of micrometre-scale wells connected by tunnels, all contained within a silicone slab called a micro-chamber. The design of the micro-chamber confined somata to the wells and allowed axons to grow through the tunnels bidirectionally but with a designed, unidirectional bias. We guided axons into the point of the arrow structure where one of the two tunnel entrances is located, making that the preferred direction. Main results. When rat cortical neurons were cultured in the wells, their axons grew through the tunnels and connected to neurons in adjoining wells. Unidirectional burst transfers and other asymmetric signal-propagation phenomena were observed via the substrate-embedded electrodes. Seventy-nine percent of burst transfers were in the forward direction. We also observed rapid propagation of activity from sites of local electrical stimulation, and significant effects of inhibitory synapse blockade on bursting activity. Significance. These results suggest that this simple, substrate-controlled neuronal circuit can be applied to develop in vitro models of the function of cortical microcircuits or deep neural networks, better to elucidate the laws governing the dynamics of neuronal networks.

  9. Qualitative-Modeling-Based Silicon Neurons and Their Networks

    Science.gov (United States)

    Kohno, Takashi; Sekikawa, Munehisa; Li, Jing; Nanami, Takuya; Aihara, Kazuyuki

    2016-01-01

    The ionic conductance models of neuronal cells can finely reproduce a wide variety of complex neuronal activities. However, the complexity of these models has prompted the development of qualitative neuron models. They are described by differential equations with a reduced number of variables and their low-dimensional polynomials, which retain the core mathematical structures. Such simple models form the foundation of a bottom-up approach in computational and theoretical neuroscience. We proposed a qualitative-modeling-based approach for designing silicon neuron circuits, in which the mathematical structures in the polynomial-based qualitative models are reproduced by differential equations with silicon-native expressions. This approach can realize low-power-consuming circuits that can be configured to realize various classes of neuronal cells. In this article, our qualitative-modeling-based silicon neuron circuits for analog and digital implementations are quickly reviewed. One of our CMOS analog silicon neuron circuits can realize a variety of neuronal activities with a power consumption less than 72 nW. The square-wave bursting mode of this circuit is explained. Another circuit can realize Class I and II neuronal activities with about 3 nW. Our digital silicon neuron circuit can also realize these classes. An auto-associative memory realized on an all-to-all connected network of these silicon neurons is also reviewed, in which the neuron class plays important roles in its performance. PMID:27378842

  10. Bursts in intermittent aeolian saltation

    CERN Document Server

    Carneiro, M V; Herrmann, H J

    2014-01-01

    Close to the onset of Aeolian particle transport through saltation we find in wind tunnel experiments a regime of intermittent flux characterized by bursts of activity. Scaling laws are observed in the time delay between each burst and in the measurements of the wind fluctuations at the critical Shields number $\\theta_c$. The time delay between each burst decreases on average with the increase of the Shields number until saltation becomes non-intermittent and the sand flux becomes continuous. A numerical model for saltation including the wind-entrainment from the turbulent fluctuations can reproduce these observations and gives insight about their origin. We present here also for the first time measurements showing that with feeding it becomes possible to sustain intermittent flux even below the threshold $\\theta_c$ for natural saltation initiation.

  11. Improved quality of life after treatment of prolonged asystole during breath holding spells with a cardiac pacemaker

    Directory of Open Access Journals (Sweden)

    Bruno Kolterer

    2015-01-01

    Conclusion: Cardiac pacing using appropriate pacemaker settings seems effective in the prevention of LOC and reduction of the frequency of BHS. Our results imply a reduction of subjective stress levels of patients and parents as well as an increased quality of everyday life. After all, randomized controlled trials of the influence of cardiac pacemaker implantation on subjective stress levels in patients with BHS are needed.

  12. Analysis of Cumulative Dose to Implanted Pacemaker According to Various IMRT Delivery Methods: Optimal Dose Delivery Versus Dose Reduction Strategy

    International Nuclear Information System (INIS)

    Cancer patients with implanted cardiac pacemaker occasionally require radiotherapy. Pacemaker may be damaged or malfunction during radiotherapy due to ionizing radiation or electromagnetic interference. Although radiotherapy should be planned to keep the dose to pacemaker as low as possible not to malfunction ideally, current radiation treatment planning (RTP) system does not accurately calculate deposited dose to adjacent field border or area beyond irradiated fields. In terms of beam delivery techniques using multiple intensity modulated fields, dosimetric effect of scattered radiation in high energy photon beams is required to be detailed analyzed based on measurement data. The aim of this study is to evaluate dose discrepancies of pacemaker in a RTP system as compared to measured doses. We also designed dose reduction strategy limited value of 2 Gy for radiation treatment patients with cardiac implanted pacemaker. Total accumulated dose of 145 cGy based on in-vivo dosimetry was satisfied with the recommendation criteria to prevent malfunction of pacemaker in SS technique. However, the 2 mm lead shielder enabled the scattered doses to reduce up to 60% and 40% in the patient and the phantom, respectively. The SS technique with the lead shielding could reduce the accumulated scattered doses less than 100 cGy. Calculated and measured doses were not greatly affected by the beam delivery techniques. In-vivo and measured doses on pacemaker position showed critical dose discrepancies reaching up to 4 times as compared to planned doses in RTP. The current SS technique could deliver lower scattered doses than recommendation criteria, but use of 2 mm lead shielder contributed to reduce scattered doses by 60%. The tertiary lead shielder can be useful to prevent malfunction or electrical damage of implanted pacemakers during radiotherapy. It is required to estimate more accurate scattered doses of the patient or medical device in RTP to design proper dose reduction strategy.

  13. A premature low-birth-weight infant with congenital complete atrioventricular block and myocarditis successfully treated by staged pacemaker implantation.

    Science.gov (United States)

    Fujioka, Tao; Nii, Masaki; Tanaka, Yasuhiko

    2016-06-01

    Congenital complete atrioventricular block is a known lethal condition. Although antenatal diagnosis and the technical advances of pacemaker treatment have reduced its mortality, treatment of premature babies with significant myocardial damage remains a challenge. In this paper, we report the case of a premature low-birth-weight infant with congenital complete atrioventricular block and extremely low ventricular rate, fetal hydrops, and myocarditis who was successfully treated with staged permanent pacemaker implantation. PMID:27071550

  14. Hierarchical Micro- and Nanostructured Superhydrophobic Surfaces to Reduce Fibrous Encapsulation of Pacemaker Leads : Nanotechnology in Practical Applications

    OpenAIRE

    Carlsson, Louise

    2008-01-01

    The purpose of this master’s thesis was to, by the use of nanotechnology, improve material properties of the biomedical polymer Optim™, used as the insulation of pacemaker leads. Improved material properties are required to reduce the extent of fibrous encapsulation of the leads. Today, laser ablation is used to be able to remove the pacemaker lead because of the fibrous tissue, which can cause the lead to adhere to vascular structures. Consequently, the laser ablation results in risks of dam...

  15. ANAESTHETIC MANAGEMENT OF ELDERLY PATIENT WITH PERMANENT PACEMAKER FOR EXCISION OF SUSPECTED ADRENAL MASS – A CHALLENGING CASE

    Directory of Open Access Journals (Sweden)

    Ketaki

    2014-01-01

    Full Text Available Pacemakers and the underlying pathophysiologies leading to their implantation present challenges to the anesthetist 1 . Patients with an implanted cardiac pulse generator often have significant co - morbid disease in addition to their cardiac rhythm disturbance. Our ability to care for these patients requires attention to both their medical , psychological and surgical problems. We present the case of a 60 year old man with a permanent pacemaker posted for excision of a suspected adrenal mass.

  16. The Intrinsic Electrophysiological Properties of Mammalian Neurons: Insights into Central Nervous System Function

    Science.gov (United States)

    Llinas, Rodolfo R.

    1988-12-01

    This article reviews the electroresponsive properties of single neurons in the mammalian central nervous system (CNS). In some of these cells the ionic conductances responsible for their excitability also endow them with autorhythmic electrical oscillatory properties. Chemical or electrical synaptic contacts between these neurons often result in network oscillations. In such networks, autorhytmic neurons may act as true oscillators (as pacemakers) or as resonators (responding preferentially to certain firing frequencies). Oscillations and resonance in the CNS are proposed to have diverse functional roles, such as (i) determining global functional states (for example, sleep-wakefulness or attention), (ii) timing in motor coordination, and (iii) specifying connectivity during development. Also, oscillation, especially in the thalamo-cortical circuits, may be related to certain neurological and psychiatric disorders. This review proposes that the autorhythmic electrical properties of central neurons and their connectivity form the basis for an intrinsic functional coordinate system that provides internal context to sensory input.

  17. Local vasotocin modulation of the pacemaker nucleus resembles distinct electric behaviors in two species of weakly electric fish.

    Science.gov (United States)

    Perrone, Rossana; Migliaro, Adriana; Comas, Virginia; Quintana, Laura; Borde, Michel; Silva, Ana

    2014-01-01

    The neural bases of social behavior diversity in vertebrates have evolved in close association with hypothalamic neuropeptides. In particular, arginine-vasotocin (AVT) is a key integrator underlying differences in behavior across vertebrate taxa. Behavioral displays in weakly electric fish are channeled through specific patterns in their electric organ discharges (EODs), whose rate is ultimately controlled by a medullary pacemaker nucleus (PN). We first explored interspecific differences in the role of AVT as modulator of electric behavior in terms of EOD rate between the solitary Gymnotus omarorum and the gregarious Brachyhypopomus gauderio. In both species, AVT IP injection (10μg/gbw) caused a progressive increase of EOD rate of about 30%, which was persistent in B. gauderio, and attenuated after 30min in G. omarorum. Secondly, we demonstrated by in vitro electrophysiological experiments that these behavioral differences can be accounted by dissimilar effects of AVT upon the PN in itself. AVT administration (1μM) to the perfusion bath of brainstem slices containing the PN produced a small and transient increase of PN activity rate in G. omarorum vs the larger and persistent increase previously reported in B. gauderio. We also identified AVT neurons, for the first time in electric fish, using immunohistochemistry techniques and confirmed the presence of hindbrain AVT projections close to the PN that might constitute the anatomical substrate for AVT influences on PN activity. Taken together, our data reinforce the view of the PN as an extremely plastic medullary central pattern generator that not only responds to higher influences to adapt its function to diverse contexts, but also is able to intrinsically shape its response to neuropeptide actions, thus adding a hindbrain target level to the complexity of the global integration of central neuromodulation of electric behavior. PMID:25125289

  18. Dynamical state of the network determines the efficacy of single neuron properties in shaping the network activity

    OpenAIRE

    Ajith Sahasranamam; Ioannis Vlachos; Ad Aertsen; Arvind Kumar

    2016-01-01

    Spike patterns are among the most common electrophysiological descriptors of neuron types. Surprisingly, it is not clear how the diversity in firing patterns of the neurons in a network affects its activity dynamics. Here, we introduce the state-dependent stochastic bursting neuron model allowing for a change in its firing patterns independent of changes in its input-output firing rate relationship. Using this model, we show that the effect of single neuron spiking on the network dynamics is ...

  19. Transition to complete synchronization via near-synchronization in two coupled chaotic neurons

    Institute of Scientific and Technical Information of China (English)

    Wang Qing-Yun; Lu Qi-Shao; Wang Hai-Xia

    2005-01-01

    The synchronization transition in two coupled chaotic Morris-Lecar (ML) neurons with gap junction is studied with the coupling strength increasing. The conditional Lyapunov exponents, along with the synchronization errors are calculated to diagnose synchronization of two coupled chaotic ML neurons. As a result, it is shown that the increase in the coupling strength leads to incoherence, then induces a transition process consisting of three different synchronization states in succession, namely, burst synchronization, near-synchronization and embedded burst synchronization, and achieves complete synchronization of two coupled neurons finally. These sequential transitions to synchronization reveal a new transition route from incoherence to complete synchronization in coupled systems with multi-time scales.

  20. Cannabinoid receptor activation reverses kainate-induced synchronized population burst firing in rat hippocampus

    Directory of Open Access Journals (Sweden)

    Rob Mason

    2009-06-01

    Full Text Available Cannabinoids have been shown to possess anticonvulsant properties in whole animal models of epilepsy. The present investigation sought to examine the effects of cannabinoid receptor activation on kainic acid (KA-induced epileptiform neuronal excitability. Under urethane anesthesia, acute KA treatment (10 mg/kg, i.p. entrained the spiking mode of simultaneously recorded neurons from random firing to synchronous bursting (% change in burst rate. Injection of the high-affinity cannabinoid agonist (--11-hydroxy-8-tetrahydrocannabinol-dimethyl-heptyl (HU210, 100 µg/kg, i.p. following KA markedly reduced the burst frequency (% decrease in burst frequency and reversed synchronized firing patterns back to baseline levels. Pre-treatment with the central cannabinoid receptor (CB1 antagonist N-piperidino-5-(4-clorophenyl-1-(2,4-dichlorophenyl-4-methyl-3-pyrazole-carboxamide (rimonabant, SR141716A 3 mg/kg, i.p. completely prevented the actions of HU210. The present results indicate that cannabinoids exert their antiepileptic effects by impeding pathological synchronization of neuronal networks in the hippocampus.

  1. Cannabinoid receptor activation reverses kainate-induced synchronized population burst firing in rat hippocampus.

    Science.gov (United States)

    Mason, Rob; Cheer, Joseph F

    2009-01-01

    Cannabinoids have been shown to possess anticonvulsant properties in whole animal models of epilepsy. The present investigation sought to examine the effects of cannabinoid receptor activation on kainic acid (KA)-induced epileptiform neuronal excitability. Under urethane anesthesia, acute KA treatment (10 mg kg(-1), i.p.) entrained the spiking mode of simultaneously recorded neurons from random firing to synchronous bursting (% change in burst rate). Injection of the high-affinity cannabinoid agonist (-)-11-hydroxy-8-tetrahydrocannabinol-dimethyl-heptyl (HU210, 100 mug kg(-1), i.p.) following KA markedly reduced the burst frequency (% decrease in burst frequency) and reversed synchronized firing patterns back to baseline levels. Pre-treatment with the central cannabinoid receptor (CB1) antagonist N-piperidino-5-(4-clorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole-carboxamide (rimonabant, SR141716A 3 mg kg(-1), i.p.) completely prevented the actions of HU210. The present results indicate that cannabinoids exert their antiepileptic effects by impeding pathological synchronization of neuronal networks in the hippocampus. PMID:19562087

  2. M-Type Potassium Channels Modulate the Intrinsic Excitability of Infralimbic Neurons and Regulate Fear Expression and Extinction

    OpenAIRE

    Santini, Edwin; James T. Porter

    2010-01-01

    Growing evidence indicates that the activity of infralimbic prefrontal cortex (IL) is critical for inhibiting inappropriate fear responses following extinction learning. Recently, we showed that fear conditioning and extinction alter the intrinsic excitability and bursting of IL pyramidal neurons in brain slices. IL neurons from Sprague Dawley rats expressing high fear had lower intrinsic excitability and bursting than those from rats expressing low fear, suggesting that regulating the intrin...

  3. Study on incidence of pulmonary embolism in patients with cardiac pacemakers using lung perfusion mapping and ventilation scanning

    International Nuclear Information System (INIS)

    We investigated pulmonary perfusion mapping and ventilation scanning employing 99mTC-MMA and 81mKr-Gas in patients with DDD and VVI cardiac pacemaker implantation. In 51 cases among 175 patients we observed some defects which matched the results from lung perfusion scanning in the pulmonary segments and sub-segments. These were diagnosed as pulmonary embolism after the possibility of other pulmonary diseases was rejected. The incidence rate of pulmonary embolism in patients with VVI (Ventricular pacing/sensing, inhibited type) pacemakers was 47 out of 138, or 34.1%, especially for those who received a pulmonary scanning examination whithin 6 months after pacemaker implantation. In contrast, those who were examined after 6 months had lower rates as well as chronological factors. The incidence rate of pulmonary embolism in 37 patients with DDD (Double chamber pacing/sensing, double modes of response) pacemakers was 10.8%, considerably lower than that for patients with VVI pacemakers. Therefore, one main factor of pulmonary embolism in patients with pacemakers could be the non-physiological phase of the contractions of both atria and ventricles. Other factors, such as the presence of foreign bodies in the endocardium, aging, and hypertension, could also promote pulmonary embolism. (author)

  4. Prevalence of sleep-disordered breathing in elderly patients with cardiac pacemaker: a case-control study

    Institute of Scientific and Technical Information of China (English)

    Haiyun WU; Shiwen WANG; Jianping JIA; Wenli ZHANG; Qiang XU

    2005-01-01

    Objective To investigate the prevalence of sleep-disordered breathing in elderly patients with permanent cardiac pacemaker implantation due to bradyarrhythmias, and the relationship between pacing mode and patients' sleep apnea-hypopnea index.Methods Forty-four elderly patients (>60 years) with cardiac pacemaker and their 44 controls matched for gender, age, body mass index and cardiovascular morbidity were studied using polysomnography or portable sleep monitoring device. Results Prevalence of sleep-disordered breathing (apnea-hypopnea index ≥5/h) was 44.7% and the mean apnea-hypopnea index was 8.2 ±4.1/h in the cardiac pacemaker group, which were significantly higher than those in control subjects (25% and 4.6±2.4/h, respectively, P<0.01 and P<0.05). The mean apnea-hypopnea index of patients with DDD or AAI pacemaker was significantly lower than that of patients with VVI pacemaker. Conclusions Sleep-disordered breathing was more common in patients who had their cardiac pacemaker implanted due to bradyarrhythmias than in their matched controls. Compared with VVI pacing, DDD or AAI pacing may be more beneficial to patients with bradyarrhythmias and sleep-disordered breathing.

  5. US Army Nuclear Burst Detection System (NBDS)

    International Nuclear Information System (INIS)

    The Nuclear Burst Detection System (NBDS) was developed to meet the Army requirements of an unattended, automatic nuclear burst reporting system. It provides pertinent data for battlefield commanders on a timely basis with high reliability

  6. Preemption window for burst differentiation in OBS

    OpenAIRE

    Klinkowski, Miroslaw; Careglio, Davide; Morató, Daniel; Solé Pareta, Josep

    2008-01-01

    This paper presents a novel control architecture for optical burst switching networks to efficiently apply burst preemption without the resources overbooking, which is specific to conventional OBS. Simulation results prove the effectiveness of this proposal.

  7. Persistent wandering atrial pacemaker after epinephrine overdosing – a case report

    Directory of Open Access Journals (Sweden)

    Aburawi Elhadi H

    2013-01-01

    Full Text Available Abstract Background Long-term complications of sympathomimetic drug overdosing have not been adequately investigated in infants and young children. Despite reports discouraging their use in children, these formulations are frequently administered for “cold-like symptoms”. Their frequent adverse events are different forms of arrhythmias, including multifocal atrial tachycardia. Case presentation A 3-year-old toddler developed multifocal atrial tachycardia following an iatrogenic overdose of epinephrine accidentally administered intravenously. His ECG showed wandering atrial pacemaker (p-waves with different origins and configurations that persisted for at least one year. This event demonstrated the sensitivity of young children to the sympathomimetic drugs, especially overdosing. Conclusions Health care providers and parents should be warned of toxicities associated with sympathomimetic drug overdosing. Future studies are needed to determine whether wandering atrial pacemaker is a potential long-term complication of high-dose sympathomimetics.

  8. Percutaneous extraction of inadvertently placed left-sided pacemaker leads with complete cerebral embolic protection.

    Science.gov (United States)

    Bahadorani, John N; Schricker, Amir A; Pretorius, Victor G; Birgersdotter-Green, Ulrika; Dominguez, Arturo; Mahmud, Ehtisham

    2015-10-01

    Lead wire malposition is a known, but rare complication of permanent pacemaker or defibrillator implantation. The actual incidence and prevalence is unknown and management options for inadvertent left ventricular lead malposition have not been uniform. Current recommendations include systemic anticoagulation with warfarin or surgical lead removal with circulatory arrest for compelling clinical scenarios. Percutaneous left-sided lead extraction is contraindicated due to the potentially increased risk of thromboembolic complications associated with this procedure. To our knowledge, this is the first report of percutaneous extraction of inadvertently placed left ventricular and left atrial endocardial pacemaker leads with flow-preserving complete cerebral embolic protection. We also review the current literature regarding the incidence, management, and percutaneous extraction of left-sided cardiac leads. PMID:25581608

  9. Pacemakers and implantable cardioverter defibrillators, unknown to chest radiography: Review, complications and systematic reading

    International Nuclear Information System (INIS)

    Highlights: •Radiologists have an important function in the evaluation of these devices. •We revise their radiological appearances and possible complications. •The knowledge in normal aspects and complications is important for radiologist. •To ensure an accurate reading of the chest x-ray, we present a systematic approach. -- Abstract: Chest X-ray is the imaging technique of choice for an initial study of pacemakers and implantable cardio-defibrillators (ICD). Radiologists have an important role in the evaluation of its initial placement and in the assessment during its follow-up. For this reason, it is necessary to know not only the different existing devices and its components but also the reasons of malfunction or possible complications. The purpose of this article is to do a systematic review of the different types of pacemakers and ICD. We review their usual radiological appearances, the possible complications which might take place and its causes of malfunctioning

  10. Pacemakers and implantable cardioverter defibrillators, unknown to chest radiography: Review, complications and systematic reading

    Energy Technology Data Exchange (ETDEWEB)

    Alandete Germán, Salvador Pascual, E-mail: salaiger@gmail.com; Isarria Vidal, Santiago, E-mail: isarria@comv.es; Domingo Montañana, María Luisa, E-mail: domingo.luimon@gmail.com; De la vía Oraá, Esperanza, E-mail: esviao82@gmail.com; Vilar Samper, José, E-mail: vilarsamper@gmail.com

    2015-03-15

    Highlights: •Radiologists have an important function in the evaluation of these devices. •We revise their radiological appearances and possible complications. •The knowledge in normal aspects and complications is important for radiologist. •To ensure an accurate reading of the chest x-ray, we present a systematic approach. -- Abstract: Chest X-ray is the imaging technique of choice for an initial study of pacemakers and implantable cardio-defibrillators (ICD). Radiologists have an important role in the evaluation of its initial placement and in the assessment during its follow-up. For this reason, it is necessary to know not only the different existing devices and its components but also the reasons of malfunction or possible complications. The purpose of this article is to do a systematic review of the different types of pacemakers and ICD. We review their usual radiological appearances, the possible complications which might take place and its causes of malfunctioning.

  11. α-Calcium calmodulin kinase II modulates the temporal structure of hippocampal bursting patterns.

    Directory of Open Access Journals (Sweden)

    Jeiwon Cho

    Full Text Available The alpha calcium calmodulin kinase II (α-CaMKII is known to play a key role in CA1/CA3 synaptic plasticity, hippocampal place cell stability and spatial learning. Additionally, there is evidence from hippocampal electrophysiological slice studies that this kinase has a role in regulating ion channels that control neuronal excitability. Here, we report in vivo single unit studies, with α-CaMKII mutant mice, in which threonine 305 was replaced with an aspartate (α-CaMKII(T305D mutants, that indicate that this kinase modulates spike patterns in hippocampal pyramidal neurons. Previous studies showed that α-CaMKII(T305D mutants have abnormalities in both hippocampal LTP and hippocampal-dependent learning. We found that besides decreased place cell stability, which could be caused by their LTP impairments, the hippocampal CA1 spike patterns of α-CaMKII(T305D mutants were profoundly abnormal. Although overall firing rate, and overall burst frequency were not significantly altered in these mutants, inter-burst intervals, mean number of intra-burst spikes, ratio of intra-burst spikes to total spikes, and mean intra-burst intervals were significantly altered. In particular, the intra burst intervals of place cells in α-CaMKII(T305D mutants showed higher variability than controls. These results provide in vivo evidence that besides its well-known function in synaptic plasticity, α-CaMKII, and in particular its inhibitory phosphorylation at threonine 305, also have a role in shaping the temporal structure of hippocampal burst patterns. These results suggest that some of the molecular processes involved in acquiring information may also shape the patterns used to encode this information.

  12. Detecting pipe bursts by monitoring water demand

    NARCIS (Netherlands)

    Bakker, M.; Vreeburg, J.H.G.; Van der Roer, M.; Sperber, V.

    2012-01-01

    An algorithm which compares measured and predicted water demands to detect pipe bursts was developed and tested on three data sets of water demand and reported pipe bursts of three years. The algorithm proved to be able to detect bursts where the water loss exceeds 30% of the average water demand in

  13. Periodicities in gamma ray bursts

    International Nuclear Information System (INIS)

    Gamma ray burst models based on magnetic neutron stars face a problem of account for the scarcity of observed periods. Both this scarcity and the typical period found when any is detected are explained if the neutron stars are accreting in binary systems

  14. Timing of human sleep: recovery process gated by a circadian pacemaker

    OpenAIRE

    DAAN, S; BEERSMA, DGM; BORBELY, AA

    1984-01-01

    A model for the timing of human sleep is presented, It is based on a sleep-regulating variable (S)-possibly, but not necessarily, associated with a neurochemical substance-which increases during wakefulness and decreases during sleep. Sleep onset is triggered when S approaches an upper threshold (H); awakening occurs when S reaches a lower threshold (L). The thresholds show a circadian rhythm controlled by a single circadian pacemaker. Time constants of the S process were derived from rates o...

  15. Treatment of pacemaker-induced superior vena cava syndrome by balloon angioplasty and stenting.

    LENUS (Irish Health Repository)

    Klop, B

    2011-01-01

    Superior vena cava (SVC) syndrome is a rare but serious complication after pacemaker implantation. This report describes three cases of SVC syndrome treated with venoplasty and venous stenting, with an average follow-up of 30.7 (±3.1) months. These cases illustrate that the definitive diagnosis, and the extent and location of venous obstruction, can only be determined by venography.

  16. Involvement of Adherence and Adhesion Staphylococcus epidermidis Genes in Pacemaker Lead-Associated Infections

    OpenAIRE

    Klug, Didier; Wallet, Frédéric; Kacet, Salem; Courcol, René J.

    2003-01-01

    We explored three genes of attachment (fbe and atlE) and adhesion (ica) in 27 and 10 Staphylococcus epidermidis strains involved in pacemaker-related infections (PMI) and intravascular-catheter-related infections (IVCI), respectively, and in 25 saprophytic strains. The detection rates of fbe and atlE were identical in PMI and IVCI strains, but ica detection rates were identical in PMI and saprophytic strains.

  17. Shengmaisan Regulates Pacemaker Potentials in Interstitial Cells of Cajal in Mice

    OpenAIRE

    Kim Byung Joo

    2013-01-01

    Objectives: Shengmaisan (SMS) is a traditional Chinese medicine prescription widely used for the treatment of diverse organs in Korea. The interstitial cells of Cajal (ICCs) are pacemaker cells that play an important role in the generation of coordinated gastrointestinal (GI) motility. We have aimed to investigate the effects of SMS in the ICCs in the mouse small intestine. Methods: To dissociate the ICCs, we used enzymatic digestions from the small intestine in a mouse. After that, the ICCs ...

  18. Traveling waves and dynamical formation of autonomous pacemakers in a bistable medium with periodic boundary conditions

    Science.gov (United States)

    Shepelev, Igor A.; Vadivasova, Tatiana E.; Postnov, Dmitry E.

    2015-03-01

    The problem of spatiotemporal pattern formation in the wall of arterial vesselsmay be reduced to 1D or 2D models of nonlinear active medium. We address this problem using the discrete array of non-oscillating (bistable) active units. We show how the specific choice of initial conditions in a 1D model with periodic boundary conditions triggers the self-sustained behaviour. We reveal the core of observed effects being the dynamical formation of localized (few-element size) autonomous pacemakers.

  19. Self-powered cardiac pacemaker enabled by flexible single crystalline PMN-PT piezoelectric energy harvester.

    Science.gov (United States)

    Hwang, Geon-Tae; Park, Hyewon; Lee, Jeong-Ho; Oh, SeKwon; Park, Kwi-Il; Byun, Myunghwan; Park, Hyelim; Ahn, Gun; Jeong, Chang Kyu; No, Kwangsoo; Kwon, HyukSang; Lee, Sang-Goo; Joung, Boyoung; Lee, Keon Jae

    2014-07-23

    A flexible single-crystalline PMN-PT piezoelectric energy harvester is demonstrated to achieve a self-powered artificial cardiac pacemaker. The energy-harvesting device generates a short-circuit current of 0.223 mA and an open-circuit voltage of 8.2 V, which are enough not only to meet the standard for charging commercial batteries but also for stimulating the heart without an external power source. PMID:24740465

  20. Defect in Lung Perfusion and Ventilation Scanning of Patients with Permanent Transvenous Implantable Pacemaker

    OpenAIRE

    Matsuura, Yuichiro; Tamura, Mutsuo; Yamashina, Hideki; Higo, Masanori; Fujii, Takanori; Shimamoto, Hiroyuki; Kinoshita, Hirofumi

    1984-01-01

    Lung perfusion and ventilation scanning with 99mTc-MAA and 81mKr-Gass were studied in 138 patients with permanent transvenous implantable pacemaker. There were observed segmental or subsegmental defects in lung perfusion and ventilation scanning which were considered to be probably lung embolism of 47 cases. The incidence of lung embolism was high during the first postoperative 6 months, and it also increased progressively with aging. The patient with ischemic heart disease or va...

  1. High Altitude and Intracardiac Devices(Pacemaker and Intracardiac Defibrillator andCardiac Resynchronisation Therapy)

    OpenAIRE

    Gürsoy, Mustafa Ozan; Yıldız, Banu Şahin; Yıldız, Mustafa

    2013-01-01

    Cardiovascular system responds to high altitude short after exposure. Hypoxia induces increase in heart rate, myocardial contractility, and cardiac output. This may have clinical implications in patients with underlying heart disease such as coronary artery disease, heart failure and rhythm disorders. Past studies have showed that patients may experience altitude-induced arrhythmias. However, there are conflicting data for patients with cardiac devices such as permanent pacemaker, intracardia...

  2. Neuronal Complexity in Subthalamic Nucleus is Reduced in Parkinson's Disease.

    Science.gov (United States)

    Vyas, Saurabh; Huang, He; Gale, John T; Sarma, Sridevi V; Montgomery, Erwin B

    2016-01-01

    Several theories posit increased Subthalamic Nucleus (STN) activity is causal to Parkinsonism, yet in our previous study we showed that activity from 113 STN neurons from two epilepsy patients and 103 neurons from nine Parkinson's disease (PD) patients demonstrated no significant differences in frequencies or in the coefficients of variation of mean discharge frequencies per 1-s epochs. We continued our analysis using point process modeling to capture higher order temporal dynamics; in particular, bursting, beta-band oscillations, excitatory and inhibitory ensemble interactions, and neuronal complexity. We used this analysis as input to a logistic regression classifier and were able to differentiate between PD and epilepsy neurons with an accuracy of 92%. We also found neuronal complexity, i.e., the number of states in a neuron's point process model, and inhibitory ensemble dynamics, which can be interpreted as a reduction in complexity, to be the most important features with respect to classification accuracy. Even in a dataset with no significant differences in firing rate, we observed differences between PD and epilepsy for other single-neuron measures. Our results suggest PD comes with a reduction in neuronal "complexity," which translates to a neuron's ability to encode information; the more complexity, the more information the neuron can encode. This is also consistent with studies correlating disease to loss of variability in neuronal activity, as the lower the complexity, the less variability. PMID:26168436

  3. Measurement of neutron doses from the models 9000 and 9090 cardiac pacemakers

    International Nuclear Information System (INIS)

    Dose distribution in various points within the body of a patient implanted with a cardiac pacemaker must be known in order to assess long-term risks for patients. Absorbed doses due to neutrons were computed by means of a method based on the use of the TRIPOLI code initially developed for reactor neutronic calculations. For this purpose, the human trunk was assimilated to an elliptical cylinder as proposed by Snyder et al. The results were compared with those obtained in other laboratories: data for surface doses for the pacemaker 9000 and the phantom are in good agreement with the results of Battelle Pacific Northwest Laboratory; contact doses for both models 9000 and 9090 are much similar to the results obtained using PLESCH's formula. The results show that absorbed doses at the level of the various organs, i.e. at fairly large distances, are little modified as a function of the pacemaker size, the source geometry remaining the same. However, contact doses may vary by a large factor (about 2) on account of the variation of distances to the source

  4. Radiation therapy in patients with cardiac pacemakers or implantable cardioverter defibrillators. Interdisciplinary safety recommendations

    International Nuclear Information System (INIS)

    Background: With increasing numbers of implanted pacemakers and implantable cardioverter defibrillators (ICD) and a rising incidence of malignant tumors, there is a growing probability of radiation-mediated device dysfunction. The only guidelines for the management of patients with cardiac pacemakers in the case of radiation therapy were published in 1994 and have not been updated since then. Based on the current evidence and modern device technology, the present paper aims to develop contemporary and interdisciplinary safety recommendations for the minimization of patient risk. Methods and results: A systematic literature research was carried out including the most relevant medical electronic databases. The search yielded 147 articles published between 1994 and 2012 of which 45 met the selection criteria and of these studies 34 presented primary data (9 in vitro and 25 in vivo studies). The impact of ionizing radiation varied significantly between implanted devices and ranged from no functional changes to complete loss of function. Important device dysfunctions included changes in sensing capability, altered pacing pulses or rate, changed or disabled tachyarrhythmia ICD therapies, early battery depletion and loss of telemetry. Modern pacemakers and ICDs are more sensitive to radiation than older models. Potentially life-threatening complications were observed after exposure of the pulse generator to comparatively low radiation doses (0.11 Gy). Conclusions: Practical recommendations for patient management and safety are presented that can be readily adopted by any institution carrying out radiation therapy. (orig.)

  5. Spontaneous electrical activity of guinea-pig sinoatrial cells under modulation of two different pacemaker mechanisms

    Directory of Open Access Journals (Sweden)

    Francesca Cacciani

    2014-01-01

    Full Text Available The main cellular determinants of cardiac automaticity are the hyperpolarization-activated cationic current If, and the electrogenic Na+/Ca2+ exchanger which generates an inward current after each action potential (AP. Our goal was to evaluate their relative role in pacemaking, by means of application of Ivabradine (IVA (specific If blocker and Ryanodine (RYA (known to abolish calcium transient on enzimatically isolated guinea-pig pacemaker cells. Spontaneous APs were recorded in patch-clamp whole cell configuration at 36°C from 7 cells perfused with the following sequence of solutions: physiological normal tyrode (NT, IVA 3 mM, NT and RYA 3 mM. Cycle length (CL, ms and diastolic depolarization rate (DDR, V/s were also calculated. Both blockers displayed similar effects, increasing CL (by 27 and 30%, respectively, and decreasing DDR (by 34 and 42% with respect to NT exposure. These results suggest that both mechanisms are involved into pacemaking mechanism at a similar degree.

  6. Neuronal excitability level transition induced by electrical stimulation

    Science.gov (United States)

    Florence, G.; Kurths, J.; Machado, B. S.; Fonoff, E. T.; Cerdeira, H. A.; Teixeira, M. J.; Sameshima, K.

    2014-12-01

    In experimental studies, electrical stimulation (ES) has been applied to induce neuronal activity or to disrupt pathological patterns. Nevertheless, the underlying mechanisms of these activity pattern transitions are not clear. To study these phenomena, we simulated a model of the hippocampal region CA1. The computational simulations using different amplitude levels and duration of ES revealed three states of neuronal excitability: burst-firing mode, depolarization block and spreading depression wave. We used the bifurcation theory to analyse the interference of ES in the cellular excitability and the neuronal dynamics. Understanding this process would help to improve the ES techniques to control some neurological disorders.

  7. Fuzzy-Based Adaptive Hybrid Burst Assembly Technique for Optical Burst Switched Networks

    OpenAIRE

    Abubakar Muhammad Umaru; Muhammad Shafie Abd Latiff; Yahaya Coulibaly

    2014-01-01

    The optical burst switching (OBS) paradigm is perceived as an intermediate switching technology for future all-optical networks. Burst assembly that is the first process in OBS is the focus of this paper. In this paper, an intelligent hybrid burst assembly algorithm that is based on fuzzy logic is proposed. The new algorithm is evaluated against the traditional hybrid burst assembly algorithm and the fuzzy adaptive threshold (FAT) burst assembly algorithm via simulation. Simulation results sh...

  8. Two-dimensional burst identification codes and their use in burst correction

    OpenAIRE

    1988-01-01

    A new class of codes, called burst identification codes, is defined and studied. These codes can be used to determine the patterns of burst errors. Two-dimensional burst correcting codes can be easily constructed from burst identification codes. The resulting class of codes is simple to implement and has lower redundancy than other comparable codes. The results are pertinent to the study of radiation effects on VLSI RAM chips, which can cause two-dimensional bursts of errors.

  9. Low frequency magnetic emissions and resulting induced voltages in a pacemaker by iPod portable music players

    Science.gov (United States)

    Bassen, Howard

    2008-01-01

    Background Recently, malfunctioning of a cardiac pacemaker electromagnetic, caused by electromagnetic interference (EMI) by fields emitted by personal portable music players was highly publicized around the world. A clinical study of one patient was performed and two types of interference were observed when the clinicians placed a pacemaker programming head and an iPod were placed adjacent to the patient's implanted pacemaker. The authors concluded that "Warning labels may be needed to avoid close contact between pacemakers and iPods". We performed an in-vitro study to evaluate these claims of EMI and present our findings of no-effects" in this paper. Methods We performed in-vitro evaluations of the low frequency magnetic field emissions from various models of the Apple Inc. iPod music player. We measured magnetic field emissions with a 3-coil sensor (diameter of 3.5 cm) placed within 1 cm of the surface of the player. Highly localized fields were observed (only existing in a one square cm area). We also measured the voltages induced inside an 'instrumented-can' pacemaker with two standard unipolar leads. Each iPod was placed in the air, 2.7 cm above the pacemaker case. The pacemaker case and leads were placed in a saline filled torso simulator per pacemaker electromagnetic compatibility standard ANSI/AAMI PC69:2000. Voltages inside the can were measured. Results Emissions were strongest (≈ 0.2 μT pp) near a few localized points on the cases of the two iPods with hard drives. Emissions consisted of 100 kHz sinusoidal signal with lower frequency (20 msec wide) pulsed amplitude modulation. Voltages induced in the iPods were below the noise level of our instruments (0.5 mV pp in the 0 – 1 kHz band or 2 mV pp in the 0 – 5 MHz bandwidth. Conclusion Our measurements of the magnitude and the spatial distribution of low frequency magnetic flux density emissions by 4 different models of iPod portable music players. Levels of less than 0.2 μT exist very close (1 cm

  10. Low frequency magnetic emissions and resulting induced voltages in a pacemaker by iPod portable music players

    Directory of Open Access Journals (Sweden)

    Bassen Howard

    2008-02-01

    Full Text Available Abstract Background Recently, malfunctioning of a cardiac pacemaker electromagnetic, caused by electromagnetic interference (EMI by fields emitted by personal portable music players was highly publicized around the world. A clinical study of one patient was performed and two types of interference were observed when the clinicians placed a pacemaker programming head and an iPod were placed adjacent to the patient's implanted pacemaker. The authors concluded that "Warning labels may be needed to avoid close contact between pacemakers and iPods". We performed an in-vitro study to evaluate these claims of EMI and present our findings of no-effects" in this paper. Methods We performed in-vitro evaluations of the low frequency magnetic field emissions from various models of the Apple Inc. iPod music player. We measured magnetic field emissions with a 3-coil sensor (diameter of 3.5 cm placed within 1 cm of the surface of the player. Highly localized fields were observed (only existing in a one square cm area. We also measured the voltages induced inside an 'instrumented-can' pacemaker with two standard unipolar leads. Each iPod was placed in the air, 2.7 cm above the pacemaker case. The pacemaker case and leads were placed in a saline filled torso simulator per pacemaker electromagnetic compatibility standard ANSI/AAMI PC69:2000. Voltages inside the can were measured. Results Emissions were strongest (≈ 0.2 μT pp near a few localized points on the cases of the two iPods with hard drives. Emissions consisted of 100 kHz sinusoidal signal with lower frequency (20 msec wide pulsed amplitude modulation. Voltages induced in the iPods were below the noise level of our instruments (0.5 mV pp in the 0 – 1 kHz band or 2 mV pp in the 0 – 5 MHz bandwidth. Conclusion Our measurements of the magnitude and the spatial distribution of low frequency magnetic flux density emissions by 4 different models of iPod portable music players. Levels of less than 0.2

  11. Clique of functional hubs orchestrates population bursts in developmentally regulated neural networks

    Science.gov (United States)

    Torcini, Alessandro; Luccioli, Stefano; Bonifazi, Paolo; Ben-Jacob, Eshel; Barzilai, Ari

    2015-03-01

    It has recently been discovered that single neuron stimulation can impact network dynamics in immature and adult neuronal circuits. Here we report a novel mechanism which can explain in developing neuronal circuits, typically composed of only excitatory cells, the peculiar role played by a few specific neurons in promoting/arresting the population activity. For this purpose, we consider a standard neuronal network model, with short-term synaptic plasticity, whose population activity is characterized by bursting behavior. The addition of developmentally regulated constraints on single neuron excitability and connectivity leads to the emergence of functional hub neurons, whose stimulation/deletion is critical for the network activity. Functional hubs form a clique, where a precise sequential activation of the neurons is essential to ignite collective events without any need for a specific topological architecture. Unsupervised time-lagged firings of supra-threshold cells, in connection with coordinated entrainments of near-threshold neurons, are the key ingredients to orchestrate population activity. This work is part of the activity of the Joint Italian-Israeli Laboratory on Integrative Network Neuroscience supported by the Italian Ministry of Foreign Affairs.

  12. Clique of functional hubs orchestrates population bursts in developmentally regulated neural networks.

    Directory of Open Access Journals (Sweden)

    Stefano Luccioli

    2014-09-01

    Full Text Available It has recently been discovered that single neuron stimulation can impact network dynamics in immature and adult neuronal circuits. Here we report a novel mechanism which can explain in neuronal circuits, at an early stage of development, the peculiar role played by a few specific neurons in promoting/arresting the population activity. For this purpose, we consider a standard neuronal network model, with short-term synaptic plasticity, whose population activity is characterized by bursting behavior. The addition of developmentally inspired constraints and correlations in the distribution of the neuronal connectivities and excitabilities leads to the emergence of functional hub neurons, whose stimulation/deletion is critical for the network activity. Functional hubs form a clique, where a precise sequential activation of the neurons is essential to ignite collective events without any need for a specific topological architecture. Unsupervised time-lagged firings of supra-threshold cells, in connection with coordinated entrainments of near-threshold neurons, are the key ingredients to orchestrate population activity.

  13. Gamma-Ray Bursts: The End Game

    Science.gov (United States)

    Lamb, Don

    1997-11-01

    The nature of gamma-ray bursts has been one of the greatest unsolved mysteries in astrophysics for more than a quarter century. A major reason for this is that no definite counterparts to the bursts could be found at other wavelengths, despite intense efforts spanning more than two decades. Consequently, the study of gamma-ray bursts has been isolated from the rest of astronomy. Scientists studying them have had only the laws of physics and the bursts themselves to guide them in attempting to solve the burst mystery. All of this changed dramatically with the discovery earlier this year of fading X-ray and optical sources in the arcminute-sized positional error boxes of several gamma-ray bursts. For the first time, temporal, as well as spatial, coincidence could be used to associate these X-ray and optical sources with the gamma-ray bursts. As a result, the odds are great that the fading X-ray and optical sources are counterparts of the bursts, and that the study of gamma-ray bursts has finally been connected with the rest of astronomy. In this talk, we describe the dramatic new information about the nature of gamma-ray bursts that the X-ray, optical, and radio observations of the fading sources have provided, and emphasize the implications that this information has for the distance scale to the bursts.

  14. Quantum Key Based Burst Confidentiality in Optical Burst Switched Networks

    OpenAIRE

    Balamurugan, A. M.; A. Sivasubramanian

    2014-01-01

    The optical burst switching (OBS) is an emergent result to the technology concern that could achieve a feasible network in future. They are endowed with the ability to meet the bandwidth requirement of those applications that require intensive bandwidth. There are more domains opening up in the OBS that evidently shows their advantages and their capability to face the future network traffic. However, the concept of OBS is still far from perfection facing issues in case of security threat. The...

  15. Bubbles and Monetary Policy: To Burst or not to Burst?

    OpenAIRE

    König, Philipp; POTHIER, David

    2015-01-01

    The question of whether monetary policy should target asset prices remains a contentious issue. Prior to the 2007/08 financial crisis, central banks opted for a wait-and-see approach, remaining passive during the build-up of asset price bubbles but actively seeking to stabilize prices and output after they burst. The macroeconomic and financial turbulence that followed the subprime housing bubble has led to a renewed debate concerning monetary policy’s role in maintaining financial stability....

  16. SU-D-18C-06: Initial Experience with Implementing MRI Safety Guidelines for Patients with Pacemakers - Medical Physicist Perspective

    Energy Technology Data Exchange (ETDEWEB)

    James, J; Place, V; Panda, A [Mayo Clinic, Scottsdale, AZ (United States); Edmonson, H [Mayo Clinic College of Medicine, Rochester, MN (United States); Felmlee, J [Mayo Clinic, Rochester, MN (United States); Pooley, R [Mayo Clinic, Jacksonville, FL (United States)

    2014-06-01

    Purpose: Several institutions have developed MRI guidelines for patients with MR-unsafe or MR-conditional pacemakers. Here we highlight the role of a medical physicist in implementing these guidelines for non-pacemaker dependent patients. Guidelines: Implementing these guidelines requires involvement from several medical specialties and a strong collaboration with the site MRI supervisor to develop a structured workflow. A medical physicist is required to be present during the scan to supervise the MR scanning and to maintain a safety checklist that ensures: 1) uninterrupted patient communication with the technologist, 2) continuous patient physiologic monitoring (e.g. blood pressure and electrocardiography) by a trained nurse, 3) redundant patient vitals monitoring (e.g. pulse oximetry) due to the possibility of in vivo electrocardiography reading fluctuations during image acquisition. A radiologist is strongly recommended to be available to review the images before patients are discharged from the scanner. Pacemaker MRI should be restricted to 1.5T field strength. The MRI sequences should be optimized by the physicist with regards to: a) SAR: limited to <1.5 W/Kg for MR-unsafe pacemakers in normal operating mode, b) RF exposure time: <30 min, c) Coils: use T/R coils but not restricted to such, d) Artifacts: further optimization of sequences whenever image quality is compromised due to the pacemaker. In particular, cardiac, breast and left-shoulder MRIs are most susceptible to these artifacts. Possible strategies to lower the SAR include: a) BW reduction, 2) echo-train-length reduction, 3) increase TR, 4) decrease number of averages, 5) decrease flip angle, 6) reduce slices and/or a combination of all the options. Conclusion: A medical physicist in collaboration with the MR supervisor plays an important role in the supervision/implementation of safe MR scanning of pacemaker patients. Developing and establishing a workflow has enabled our institution to scan over

  17. SU-D-18C-06: Initial Experience with Implementing MRI Safety Guidelines for Patients with Pacemakers - Medical Physicist Perspective

    International Nuclear Information System (INIS)

    Purpose: Several institutions have developed MRI guidelines for patients with MR-unsafe or MR-conditional pacemakers. Here we highlight the role of a medical physicist in implementing these guidelines for non-pacemaker dependent patients. Guidelines: Implementing these guidelines requires involvement from several medical specialties and a strong collaboration with the site MRI supervisor to develop a structured workflow. A medical physicist is required to be present during the scan to supervise the MR scanning and to maintain a safety checklist that ensures: 1) uninterrupted patient communication with the technologist, 2) continuous patient physiologic monitoring (e.g. blood pressure and electrocardiography) by a trained nurse, 3) redundant patient vitals monitoring (e.g. pulse oximetry) due to the possibility of in vivo electrocardiography reading fluctuations during image acquisition. A radiologist is strongly recommended to be available to review the images before patients are discharged from the scanner. Pacemaker MRI should be restricted to 1.5T field strength. The MRI sequences should be optimized by the physicist with regards to: a) SAR: limited to <1.5 W/Kg for MR-unsafe pacemakers in normal operating mode, b) RF exposure time: <30 min, c) Coils: use T/R coils but not restricted to such, d) Artifacts: further optimization of sequences whenever image quality is compromised due to the pacemaker. In particular, cardiac, breast and left-shoulder MRIs are most susceptible to these artifacts. Possible strategies to lower the SAR include: a) BW reduction, 2) echo-train-length reduction, 3) increase TR, 4) decrease number of averages, 5) decrease flip angle, 6) reduce slices and/or a combination of all the options. Conclusion: A medical physicist in collaboration with the MR supervisor plays an important role in the supervision/implementation of safe MR scanning of pacemaker patients. Developing and establishing a workflow has enabled our institution to scan over

  18. Information Diversity in Structure and Dynamics of Simulated Neuronal Networks

    Directory of Open Access Journals (Sweden)

    Tuomo eMäki-Marttunen

    2011-06-01

    Full Text Available Neuronal networks exhibit a wide diversity of structures, which contributes to the diversity of the dynamics therein. The presented work applies an information theoretic framework to simultaneously analyze structure and dynamics in neuronal networks. Information diversity within the structure and dynamics of a neuronal network is studied using the normalized compression distance (NCD. To describe the structure, a scheme for generating distance-dependent networks with identical in-degree distribution but variable strength of dependence on distance is presented. The resulting network structure classes possess differing path length and clustering coefficient distributions. In parallel, comparable realistic neuronal networks are generated with NETMORPH simulator and similar analysis is done on them. To describe the dynamics, network spike trains are simulated using different network structures and their bursting behaviours are analyzed. For the simulation of the network activity the Izhikevich model of spiking neurons is used together with the Tsodyks model of dynamical synapses.We show that the structure of the simulated neuronal networks affects the spontaneous bursting activity when measured with bursting frequency and a set of intraburst measures: the more locally connected networks produce more and longer bursts than the more random networks. The information diversity of the structure of a network is greatest in the most locally connected networks, smallest in random networks, and somewhere in between in the networks between order and disorder. As for the dynamics, the most locally connected networks and some of the in-between networks produce the most complex intraburst spike trains. The same result also holds for sparser of the two considered network densities in the case of full spike trains.

  19. Dynamical behaviour of the firing in coupled neuronal system

    International Nuclear Information System (INIS)

    The time interval sequences and the spatio-temporal patterns of the firings of a coupled neuronal network are investigated in this paper. For a single neuron stimulated by an external stimulus I, the time interval sequences show a low frequency firing of bursts of spikes, and reversed period-doubling cascade to a high frequency repetitive firing state as the stimulus I is increased. For two neurons coupled to each other through the firing of the spikes, the complexity of the time interval sequences becomes simple as the coupling strength increases. A network with large numbers of neurons shows a complex spatio-temporal pattern structure. As the coupling strength increases, the numbers of phase locked neurons increase and the time interval diagram shows temporal chaos and a bifurcation in the space. The dynamical behaviour is also verified by the Lyapunov exponent. (author). 17 refs, 6 figs

  20. A Hamilton-Jacobi-Bellman approach for termination of seizure-like bursting.

    Science.gov (United States)

    Wilson, Dan; Moehlis, Jeff

    2014-10-01

    We use Hamilton-Jacobi-Bellman methods to find minimum-time and energy-optimal control strategies to terminate seizure-like bursting behavior in a conductance-based neural model. Averaging is used to eliminate fast variables from the model, and a target set is defined through bifurcation analysis of the slow variables of the model. This method is illustrated for a single neuron model and for a network model to illustrate its efficacy in terminating bursting once it begins. This work represents a numerical proof-of-concept that a new class of control strategies can be employed to mitigate bursting, and could ultimately be adapted to treat medically intractible epilepsy in patient-specific models. PMID:24965911

  1. Preserved dichotomy but highly irregular and burst discharge in the basal ganglia in alert dystonic rats at rest.

    Science.gov (United States)

    Kumbhare, Deepak; Chaniary, Kunal D; Baron, Mark S

    2015-10-22

    Despite its prevalence, the underlying pathophysiology of dystonia remains poorly understood. Using our novel tri-component classification algorithm, extracellular neuronal activity in the globus pallidus (GP), STN, and the entopeduncular nucleus (EP) was characterized in 34 normal and 25 jaundiced dystonic Gunn rats with their heads restrained while at rest. In normal rats, neurons in each nucleus were similarly characterized by two physiologically distinct types: regular tonic with moderate discharge frequencies (mean rates in GP, STN and EP ranging from 35-41 spikes/s) or irregular at slower frequencies (17-20 spikes/s), with a paucity of burst activity. In dystonic rats, these nuclei were also characterized by two distinct principal neuronal patterns. However, in marked difference, in the dystonic rats, neurons were primarily slow and highly irregular (12-15 spikes/s) or burst predominant (14-17 spikes/s), with maintained modest differences between nuclei. In GP and EP, with increasing severity of dystonia, burstiness was moderately further increased, irregularity mildly further increased, and discharge rates mildly further reduced. In contrast, these features did not appreciably change in STN with worsening dystonia. Findings of a lack of bursting in GP, STN and EP in normal rats in an alert resting state and prominent bursting in dystonic Gunn rats suggest that cortical or other external drive is normally required for bursting in these nuclei and that spontaneous bursting, as seen in dystonia and Parkinson's disease, is reflective of an underlying pathophysiological state. Moreover, the extent of burstiness appears to most closely correlate with the severity of the dystonia. PMID:26210616

  2. Ordering chaos and synchronization transitions by chemical delay and coupling on scale-free neuronal networks

    Energy Technology Data Exchange (ETDEWEB)

    Gong Yubing, E-mail: gongyubing09@hotmail.co [School of Physics, Ludong University, Yantai 264025 (China); Xie Yanhang; Lin Xiu; Hao Yinghang; Ma Xiaoguang [School of Physics, Ludong University, Yantai 264025 (China)

    2010-12-15

    Research highlights: Chemical delay and chemical coupling can tame chaotic bursting. Chemical delay-induced transitions from bursting synchronization to intermittent multiple spiking synchronizations. Chemical coupling-induced different types of delay-dependent firing transitions. - Abstract: Chemical synaptic connections are more common than electric ones in neurons, and information transmission delay is especially significant for the synapses of chemical type. In this paper, we report a phenomenon of ordering spatiotemporal chaos and synchronization transitions by the delays and coupling through chemical synapses of modified Hodgkin-Huxley (MHH) neurons on scale-free networks. As the delay {tau} is increased, the neurons exhibit transitions from bursting synchronization (BS) to intermittent multiple spiking synchronizations (SS). As the coupling g{sub syn} is increased, the neurons exhibit different types of firing transitions, depending on the values of {tau}. For a smaller {tau}, there are transitions from spatiotemporal chaotic bursting (SCB) to BS or SS; while for a larger {tau}, there are transitions from SCB to intermittent multiple SS. These findings show that the delays and coupling through chemical synapses can tame the chaotic firings and repeatedly enhance the firing synchronization of neurons, and hence could play important roles in the firing activity of the neurons on scale-free networks.

  3. Ordering chaos and synchronization transitions by chemical delay and coupling on scale-free neuronal networks

    International Nuclear Information System (INIS)

    Research highlights: → Chemical delay and chemical coupling can tame chaotic bursting. → Chemical delay-induced transitions from bursting synchronization to intermittent multiple spiking synchronizations. → Chemical coupling-induced different types of delay-dependent firing transitions. - Abstract: Chemical synaptic connections are more common than electric ones in neurons, and information transmission delay is especially significant for the synapses of chemical type. In this paper, we report a phenomenon of ordering spatiotemporal chaos and synchronization transitions by the delays and coupling through chemical synapses of modified Hodgkin-Huxley (MHH) neurons on scale-free networks. As the delay τ is increased, the neurons exhibit transitions from bursting synchronization (BS) to intermittent multiple spiking synchronizations (SS). As the coupling gsyn is increased, the neurons exhibit different types of firing transitions, depending on the values of τ. For a smaller τ, there are transitions from spatiotemporal chaotic bursting (SCB) to BS or SS; while for a larger τ, there are transitions from SCB to intermittent multiple SS. These findings show that the delays and coupling through chemical synapses can tame the chaotic firings and repeatedly enhance the firing synchronization of neurons, and hence could play important roles in the firing activity of the neurons on scale-free networks.

  4. Modeling the emergence of circadian rhythms in a clock neuron network.

    Directory of Open Access Journals (Sweden)

    Luis Diambra

    Full Text Available Circadian rhythms in pacemaker cells persist for weeks in constant darkness, while in other types of cells the molecular oscillations that underlie circadian rhythms damp rapidly under the same conditions. Although much progress has been made in understanding the biochemical and cellular basis of circadian rhythms, the mechanisms leading to damped or self-sustained oscillations remain largely unknown. There exist many mathematical models that reproduce the circadian rhythms in the case of a single cell of the Drosophila fly. However, not much is known about the mechanisms leading to coherent circadian oscillation in clock neuron networks. In this work we have implemented a model for a network of interacting clock neurons to describe the emergence (or damping of circadian rhythms in Drosophila fly, in the absence of zeitgebers. Our model consists of an array of pacemakers that interact through the modulation of some parameters by a network feedback. The individual pacemakers are described by a well-known biochemical model for circadian oscillation, to which we have added degradation of PER protein by light and multiplicative noise. The network feedback is the PER protein level averaged over the whole network. In particular, we have investigated the effect of modulation of the parameters associated with (i the control of net entrance of PER into the nucleus and (ii the non-photic degradation of PER. Our results indicate that the modulation of PER entrance into the nucleus allows the synchronization of clock neurons, leading to coherent circadian oscillations under constant dark condition. On the other hand, the modulation of non-photic degradation cannot reset the phases of individual clocks subjected to intrinsic biochemical noise.

  5. Power spectrum analysis of bursting cells in area MT in the behaving monkey

    OpenAIRE

    Bair, Wyeth; Koch, Christof; Newsome, W.; Britten, K.

    1994-01-01

    It is widely held that visual cortical neurons encode information primarily in their mean firing rates. Some proposals, however, emphasize the information potentially available in the temporal structure of spike trains (Optican and Richmond, 1987; Bialek et al., 1991), in particular with respect to stimulus-related synchronized oscillations in the 30–70 Hz range (Eckhorn et al., 1988; Gray et al., 1989; Kreiter and Singer, 1992) as well as via bursting cells (Cattaneo et al., 1981a; Bonds, 19...

  6. Neuronal Migration Disorders

    Science.gov (United States)

    ... Enhancing Diversity Find People About NINDS NINDS Neuronal Migration Disorders Information Page Table of Contents (click to ... being done? Clinical Trials Organizations What are Neuronal Migration Disorders? Neuronal migration disorders (NMDs) are a group ...

  7. Motor Neuron Diseases

    Science.gov (United States)

    ... Awards Enhancing Diversity Find People About NINDS Motor Neuron Diseases Fact Sheet See a list of all ... can I get more information? What are motor neuron diseases? The motor neuron diseases (MNDs) are a ...

  8. Electrogenesis in the lower Metazoa and implications for neuronal integration.

    Science.gov (United States)

    Meech, Robert W

    2015-02-15

    Electrogenic communication appears to have evolved independently in a variety of animal and plant lineages. Considered here are metazoan cells as disparate as the loose three-dimensional parenchyma of glass sponges, the two-dimensional epithelial sheets of hydrozoan jellyfish and the egg cell membranes of the ctenophore Beroe ovata, all of which are capable of generating electrical impulses. Neuronal electrogenesis may have evolved independently in ctenophores and cnidarians but the dearth of electrophysiological data relating to ctenophore nerves means that our attention is focused on the Cnidaria, whose nervous systems have been the subject of extensive study. The aim here is to show how their active and passive neuronal properties interact to give integrated behaviour. Neuronal electrogenesis, goes beyond simply relaying 'states of excitement' and utilizes the equivalent of a set of basic electrical 'apps' to integrate incoming sensory information with internally generated pacemaker activity. A small number of membrane-based processes make up these analogue applications. Passive components include the decremental spread of current determined by cellular anatomy; active components include ion channels specified by their selectivity and voltage dependence. A recurring theme is the role of inactivating potassium channels in regulating performance. Although different aspects of cnidarian behaviour are controlled by separate neuronal systems, integrated responses and coordinated movements depend on interactions between them. Integrative interactions discussed here include those between feeding and swimming, between tentacle contraction and swimming and between slow and fast swimming in the hydrozoan jellyfish Aglantha digitale. PMID:25696817

  9. Pulse Phase Dependence of the Magnetar Bursts

    Indian Academy of Sciences (India)

    Chetana Jain; Anjan Dutta; Biswajit Paul

    2007-12-01

    We report here results from a study of X-ray bursts from 3 magnetar candidates (SGR 1806–20, SGR 1900+14 and AXP 1E 2259+586). We have searched for a pulse phase dependence of the X-ray burst rate from these sources. X-ray light curves were obtained with the Proportional Counter Array on-board the Rossi X-ray Timing Explorer during the periods of intense burst activity in these sources. On detailed analysis of the three sources, we found a very significant burst rate for all pulsar phases. However, some locations appear to produce bursts slightly more often, rendering the non-isotropic distribution. Only in the case of SGR 1900+14, there is a clear pulse phase dependence of burst rate.

  10. Bursting for enhanced ablation of materials

    Science.gov (United States)

    Hendow, Sami; Rea, Edward; Kosa, Nadhir; Bengtsson, Magnus; Shakir, Sami

    2014-03-01

    A significant enhancement in the rate of material removal is demonstrated using a nanosecond-pulsed UV fiber laser in multi-pulsing burst mode, as compared to the case without bursting. Percussion drilling and scribing of thin-film and bulk material tests show that, in general, laser bursts with increased pulse count and reduced pulse spacing show higher rates of material removal. A considerable improvement in removal rate is demonstrated, when bursting is applied to scribing of mono-crystalline silicon (m-Si) and up to 30% in percussion drilling speed. Likewise, improved material removal is demonstrated for scribing of thin film of indium tin oxide (ITO) on glass or metal film on sapphire. Examples of material processing are given with and without bursting at similar experimental conditions of average power, scan speed, and burst/pulse energies. Experimental results included are for m-Si, ITO thin films on glass, and metal films on sapphire.

  11. EXTRACELLULAR Ca2+ FLUCTUATIONS IN VIVO AFFECT AFTERHYPERPOLARIZATION POTENTIAL AND MODIFY FIRING PATTERNS OF NEOCORTICAL NEURONS

    OpenAIRE

    Sofiane, Boucetta; Sylvain, Crochet; Sylvain, Chauvette; Josée, Seigneur; Igor, Timofeev

    2012-01-01

    Neocortical neurons can be classified in four major electrophysiological types according to their pattern of discharge: Regular-Spiking (RS), Intrinsically-Bursting (IB), Fast-Rhythmic-Bursting (FRB), and Fast-Spiking (FS). Previously, we have shown that these firing patterns are not fixed and can change as a function of membrane potential and states of vigilance. Other studies have reported that extracellular calcium concentration ([Ca2+]o) fluctuates as a function of the phase of the cortic...

  12. Electrophysiology of the mammillary complex in vitro. I. Tuberomammillary and lateral mammillary neurons

    Science.gov (United States)

    Llinas, R. R.; Alonso, A.

    1992-01-01

    -sensitive, plateau potentials were always elicited following Ca2+ block with Cd2+ when K+ currents were reduced by superfusion with tetraethylammonium. 6. The gNap in tuberomammillary neurons may subserve the pacemaker current underlying the spontaneous firing of these cells. The large-amplitude spike afterhyperpolarization of these neurons sets the availability of the transient outward rectifier, which, in conjunction with the pacemaker current, establishes the rate at which membrane potential approaches spike threshold. 7. Repetitive firing elicited by direct depolarization enhanced the spike shoulder of tuberomammillary neurons. Spike trains were followed by a Ca(2+)-dependent, apamine-sensitive, slow afterhyperpolarization. 8. Lateral mammillary neurons were morphologically and electrophysiologically different from tuberomammillary neurons. All lateral mammillary neurons neurons recorded (n = 44) were silent at rest (-60 mV).(ABSTRACT TRUNCATED AT 400 WORDS).

  13. Beam Profile Disturbances from Implantable Pacemakers or Implantable Cardioverter-Defibrillator Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Gossman, Michael S., E-mail: mgossman@tsrcc.com [Tri-State Regional Cancer Center, Medical Physics Section, Ashland, KY (United States); Comprehensive Heart and Vascular Associates, Heart and Vascular Center, Ashland, KY (United States); Medtronic, Inc., External Research Program, Mounds View, MN (United States); Nagra, Bipinpreet; Graves-Calhoun, Alison; Wilkinson, Jeffrey [Tri-State Regional Cancer Center, Medical Physics Section, Ashland, KY (United States); Comprehensive Heart and Vascular Associates, Heart and Vascular Center, Ashland, KY (United States); Medtronic, Inc., External Research Program, Mounds View, MN (United States)

    2011-01-01

    The medical community is advocating for progressive improvement in the design of implantable cardioverter-defibrillators and implantable pacemakers to accommodate elevations in dose limitation criteria. With advancement already made for magnetic resonance imaging compatibility in some, a greater need is present to inform the radiation oncologist and medical physicist regarding treatment planning beam profile changes when such devices are in the field of a therapeutic radiation beam. Treatment plan modeling was conducted to simulate effects induced by Medtronic, Inc.-manufactured devices on therapeutic radiation beams. As a continuation of grant-supported research, we show that radial and transverse open beam profiles of a medical accelerator were altered when compared with profiles resulting when implantable pacemakers and cardioverter-defibrillators are placed directly in the beam. Results are markedly different between the 2 devices in the axial plane and the sagittal planes. Vast differences are also presented for the therapeutic beams at 6-MV and 18-MV x-ray energies. Maximum changes in percentage depth dose are observed for the implantable cardioverter-defibrillator as 9.3% at 6 MV and 10.1% at 18 MV, with worst distance to agreement of isodose lines at 2.3 cm and 1.3 cm, respectively. For the implantable pacemaker, the maximum changes in percentage depth dose were observed as 10.7% at 6 MV and 6.9% at 18 MV, with worst distance to agreement of isodose lines at 2.5 cm and 1.9 cm, respectively. No differences were discernible for the defibrillation leads and the pacing lead.

  14. United assembly algorithm for optical burst switching

    Institute of Scientific and Technical Information of China (English)

    Jinhui Yu(于金辉); Yijun Yang(杨教军); Yuehua Chen(陈月华); Ge Fan(范戈)

    2003-01-01

    Optical burst switching (OBS) is a promising optical switching technology. The burst assembly algorithm controls burst assembly, which significantly impacts performance of OBS network. This paper provides a new assembly algorithm, united assembly algorithm, which has more practicability than conventional algorithms. In addition, some factors impacting selections of parameters of this algorithm are discussed and the performance of this algorithm is studied by computer simulation.

  15. Ballerina - pirouettes in search of gamma bursts

    DEFF Research Database (Denmark)

    Brandt, Søren Kristian; Lund, Niels; Pedersen, Henrik; Hjorth, J.

    1999-01-01

    The cosmological origin of gamma ray bursts has now been established with reasonable certainty, Many more bursts will need to be studied to establish the typical distance scale, and to map out the large diversity in properties which have been indicated by the first handful of events. We are...... proposing Ballerina, a small satellite to provide accurate positions and new data on the gamma-ray bursts. We anticipate a detection rate an order of magnitude larger than obtained from Beppo-SAX....

  16. Contributions of intrinsic motor neuron properties to the production of rhythmic motor output in the mammalian spinal cord

    DEFF Research Database (Denmark)

    Kiehn, O; Kjaerulff, O; Tresch, M C; Harris-Warrick, R M

    2000-01-01

    firing. Motor neurons were recorded intracellularly during locomotion induced with a mixture of N-methyl-D-aspartate (NMDA) and serotonin, after pharmacological blockade of I(h). I(h) was then replaced by using dynamic clamp, a computer program that allows artificial conductances to be inserted into real...... neurons. I(h) was simulated with biophysical parameters determined in voltage clamp experiments. The data showed that electronic replacement of the native I(h) caused a depolarization of the average membrane potential, a phase-advance of the locomotor drive potential, and increased motor neuron spiking...... showing that the neonatal rat spinal cord can produce a stable motor rhythm in the absence of spike activity in premotor interneuronal networks. These coordinated motor neuron oscillations are dependent on NMDA-evoked pacemaker properties, which are synchronized across gap junctions. We discuss the...

  17. Medical treatment of a pacemaker endocarditis due to Candida albicans and to Candida glabrata.

    Science.gov (United States)

    Roger, P M; Boissy, C; Gari-Toussaint, M; Foucher, R; Mondain, V; Vandenbos, F; le Fichoux, Y; Michiels, J F; Dellamonica, P

    2000-09-01

    We describe a case of pacemaker infection due to two fungal species: Candida albicans and C. glabrata. Transthoracic echocardiography showed a large vegetation on the intraventricular wires. Because of severe underlying diseases, surgery was believed to be contraindicated. The patient was treated using high dose of fluconazole, resulting in clinical improvement and negative blood cultures. However, 2 months later, the patient underwent a fatal stroke. At autopsy, a large vegetation was found only all along the wires. Postmortem culture of the infected material was positive for both C. albicans and C. glabrata. PMID:11023765

  18. Apical Ballooning Syndrome (Takotsubo Cardiomyopathy after Permanent Dual-Chamber Pacemaker Implantation

    Directory of Open Access Journals (Sweden)

    Armando Gardini

    2012-01-01

    Full Text Available Apical ballooning syndrome, also called takotsubo cardiomyopathy, has been recently reported. It may mimic acute myocardial infarction and is typically observed in postmenopausal women after stressful events. A 75-year-old female after permanent dual chamber pacemaker implant complained of chest pain with repolarization alterations suggesting acute myocardial ischemia. Echocardiography showed a left ventricle with akinesia of the apical portions and reduced global systolic function. The patient was treated with antithrombotic agents and intravenous nitrates. No coronary lesions were found at angiography. At ventriculography, a typical takotsubo-like shape of the left ventricle was observed. The clinical and echocardiographic picture normalized at discharge.

  19. Evaluation of patients' quality of life aspects after cardiac pacemaker implantation

    OpenAIRE

    de Barros, Rubens Tofano; de Carvalho, Sebastião Marcos Ribeiro; Silva, Marcos Augusto de Moraes; Borges, Juliana Bassalobre Carvalho

    2014-01-01

    Objective To evaluate patients' quality of life aspects after pacemaker implantation, relating it to gender, age, and implantation timespan. Methods A total of 107 clinically stable patients of both genders (49.5% women and 50.5% men) over 18 years old (average 69.3±12.6 years) and presenting an implantation timespan of three to 12 months (average 6.36±2.99 months) were evaluated. The evaluation included personal, clinical, and implant data as well as quality of life questionnaires (AQUAREL ...

  20. Changes in Heart Rate in Patients with a Pacemaker do not Affect Cardiac Output

    Czech Academy of Sciences Publication Activity Database

    Vondra, Vlastimil; Soukup, L.; Jurák, Pavel; Halámek, Josef; Viščor, Ivo; Lipoldová, J.; Leinveber, Pavel

    Piscataway : IEEE, 2012, s. 511. ISBN 978-1-4244-4119-8. [EMBC 2012. Annual International Conference of the IEEE Engineering in Medicine and Biology Society /34./. San Diego (US), 28.08.2012-01.09.2012] R&D Projects: GA MŠk ME09050; GA MŠk ED0017/01/01; GA ČR GAP102/12/2034 Institutional support: RVO:68081731 Keywords : Pacemaker * Changes in Heart Rate * Cardiac Output Subject RIV: FA - Cardiovascular Diseases incl. Cardiotharic Surgery

  1. The effects of temperature on the stability of a neuronal oscillator.

    Directory of Open Access Journals (Sweden)

    Anatoly Rinberg

    Full Text Available The crab Cancer borealis undergoes large daily fluctuations in environmental temperature (8-24°C and must maintain appropriate neural function in the face of this perturbation. In the pyloric circuit of the crab stomatogastric ganglion, we pharmacologically isolated the pacemaker kernel (the AB and PD neurons and characterized its behavior in response to temperature ramps from 7°C to 31°C. For moderate temperatures, the pacemaker displayed a frequency-temperature curve statistically indistinguishable from that of the intact circuit, and like the intact circuit maintained a constant duty cycle. At high temperatures (above 23°C, a variety of different behaviors were seen: in some preparations the pacemaker increased in frequency, in some it slowed, and in many preparations the pacemaker stopped oscillating ("crashed". Furthermore, these crashes seemed to fall into two qualitatively different classes. Additionally, the animal-to-animal variability in frequency increased at high temperatures. We used a series of Morris-Lecar mathematical models to gain insight into these phenomena. The biophysical components of the final model have temperature sensitivities similar to those found in nature, and can crash via two qualitatively different mechanisms that resemble those observed experimentally. The crash type is determined by the precise parameters of the model at the reference temperature, 11°C, which could explain why some preparations seem to crash in one way and some in another. Furthermore, even models with very similar behavior at the reference temperature diverge greatly at high temperatures, resembling the experimental observations.

  2. 50th Anniversary of the first successful permanent pacemaker implantation in the United States: historical review and future directions.

    Science.gov (United States)

    Beck, Hiroko; Boden, William E; Patibandla, Sushmitha; Kireyev, Dmitriy; Gutpa, Vipul; Campagna, Franklin; Cain, Michael E; Marine, Joseph E

    2010-09-15

    June 2010 marks the 50th anniversary of the first successful human cardiac pacemaker implantation in the United States. On June 6, 1960, in Buffalo, New York, Dr. William Chardack implanted a pacemaker, designed and built by Wilson Greatbatch, an electrical engineer and inventor, in a 77-year old man with complete atrioventricular block, extending the patient's life by 18 months. This landmark event ushered in a new era of implantable cardiac pacemakers with batteries and leads of high reliability and increasing durability. Over the past half century, the field of electrophysiology and implantable devices for the management of cardiac conduction disturbances has evolved dramatically. Today's pacemakers include increasingly complex features such as telemetry monitoring, auto programmability, and hemodynamic sensors. New-generation leads present a sophisticated design with improved geometry and steroid-eluting tips to reduce chronic inflammation, maintaining a low pacing threshold and high sensing capability. The lithium iodide battery remains the mainstay of implantable pacemaker systems, exhibiting a multiple-year lifespan, slow terminal decay, and a reduced size and cost of production. Although Greatbatch's first successful pacemaker implantation remains a seminal scientific contribution to modern cardiovascular disease management, emerging developments in this field may challenge its preeminence. Important challenges such as imaging compatibility, lead durability, and infection prevention are being addressed. Novel concepts such as leadless and biologic pacing are under active investigation. In conclusion, Greatbatch's historic achievement 50 years ago reminds us that technologic progress is timeless, as efforts to enhance clinical outcomes and the quality of life continue unimpeded into the 21st century. PMID:21391322

  3. Bubble burst as jamming phase transition

    CERN Document Server

    Nishinari, Katsuhiro; Saito, Yukiko Umeno; Watanabe, Tsutomu

    2010-01-01

    Recently research on bubble and its burst attract much interest of researchers in various field such as economics and physics. Economists have been regarding bubble as a disorder in prices. However, this research strategy has overlooked an importance of the volume of transactions. In this paper, we have proposed a bubble burst model by focusing the transactions incorporating a traffic model that represents spontaneous traffic jam. We find that the phenomenon of bubble burst shares many similar properties with traffic jam formation by comparing data taken from US housing market. Our result suggests that the transaction could be a driving force of bursting phenomenon.

  4. Bursting behaviour in coupled Josephson junctions.

    Science.gov (United States)

    Hongray, Thotreithem; Balakrishnan, J; Dana, Syamal K

    2015-12-01

    We report an interesting bow-tie shaped bursting behaviour in a certain parameter regime of two resistive-capacitative shunted Josephson junctions, one in the oscillatory and the other in the excitable mode and coupled together resistively. The burst emerges in both the junctions and they show near-complete synchronization for strong enough couplings. We discuss a possible bifurcation scenario to explain the origin of the burst. An exhaustive study on the parameter space of the system is performed, demarcating the regions of bursting from other solutions. PMID:26723143

  5. Burst Fragmentation Model Based on Sequential Burst Allocation Algorithm for Mobile WiMAX

    OpenAIRE

    Zaid G. Ali; Prof. R. B. Ahmad; Dr. Abid Yahya

    2013-01-01

    the downlink Bandwidth resources of WiMAX are allocated by the burst allocation algorithm. The algorithm is responsible for calculating the appropriate location of a number of the smallest unit of bandwidth which is called the slot for all users within the downlink subframe in the form of bursts. Resource wastage in the form of unused and unallocated slots is a real common problem accompanies resource management in the burst allocation algorithms. This paper investigates the Sequential Burst ...

  6. Fast radio burst/gamma-ray burst cosmography

    International Nuclear Information System (INIS)

    Recently, both theoretical arguments and observational evidence suggested that a small fraction of fast radio bursts (FRBs) could be associated with gamma-ray bursts (GRBs). If such FRB/GRB association systems are commonly detected in the future, the combination of dispersion measures (DM) derived from FRBs and redshifts derived from GRBs makes these systems a plausible tool to conduct cosmography. We quantify uncertainties in deriving the redshift-dependent DMIGM as a function of z and test how well dark energy models can be constrained with Monte Carlo simulations. We show that with several tens of FRB/GRB systems potentially detected in a decade or so, one may reach reasonable constraints on wCDM models. When combined with Type Ia supernova (SN Ia) data, unprecedented constraints on the dark energy equation of state may be achieved, thanks to the prospects of detecting FRB/GRB systems at relatively high redshifts. The ratio between the mean value and luminosity distance (D L(z)) is insensitive to dark energy models. This gives the prospect of applying SN Ia data to calibrate using a relatively small sample of FRB/GRB systems, allowing a reliable constraint on the baryon inhomogeneity distribution as a function of redshift. The methodology developed in this paper can also be applied if the FRB redshifts can be measured by other means. Some caveats of putting this method into practice are also discussed.

  7. Emergent pacemaker placement in a patient with Lyme carditis-induced complete heart block and ventricular asystole.

    Science.gov (United States)

    Brownstein, Adam J; Gautam, Samir; Bhatt, Paras; Nanna, Michael

    2016-01-01

    We report a case of a 31-year-old man who presented to the emergency department after four episodes of syncope within a 24 h time span. He was found to have symptomatic complete heart block associated with episodes of ventricular asystole lasting 5-6 s. He underwent emergent permanent pacemaker insertion during which he was found to have no underlying rhythm. He was later found to have positive serologies for Lyme disease despite no known exposure to ticks and neither signs nor symptoms of the disease. The pacemaker was ultimately removed due to resolution of his heart block with antibiotic therapy. PMID:27207985

  8. Six types of multistability in a neuronal model based on slow calcium current.

    Directory of Open Access Journals (Sweden)

    Tatiana Malashchenko

    Full Text Available BACKGROUND: Multistability of oscillatory and silent regimes is a ubiquitous phenomenon exhibited by excitable systems such as neurons and cardiac cells. Multistability can play functional roles in short-term memory and maintaining posture. It seems to pose an evolutionary advantage for neurons which are part of multifunctional Central Pattern Generators to possess multistability. The mechanisms supporting multistability of bursting regimes are not well understood or classified. METHODOLOGY/PRINCIPAL FINDINGS: Our study is focused on determining the bio-physical mechanisms underlying different types of co-existence of the oscillatory and silent regimes observed in a neuronal model. We develop a low-dimensional model typifying the dynamics of a single leech heart interneuron. We carry out a bifurcation analysis of the model and show that it possesses six different types of multistability of dynamical regimes. These types are the co-existence of 1 bursting and silence, 2 tonic spiking and silence, 3 tonic spiking and subthreshold oscillations, 4 bursting and subthreshold oscillations, 5 bursting, subthreshold oscillations and silence, and 6 bursting and tonic spiking. These first five types of multistability occur due to the presence of a separating regime that is either a saddle periodic orbit or a saddle equilibrium. We found that the parameter range wherein multistability is observed is limited by the parameter values at which the separating regimes emerge and terminate. CONCLUSIONS: We developed a neuronal model which exhibits a rich variety of different types of multistability. We described a novel mechanism supporting the bistability of bursting and silence. This neuronal model provides a unique opportunity to study the dynamics of networks with neurons possessing different types of multistability.

  9. Mechanical stress activates neurites and somata of myenteric neurons

    Directory of Open Access Journals (Sweden)

    Eva Maria Kugler

    2015-09-01

    Full Text Available The particular location of myenteric neurons, sandwiched between the 2 muscle layers of the gut, implies that their somata and neurites undergo mechanical stress during gastrointestinal motility. Existence of mechanosensitive enteric neurons (MEN is undoubted but many of their basic features remain to be studied. In this study, we used ultra-fast neuroimaging to record activity of primary cultured myenteric neurons of guinea pig and human intestine after von Frey hair evoked deformation of neurites and somata. Independent component analysis was applied to reconstruct neuronal morphology and follow neuronal signals. Of the cultured neurons 45% (114 out of 256, 30 guinea pigs responded to neurite probing with a burst spike frequency of 13.4 Hz. Action potentials generated at the stimulation site invaded the soma and other neurites. Mechanosensitive sites were expressed across large areas of neurites. Many mechanosensitive neurites appeared to have afferent and efferent functions as those that responded to deformation also conducted spikes coming from the soma. Mechanosensitive neurites were also activated by nicotine application. This supported the concept of multifunctional MEN. 14% of the neurons (13 out of 96, 18 guinea pigs responded to soma deformation with burst spike discharge of 17.9 Hz. Firing of MEN adapted rapidly (RAMEN, slowly (SAMEN or ultra-slowly (USAMEN. The majority of MEN showed SAMEN behavior although significantly more RAMEN occurred after neurite probing. Cultured myenteric neurons from human intestine had similar properties. Compared to MEN, dorsal root ganglion neurons were activated by neurite but not by soma deformation with slow adaptation of firing. We demonstrated that MEN exhibit specific features very likely reflecting adaptation to their specialized functions in the gut.

  10. Temporal characteristics of gustatory responses in rat parabrachial neurons vary by stimulus and chemosensitive neuron type.

    Directory of Open Access Journals (Sweden)

    Laura Geran

    Full Text Available It has been demonstrated that temporal features of spike trains can increase the amount of information available for gustatory processing. However, the nature of these temporal characteristics and their relationship to different taste qualities and neuron types are not well-defined. The present study analyzed the time course of taste responses from parabrachial (PBN neurons elicited by multiple applications of "sweet" (sucrose, "salty" (NaCl, "sour" (citric acid, and "bitter" (quinine and cycloheximide stimuli in an acute preparation. Time course varied significantly by taste stimulus and best-stimulus classification. Across neurons, the ensemble code for the three electrolytes was similar initially but quinine diverged from NaCl and acid during the second 500 ms of stimulation and all four qualities became distinct just after 1s. This temporal evolution was reflected in significantly broader tuning during the initial response. Metric space analyses of quality discrimination by individual neurons showed that increases in information (H afforded by temporal factors was usually explained by differences in rate envelope, which had a greater impact during the initial 2s (22.5% increase in H compared to the later response (9.5%. Moreover, timing had a differential impact according to cell type, with between-quality discrimination in neurons activated maximally by NaCl or citric acid most affected. Timing was also found to dramatically improve within-quality discrimination (80% increase in H in neurons that responded optimally to bitter stimuli (B-best. Spikes from B-best neurons were also more likely to occur in bursts. These findings suggest that among PBN taste neurons, time-dependent increases in mutual information can arise from stimulus- and neuron-specific differences in response envelope during the initial dynamic period. A stable rate code predominates in later epochs.

  11. Reciprocal inhibitory coupling: Measure and control of chaos on a biophysically motivated model of bursting

    Science.gov (United States)

    Duarte, Jorge; Januário, Cristina; Martins, Nuno

    2009-06-01

    Bursting activity is an interesting feature of the temporal organization in many cell firing patterns. This complex behavior is characterized by clusters of spikes (action potentials) interspersed with phases of quiescence. As shown in experimental recordings, concerning the electrical activity of real neurons, the analysis of bursting models reveals not only patterned periodic activity but also irregular behavior 1,2]. The interpretation of experimental results, particularly the study of the influence of coupling on chaotic bursting oscillations, is of great interest from physiological and physical perspectives. The inability to predict the behavior of dynamical systems in presence of chaos suggests the application of chaos control methods, when we are more interested in obtaining regular behavior. In the present article, we focus our attention on a specific class of biophysically motivated maps, proposed in the literature to describe the chaotic activity of spiking-bursting cells [Cazelles B, Courbage M, Rabinovich M. Anti-phase regularization of coupled chaotic maps modelling bursting neurons. Europhys Lett 2001;56:504-9]. More precisely, we study a map that reproduces the behavior of a single cell and a map used to examine the role of reciprocal inhibitory coupling, specially on two symmetrically coupled bursting neurons. Firstly, using results of symbolic dynamics, we characterize the topological entropy associated to the maps, which allows us to quantify and to distinguish different chaotic regimes. In particular, we exhibit numerical results about the effect of the coupling strength on the variation of the topological entropy. Finally, we show that complicated behavior arising from the chaotic coupled maps can be controlled, without changing of its original properties, and turned into a desired attracting time periodic motion (a regular cycle). The control is illustrated by an application of a feedback control technique developed by Romeiras et al. [Romeiras

  12. Real burst traffic amplification in optically gain clamped amplifier

    OpenAIRE

    Ennser, Karin; Taccheo, Stefano; Careglio, Davide; Solé Pareta, Josep; Aracil Rico, Javier

    2008-01-01

    Optical burst amplification in a gain-stabilized amplifier is theoretically investigated using real burst traffic data. The results show that excellent performance are obtained for WDM transmission with negligible interplay due to burst arrival statistics.

  13. German Roentgen Society statement on MR imaging of patients with cardiac pacemakers

    International Nuclear Information System (INIS)

    The aim of this paper is to inform physicians, especially radiologists and cardiologists, about the technical and electrophysiological background of MR imaging of patients with implanted cardiac pacemakers (PM) and to provide dedicated clinical practice guidelines how to perform MR exams in this patient group. The presence of a conventional PM system is not any more considered an absolute contraindication for MR imaging. The prerequisites for MR imaging on pacemaker patients include the assessment of the individual risk/benefit ratio as well as to obtain full informed consent about the off label character of the procedure and all associated risks. Furthermore the use of special PM-related (e.g. re-programming of the PM) and MRI-related (e.g. limitation of whole body SAR to 2 W/kg) precautions is required and needs to be combined with adequate monitoring during MR imaging using continuous pulsoximetry. MR conditional PM devices are tested and approved for the use in the MR environment under certain conditions, including the field strength and gradient slew rate of the MR system, the maximum whole body SAR value and the presence of MR imaging exclusion zones. Safe MR imaging of patients with MR conditional PM requires the knowledge of the specific conditions of each PM system. If MR imaging within these specific conditions cannot be guaranteed in a given patient, the procedure guidelines for conventional PM should be used. The complexity of MR imaging of PM patients requires close cooperation of radiologists and cardiologists.

  14. Recurrent syncope in a hypertensive subject with vascular cognitive impairment and permanent pacemaker

    Directory of Open Access Journals (Sweden)

    Alberto Mazza

    2012-09-01

    Full Text Available Syncope following permanent pacemaker (PM implantation is a nightmare for electrophysiologists. We describe a case of daily recurrent syncope in an 84-year-old man having a dual-chamber pacemaker implanted for complete atrio-ventricular block occurred 4 years before the admission to our department. He had a history of arterial hypertension, parossistic atrial fibrillation, chronic obstructive pulmonary disease, stage-III chronic renal failure, mild vascular cognitive impairment and glaucoma. The initial work-up including electrocardiogram (ECG, repeated PM inter- rogations, Holter electrocardiogram, blood pressure measurement in orthostatic position, complete blood count, serum glycaemia, electrolytes and thyroid function tests showed normal findings. Syncope occurred in lying position and during 90° left clockwise neck rotation and was associated to pallor, sweating, tonic-clonic seizures and transient self-limited loss of consciousness lasting a few seconds. Electroencephalogram was normal. During continuous ECG monitoring, the right rotation of the head determined a ventricular asystolic pause lasting 9 seconds associated with loss of consciousness. Restoration of sinus rhythm was observed after bringing back the head in axis. The PM interrogation, performed during pacing failure, recorded low impedance of bipolar ventricular lead, suggesting a damage in lead insulation. It is likely that lead movements during clockwise neck rotation produced an intermittent short circuit that prevented sufficient energy delivery to the myocardium with a consequence of sudden loss of capture.

  15. Cardiorespiratory Mechanical Simulator for In Vitro Testing of Impedance Minute Ventilation Sensors in Cardiac Pacemakers.

    Science.gov (United States)

    Marcelli, Emanuela; Cercenelli, Laura

    2016-01-01

    We developed a cardiorespiratory mechanical simulator (CRMS), a system able to reproduce both the cardiac and respiratory movements, intended to be used for in vitro testing of impedance minute ventilation (iMV) sensors in cardiac pacemakers. The simulator consists of two actuators anchored to a human thorax model and a software interface to control the actuators and to acquire/process impedance signals. The actuators can be driven separately or simultaneously to reproduce the cardiac longitudinal shortening at a programmable heart rate and the diaphragm displacement at a programmable respiratory rate (RR). A standard bipolar pacing lead moving with the actuators and a pacemaker case fixed to the thorax model have been used to measure impedance (Z) variations during the simulated cardiorespiratory movements. The software is able to discriminate the low-frequency component because of respiration (Z(R)) from the high-frequency ripple because of cardiac effect (Z(C)). Impedance minute ventilation is continuously calculated from Z(R) and RR. From preliminary tests, the CRMS proved to be a reliable simulator for in vitro evaluation of iMV sensors. Respiration impedance recordings collected during cardiorespiratory movements reproduced by the CRMS were comparable in morphology and amplitude with in vivo assessments of transthoracic impedance variations. PMID:26501915

  16. Quantification of fiber orientation in the canine atrial pacemaker complex using optical coherence tomography

    Science.gov (United States)

    Ambrosi, Christina M.; Fedorov, Vadim V.; Schuessler, Richard B.; Rollins, Andrew M.; Efimov, Igor R.

    2012-07-01

    The atrial pacemaker complex is responsible for the initiation and early propagation of cardiac impulses. Optical coherence tomography (OCT), a nondestructive imaging modality with spatial resolutions of ˜1 to 15 μm, can be used to identify unique fiber orientation patterns in this region of the heart. Functionally characterized canine sinoatrial nodes (SAN) (n=7) were imaged using OCT up to ˜1 mm below the endocardial tissue surface. OCT images were directly compared to their corresponding histological sections. Fiber orientation patterns unique to the crista terminalis (CT), SAN, and surrounding atrial myocardium were identified with dominant average fiber angles of 89±12 deg, 110±16 deg, and 95±35 deg, respectively. Both the CT and surrounding atrial myocardium displayed predominantly unidirectionally based fiber orientation patterns within each specimen, whereas the SAN displayed an increased amount of fiber disarray manifested quantitatively as a significantly greater standard deviation in fiber angle distribution within specimens [33±7 deg versus 23±5 deg, atrium (p=0.02); 18±3 deg, CT (p=0.0003)]. We also identified unique, local patterns of fiber orientation specific to the functionally characterized block zone. We demonstrate the ability of OCT in detecting components of the atrial pacemaker complex which are intimately involved in both normal and abnormal cardiac conduction.

  17. Light microscopy of the lymphatics of the human atrial wall and lymphatic drainage of supraventricular pacemakers.

    Science.gov (United States)

    Elisková, M; Eliska, O

    1989-01-01

    After injection of Indian ink stained 2% gelatine in 42 human hearts the lymph drainage of the regions of supraventricular cardiac pacemakers and the patterns of the lymphatic vascular bed in the atrial wall were studied. From the sites of the pacemakers the lymph is drained into the tracheobronchial nodes in 100%. Only two of those regions are drained through additional pathways, namely the SAN region into the anterior mediastinal node situated at the azygos vein and the coronary sinus area into the anterior mediastinal lateropericardiac nodes. In the cleared specimens as microscopically the epicardial lymph vessels produce polygonal superficial network; oblique anastomoses of that network run into the deeper layers of subepicardial tissue where they join with deep irregular lymphatic network. Deep subepicardial lymph vessels are often accompanied by veins and nerves. The course of most of myocardial lymph vessels follows the position of muscle cells. In the connective septa these vessels join to form larger trunks and open into the subepicardial vessels. PMID:2475557

  18. Electron-beam CT coronary angiography in the patients with high heart rate arrhythmia or pacemaker

    International Nuclear Information System (INIS)

    Objective: To report the clinical applicability of coronary angiography for patients with high heart rate, arrhythmia or cardiac pacing using the new-generation of electron-beam CT (e-Speed). Methods: EBCT (GE e-Speed) coronary angiography was performed in 36 eases (male 27, female 9, mean age 58), including the heart rate more than 90 bpm in 20 patients, frequent ectopic beats in 11 cases, implantation of cardiac pacemaker in 4 patients and the unacceptable MSCT image quality due to variability of interscan heart rate (from 82 bpm to 104 bpm) in 1 case. After volume data set was acquired using spiral mode with prospective ECG-gating, the reconstructions of MIP, CPR, VR and Cine were performed. The VR quality was evaluated using a five-point scale. Results: The quality of coronary imaging in all of 36 cases were acceptable. The total visualization rate of coronary artery branches was 80.0%. Left main, left anterior artery and right coronary artery were visualized in all patients and in 94.3% of all cases circumflex artery were visible. Conclusion: EBCT (e-Speed) is applicable in noninvasive coronary angiography for patients with high heart rate, arrhythmia or implanted cardiac pacemaker', and this examination can obtain satisfied diagnosis. (authors)

  19. Cost-based burst dropping strategy in optical burst switching networks

    OpenAIRE

    Klusek, Bartlomiej; Murphy, John; Barry, Liam P.

    2005-01-01

    Optical burst switching (OBS) is a new paradigm for future all-optical networks. Intentional burst dropping is one of techniques used to achieve desired quality of service. In this paper we note that some bursts are more likely to cause contention. We propose a cost function that can be used to predict the likelihood that a given burst will interfere with other traffic, then we explain how, by using this information a new burst dropping strategy can be designed. We compare our method with a r...

  20. Coding Bounds for Multiple Phased-Burst Correction and Single Burst Correction Codes

    OpenAIRE

    Fong, Wai Han

    2011-01-01

    In this paper, two upper bounds on the achievable code rate of linear block codes for multiple phased-burst correction (MPBC) are presented. One bound is constrained to a maximum correctable cyclic burst length within every subblock, or equivalently a constraint on the minimum error free length or gap within every phased-burst. This bound, when reduced to the special case of a bound for single burst correction (SBC), is shown to be the Abramson bound when the cyclic burst length is less than ...

  1. Coherence resonance and synchronization of Hindmarsh-Rose neurons with noise

    Institute of Scientific and Technical Information of China (English)

    Shi Xia; Lu Qi-Shao

    2005-01-01

    Noise effects on coherence resonance and synchronization of Hindmarsh-Rose (HR) neuron model are studied. The coherence resonance of a single HR neuron with Gaussian white noise added to the membrane potential is investigated in situations before, near and after the Hopf bifurcation, separately, with the external direct current as a bifurcation parameter. It is shown that even though there is no coupling between neurons, uncoupled identical HR neurons driven by a common noise can achieve complete synchronization when the noise intensity is higher than a critical value. Furthermore, noise also enhances complete synchronization of weakly coupled neurons. It is concluded that synchronization in bursting neurons is easier to be induced than in spiking ones, and coupling enhances the sensitivity of synchronization of neurons to noise stimulus.

  2. The Case of the Disappearing Spindle Burst.

    Science.gov (United States)

    Tiriac, Alexandre; Blumberg, Mark S

    2016-01-01

    Sleep spindles are brief cortical oscillations at 10-15 Hz that occur predominantly during non-REM (quiet) sleep in adult mammals and are thought to contribute to learning and memory. Spindle bursts are phenomenologically similar to sleep spindles, but they occur predominantly in early infancy and are triggered by peripheral sensory activity (e.g., by retinal waves); accordingly, spindle bursts are thought to organize neural networks in the developing brain and establish functional links with the sensory periphery. Whereas the spontaneous retinal waves that trigger spindle bursts in visual cortex are a transient feature of early development, the myoclonic twitches that drive spindle bursts in sensorimotor cortex persist into adulthood. Moreover, twitches-and their associated spindle bursts-occur exclusively during REM (active) sleep. Curiously, despite the persistence of twitching into adulthood, twitch-related spindle bursts have not been reported in adult sensorimotor cortex. This raises the question of whether such spindle burst activity does not occur in adulthood or, alternatively, occurs but has yet to be discovered. If twitch-related spindle bursts do occur in adults, they could contribute to the calibration, maintenance, and repair of sensorimotor systems. PMID:27119028

  3. CT Burst Error Weight Enumerator of Array Codes

    OpenAIRE

    Irfan Siap

    2008-01-01

    Recently, CT burst errors originally dened for block codes havebeen generalized to CT burst errors for array codes [6]. In order to establish aRieger's type bound for array codes with respect to CT burst errors. Here, weintroduce a CT burst error weight enumerator whose coecients represent thenumber of CT burst errors of a particular weight. The method of obtainingthe CT burst error weight enumerator is obtained by generating function likeapproach and it does not involve solving equations as ...

  4. Do brainstem omnipause neurons terminate saccades?

    Science.gov (United States)

    Rucker, Janet C; Ying, Sarah H; Moore, Willa; Optican, Lance M; Büttner-Ennever, Jean; Keller, Edward L; Shapiro, Barbara E; Leigh, R John

    2011-09-01

    Saccade-generating burst neurons (BN) are inhibited by omnipause neurons (OPN), except during saccades. OPN activity pauses before saccade onset and resumes at the saccade end. Microstimulation of OPN stops saccades in mid-flight, which shows that OPN can end saccades. However, OPN pause duration does not correlate well with saccade duration, and saccades are normometric after OPN lesions. We tested whether OPN were responsible for stopping saccades both in late-onset Tay-Sachs, which causes premature saccadic termination, and in individuals with cerebellar hypermetria. We studied gaze shifts between two targets at different distances aligned on one eye, which consist of a disjunctive saccade followed by vergence. High-frequency conjugate oscillations during the vergence movements that followed saccades were present in all subjects studied, indicating OPN silence. Thus, mechanisms other than OPN discharge (e.g., cerebellar caudal fastigial nucleus-promoting inhibitory BN discharge) must contribute to saccade termination. PMID:21950975

  5. Cycle-by-cycle assembly of respiratory network activity is dynamic and stochastic

    OpenAIRE

    Carroll, Michael S.; Ramirez, Jan-Marino

    2012-01-01

    Rhythmically active networks are typically composed of neurons that can be classified as silent, tonic spiking, or rhythmic bursting based on their intrinsic activity patterns. Within these networks, neurons are thought to discharge in distinct phase relationships with their overall network output, and it has been hypothesized that bursting pacemaker neurons may lead and potentially trigger cycle onsets. We used multielectrode recording from 72 experiments to test these ideas in rhythmically ...

  6. Delay-induced diversity of firing behavior and ordered chaotic firing in adaptive neuronal networks

    International Nuclear Information System (INIS)

    In this paper, we study the effect of time delay on the firing behavior and temporal coherence and synchronization in Newman–Watts thermosensitive neuron networks with adaptive coupling. At beginning, the firing exhibit disordered spiking in absence of time delay. As time delay is increased, the neurons exhibit diversity of firing behaviors including bursting with multiple spikes in a burst, spiking, bursting with four, three and two spikes, firing death, and bursting with increasing amplitude. The spiking is the most ordered, exhibiting coherence resonance (CR)-like behavior, and the firing synchronization becomes enhanced with the increase of time delay. As growth rate of coupling strength or network randomness increases, CR-like behavior shifts to smaller time delay and the synchronization of firing increases. These results show that time delay can induce diversity of firing behaviors in adaptive neuronal networks, and can order the chaotic firing by enhancing and optimizing the temporal coherence and enhancing the synchronization of firing. However, the phenomenon of firing death shows that time delay may inhibit the firing of adaptive neuronal networks. These findings provide new insight into the role of time delay in the firing activity of adaptive neuronal networks, and can help to better understand the complex firing phenomena in neural networks.

  7. IMAGING DIAGNOSIS OF THORACOLUMBAR BURST FRACTURES

    Institute of Scientific and Technical Information of China (English)

    Li-yang Dai

    2004-01-01

    Objective To review imaging use in the diagnosis ofthoracolumbar burst fractures and to determine the diagnostic value of different imaging methods.Methods One hundred and fourteen patients with 120 thoracolumbar burst fractures were retrospectively reviewed. Plain radiographs were available in all cases; CT scans and MRI were obtained in 96 and 74 cases, respectively.Results A total of 27 burst fractures were misdiagnosed as other types of fractures on radiographs alone, and accounted for 22.5% of all fractures. The results indicated that plain radiographs often fail to delineate the pathological features of thoracolumbar burst fractures, leading to delay in diagnosis.Conclusion In regard to thoracolumbar injury diagnosis, burst fractures should be differentiated from compression fractures. CT should be routinely indicated and MRI examination, when necessary, may be simultaneously considered.

  8. Bright 30 THz Impulsive Solar Bursts

    CERN Document Server

    Kaufmann, P; Marcon, R; Kudaka, A S; Cabezas, D P; Cassiano, M M; Francile, C; Fernandes, L O T; Ramirez, R F Hidalgo; Luoni, M; Marun, A; Pereyra, P; de Souza, R V

    2015-01-01

    Impulsive 30 THz continuum bursts have been recently observed in solar flares, utilizing small telescopes with a unique and relatively simple optical setup concept. The most intense burst was observed together with a GOES X2 class event on October 27, 2014, also detected at two sub-THz frequencies, RHESSI X-rays and SDO/HMI and EUV. It exhibits strikingly good correlation in time and in space with white light flare emission. It is likely that this association may prove to be very common. All three 30 THz events recently observed exhibited intense fluxes in the range of 104 solar flux units, considerably larger than those measured for the same events at microwave and sub-mm wavelengths. The 30 THz burst emission might be part of the same spectral burst component found at sub-THz frequencies. The 30 THz solar bursts open a promising new window for the study of flares at their origin

  9. Video-assisted thoracoscopic implantation of a diaphragmatic pacemaker in a child with tetraplegia: indications, technique, and results

    Directory of Open Access Journals (Sweden)

    Darcy Ribeiro Pinto Filho

    2015-02-01

    Full Text Available We report the case of a child with tetraplegia after cervical trauma, who subsequently underwent diaphragmatic pacemaker implantation. We reviewed the major indications for diaphragmatic pacing and the types of devices employed. We highlight the unequivocal benefit of diaphragmatic pacing in the social and educational reintegration of individuals with tetraplegia.

  10. Superior transseptal approach to mitral valve is associated with a higher need for pacemaker implantation than the left atrial approach

    DEFF Research Database (Denmark)

    Lukac, Peter; Hjortdal, Vibeke E; Pedersen, Anders K; Mortensen, Peter; Jensen, Henrik Kjærulf; Hansen, Peter S

    2006-01-01

    retrospectively evaluated. The surgeons used either the superior transseptal (group A) or left atrial approach (group B). The risk of pacemaker implantation associated with the superior transseptal approach as compared with the left atrial approach was estimated using the multivariate Cox regression analysis to...

  11. Subclavian Vein Stenosis/Occlusion Following Transvenous Cardiac Pacemaker and Defibrillator Implantation: Incidence, Pathophysiology and Current Management

    Directory of Open Access Journals (Sweden)

    Brian O'Leary

    2015-08-01

    Full Text Available Subclavian vein stenosis is a common, but usually asymptomatic, complication following cardiac device placement. In addition to reviewing the literature on incidence, pathogenesis and management options for this important clinical problem, we describe two cases of symptomatic subclavian vein occlusion following pacemaker/defibrillator placement and successful treatment with venoplasty and stenting.

  12. Study on non-coplanar intensity modulated radiation therapy in esophageal carcinoma implanted with permanent cardiac pacemaker

    International Nuclear Information System (INIS)

    The aim is to evaluate the physical dose distributions in esophageal carcinoma implanted with permanent cardiac pacemaker treated with non-coplanar intensity modulated radiation therapy (no-co-IMRT). Eight patients with esophageal carcinoma implanted cardiac pacemaker proven by histology were treated by IMRT. For each patient, we designed two IMRT plans by Eclipse IMRT inverse plan system: non-coplanar IMRT plan (3 coplanar fields and 2 non-coplanar fields) and coplanar IMRT plan (5 coplanar fields). The same physical parameter was applied to the same patient in both plans. Plans were evaluated in terms of dose-volume histogram, conformity index, homogeneity index monitor unit and control points. The results showed that no-co-IMRT plan could significantly reduce the max dose of implantable cardiac pacemaker and the wires (p<0.05), but no significant difference was found between no-co-IMRT plan and co-IMRT plan in target volume and other normal tissues Compared with co-IMRT plan, the monitor unit (MU) and control points of no-co-IMRT plan were not increased significantly (p>0.05). These findings indicate that the technique of no-co-IMRT can obtain the fewer max dose of implantable cardiac pacemaker and the wires during intensity modulated radiation therapy of esophageal carcinoma. (authors)

  13. Normal D-dimer ved dyb venøs trombose i en overekstremitet hos to patienter med pacemaker

    DEFF Research Database (Denmark)

    Byrne, Christina; Abdulla, Jawdat; Christensen, Jan Kim

    2015-01-01

    Danish guidelines recommend the use of D-dimer to exclude deep venous thrombosis (DVT) in the lower extremities. However, guidelines are lacking for DVT in the upper extremities. We describe two young women with transvenous pacemaker electrodes and symptomatic DVT in related veins. Despite a norm...

  14. Novel insights on effect of atrioventricular programming of biventricular pacemaker in heart failure – a case series

    Directory of Open Access Journals (Sweden)

    Rafique Asim M

    2006-10-01

    Full Text Available Abstract Background Echocardiography plays an integral role in the diagnosis of congestive heart failure including measurement of left heart pressure as well as mechanical dyssynchrony. Methods In this report we describe novel therapeutic uses of echo pulsed wave Doppler in atrioventricular pacemaker optimization in patients who had either not derived significant symptomatic benefit post biventricular pacemaker implantation or deteriorated after deriving initial benefit. In these patients atrioventricular optimization showed novel findings and improved cardiac output and symptoms. Results In 3 patients with Cheyne Stokes pattern of respiration echo Doppler showed worsening of mitral regurgitation during hyperpneac phase in one patient, marked E and A fusion in another patient and exaggerated ventricular interdependence in a third patient thus highlighting mechanisms of adverse effects of Cheyne Stokes respiration in patients with heart failure. All 3 patients required a very short atrioventricular delay programming for best cardiac output. In one patient with recurrent congestive heart failure post cardiac resynchronization, mitral inflow pulse wave Doppler showed no A wave until a sensed atrioventricular delay of 190 ms was reached and showed progressive improvement in mitral inflow pattern until an atrioventricular delay of 290 ms. In 2 patients atrioventricular delay as short as 50 ms was required to allow E and A separation and prevent diastolic mitral regurgitation. All patients developed marked improvement in congestive heart failure symptoms post echo-guided biv pacemaker optimization. Conclusion These findings highlight the value of echo-guided pacemaker optimization in symptomatic patients post cardiac resynchronization treatment.

  15. The h-current in periglomerular dopaminergic neurons of the mouse olfactory bulb.

    Directory of Open Access Journals (Sweden)

    Angela Pignatelli

    Full Text Available The properties of the hyperpolarization-activated cation current (I(h were investigated in rat periglomerular dopaminergic neurons using patch-clamp recordings in thin slices. A reliable identification of single dopaminergic neurons was made possible by use of a transgenic line of mice expressing eGFP under the tyrosine hydroxylase promoter. At 37 °C and minimizing the disturbance of the intracellular milieu with perforated patches, this current shows a midpoint of activation around -82.7 mV, with a significant level of opening already at rest, thereby giving a substantial contribution to the resting potential, and ultimately playing a relevant function in the control of the cell excitability. The blockage of I(h has a profound influence on the spontaneous firing of these neurons, which result as strongly depressed. However the effect is not due to a direct role of the current in the pacemaker process, but to the I(h influence on the resting membrane potential. I(h kinetics is sensitive to the intracellular levels of cAMP, whose increase promotes a shift of the activation curve towards more positive potentials. The direct application of DA and 5-HT neurotransmitters, physiologically released onto bulbar dopaminergic neurons and known to act on metabotropic receptors coupled to the cAMP pathway, do not modifythe I(h amplitude. On the contrary, noradrenaline almost halves the I(h amplitude. Our data indicate that the HCN channels do not participate directly to the pacemaker activity of periglomerular dopaminergic neurons, but influence their resting membrane potential by controlling the excitability profile of these cells, and possibly affecting the processing of sensory information taking place at the entry of the bulbar circuitry.

  16. Pacemaker, implanted cardiac defibrillator and irradiation: Management proposal in 2010 depending on the type of cardiac stimulator and prognosis and location of cancer

    International Nuclear Information System (INIS)

    Ionizing radiation may interfere with electric components of pacemakers or implantable cardioverter defibrillators. The type, severity and extent of radiation damage to pacemakers, have previously been shown to depend on the total dose and dose rate. Over 300,000 new cancer cases are treated yearly in France, among which 60% are irradiated in the course of their disease. One among 400 of these patients has an implanted pacemaker or defibrillator. The incidence of pacemaker and implanted cardioverter defibrillator increases in an ageing population. The oncologic prognosis must be weighted against the cardiologic prognosis in a multidisciplinary and transversal setting. Innovative irradiation techniques and technological sophistications of pacemakers and implantable cardioverter-defibrillators (with the introduction of more radiosensitive complementary metal-oxide-semiconductors since 1970) have potentially changed the tolerance profiles. This review of the literature studied the geometric, dosimetric and radiobiological characteristics of the radiation beams for high energy photons, stereotactic irradiation, proton-therapy. Standardized protocols and radiotherapy optimization (particle, treatment fields, energy) are advisable in order to improve patient management during radiotherapy and prolonged monitoring is necessary following radiation therapy. The dose received at the pacemaker/heart should be calculated. The threshold for the cumulated dose to the pacemaker/implantable cardioverter-defibrillator (2 to 5 Gy depending on the brand), the necessity to remove/displace the device based on the dose-volume histogram on dosimetry, as well as the use of lead shielding and magnet are discussed. (authors)

  17. Global synchronization of two Ghostburster neurons via active control

    Energy Technology Data Exchange (ETDEWEB)

    Sun Li [School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072 (China); Wang Jiang [School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072 (China)], E-mail: jiangwang@tju.edu.cn; Deng Bin [School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072 (China)

    2009-05-15

    In this paper, active control law is derived and applied to control and synchronize two unidirectional coupled Ghostburster neurons under external electrical stimulation. Firstly, the dynamical behavior of the nonlinear Ghostburster model responding to various external electrical stimulations is studied. Then, using the results of the analysis, the active control strategy is designed for global synchronization of the two unidirectional coupled neurons and stabilizing the chaotic bursting trajectory of the slave system to desired tonic firing of the master system. Numerical simulations demonstrate the validity and feasibility of the proposed method.

  18. Spatiotemporal chaos from bursting dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Berenstein, Igal; De Decker, Yannick [Nonlinear Physical Chemistry Unit and Interdisciplinary Center for Nonlinear Phenomena and Complex Systems (CENOLI), Faculté des Sciences, Université libre de Bruxelles (ULB), Campus Plaine, C.P. 231, B-1050 Brussels (Belgium)

    2015-08-14

    In this paper, we study the emergence of spatiotemporal chaos from mixed-mode oscillations, by using an extended Oregonator model. We show that bursting dynamics consisting of fast/slow mixed mode oscillations along a single attractor can lead to spatiotemporal chaotic dynamics, although the spatially homogeneous solution is itself non-chaotic. This behavior is observed far from the Hopf bifurcation and takes the form of a spatiotemporal intermittency where the system locally alternates between the fast and the slow phases of the mixed mode oscillations. We expect this form of spatiotemporal chaos to be generic for models in which one or several slow variables are coupled to activator-inhibitor type of oscillators.

  19. Campylobacter fetus infection presenting with bacteremia and cellulitis in a 72-year-old man with an implanted pacemaker: a case report

    Directory of Open Access Journals (Sweden)

    Ledina Dragan

    2012-11-01

    Full Text Available Abstract Introduction Campylobacter is an important causative agent of intestinal infections in humans. Bacteremia is detected in less than 1% of patients, mainly in immunocompromised patients and in extreme age groups. Cellulitis is a relatively common manifestation of Campylobacter infection, but concomitant bacteremia is a rare event. Infections of the pacemaker area are caused primarily by staphylococci, followed by fungi, streptococci and Gram-negative rods. To the best of our knowledge, this is the first case report of pacemaker pocket infection and bacteremia caused by Campylobacter fetus. Case presentation A 72-year-old Croatian Caucasian man with myelodysplasia, impaired fasting glucose levels and a recently implanted permanent pacemaker was admitted to hospital after six days of fever, development of red swelling of the pacemaker pocket area and worsening of his general condition. No antibiotic therapy was introduced in the outpatient setting. He denied any recent gastrointestinal disturbances. With the exception of an elevated leukocyte count, erythrocyte sedimentation rate, and C-reactive protein and blood glucose levels, other laboratory findings were normal. Treatment with vancomycin plus netilmicin was introduced, and a surgical incision with drainage of the pacemaker pocket was performed. The entire pacemaker system was removed and a new one re-implanted after 14 days of antibiotic therapy. Transesophageal echocardiography showed no pathological findings. Three subsequent blood cultures obtained on admission as well as swab culture of the incised pacemaker area revealed Campylobacter fetus; stool and pacemaker lead cultures were negative. According to the microbiological results, antibiotic therapy was changed to ciprofloxacin plus netilmicin. A clinical examination and the results of a laboratory analysis performed after two weeks of therapy were within normal limits. Conclusion Myelodysplasia, impaired fasting glucose levels

  20. Poincare return mapping for models of elliptic neurons

    OpenAIRE

    Jeremy Wojcik

    2010-01-01

    We propose a novel computer assisted method for the effective construction and accurate examination of families of Poincaré return mappings for voltage maxima in models of elliptic bursting neurons. Such busters are adequately described by dynamical systems with two characteristic time scales: slow and fast. A feature of a slow-fast dynamical model is that its solutions stay close to the so-called slow motion manifolds, comprised of equilibria and limit cycles of its fast subs...

  1. From beat rate variability in induced pluripotent stem cell-derived pacemaker cells to heart rate variability in human subjects

    Science.gov (United States)

    Barad, Lili; Novak, Atara; Ben-Ari, Erez; Lorber, Avraham; Itskovitz-Eldor, Joseph; Rosen, Michael R; Weissman, Amir; Binah, Ofer

    2014-01-01

    Background We previously reported that induced Pluripotent Stem Cell-derived cardiomyocytes (iPSC-CM) manifest beat rate variability (BRV) resembling heart rate variability (HRV) in human sinoatrial node (SAN). We now hypothesized the BRV-HRV continuum originates in pacemaker cells. Objective To investigate whether cellular BRV is a source of HRV dynamics, we hypothesized three-levels of interaction among different cardiomyocyte entities: (1) single pacemaker cells, (2) networks of electrically coupled pacemaker cells and (3) in situ SAN. Methods We measured BRV/HRV properties in single pacemaker cells, iPSC-derived contracting embryoid bodies (EBs) and electrocardiograms from the same individual. Results Pronounced BRV/HRV were present at all three levels. Coefficient of variance (COV) of inter-beat intervals (IBI) and Poincaré plot SD1 and SD2 in single cells were 20x > EBs (P0.05). We also compared BRV magnitude among single cells, small (~5-10 cells) and larger EBs (>10 cells): BRV indices progressively increased (P<0.05) as cell number decreased. Disrupting intracellular Ca2+ handling markedly augmented BRV magnitude, revealing a unique bi-modal firing pattern, suggesting intracellular mechanisms contribute to BRV/HRV and the fractal behavior of heart rhythm. Conclusions The decreased BRV magnitude in transitioning from single cell to EB suggests HRV of hearts in situ originates from summation and integration of multiple cell-based oscillators. Hence, complex interactions among multiple pacemaker cells and intracellular Ca2+ handling determine HRV in humans and isolated cardiomyocyte networks. PMID:25052725

  2. Electrophysiology of the mammillary complex in vitro. II. Medial mammillary neurons

    Science.gov (United States)

    Alonso, A.; Llinas, R. R.

    1992-01-01

    1. The electrophysiological properties of guinea pig medial mammillary body (MMB) neurons were studied using an in vitro slice preparation. 2. The neurons (n = 80) had an average resting potential of -57 +/- 5.5 (SD) mV, an input resistance of 176 +/- 83 M omega, and a spike amplitude of 58 +/- 15.7 mV. Most of the neurons were silent at rest (n = 52), but some fired spontaneous single spikes (n = 16) or spike bursts (n = 14). 3. The main electrophysiological characteristic of MMB neurons was the ability to generate Ca(2+)-dependent regenerative events, which resulted in very robust burst responses. However, this regenerative event was not the same for all neurons, ranging from typical low-threshold Ca2+ spikes (LTSs) to intermediate-threshold plateau potentials (ITPs). 4. The ITPs were distinct from the LTSs in that they lasted > or = 100 ms and were not inactivated at membrane potentials at or positive to -55 mV. 5. Some cells with a prominent ITP and no LTS (n = 36) displayed repetitive, usually rhythmic, bursting (n = 14). This ITP could be powerful enough to maintain rhythmic membrane potential oscillations after pharmacological block of Na+ conductances. 6. A group of 32 MMB neurons displayed complex bursting that was generated by activation of both LTSs and ITPs. This was established on the basis of their distinct time- and voltage-dependent characteristics. In a group of neurons (n = 14), the burst responses were exclusively generated by an LTS; however, a Ca(2+)-dependent plateau potential contributed to the generation of rebound-triggered oscillatory firing. 7. In addition to the Ca(2+)-dependent LTS and/or ITP, MMB neurons always displayed high-threshold Ca2+ spikes after reduction of K+ conductances with tetraethylammonium. 8. MMB neurons display one of the richer varieties of voltage-dependent Ca2+ conductances so far encountered in mammalian CNS. We propose that the very prominent endogenous bursting and oscillatory properties of MB neurons allow this

  3. Heart pacemaker

    Science.gov (United States)

    ... Elsevier Saunders; 2015:chap 36. Read More Arrhythmias Atrial fibrillation or flutter Cardiac ablation procedures Heart failure - overview Implantable cardioverter-defibrillator Sick sinus syndrome Wolff- ...

  4. Conceptual design of GaN betavoltaic battery using in cardiac pacemaker

    International Nuclear Information System (INIS)

    Introduction: Pacemaker is an electronic biomedical device which stimulates and regulates or amplify the human heartbeat by delivering weak electrical pulses to the cardiac muscle at regular intervals when its natural regulating mechanisms break down. Developments in design and implementation of power source in adjacent to advances in electronic circuitry is an important aspect in optimization of pacemakers. For instance, many implant patients continue to outlive their batteries and require costly and risky replacement surgery. So such device needs to have high energy density power source and maintain a stable current and voltage for a long period of time to avoid frequent replacements. In addition, the size is also an important consideration for implantable batteries. Betavoltaic batteries are being researched as a suitable source for these applications. Also, these batteries have vast application in which the replacement of batteries is highly inconvenient, such as in oil and mining industries, which often place sensors in dangerous or hard-to-reach locations. The purpose of the present investigation is determination of the optimal parameters of low energy GaN betavoltaic battery in artificial cardiac pacemakers using MCNP code which have higher efficiency than those available with previous devices, especially thermoelectric converters (∼15%). Material and Methods: In this design, two p-n diode structures from GaN semiconductor were used to collect the charge from a layer of 63Ni as a source which is centered between the two p-n junctions. MCNP simulation results have been used to determine the amount of electron current from interaction of beta particles in p-n junctions. Results and Discussion: Calculation results indicate that the short circuit current, open circuit voltage and efficiency of a single device are 1.1 μA/cm2, 2.7 volt and 25%, respectively. Also, it's concluded that with suitable arrangement of these single devices, one could construct a

  5. Ca2+-Clock-Dependent Pacemaking in the Sinus Node Is Impaired in Mice with a Cardiac Specific Reduction in SERCA2 Abundance

    OpenAIRE

    Logantha, Sunil Jit R.J.; Stokke, Mathis K.; Atkinson, Andrew J.; Kharche, Sanjay R.; Parveen, Sajida; Saeed, Yawer; Sjaastad, Ivar; Sejersted, Ole M; Dobrzynski, Halina

    2016-01-01

    Background: The sarcoplasmic reticulum Ca2+-ATPase (SERCA2) pump is an important component of the Ca2+-clock pacemaker mechanism that provides robustness and flexibility to sinus node pacemaking. We have developed transgenic mice with reduced cardiac SERCA2 abundance (Serca2 KO) as a model for investigating SERCA2's role in sinus node pacemaking. Methods and Results: In Serca2 KO mice, ventricular SERCA2a protein content measured by Western blotting was 75% (P < 0.05) lower than that in contr...

  6. Observing a Burst with Sunglasses

    Science.gov (United States)

    2003-11-01

    Unique Five-Week VLT Study of the Polarisation of a Gamma-Ray Burst Afterglow "Gamma-ray bursts (GRBs)" are certainly amongst the most dramatic events known in astrophysics. These short flashes of energetic gamma-rays, first detected in the late 1960's by military satellites, last from less than one second to several minutes. GRBs have been found to be situated at extremely large ("cosmological") distances. The energy released in a few seconds during such an event is larger than that of the Sun during its entire lifetime of more than 10,000 million years. The GRBs are indeed the most powerful events since the Big Bang known in the Universe, cf. ESO PR 08/99 and ESO PR 20/00. During the past years circumstantial evidence has mounted that GRBs signal the collapse of extremely massive stars, the so-called hypernovae. This was finally demonstrated some months ago when astronomers, using the FORS instrument on ESO's Very Large Telescope (VLT), documented in unprecedented detail the changes in the spectrum of the light source ("the optical afterglow") of the gamma-ray burst GRB 030329 (cf. ESO PR 16/03). A conclusive and direct link between cosmological gamma-ray bursts and explosions of very massive stars was provided on this occasion. Gamma-Ray Burst GRB 030329 was discovered on March 29, 2003 by NASA's High Energy Transient Explorer spacecraft. Follow-up observations with the UVES spectrograph at the 8.2-m VLT KUEYEN telescope at the Paranal Observatory (Chile) showed the burst to have a redshift of 0.1685 [1]. This corresponds to a distance of about 2,650 million light-years, making GRB 030329 the second-nearest long-duration GRB ever detected. The proximity of GRB 030329 resulted in very bright afterglow emission, permitting the most extensive follow-up observations of any afterglow to date. A team of astronomers [2] led by Jochen Greiner of the Max-Planck-Institut für extraterrestrische Physik (Germany) decided to make use of this unique opportunity to study the

  7. The Case of the Disappearing Spindle Burst

    Directory of Open Access Journals (Sweden)

    Alexandre Tiriac

    2016-01-01

    Full Text Available Sleep spindles are brief cortical oscillations at 10–15 Hz that occur predominantly during non-REM (quiet sleep in adult mammals and are thought to contribute to learning and memory. Spindle bursts are phenomenologically similar to sleep spindles, but they occur predominantly in early infancy and are triggered by peripheral sensory activity (e.g., by retinal waves; accordingly, spindle bursts are thought to organize neural networks in the developing brain and establish functional links with the sensory periphery. Whereas the spontaneous retinal waves that trigger spindle bursts in visual cortex are a transient feature of early development, the myoclonic twitches that drive spindle bursts in sensorimotor cortex persist into adulthood. Moreover, twitches—and their associated spindle bursts—occur exclusively during REM (active sleep. Curiously, despite the persistence of twitching into adulthood, twitch-related spindle bursts have not been reported in adult sensorimotor cortex. This raises the question of whether such spindle burst activity does not occur in adulthood or, alternatively, occurs but has yet to be discovered. If twitch-related spindle bursts do occur in adults, they could contribute to the calibration, maintenance, and repair of sensorimotor systems.

  8. Firing Dynamics and Modulatory Actions of Supraspinal Dopaminergic Neurons during Zebrafish Locomotor Behavior

    OpenAIRE

    Jay, Michael; De Faveri, Francesca; McDearmid, Jonathan Robert

    2015-01-01

    Summary Background Dopamine (DA) has long been known to have modulatory effects on vertebrate motor circuits. However, the types of information encoded by supraspinal DAergic neurons and their relationship to motor behavior remain unknown. Results By conducting electrophysiological recordings from awake, paralyzed zebrafish larvae that can produce behaviorally relevant activity patterns, we show that supraspinal DAergic neurons generate two forms of output: tonic spiking and phasic bursting. ...

  9. The synaptic connections of pyramidal neurones and interneurones in rat and cat neocortex.

    OpenAIRE

    Bannister, A. P.

    2004-01-01

    The layer 4 neurones of the mammalian primary sensory neocortex comprise diverse functional components for the first stage of cortical sensory processing. Dual intracellular recordings of synaptically connected pairs of neurones with biocytin-filling were used to study intra-laminar layer 4 connections in adult cat and rat slices. Interestingly, all excitatory cells involved in intralaminar layer 4 connections were regular spiking despite burst firing cells comprising 37% of the population re...

  10. CAMKII Activation Is Not Required for Maintenance of Learning-Induced Enhancement of Neuronal Excitability

    OpenAIRE

    Ori Liraz; Kobi Rosenblum; Edi Barkai

    2009-01-01

    Pyramidal neurons in the piriform cortex from olfactory-discrimination trained rats show enhanced intrinsic neuronal excitability that lasts for several days after learning. Such enhanced intrinsic excitability is mediated by long-term reduction in the post-burst after-hyperpolarization (AHP) which is generated by repetitive spike firing. AHP reduction is due to decreased conductance of a calcium-dependent potassium current, the sI(AHP). We have previously shown that learning-induced AHP redu...

  11. Gamma-Ray Bursts: Jets and Energetics

    CERN Document Server

    Frail, D A

    2003-01-01

    The relativistic outflows from gamma-ray bursts are now thought to be narrowly collimated into jets. After correcting for this jet geometry there is a remarkable constancy of both the energy radiated by the burst and the kinetic energy carried by the outflow. Gamma-ray bursts are still the most luminous explosions in the Universe, but they release energies that are comparable to supernovae. The diversity of cosmic explosions appears to be governed by the fraction of energy that is coupled to ultra-relativistic ejecta.

  12. EXIST's Gamma-Ray Burst Sensitivity

    OpenAIRE

    Band, D. L.; Grindlay, J. E.; Hong, J.; Fishman, G.; Hartmann, D. H.; Garson III, A.; Krawczynski, H.; Barthelmy, S.; Gehrels, N.; Skinner, G.

    2007-01-01

    We use semi-analytic techniques to evaluate the burst sensitivity of designs for the EXIST hard X-ray survey mission. Applying these techniques to the mission design proposed for the Beyond Einstein program, we find that with its very large field-of-view and faint gamma-ray burst detection threshold, EXIST will detect and localize approximately two bursts per day, a large fraction of which may be at high redshift. We estimate that EXIST's maximum sensitivity will be ~4 times greater than that...

  13. Radiation exposure due to implanted pacemakers with 238Pu-nuclide batteries

    International Nuclear Information System (INIS)

    The radiation exposure of patients and environment due to neutron and γ-radiation was determined using the results of outdoor and model measurements and direct measurements carried out on 7 patients with implanted 238Pu-pacemakers. For measuring the neutron dose equivalent a directly recording proportional counter was used, which was calibrated with a 238Pu-neutron source for various tissue depths. The distribution of fluence in the tissue surrounding the neutron source was determined by means of 0,3 mm thick nuclear track etching detectors in a phantom. Corresponding measurings of γ-doses were carried out with LiF-dosimeters. The dose equivalent of neutrons and gamma radiation is determined as function of the distance from the source; the build-up and the attenuation in the tissue being taken into account. The radiation exposure of the patient and environment is compared with the long-term radiation exposure due to natural and civilizing factors. (orig.)

  14. Electrical Injury-Induced Complete Atrioventricular Block: Is Permanent Pacemaker Required?

    Directory of Open Access Journals (Sweden)

    Osman Beton

    2015-01-01

    Full Text Available A considerable percentage of electrical injuries occur as a result of work activities. Electrical injury can lead to various cardiovascular disorders: acute myocardial necrosis, myocardial ischemia, heart failure, arrhythmias, hemorrhagic pericarditis, acute hypertension with peripheral vasospasm, and anomalous, nonspecific ECG alterations. Ventricular fibrillation is the most common arrhythmia resulting from electrical injury and is the leading cause of death in electrical (especially low voltage alternating current injury cases. Asystole, premature ventricular contractions, ventricular tachycardia, conduction disorders (various degrees of heart blocks, bundle-brunch blocks, supraventricular tachycardia, and atrial fibrillation are the other arrhythmic complications of electrical injury. Complete atrioventricular block has rarely been reported and permanent pacemaker was required for the treatment in some of these cases. Herein, we present a case of reversible complete atrioventricular block due to low voltage electrical injury in a young electrical technician.

  15. Electrical Injury-Induced Complete Atrioventricular Block: Is Permanent Pacemaker Required?

    Science.gov (United States)

    Beton, Osman; Efe, Tolga Han; Kaya, Hakki; Bilgin, Murat; Dinc Asarcikli, Lale; Yilmaz, Mehmet Birhan

    2015-01-01

    A considerable percentage of electrical injuries occur as a result of work activities. Electrical injury can lead to various cardiovascular disorders: acute myocardial necrosis, myocardial ischemia, heart failure, arrhythmias, hemorrhagic pericarditis, acute hypertension with peripheral vasospasm, and anomalous, nonspecific ECG alterations. Ventricular fibrillation is the most common arrhythmia resulting from electrical injury and is the leading cause of death in electrical (especially low voltage alternating current) injury cases. Asystole, premature ventricular contractions, ventricular tachycardia, conduction disorders (various degrees of heart blocks, bundle-brunch blocks), supraventricular tachycardia, and atrial fibrillation are the other arrhythmic complications of electrical injury. Complete atrioventricular block has rarely been reported and permanent pacemaker was required for the treatment in some of these cases. Herein, we present a case of reversible complete atrioventricular block due to low voltage electrical injury in a young electrical technician. PMID:26839721

  16. The Arecibo Fast Radio Burst: Dense Circum-burst Medium

    CERN Document Server

    Kulkarni, S R; Neill, J D

    2015-01-01

    The nature of fast radio bursts (FRB) has been extensively debated. Here we investigate FRB121102, detected at Arecibo telescope and remarkable for its unusually large spectral index. After extensive study we conclude that the spectral index is caused by a nebula with free-free absorption. We find that putative nebula must lie beyond the Milky Way. We conclude that FRBs are of extra-galactic origin and that they arise in dense star-forming regions. The challenge with extra-galactic models is the the high volumetric rate of FRBs. This high rate allows us to eliminate all models of catastrophic stellar deaths. Hyper-giant flares from young magnetars emerge as the most likely progenitors. Some of the consequences are: (i) Intergalactic FRB models can be safely ignored. (ii) The rich ISM environment of young magnetars can result in significant contribution to DM, Rotation Measure (RM) and in some cases to significant free-free optical depth. (iii) The star-forming regions in the host galaxies can contribute signi...

  17. The propensity to bi-stability of bursting and silence of the leech heart interneuron

    Science.gov (United States)

    Malaschenko, Tatiana; Williams, Diana; Shilnikov, Andrey; Cymbalyuk, Gennady

    2009-11-01

    Bursting is one of primary activity regimes of neurons. Our previous study was focused on determining a generic biophysical mechanism underlying the transition between bursting and silence and the co-existence of these two regimes observed in a neuron model. We show that this co-existence can be explained by the unstable sub-threshold oscillations (USTO) separating silence and bursting. The range of the controlling parameters, where the co-existence is observed, is limited by the critical values of the system at which the Andronov-Hopf and homoclinic bifurcations occur. We investigate how different parameters of the model affect the width of the co-existence area. We study the effects of the variations of maximal conductances of every voltage-dependent current. The influence of each current was tested individually, one at the time. We found that only two of them had a significant effect on the range of co-existence. The increase of the maximal conductance of the hyperpolarization-activated cationic current Ih would expand the area of co-existence. The decrease of the conductance of the LVA fast Ca^2+ current has the opposite effect.

  18. ESTIMATE OF BURSTING PRESSURE OF MILD STEEL PRESSURE VESSEL AND PRESENTATION OF BURSTING FORMULA

    Institute of Scientific and Technical Information of China (English)

    ZHENG Chuanxiang

    2006-01-01

    In order to get more precise bursting pressure formula of mild steel, hundreds of bursting experiments of mild steel pressure vessels such as Q235(Gr.D) and 20R(1020) are done. Based on statistical data of bursting pressure and modification of Faupel formula, a more precise modified formula is given out according to the experimental data. It is proved to be more accurate after examining other bursting pressure value presented in many references. This bursting formula is very accurate in these experiments using pressure vessels with different diameter and shell thickness.Obviously, this modified bursting formula can be used in mild steel pressure vessels with different diameter and thickness of shell.

  19. Diversity of Layer 5 Projection Neurons in the Mouse Motor Cortex

    Directory of Open Access Journals (Sweden)

    Manfred J Oswald

    2013-10-01

    Full Text Available In the primary motor cortex (M1, layer 5 projection neurons signal directly to distant motor structures to drive movement. Despite their pivotal position and acknowledged diversity these neurons are traditionally separated into broad commissural and corticofugal types, and until now no attempt has been made at resolving the basis for their diversity. We therefore probed the electrophysiological and morphological properties of retrogradely labelled M1 corticospinal (CSp, corticothalamic (CTh, and commissural projecting corticostriatal (CStr and corticocortical (CC neurons. An unsupervised cluster analysis established at least four phenotypes with additional differences between lumbar and cervical projecting CSp neurons. Distinguishing parameters included the action potential (AP waveform, firing behaviour, the hyperpolarisation-activated sag potential, sublayer position, and soma and dendrite size. CTh neurons differed from CSp neurons in showing spike frequency acceleration and a greater sag potential. CStr neurons had the lowest AP amplitude and maximum rise rate of all neurons. Temperature influenced spike train behaviour in corticofugal neurons. At 26 ºC CTh neurons fired bursts of APs more often than CSp neurons, but at 36 ºC both groups fired regular APs. Our findings provide reliable phenotypic fingerprints to identify distinct M1 projection neuron classes as a tool to understand their unique contributions to motor function.

  20. One-Year Follow-Up of Patients Undergoing Transvenous Extraction of Pacemaker and Defibrillator Leads.

    Directory of Open Access Journals (Sweden)

    Maciej Kempa

    Full Text Available The number of pacemaker and ICD implantations has increased substantially in the recent years. Therefore, complications are also observed in a greater number. In many cases, transvenous extraction of the previously implanted device (pacemaker or ICD is the only solution. One may find in the literature information about the efficacy and safety of that procedure, but data concerning the results of long-term follow up are still limited.The aim of the study was to assess the one-year mortality in the cohort of patients undergoing transvenous lead extraction procedures in our centre.Records of the patients undergoing transvenous lead removal in the Department of Cardiology and Electrotherapy of the Medical University of Gdańsk were analyzed. We collected detailed information about 192 patients that had undergone the procedure from January 2003 until June 2012. Data were collected from medical and surgical records. We analyzed concomitant diseases, indications, and possible complications. Long-term follow-up data were gathered in the follow-up ambulatory records and over-the-phone interviews with patients or families. In several cases, we consulted the database of the Polish National Health Fund.During the early post-operative period 5 patients died, although none of those deaths was associated with the procedure itself. No other major complications were observed. During one-year follow-up other 5 patients died, which gave the overall one-year survival rate of 92.7%. Heart failure, renal failure and an infective indication showed significant association with increased mortality.Results of transvenous lead extraction, a relatively safe procedure, should be assessed over time extending beyond the sole perioperative period. Some complications may be delayed in their nature, and may be observed only during the long-term follow up.

  1. Effects of bursting dynamic features on the generation of multi-clustered structure of neural network with symmetric spike-timing-dependent plasticity learning rule.

    Science.gov (United States)

    Liu, Hui; Song, Yongduan; Xue, Fangzheng; Li, Xiumin

    2015-11-01

    In this paper, the generation of multi-clustered structure of self-organized neural network with different neuronal firing patterns, i.e., bursting or spiking, has been investigated. The initially all-to-all-connected spiking neural network or bursting neural network can be self-organized into clustered structure through the symmetric spike-timing-dependent plasticity learning for both bursting and spiking neurons. However, the time consumption of this clustering procedure of the burst-based self-organized neural network (BSON) is much shorter than the spike-based self-organized neural network (SSON). Our results show that the BSON network has more obvious small-world properties, i.e., higher clustering coefficient and smaller shortest path length than the SSON network. Also, the results of larger structure entropy and activity entropy of the BSON network demonstrate that this network has higher topological complexity and dynamical diversity, which benefits for enhancing information transmission of neural circuits. Hence, we conclude that the burst firing can significantly enhance the efficiency of clustering procedure and the emergent clustered structure renders the whole network more synchronous and therefore more sensitive to weak input. This result is further confirmed from its improved performance on stochastic resonance. Therefore, we believe that the multi-clustered neural network which self-organized from the bursting dynamics has high efficiency in information processing. PMID:26627568

  2. Effects of bursting dynamic features on the generation of multi-clustered structure of neural network with symmetric spike-timing-dependent plasticity learning rule

    International Nuclear Information System (INIS)

    In this paper, the generation of multi-clustered structure of self-organized neural network with different neuronal firing patterns, i.e., bursting or spiking, has been investigated. The initially all-to-all-connected spiking neural network or bursting neural network can be self-organized into clustered structure through the symmetric spike-timing-dependent plasticity learning for both bursting and spiking neurons. However, the time consumption of this clustering procedure of the burst-based self-organized neural network (BSON) is much shorter than the spike-based self-organized neural network (SSON). Our results show that the BSON network has more obvious small-world properties, i.e., higher clustering coefficient and smaller shortest path length than the SSON network. Also, the results of larger structure entropy and activity entropy of the BSON network demonstrate that this network has higher topological complexity and dynamical diversity, which benefits for enhancing information transmission of neural circuits. Hence, we conclude that the burst firing can significantly enhance the efficiency of clustering procedure and the emergent clustered structure renders the whole network more synchronous and therefore more sensitive to weak input. This result is further confirmed from its improved performance on stochastic resonance. Therefore, we believe that the multi-clustered neural network which self-organized from the bursting dynamics has high efficiency in information processing

  3. Effects of bursting dynamic features on the generation of multi-clustered structure of neural network with symmetric spike-timing-dependent plasticity learning rule

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hui; Song, Yongduan; Xue, Fangzheng; Li, Xiumin, E-mail: xmli@cqu.edu.cn [Key Laboratory of Dependable Service Computing in Cyber Physical Society of Ministry of Education, Chongqing University, Chongqing 400044 (China); College of Automation, Chongqing University, Chongqing 400044 (China)

    2015-11-15

    In this paper, the generation of multi-clustered structure of self-organized neural network with different neuronal firing patterns, i.e., bursting or spiking, has been investigated. The initially all-to-all-connected spiking neural network or bursting neural network can be self-organized into clustered structure through the symmetric spike-timing-dependent plasticity learning for both bursting and spiking neurons. However, the time consumption of this clustering procedure of the burst-based self-organized neural network (BSON) is much shorter than the spike-based self-organized neural network (SSON). Our results show that the BSON network has more obvious small-world properties, i.e., higher clustering coefficient and smaller shortest path length than the SSON network. Also, the results of larger structure entropy and activity entropy of the BSON network demonstrate that this network has higher topological complexity and dynamical diversity, which benefits for enhancing information transmission of neural circuits. Hence, we conclude that the burst firing can significantly enhance the efficiency of clustering procedure and the emergent clustered structure renders the whole network more synchronous and therefore more sensitive to weak input. This result is further confirmed from its improved performance on stochastic resonance. Therefore, we believe that the multi-clustered neural network which self-organized from the bursting dynamics has high efficiency in information processing.

  4. Burst suppression probability algorithms: state-space methods for tracking EEG burst suppression

    OpenAIRE

    Chemali, Jessica; Ching, ShiNung; Purdon, Patrick L; Solt, Ken; Brown, Emery N.

    2013-01-01

    Objective. Burst suppression is an electroencephalogram pattern in which bursts of electrical activity alternate with an isoelectric state. This pattern is commonly seen in states of severely reduced brain activity such as profound general anesthesia, anoxic brain injuries, hypothermia and certain developmental disorders. Devising accurate, reliable ways to quantify burst suppression is an important clinical and research problem. Although thresholding and segmentation algorithms readily ident...

  5. Directivity of low-frequency solar type 3 radio bursts

    International Nuclear Information System (INIS)

    The occurrence rate of type 3 solar bursts in the frequency range 4.9 MHz to 30 kHz was analyzed as a function of burst intensity and burst arrival direction. Results show that the occurrence rate of bursts falls off with increasing flux and the distribution of burst arrival directions at each frequency shows a significantly larger number of bursts observed west of the earth--sun line than east of it. This western excess in occurrence rate appears to be correlated with the direction of the average interplanetary magnetic field, and is interpreted as beaming of the observed burst radiation along the magnetic field direction

  6. Juvenil neuronal ceroid lipofuscinosis

    DEFF Research Database (Denmark)

    Ostergaard, J R; Hertz, Jens Michael

    1998-01-01

    Neuronal ceroid-lipofuscinosis is a group of neurodegenerative diseases which are characterized by an abnormal accumulation of lipopigment in neuronal and extraneuronal cells. The diseases can be differentiated into several subgroups according to age of onset, the clinical picture...

  7. Long Burst Error Correcting Codes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Long burst error mitigation is an enabling technology for the use of Ka band for high rate commercial and government users. Multiple NASA, government, and...

  8. Relativistic effects in gamma-ray bursts

    International Nuclear Information System (INIS)

    According to recent models of the sources of gamma-ray bursts the extremely energetic emission is caused by shells expanding with ultrarelativistic velocity. With the recent identification of optical sources at the positions of some gamma-ray bursts these ''fireball'' models have acquired an actuality that invites to use them as a motivating application when teaching special relativity. We demonstrate several relativistic effects associated with these models which are very pronounced due to the great velocity of the shell. For example a burst lasting for a month in the rest frame of an element of the shell lasts for a few seconds only, in the rest frame of our detector. It is shown how the observed properties of a burst are modified by aberration and the Doppler effect. The apparent luminosity as a function of time is calculated. Modifications due to the motion of the star away from the observer are calculated. (Author)

  9. FRBCAT: The Fast Radio Burst Catalogue

    CERN Document Server

    Petroff, E; Jameson, A; Keane, E F; Bailes, M; Kramer, M; Morello, V; Tabbara, D; van Straten, W

    2016-01-01

    Here we present a catalogue of known Fast Radio Burst (FRB) sources in the form of an online catalogue, FRBCAT. The catalogue includes information about the instrumentation used for the observations for each detected burst, the measured quantities from each observation, and model-dependent quantities derived from observed quantities. To aid in consistent comparisons of burst properties such as width and signal-to-noise ratios we have reprocessed all the bursts for which we have access to the raw data, with software which we make available. The originally derived properties are also listed for comparison. The catalogue is hosted online as a MySQL database which can also be downloaded in tabular or plain text format for off-line use. This database will be maintained for use by the community for studies of the FRB population as it grows.

  10. Bursts of intermediate ions in atmospheric air

    Science.gov (United States)

    Hõrrak, U.; Salm, J.; Tammet, H.

    1998-06-01

    The mobility spectrum of air ions has been measured at Tahkuse Observatory in Estonia for several years. The average concentration of intermediate ions with mobilities of 0.05-0.5 cm2 V-1 s-1 in atmospheric air is about 50 cm-3. On the level of this low background, high concentration bursts of intermediate air ions occur occasionally. A burst can be followed by subsequent evolution of intermediate ions into larger ones. To explain the bursts of intermediate air ions, two hypotheses can be advanced: (1)A burst of neutral particles occurs due to homogeneous nucleation, and the particles are charged by the attachment of cluster ions. (2) The cluster ions grow by ion-induced nucleation in proper environmental conditions.

  11. Burst Fragmentation Model Based on Sequential Burst Allocation Algorithm for Mobile WiMAX

    Directory of Open Access Journals (Sweden)

    Zaid G. Ali

    2013-07-01

    Full Text Available the downlink Bandwidth resources of WiMAX are allocated by the burst allocation algorithm. The algorithm is responsible for calculating the appropriate location of a number of the smallest unit of bandwidth which is called the slot for all users within the downlink subframe in the form of bursts. Resource wastage in the form of unused and unallocated slots is a real common problem accompanies resource management in the burst allocation algorithms. This paper investigates the Sequential Burst Allocation (SBA that based on sequential slot allocation and burst fragmentation. An analytical model of frame utilization has been derived. Moreover, this paper presents criteria of burst fragmentation and investigates the effect of burst fragmentation to the allocation efficiency. It has been observed from the results that the SBA algorithm outperforms the Standard (ST algorithm in term of number of users and resource wastage reduction per frame. The research results illustrates that burst fragmentation can enhance the proportion of frame utilization with minor effect to the overhead size. As well as, the results are useful to be a heuristic guide line for MAC layer scheduler to decide the best burst size that can be used.

  12. Design of assembly control algorithm based on burst-size feedback for optical burst switching network

    Institute of Scientific and Technical Information of China (English)

    Minglei Fu; Zichun Le

    2009-01-01

    A novel assembly control algorithm named burst-size feedback adaptive assembly period(BFAAP)is proposed.The major difference between BFAAP and other similar adaptive assembly algorithms is that the control curve of BFAAP is dynamically adjusted according to the feedback of outgoing burst size.BFAAP is compared with two typical algorithms fixed assembly period(FAP)aild min-burst length max assembly period(MBMAP)in simulation in terms of burst size distribution and assembly period.Moreover,the transmission control protocol(TCP)performance over BFAAP is also considered and simulated.

  13. A Burst-by-Burst Adaptive Joint-Detection Based CDMA Speech Transceiver

    OpenAIRE

    How, HT; Liew, TH; Kuan, EL; Hanzo, L.

    2001-01-01

    A burst-by-burst adaptive speech transceiver is proposed, which can drop its source coding rate and speech quality under transceiver control in order to invoke a more error resilient modem mode amongst less favourable channel conditions. The novel, high-quality, Adaptive Multi-Rate (AMR) speech codec [5], operated at bit rates of 4.75 and 10.2 kbps and combined with sourcesensitivity-matched Redundant Residue Number Systems (RRNS) based channel codes. Burst-by-burst adaptive Joint-Detection b...

  14. Optimal Codes for the Burst Erasure Channel

    Science.gov (United States)

    Hamkins, Jon

    2010-01-01

    Deep space communications over noisy channels lead to certain packets that are not decodable. These packets leave gaps, or bursts of erasures, in the data stream. Burst erasure correcting codes overcome this problem. These are forward erasure correcting codes that allow one to recover the missing gaps of data. Much of the recent work on this topic concentrated on Low-Density Parity-Check (LDPC) codes. These are more complicated to encode and decode than Single Parity Check (SPC) codes or Reed-Solomon (RS) codes, and so far have not been able to achieve the theoretical limit for burst erasure protection. A block interleaved maximum distance separable (MDS) code (e.g., an SPC or RS code) offers near-optimal burst erasure protection, in the sense that no other scheme of equal total transmission length and code rate could improve the guaranteed correctible burst erasure length by more than one symbol. The optimality does not depend on the length of the code, i.e., a short MDS code block interleaved to a given length would perform as well as a longer MDS code interleaved to the same overall length. As a result, this approach offers lower decoding complexity with better burst erasure protection compared to other recent designs for the burst erasure channel (e.g., LDPC codes). A limitation of the design is its lack of robustness to channels that have impairments other than burst erasures (e.g., additive white Gaussian noise), making its application best suited for correcting data erasures in layers above the physical layer. The efficiency of a burst erasure code is the length of its burst erasure correction capability divided by the theoretical upper limit on this length. The inefficiency is one minus the efficiency. The illustration compares the inefficiency of interleaved RS codes to Quasi-Cyclic (QC) LDPC codes, Euclidean Geometry (EG) LDPC codes, extended Irregular Repeat Accumulate (eIRA) codes, array codes, and random LDPC codes previously proposed for burst erasure

  15. Infection after pacemaker implantation: infection rates and risk factors associated with infection in a population-based cohort study of 46299 consecutive patients

    DEFF Research Database (Denmark)

    Johansen, Jens Brock; Jørgensen, Ole Dan; Møller, Mogens; Arnsbo, Per; Mortensen, Peter Thomas; Nielsen, Jens Cosedis

    2011-01-01

    Infection is a serious complication of pacemaker (PM) systems. Although the rate of infection has been debated, the figures are largely unknown. We therefore studied the incidence of PM infection and its associated risk factors in the Danish population....

  16. ELECTROPHYSIOLOGICAL CHARACTERIZATION OF DOPAMINERGIC AND NONDOPAMINERGIC NEURONS IN ORGANOTYPIC SLICE CULTURES OF THE RAT VENTRAL MESENCEPHALON

    DEFF Research Database (Denmark)

    STEENSEN, BH; NEDERGAARD, S; OSTERGAARD, K;

    1995-01-01

    The aim of the present study was to characterize electrophysiologically neurones in organotypic cultures of the rat ventral mesencephalon and to compare these results with results published for the same neurones in other types of preparation. Intracellular recordings were obtained in 3- to 8-week...... (UV) light (365 nm). Short exposures to UV light did not affect the electrophysiological properties. There were no significant differences between dopaminergic and non-dopaminergic neurones with regard to resting membrane potential or action potential threshold and amplitude, and in both types of...... neurone spontaneous burst activity and glutamatergic excitatory postsynaptic potentials were seen. There were differences in the following parameters, which can be used to distinguish between the two types of neurone. Dopa minergic neurones had broad action potentials (2-9 ms), high input resistance (mean...

  17. Tunable neuromimetic integrated system for emulating cortical neuron models

    Directory of Open Access Journals (Sweden)

    SylvainSaïghi

    2011-12-01

    Full Text Available Nowadays, many software solutions are currently available for simulating neuron models. Less conventional than software-based systems, hardware-based solutions generally combine digital and analog forms of computation. In previous work, we designed several neuromimetic chips, included Galway chip that we used for this paper. These silicon neurons are based on the Hodgkin-Huxley formalism and they are optimized for reproducing a large variety of neuron behaviors thanks to tunable parameters. Due to process variation and device mismatch in analog chips, we use a full-custom fitting method in voltage-clamp mode to tune our neuromimetic integrated circuits. By comparing them with experimental electrophysiological data of these cells, we show that the circuits can reproduce the main firing features of cortical cell types. In this paper, we present the experimental measurements of our system which mimic the four most prominent biological cells: Fast Spiking (FS, Regular Spiking (RS, Intrinsically Bursting (IB and Low Threshold Spiking (LTS neurons into analog neuromimetic integrated circuit dedicated to cortical neuron simulations. This hardware and software platform will allow improvements the hybrid technique, also called ‘dynamic-clamp’, that consists of connecting artificial and biological neurons to study the function of neuronal circuits.

  18. Tunable neuromimetic integrated system for emulating cortical neuron models.

    Science.gov (United States)

    Grassia, Filippo; Buhry, Laure; Lévi, Timothée; Tomas, Jean; Destexhe, Alain; Saïghi, Sylvain

    2011-01-01

    Nowadays, many software solutions are currently available for simulating neuron models. Less conventional than software-based systems, hardware-based solutions generally combine digital and analog forms of computation. In previous work, we designed several neuromimetic chips, including the Galway chip that we used for this paper. These silicon neurons are based on the Hodgkin-Huxley formalism and they are optimized for reproducing a large variety of neuron behaviors thanks to tunable parameters. Due to process variation and device mismatch in analog chips, we use a full-custom fitting method in voltage-clamp mode to tune our neuromimetic integrated circuits. By comparing them with experimental electrophysiological data of these cells, we show that the circuits can reproduce the main firing features of cortical cell types. In this paper, we present the experimental measurements of our system which mimic the four most prominent biological cells: fast spiking, regular spiking, intrinsically bursting, and low-threshold spiking neurons into analog neuromimetic integrated circuit dedicated to cortical neuron simulations. This hardware and software platform will allow to improve the hybrid technique, also called "dynamic-clamp," that consists of connecting artificial and biological neurons to study the function of neuronal circuits. PMID:22163213

  19. Refractory Neuron Circuits

    OpenAIRE

    Sarpeshkar, Rahul; Watts, Lloyd; Mead, Carver

    1992-01-01

    Neural networks typically use an abstraction of the behaviour of a biological neuron, in which the continuously varying mean firing rate of the neuron is presumed to carry information about the neuron's time-varying state of excitation. However, the detailed timing of action potentials is known to be important in many biological systems. To build electronic models of such systems, one must have well-characterized neuron circuits that capture the essential behaviour of real neur...

  20. NEURON and Python

    OpenAIRE

    Michael Hines; Davison, Andrew P.; Eilif Muller

    2009-01-01

    The NEURON simulation program now allows Python to be used, alone or in combination with NEURON's traditional Hoc interpreter. Adding Python to NEURON has the immediate benefit of making available a very extensive suite of analysis tools written for engineering and science. It also catalyzes NEURON software development by offering users a modern programming tool that is recognized for its flexibility and power to create and maintain complex programs. At the same time, nothing is lost because ...

  1. Black Hole Lensing and Wave Bursts

    CERN Document Server

    Gogberashvili, Merab

    2016-01-01

    It is shown that close to a black hole horizon wave equations have real-valued exponentially time-dependent solutions and to investigate strong gravitational lensing we need to introduce an effective negative cosmological constant between the Schwarzschild and photon spheres. Then exponentially amplified reflected waves from this effective AdS space could explain properties of some gamma ray bursts, fast radio bursts and gravitational waves.

  2. Supernovae and gamma-ray bursts connection

    Energy Technology Data Exchange (ETDEWEB)

    Valle, Massimo Della [INAF-Napoli, Capodimonte Observatory, Salita Moiariello, 16, I-80131 Napoli (Italy); International Center for Relativistic Astrophysics Network, Piazzale della Repubblica 10, I-65122, Pescara (Italy)

    2015-12-17

    I’ll review the status of the Supernova/Gamma-Ray Burst connection. Several pieces of evidence suggest that long duration Gamma-ray Bursts are associated with bright SNe-Ic. However recent works suggest that GRBs might be produced in tight binary systems composed of a massive carbon-oxygen cores and a neutron star companion. Current estimates of the SN and GRB rates yield a ratio GRB/SNe-Ibc in the range ∼ 0.4% − 3%.

  3. Cosmological parametrization of $\\gamma$ ray burst models

    CERN Document Server

    Linder, E V

    1996-01-01

    Using three parametrizations of the gamma ray burst count data comparison is made to cosmological source models. While simple models can fit and faint end slope constraints, the addition of a logarithmic count range variable describing the curvature of the counts shows that models with no evolution or evolution power law in redshift with index less than 10 fail to satisfy simultaneously all three descriptors of the burst data. The cosmological source density that would be required for a fit is illustrated.

  4. Supernovae and gamma-ray bursts connection

    Science.gov (United States)

    Valle, Massimo Della

    2015-12-01

    I'll review the status of the Supernova/Gamma-Ray Burst connection. Several pieces of evidence suggest that long duration Gamma-ray Bursts are associated with bright SNe-Ic. However recent works suggest that GRBs might be produced in tight binary systems composed of a massive carbon-oxygen cores and a neutron star companion. Current estimates of the SN and GRB rates yield a ratio GRB/SNe-Ibc in the range ˜ 0.4% - 3%.

  5. Electrophysiology of hypothalamic magnocellular neurons in vitro: a rhythmic drive in organotypic cultures and acute slices

    Directory of Open Access Journals (Sweden)

    Jean-Marc eIsrael

    2016-03-01

    Full Text Available Hypothalamic neurohormones are released in a pulsatile manner. The mechanisms of this pulsatility remain poorly understood and several hypotheses are available, depending upon the neuroendocrine system considered. Among these systems, hypothalamo-neurohypophyseal magnocellular neurons have been early-considered models, as they typically display an electrical activity consisting of bursts of action potentials that is optimal for the release of boluses of the neurohormones oxytocin and vasopressin. The cellular mechanisms underlying this bursting behavior have been studied in vitro, using either acute slices of the adult hypothalamus, or organotypic cultures of neonatal hypothalamic tissue. We have recently proposed, from experiments in organotypic cultures, that specific central pattern generator networks, upstream of magnocellular neurons, determine their bursting activity. Here, we have tested whether a similar hypothesis can be derived from in vitro experiments in acute slices of the adult hypothalamus. To this aim we have screened our electrophysiological recordings of the magnocellular neurons, previously obtained from acute slices, with an analysis of autocorrelation of action potentials to detect a rhythmic drive as we recently did for organotypic cultures. This confirmed that the bursting behavior of magnocellular neurons is governed by central pattern generator networks whose rhythmic drive, and thus probably integrity, is however less satisfactorily preserved in the acute slices from adult brains.

  6. Neutrinos from Gamma Ray Bursts

    CERN Document Server

    Mannheim, K

    2000-01-01

    The observed fluxes of cosmic rays and gamma rays are used to infer the maximum allowed high-energy neutrino flux allowed for Gamma Ray Bursts (GRBs), following Mannheim, Protheroe, and Rachen (2000). It is shown that if GRBs produce the ultrahigh-energy cosmic rays, they should contribute (a) at least 10% of the extragalactic gamma ray background between 3 MeV and 30 GeV, contrary to their observed energy flux which is only a minute fraction of this flux, and (b) a cumulative neutrino flux a factor of 20 below the AMANDA (Neutrino 2000) limit on isotropic neutrinos. This could have two implications, either GRBs do not produce the ultrahigh energy cosmic rays or that the GRBs are strongly beamed and emit most of their power at energies well above 100 GeV implausibly increasing the energy requirements, but consistent with the marginal detections of a few low-redshift GRBs by MILAGRITO, HEGRA-AIROBICC, and the Tibet-Array. All crucial measurements to test the models will be available in the next few years. Thes...

  7. Gamma-ray Burst Cosmology

    CERN Document Server

    Wang, F Y; Liang, E W

    2015-01-01

    Gamma-ray bursts (GRBs) are the most luminous electromagnetic explosions in the Universe, which emit up to $8.8\\times10^{54}$ erg isotropic equivalent energy in the hard X-ray band. The high luminosity makes them detectable out to the largest distances yet explored in the Universe. GRBs, as bright beacons in the deep Universe, would be the ideal tool to probe the properties of high-redshift universe: including the cosmic expansion and dark energy, star formation rate, the reionization epoch and the metal enrichment history of the Universe. In this article, we review the luminosity correlations of GRBs, and implications for constraining the cosmological parameters and dark energy. Observations show that the progenitors of long GRBs are massive stars. So it is expected that long GRBs are tracers of star formation rate. We also review the high-redshift star formation rate derived from GRBs, and implications for the cosmic reionization history. The afterglows of GRBs generally have broken power-law spectra, so it...

  8. Meteor burst communications improvement study

    Science.gov (United States)

    Peterson, David

    1993-07-01

    Two identical Meteor Burst Radio Terminals were developed, fabricated, and delivered to the Air Force. Each is controlled by a PC computer in a menu driven manner. The mode of operation is full duplex. The RF frequency range is 40 to 60 MHz with tuning increments of 25 KHz. Data rates are 4, 8, 16, 32, 64, 128, 256, and 512 kbps. Modulation is coherent Binary Phase Shift Keying (BPSK) and incoherent Differential Phase Shift Keying (DPSK). Protocol includes Automatic Repeat Request (ARQ) with source and destination addressing, message number, start of message, and end of message. Messages are packetized, and Reed Solomon (R-S) coding is an option. The ARQ is under the control of a Cyclic Redundancy Check Code (CRCC) which detects binary errors within each packet. The terminal is intended to increase meteor trail availability and data throughput by several orders of magnitude--by operating with new antennas that provide much higher gains without sacrificing meteor trail acquisition performance.

  9. Motor Neurons that Multitask

    OpenAIRE

    Goulding, Martyn

    2012-01-01

    Animals use a form of sensory feedback termed proprioception to monitor their body position and modify the motor programs that control movement. In this issue of Neuron, Wen et al. (2012) provide evidence that a subset of motor neurons function as proprioceptors in C. elegans, where B-type motor neurons sense body curvature to control the bending movements that drive forward locomotion.

  10. Propofol and sevoflurane induce distinct burst suppression patterns in rats

    OpenAIRE

    Kenny, Jonathan D.; Westover, M. Brandon; Ching, ShiNung; Brown, Emery N.; Solt, Ken

    2014-01-01

    Burst suppression is an EEG pattern characterized by alternating periods of high-amplitude activity (bursts) and relatively low amplitude activity (suppressions). Burst suppression can arise from several different pathological conditions, as well as from general anesthesia. Here we review current algorithms that are used to quantify burst suppression, its various etiologies, and possible underlying mechanisms. We then review clinical applications of anesthetic-induced burst suppression. Final...

  11. Involvement of MAPKs and PLC Pathways in Modulation of Pacemaking Activity by So-Cheong-Ryong-Tang in Interstitial Cells of Cajal from Murine Small Intestine

    OpenAIRE

    Min Woo Hwang; Hee Jung Lee; Ho Joon Song; Byung Joo Kim

    2013-01-01

    Purpose. Interstitial cells of Cajal (ICCs) are the pacemaker cells that generate slow waves in the gastrointestinal (GI) tract. We have aimed to investigate the effects of Socheongryong-Tang (SCRT) in ICCs from mouse's small intestine. Methods. The whole-cell patch-clamp configuration was used to record membrane potentials from cultured ICCs. Intracellular Ca2+ ([Ca2+]i) increase was studied in cultured ICCs using fura-2 AM. Results. ICCs generated pacemaker potentials in mouse's small intes...

  12. Pacemaker, implanted cardiac defibrillator and irradiation: Management proposal in 2010 depending on the type of cardiac stimulator and prognosis and location of cancer; Pacemaker, defibrillateur et radiotherapie: propositions de conduite a tenir en 2010 en fonction du type de stimulateur cardiaque, du pronostic et du site du cancer

    Energy Technology Data Exchange (ETDEWEB)

    Lambert, P. [Service d' anesthesie reanimation, hopital Nord, centre hospitalier universitaire de Saint-etienne, 42055 Saint-etienne cedex 2 (France); Da Costa, A. [Service de cardiologie, hopital Nord, centre hospitalier universitaire de Saint-etienne, 42055 Saint-etienne cedex 2 (France); Marcy, P.Y. [Departement de radiologie, centre Antoine-Lacassagne, 33, avenue de Valombrose, 06189 Nice cedex 2 (France); Universite Nice Sophia-Antipolis, 33, avenue de Valombrose, 06189 Nice cedex 2 (France); Kreps, S. [Service de radiotherapie Corad, centre regional universitaire de cancerologie Henry-S.-Kaplan, hopital Bretonneau-2, CHU de Tours, boulevard Tonnelle, 37000 Tours (France); Angellier, G.; Marcie, S.; Bondiau, P.Y. [Universite Nice Sophia-Antipolis, 33, avenue de Valombrose, 06189 Nice cedex 2 (France); Departement de radiotherapie oncologie, centre CyberKnife, centre Antoine-Lacassagne, 33, avenue de Valombrose, 06189 Nice cedex 2 (France); Briand-Amoros, C. [Service de radiotherapie, hopital europeen Georges-Pompidou, 20, rue Leblanc, 75015 Paris (France); Thariat, J. [Universite Nice Sophia-Antipolis, 33, avenue de Valombrose, 06189 Nice cedex 2 (France); Departement de radiotherapie oncologie, centre CyberKnife, centre Antoine-Lacassagne, 33, avenue de Valombrose, 06189 Nice cedex 2 (France); IBDC CNRS UMR 6543, centre Antoine-Lacassagne, universite Sophia-Antipolis, 33, avenue de Valombrose, 06189 Nice cedex 2 (France)

    2011-06-15

    Ionizing radiation may interfere with electric components of pacemakers or implantable cardioverter defibrillators. The type, severity and extent of radiation damage to pacemakers, have previously been shown to depend on the total dose and dose rate. Over 300,000 new cancer cases are treated yearly in France, among which 60% are irradiated in the course of their disease. One among 400 of these patients has an implanted pacemaker or defibrillator. The incidence of pacemaker and implanted cardioverter defibrillator increases in an ageing population. The oncologic prognosis must be weighted against the cardiologic prognosis in a multidisciplinary and transversal setting. Innovative irradiation techniques and technological sophistications of pacemakers and implantable cardioverter-defibrillators (with the introduction of more radiosensitive complementary metal-oxide-semiconductors since 1970) have potentially changed the tolerance profiles. This review of the literature studied the geometric, dosimetric and radiobiological characteristics of the radiation beams for high energy photons, stereotactic irradiation, proton-therapy. Standardized protocols and radiotherapy optimization (particle, treatment fields, energy) are advisable in order to improve patient management during radiotherapy and prolonged monitoring is necessary following radiation therapy. The dose received at the pacemaker/heart should be calculated. The threshold for the cumulated dose to the pacemaker/implantable cardioverter-defibrillator (2 to 5 Gy depending on the brand), the necessity to remove/displace the device based on the dose-volume histogram on dosimetry, as well as the use of lead shielding and magnet are discussed. (authors)

  13. Phase-amplitude coupling, an indication of bursting in parkinsonism, is masked by periodic pulses.

    Science.gov (United States)

    Sanders, Teresa H

    2016-03-01

    Interactions between neural oscillations in the brain have been observed in many structures including the hippocampus, amygdala, motor cortex, and basal ganglia. In this study, one popular approach for quantifying oscillation interactions was considered: phase-amplitude coupling. The goals of the study were to use simulations to examine potential causes of elevated phase-amplitude coupling in parkinsonism, to compare simulated parkinsonian signals with recorded local field potentials from animal models of parkinsonism, to investigate possible relationships between increased bursting in parkinsonian single cells and elevated phase-amplitude coupling, and to uncover potential noise and artifact effects. First, a cell model that integrates incremental input currents and fires at realistic voltage thresholds was modified to allow control of stochastic parameters related to firing and burst rates. Next, the input currents and distribution of integration times were set to reproduce firing patterns consistent with those from parkinsonian subthalamic nucleus cells. Then, local field potentials were synthesized from the output of multiple simulated cells with varying degrees of synchronization and compared with subthalamic nucleus recordings from animal models of parkinsonism. The results showed that phase-amplitude coupling can provide important information about underlying neural activity. In particular, signals synthesized from synchronized bursting neurons showed increased oscillatory interactions similar to those observed in parkinsonian animals. Additionally, changes in bursting parameters such as the intraburst rate, the mean interburst period, and the amount of synchronization between neurons influenced the phase-amplitude coupling in predictable ways. Finally, simulation results revealed that small periodic signals can have a surprisingly large masking effect on phase-amplitude coupling. PMID:26792883

  14. Modeling gamma-ray bursts

    Science.gov (United States)

    Maxham, Amanda

    Discovered serendipitously in the late 1960s, gamma-ray bursts (GRBs) are huge explosions of energy that happen at cosmological distances. They provide a grand physical playground to those who study them, from relativistic effects such as beaming, jets, shocks and blastwaves to radiation mechanisms such as synchrotron radiation to galatic and stellar populations and history. Through the Swift and Fermi space telescopes dedicated to observing GRBs over a wide range of energies (from keV to GeV), combined with accurate pinpointing that allows ground based follow-up observations in the optical, infrared and radio, a rich tapestry of GRB observations has emerged. The general picture is of a mysterious central engine (CE) probably composed of a black hole or neutron star that ejects relativistic shells of matter into intense magnetic fields. These shells collide and combine, releasing energy in "internal shocks" accounting for the prompt emission and flaring we see and the "external shock" or plowing of the first blastwave into the ambient surrounding medium has well-explained the afterglow radiation. We have developed a shell model code to address the question of how X-ray flares are produced within the framework of the internal shock model. The shell model creates randomized GRB explosions from a central engine with multiple shells and follows those shells as they collide, merge and spread, producing prompt emission and X-ray flares. We have also included a blastwave model, which can constrain X-ray flares and explain the origin of high energy (GeV) emission seen by the Fermi telescope. Evidence suggests that gamma-ray prompt emission and X-ray flares share a common origin and that at least some flares can only be explained by long-lasting central engine activity. We pay special attention to the time history of central engine activity, internal shocks, and observed flares. We calculate the gamma-ray (Swift/BAT band) and X-ray (Swift/XRT band) lightcurves for arbitrary

  15. A biomechanical study on burst mechanisms of plant fruit: stress analysis of pericarps before bursting.

    Science.gov (United States)

    Endo, Yasuhiro; Sakamoto, Jiro; Kashiwano, Yuki; Yokota, Hideo; Nakamura, Sakiko; Kinoshita, Eichiro

    2010-10-01

    Bursting of fruit is a very interesting biomechanical phenomenon because its mechanism is directly related to the plant's reproduction. A plant that produces fruit that bursts powerfully and spreads the seeds widely has the advantage of reproduction without relying on other mechanisms such as transportation of fruit by insects. The structures of many types of fruit have likely been optimized by evolution, although the structure itself appears rather simplistic. Strain energy is stored in each pericarp because of growth deformation, swelling or desiccation just before bursting. Throughout these changes, the mechanical stress of the pericarps is at equilibrium. At the instant of bursting, the stored strain energy is released very rapidly. Quick and wide motion of the pericarps in a certain direction is advantageous for throwing the seed a long distance. The motion and deformation of bursting pericarps depend on their tissue structure and mechanical stress condition just before the burst. We tracked the bursting motion by using a high-speed camera. Then we calculated the pre-burst stress generated in a pericarp of Impatiens by using the finite-element method. The boundary condition obtained by experiments using a high-speed video camera is given, and the stress was calculated using reverse deformation analysis. The stress distribution of the pericarp is effective in causing the pericarp motion to throw the seeds far away. PMID:20696416

  16. The satiety signaling neuropeptide perisulfakinin inhibits the activity of central neurons promoting general activity.

    Science.gov (United States)

    Wicher, Dieter; Derst, Christian; Gautier, Hélène; Lapied, Bruno; Heinemann, Stefan H; Agricola, Hans-Jürgen

    2007-01-01

    The metabolic state is one of the determinants of the general activity level. Satiety is related to resting or sleep whereas hunger correlates to wakefulness and activity. The counterpart to the mammalian satiety signal cholecystokinin (CCK) in insects are the sulfakinins. The aim of this study was to resolve the mechanism by which the antifeedant activity of perisulfakinin (PSK) in Periplaneta americana is mediated. We identified the sources of PSK which is used both as hormone and as paracrine messenger. PSK is found in the neurohemal organ of the brain and in nerve endings throughout the central nervous system. To correlate the distributions of PSK and its receptor (PSKR), we cloned the gene coding for PSKR and provide evidence for its expression within the nervous system. It occurs only in a few neurons, among them are the dorsal unpaired median (DUM) neurons which release octopamine thereby regulating the general level of activity. Application of PSK to DUM neurons attenuated the spiking frequency (EC(50)=11pM) due to reduction of a pacemaker Ca(2+) current through cAMP-inhibited pTRPgamma channels. PSK increased the intracellular cAMP level while decreasing the intracellular Ca(2+) concentration in DUM neurons. Thus, the satiety signal conferred by PSK acts antagonistically to the hunger signal, provided by the adipokinetic hormone (AKH): PSK depresses the electrical activity of DUM neurons by inhibiting the pTRPgamma channel that is activated by AKH under conditions of food shortage. PMID:18946521

  17. The satiety signaling neuropeptide perisulfakinin inhibits the activity of central neurons promoting general activity

    Directory of Open Access Journals (Sweden)

    Dieter Wicher

    2007-12-01

    Full Text Available The metabolic state is one of the determinants of the general activity level. Satiety is related to resting or sleep whereas hunger correlates to wakefulness and activity. The counterpart to the mammalian satiety signal cholecystokinin (CCK in insects are the sulfakinins. The aim of this study was to resolve the mechanism by which the antifeedant activity of perisulfakinin (PSK in Periplaneta americana is mediated. We identified the sources of PSK which is used both as hormone and as paracrine messenger. PSK is found in the neurohemal organ of the brain and in nerve endings throughout the central nervous system. To correlate the distributions of PSK and its receptor (PSKR, we cloned the gene coding for PSKR and provide evidence for its expression within the nervous system. It occurs only in a few neurons, among them are the dorsal unpaired median (DUM neurons which release octopamine thereby regulating the general level of activity. Application of PSK to DUM neurons attenuated the spiking frequency (EC50=11pM due to reduction of a pacemaker Ca2+ current through cAMP-inhibited pTRPγ channels. PSK increased the intracellular cAMP level while decreasing the intracellular Ca2+ concentration in DUM neurons. Thus, the satiety signal conferred by PSK acts antagonistically to the hunger signal, provided by the adipokinetic hormone (AKH: PSK depresses the electrical activity of DUM neurons by inhibiting the pTRPγ channel that is activated by AKH under conditions of food shortage.

  18. Persistent neuronal Ube3a expression in the suprachiasmatic nucleus of Angelman syndrome model mice

    Science.gov (United States)

    Jones, Kelly A.; Han, Ji Eun; DeBruyne, Jason P.; Philpot, Benjamin D.

    2016-01-01

    Mutations or deletions of the maternal allele of the UBE3A gene cause Angelman syndrome (AS), a severe neurodevelopmental disorder. The paternal UBE3A/Ube3a allele becomes epigenetically silenced in most neurons during postnatal development in humans and mice; hence, loss of the maternal allele largely eliminates neuronal expression of UBE3A protein. However, recent studies suggest that paternal Ube3a may escape silencing in certain neuron populations, allowing for persistent expression of paternal UBE3A protein. Here we extend evidence in AS model mice (Ube3am–/p+) of paternal UBE3A expression within the suprachiasmatic nucleus (SCN), the master circadian pacemaker. Paternal UBE3A-positive cells in the SCN show partial colocalization with the neuropeptide arginine vasopressin (AVP) and clock proteins (PER2 and BMAL1), supporting that paternal UBE3A expression in the SCN is often of neuronal origin. Paternal UBE3A also partially colocalizes with a marker of neural progenitors, SOX2, implying that relaxed or incomplete imprinting of paternal Ube3a reflects an overall immature molecular phenotype. Our findings highlight the complexity of Ube3a imprinting in the brain and illuminate a subpopulation of SCN neurons as a focal point for future studies aimed at understanding the mechanisms of Ube3a imprinting.

  19. The Cosmic Gamma-Ray Bursts

    Science.gov (United States)

    Djorgovski, S. G.; Frail, D. A.; Kulkarni, S. R.; Sari, R.; Bloom, J. S.; Galama, T. J.; Harrison, F. A.; Price, P. A.; Fox, D.; Reichart, D. E.; Yost, S.; Berger, E.; Diercks, A.; Goodrich, R.; Chaffee, F.

    2002-12-01

    Cosmic γ-ray bursts are one of the great frontiers of astrophysics today. They are a playground of relativists and observers alike. They may teach us about the death of stars and the birth of black holes, the physics in extreme conditions, and help us probe star formation in the distant and obscured universe. In this review we summarise some of the remarkable progress in this field over the past few years. While the nature of the GRB progenitors is still unsettled, it now appears likely that at least some bursts originate in explosions of very massive stars, or at least occur in or near the regions of massive star formation. The physics of the burst afterglows is reasonably well understood, and has been tested and confirmed very well by the observations. Bursts are found to be beamed, but with a broad range of jet opening angles; the mean γ-ray energies after the beaming corrections are ~ 1051 erg. Bursts are associated with faint ( ~ 25 mag) galaxies at cosmological redshifts, with ~ 1. The host galaxies span a range of luminosities and morphologies, but appear to be broadly typical for the normal, actively star-forming galaxy populations at comparable redshifts and magnitudes. Some of the challenges for the future include: the nature of the short bursts and possibly other types of bursts and transients; use of GRBs to probe the obscured star formation in the universe, and possibly as probes of the very early universe; and their detection as sources of high-energy particles and gravitational waves.

  20. In-vitro mapping of E-fields induced near pacemaker leads by simulated MR gradient fields

    Directory of Open Access Journals (Sweden)

    Mendoza Gonzalo G

    2009-12-01

    Full Text Available Abstract Background Magnetic resonance imaging (MRI of patients with implanted cardiac pacemakers is generally contraindicated but some clinicians condone scanning certain patients. We assessed the risk of inducing unintended cardiac stimulation by measuring electric fields (E induced near lead tips by a simulated MRI gradient system. The objectives of this study are to map magnetically induced E near distal tips of leads in a saline tank to determine the spatial distribution and magnitude of E and compare them with E induced by a pacemaker pulse generator (PG. Methods We mapped magnetically induced E with 0.1 mm resolution as close as 1 mm from lead tips. We used probes with two straight electrodes (e.g. wire diameter of 0.2 mm separated by 0.9 mm. We generated magnetic flux density (B with a Helmholtz coil throughout 0.6% saline in a 24 cm diameter tank with (dB/dt of 1 T/sec (1 kHz sinusoidal waveform. Separately, we measured E near the tip of leads when connected to a PG set to a unipolar mode. Measurements were non-invasive (not altering the leads or PG under study. Results When scaled to 30 T/s (a clinically relevant value, magnetically-induced E exceeded the E produced by a PG. The magnetically-induced E only occurred when B was coincident with or within 15 msec of implantable pacemaker's pulse. Conclusions Potentially hazardous situations are possible during an MR scan due to gradient fields. Unintended stimulation can be induced via abandoned leads and leads connected to a pulse generator with loss of hermetic seal at the connector. Also, pacemaker-dependent patients can receive drastically altered pacing pulses.

  1. Modulation of Pacemaker Potentials by Pyungwi-San in Interstitial Cells of Cajal from Murine Small Intestine

    OpenAIRE

    Kim Jung Nam; Song Ho Jun; Lim Bora; Kwon Young Kyu; Kim Byung Joo

    2013-01-01

    Objective: Pyungwi-san (PWS) plays a role in a number of physiologic and pharmacologic functions in many organs. Interstitial cells of Cajal (ICCs) are pacemaker cells that generate slow waves in the gastrointestinal (GI) tract. We aimed to investigate the beneficial effects of PWS in mouse small-intestinal ICCs. Methods: Enzymatic digestion was used to dissociate ICCs from the small intestine of a mouse. The wholecell patch-clamp configuration was used to record membrane potentials from the ...

  2. Laser extraction of a trapped infected port catheter in a child using existing experience from pacemaker and ICD lead removal.

    Science.gov (United States)

    Bastian, Dirk; Fessele, Klaus; Bednarski, Piotr; Bodenschatz, Karl; Pauschinger, Matthias; Göhl, Konrad

    2011-01-01

    A 9-year-old girl presented with systemic infection related to a Port-a-Cath system (PAC); therefore, the urgent removal of the PAC was indicated. However, the catheter was trapped and not extractable by conventional means. Using existing comprehensive experience in the removal of pacemaker and implantable cardioverter defibrillator leads, the entrapped PAC was successfully extracted by laser technique, thus avoiding open heart surgery. PMID:20345621

  3. Coupling of a core post-translational pacemaker to a slave transcription/translation feedback loop in a circadian system.

    Directory of Open Access Journals (Sweden)

    Ximing Qin

    Full Text Available Cyanobacteria are the only model circadian clock system in which a circadian oscillator can be reconstituted in vitro. The underlying circadian mechanism appears to comprise two subcomponents: a post-translational oscillator (PTO and a transcriptional/translational feedback loop (TTFL. The PTO and TTFL have been hypothesized to operate as dual oscillator systems in cyanobacteria. However, we find that they have a definite hierarchical interdependency-the PTO is the core pacemaker while the TTFL is a slave oscillator that quickly damps when the PTO stops. By analysis of overexpression experiments and mutant clock proteins, we find that the circadian system is dependent upon the PTO and that suppression of the PTO leads to damped TTFL-based oscillations whose temperature compensation is not stable under different metabolic conditions. Mathematical modeling indicates that the experimental data are compatible with a core PTO driving the TTFL; the combined PTO/TTFL system is resilient to noise. Moreover, the modeling indicates a mechanism by which the TTFL can feed into the PTO such that new synthesis of clock proteins can phase-shift or entrain the core PTO pacemaker. This prediction was experimentally tested and confirmed by entraining the in vivo circadian system with cycles of new clock protein synthesis that modulate the phosphorylation status of the clock proteins in the PTO. In cyanobacteria, the PTO is the self-sustained core pacemaker that can operate independently of the TTFL, but the TTFL damps when the phosphorylation status of the PTO is clamped. However, the TTFL can provide entraining input into the PTO. This study is the first to our knowledge to experimentally and theoretically investigate the dynamics of a circadian clock in which a PTO is coupled to a TTFL. These results have important implications for eukaryotic clock systems in that they can explain how a TTFL could appear to be a core circadian clockwork when in fact the true

  4. ANTIARRHYTMIC EFFICACY OF SOTALOL IN PATIENTS WITH TACHY-BRADY SYNDROME HAVING ATRIAL PACEMAKER WITH DIFFERENT ATRIAL ELECTRODE POSITION

    OpenAIRE

    T. N. Novikova

    2016-01-01

    Aim. To evaluate efficacy of the combined therapy (sotalol and constant electric cardiostimulation in AAI regimen) at two atrial electrode position: in low back part of interatrial septum (IAS) and in right atrial auricle (RAA).Material and methods. 20 patients with tachy-brady syndrome were examined. They were randomized in 2 groups depending on atrial electrode position. Sotalol (160 mg daily) was prescribed to all patients in a month after implantation of constant atrial pacemaker (CAP). A...

  5. Innominate vein-right atrial bypass for relief of superior vena cava syndrome due to pacemaker lead thrombosis.

    Science.gov (United States)

    Deo, Salil V; Burkhart, Harold M; Araoz, Philip A; Brady, Peter A

    2010-11-01

    We present a patient with superior vena cava (SVC) obstruction due to multiple intraluminal pacemaker leads. Previous attempts at balloon dilatation of the SVC and surgical angioplasty did not provide a long-term solution. A Gore-Tex (W. L. Gore & Associates, Flagstaff, AZ, USA) conduit interposed between the innominate vein and right atrial appendage has resulted in symptomatic relief at a follow-up of 6 months. PMID:21039859

  6. An Intelligent Segmented Burst Assembly Mechanism in Optical Burst Switching Networks

    Institute of Scientific and Technical Information of China (English)

    XIE Yi-Yuan; ZHANG Jian-Guo

    2008-01-01

    We focus on the burst assembly mechanism and propose a new intelligent method in which the burst is assembled from several internet protocol (IP) packets in which the number of IP packets is changed according to the traffic load and the burst is segmented into several parts, called the ISOBS mechanism. The average burst assembly time of the ISOBS mechanism decreases as compared with the fixed-assembly-time and fixed-assembly-time-and-length mechanisms. The loss ratio decreases 50% as compared with the general optical burst switching (OBS) mechanism. The last segment can carry high quality of service (QOS) information. We can achieve that the loss ratio of the last segment is almost zero when the traffic load is less than 0.05. When the traffic load is 0.9, the loss ratio of the last segment is 0.0041. The ISOBS can support to transmit different QOS data.

  7. An Intelligent Segmented Burst Assembly Mechanism in Optical Burst Switching Networks

    International Nuclear Information System (INIS)

    We focus on the burst assembly mechanism and propose a new intelligent method in which the burst is assembled from several internet protocol (IP) packets in which the number of IP packets is changed according to the traffic load and the burst is segmented into several parts, called the ISOBS mechanism. The average burst assembly time of the ISOBS mechanism decreases as compared with the fixed-assembly-time and fixed-assembly-time-and-length mechanisms. The loss ratio decreases 50% as compared with the general optical burst switching (OBS) mechanism. The last segment can carry high quality of service (QOS) information. We can achieve that the loss ratio of the last segment is almost zero when the traffic load is less than 0.05. When the traffic load is 0.9, the loss ratio of the last segment is 0.0041. The ISOBS can support to transmit different QOS data. (fundamental areas of phenomenology (including applications))

  8. QKD-Based Secured Burst Integrity Design for Optical Burst Switched Networks

    Science.gov (United States)

    Balamurugan, A. M.; Sivasubramanian, A.; Parvathavarthini, B.

    2016-03-01

    The field of optical transmission has undergone numerous advancements and is still being researched mainly due to the fact that optical data transmission can be done at enormous speeds. It is quite evident that people prefer optical communication when it comes to large amount of data involving its transmission. The concept of switching in networks has matured enormously with several researches, architecture to implement and methods starting with Optical circuit switching to Optical Burst Switching. Optical burst switching is regarded as viable solution for switching bursts over networks but has several security vulnerabilities. However, this work exploited the security issues associated with Optical Burst Switching with respect to integrity of burst. This proposed Quantum Key based Secure Hash Algorithm (QKBSHA-512) with enhanced compression function design provides better avalanche effect over the conventional integrity algorithms.

  9. Stimulus information stored in lasting active and hidden network states is destroyed by network bursts.

    Science.gov (United States)

    Dranias, Mark R; Westover, M Brandon; Cash, Sidney; VanDongen, Antonius M J

    2015-01-01

    In both humans and animals brief synchronizing bursts of epileptiform activity known as interictal epileptiform discharges (IEDs) can, even in the absence of overt seizures, cause transient cognitive impairments (TCI) that include problems with perception or short-term memory. While no evidence from single units is available, it has been assumed that IEDs destroy information represented in neuronal networks. Cultured neuronal networks are a model for generic cortical microcircuits, and their spontaneous activity is characterized by the presence of synchronized network bursts (SNBs), which share a number of properties with IEDs, including the high degree of synchronization and their spontaneous occurrence in the absence of an external stimulus. As a model approach to understanding the processes underlying IEDs, optogenetic stimulation and multielectrode array (MEA) recordings of cultured neuronal networks were used to study whether stimulus information represented in these networks survives SNBs. When such networks are optically stimulated they encode and maintain stimulus information for as long as one second. Experiments involved recording the network response to a single stimulus and trials where two different stimuli were presented sequentially, akin to a paired pulse trial. We broke the sequential stimulus trials into encoding, delay and readout phases and found that regardless of which phase the SNB occurs, stimulus-specific information was impaired. SNBs were observed to increase the mean network firing rate, but this did not translate monotonically into increases in network entropy. It was found that the more excitable a network, the more stereotyped its response was during a network burst. These measurements speak to whether SNBs are capable of transmitting information in addition to blocking it. These results are consistent with previous reports and provide baseline predictions concerning the neural mechanisms by which IEDs might cause TCI. PMID:25755638

  10. Stimulus information stored in lasting active and hidden network states is destroyed by network bursts.

    Directory of Open Access Journals (Sweden)

    Mark R Dranias

    2015-02-01

    Full Text Available In both humans and animals brief synchronizing bursts of epileptiform activity known as interictal epileptiform discharges (IEDs can, even in the absence of overt seizures, cause transient cognitive impairments (TCI that include problems with perception or short-term memory. While no evidence from single units is available, it has been assumed that IEDs destroy information represented in neuronal networks. Cultured neuronal networks are a model for generic cortical microcircuits, and their spontaneous activity is characterized by the presence of synchronized network bursts (SNBs, which share a number of properties with IEDs, including the high degree of synchronization and their spontaneous occurrence in the absence of an external stimulus. As a model approach to understanding the processes underlying IEDs, optogenetic stimulation and multielectrode array recordings of cultured neuronal networks were used to study whether stimulus information represented in these networks survives SNBs. When such networks are optically stimulated they encode and maintain stimulus information for as long as one second. Experiments involved recording the network response to a single stimulus and trials where two different stimuli were presented sequentially, akin to a paired pulse trial. We broke the sequential stimulus trials into encoding, delay and readout phases and found that regardless of which phase the SNB occurs, stimulus-specific information was impaired. SNBs were observed to increase the mean network firing rate, but this did not translate monotonically into increases in network entropy. It was found that the more excitable a network, the more stereotyped its response was during a network burst. These measurements speak to whether SNBs are capable of transmitting information in addition to blocking it. These results are consistent with previous reports and provide baseline predictions concerning the neural mechanisms by which IEDs might cause TCI.

  11. Subplate cells: amplifiers of neuronal activity in the developing cerebral cortex

    Directory of Open Access Journals (Sweden)

    Heiko J Luhmann

    2009-10-01

    Full Text Available Due to their unique structural and functional properties, subplate cells are ideally suited to function as important amplifying units within the developing neocortical circuit. Subplate neurons have extensive dendritic and axonal ramifications and relatively mature functional properties, i.e. their action potential firing can exceed frequencies of 40 Hz. At earliest stages of corticogenesis subplate cells receive functional synaptic inputs from the thalamus and from other cortical and non-cortical sources. Glutamatergic and depolarizing GABAergic inputs arise from cortical neurons and neuromodulatory inputs arise from the basal forebrain and other sources. Activation of postsynaptic metabotropic receptors, i.e. muscarinic receptors, elicits in subplate neurons oscillatory burst discharges which are transmitted via electrical and chemical synapses to neighbouring subplate cells and to immature neurons in the cortical plate. The tonic nonsynaptic release of GABA from GABAergic subplate cells facilitates the generation of burst discharges. These cellular bursts are amplified by prominent gap junction coupling in the subplate and cortical plate, thereby eliciting 10 to 20 Hz oscillations in a local columnar network. Thus, we propose that neuronal networks are organized at earliest stages in a gap junction coupled columnar syncytium. We postulate that the subplate does not only serve as a transient relay station for afferent inputs, but rather as an active element amplifying the afferent and intracortical activity.

  12. Subplate Cells: Amplifiers of Neuronal Activity in the Developing Cerebral Cortex

    Science.gov (United States)

    Luhmann, Heiko J.; Kilb, Werner; Hanganu-Opatz, Ileana L.

    2009-01-01

    Due to their unique structural and functional properties, subplate cells are ideally suited to function as important amplifying units within the developing neocortical circuit. Subplate neurons have extensive dendritic and axonal ramifications and relatively mature functional properties, i.e. their action potential firing can exceed frequencies of 40 Hz. At earliest stages of corticogenesis subplate cells receive functional synaptic inputs from the thalamus and from other cortical and non-cortical sources. Glutamatergic and depolarizing GABAergic inputs arise from cortical neurons and neuromodulatory inputs arise from the basal forebrain and other sources. Activation of postsynaptic metabotropic receptors, i.e. muscarinic receptors, elicits in subplate neurons oscillatory burst discharges which are transmitted via electrical and chemical synapses to neighbouring subplate cells and to immature neurons in the cortical plate. The tonic non-synaptic release of GABA from GABAergic subplate cells facilitates the generation of burst discharges. These cellular bursts are amplified by prominent gap junction coupling in the subplate and cortical plate, thereby eliciting 10–20 Hz oscillations in a local columnar network. Thus, we propose that neuronal networks are organized at earliest stages in a gap junction coupled columnar syncytium. We postulate that the subplate does not only serve as a transient relay station for afferent inputs, but rather as an active element amplifying the afferent and intracortical activity. PMID:19862346

  13. Urethane anesthesia depresses activities of thalamocortical neurons and alters its response to nociception in terms of dual firing modes

    Directory of Open Access Journals (Sweden)

    Yeowool eHuh

    2013-10-01

    Full Text Available Anesthetics are often used to characterize the activity of single neurons in-vivo for its advantages such as reduced noise level and convenience in noxious stimulations. Of the anesthetics, urethane had been widely used in some thalamic studies under the assumption that sensory signals are still relayed to the thalamus under urethane anesthesia and that thalamic response would therefore reflect the response of the awake state. We tested whether this assumption stands by comparing thalamic activity in terms of tonic and burst firing modes during ‘the awake state’ or under ‘urethane anesthesia’ utilizing the extracellular single unit recording technique. First we have tested how thalamic relay neurons respond to the introduction of urethane and then tested how urethane influences thalamic discharges under formalin-induced nociception. Urethane significantly depressed overall firing rates of thalamic relay neurons, which was sustained despite the delayed increase of burst activity over the 4 hour recording period. Thalamic response to nociception under anesthesia was also similar overall except for the slight and transient increase of burst activity. Overall, results demonstrated that urethane suppresses the activity of thalamic relay neurons and that, despite the slight fluctuation of burst firing, formalin-induced nociception cannot significantly change the firing pattern of thalamic relay neurons that was caused by urethane.

  14. Enhancement of the non-invasive electroenterogram to identify intestinal pacemaker activity

    International Nuclear Information System (INIS)

    Surface recording of electroenterogram (EEnG) is a non-invasive method for monitoring intestinal myoelectrical activity. However, surface EEnG is seriously affected by a variety of interferences: cardiac activity, respiration, very low frequency components and movement artefacts. The aim of this study is to eliminate respiratory interference and very low frequency components from external EEnG recording by means of empirical mode decomposition (EMD), so as to obtain more robust indicators of intestinal pacemaker activity from the external EEnG signal. For this purpose, 11 recording sessions were performed in an animal model under fasting conditions and in each individual session the myoelectrical signal was recorded simultaneously in the intestinal serosa and the external abdominal surface in physiological states. Various parameters have been proposed for evaluating the efficacy of the method in reducing interferences: the signal-to-interference ratio (S/I ratio), attenuation of the target and interference signals, the normal slow wave percentage and the stability of the dominant frequency (DF) of the signal. The results show that the S/I ratio of the processed signals is significantly greater than the original values (9.66 ± 4.44 dB versus 1.23 ± 5.13 dB), while the target signal was barely attenuated (−0.63 ± 1.02 dB). The application of the EMD method also increased the percentage of the normal slow wave to 100% in each individual session and enabled the stability of the DF of the external signal to be increased considerably. Furthermore, the variation coefficient of the DF derived from the external processed signals is comparable to the coefficient obtained using internal recordings. Therefore, the EMD method could be a very useful tool to improve the quality of external EEnG recording in the low frequency range and therefore to obtain more robust indicators of the intestinal pacemaker activity from non-invasive EEnG recordings

  15. Sources of type III solar microwave bursts

    Science.gov (United States)

    Zhdanov, Dmitriy; Lesovoi, Sergey; Tokhchukova, Susanna

    2016-06-01

    Microwave fine structures allow us to study plasma evolution in an energy release region. The Siberian Solar Radio Telescope (SSRT) is a unique instrument designed to examine fine structures at 5.7 GHz. A complex analysis of data from RATAN-600, 4-8 GHz spectropolarimeter, and SSRT, simultaneously with extreme UV data, made it possible to localize sources of III type microwave drift bursts in August 10, 2011 event within the entire frequency band of burst occurrences, as well as to determine the most probable region of primary energy release. To localize sources of III type bursts from RATAN-600 data, an original method for data processing has been worked out. At 5.7 GHz, the source of bursts was determined along two coordinates whereas at 4.5, 4.7, 4.9, 5.1, 5.3, 5.5 and 6.0 GHz, their locations were identified along one coordinate. The size of the burst source at 5.1 GHz was found to be maximum as compared to source sizes at other frequencies.

  16. Diagnostics From Three Rising Submillimeter Bursts

    CERN Document Server

    Zhou, Ai-Hua; Wang, Xin-Dong

    2015-01-01

    In the paper we investigate three novel rising submillimeter (THz) bursts occurred sequentially in a super-Active Region NOAA 10486. The average rising rate of the flux density above 200 GHz is only 20 sfu/GHz (corresponding spectral index $\\alpha$ of 1.6) for the THz spectral components of 2003 October 28 and November 4 bursts, while it can attain values of 235 sfu/GHz ($\\alpha$=4.8) for 2003 November 2 burst. The steeply rising THz spectrum can be produced by a population of high relativistic electrons with a low-energy cutoff of 1 MeV , while it only requires a low-energy cutoff of 30 keV for the two slowly rising THz bursts, via gyrosynchrotron (GS) radiation based on our numerical simulations of burst spectra in the magnetic dipole field case. The electron density variation is much larger in the THz source than that in microwave (MW) one. It is interesting that the THz source radius decreased by 20--50$\\%$ during the decay phase for the three events, but the MW one increased by 28$\\%$ for the 2003 Novemb...

  17. The Fermi Gamma-Ray Burst Monitor

    CERN Document Server

    Meegan, Charles; Bhat, P N; Bissaldi, Elisabetta; Briggs, Michael S; Connaughton, Valerie; Diehl, Roland; Fishman, Gerald; Greiner, Jochen; Hoover, Andrew S; van der Horst, Alexander J; von Kienlin, Andreas; Kippen, R Marc; Kouveliotou, Chryssa; McBreen, Sheila; Paciesas, W S; Preece, Robert; Steinle, Helmut; Wallace, Mark S; Wilson, Robert B; Wilson-Hodge, Colleen

    2009-01-01

    The Gamma-Ray Burst Monitor (GBM) will significantly augment the science return from the Fermi Observatory in the study of Gamma-Ray Bursts (GRBs). The primary objective of GBM is to extend the energy range over which bursts are observed downward from the energy range of the Large Area Telescope (LAT) on Fermi into the hard X-ray range where extensive previous data exist. A secondary objective is to compute burst locations on-board to allow re-orientiong the spacecraft so that the LAT can observe delayed emission from bright bursts. GBM uses an array of twelve sodium iodide scintillators and two bismuth germanate scintillators to detect gamma rays from ~8 keV to ~40 MeV over the full unocculted sky. The on-board trigger threshold is ~0.7 photons/cm2/s (50-300 keV, 1 s peak). GBM generates on-board triggers for ~250 GRBs per year.

  18. Swift: A Gamma Ray Bursts Explorer

    Science.gov (United States)

    Gehrels, Neil

    2003-01-01

    Swift is a NASA gamma-ray burst MIDEX mission that is in development for launch in December 2003. It is a multiwavelength transient observatory for GRB astronomy. The goals of the mission are to determine the origin of GRBs and their afterglows and use bursts to probe the early Universe. It will also.perform a survey of the hard X-ray sky to a sensitivity level of -1 mCrab. A wide-field camera will detect more than a hundred GRBs per year to 5 times fainter than BATSE. Sensitive narrow-field X-ray and UV/optical telescopes will be pointed at the burst location in 20 to 70 sec by an autonomously controlled 'swift' spacecraft. For each burst, arcsec positions will be determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Measurements of redshift will be made for many of the bursts. The instrumentation is a combination of superb existing flight-spare hardware and design from XMM and Spectrum-X/JET-X contributed by collaborators in the UK and Italy and development of a coded-aperture camera with a large-area (approximately 0.5 square meter) CdZnTe detector array. The hardware is currently in final stages of fabrication and initial stages of integration and test. Key components of the mission are vigorous follow-up and outreach programs to engage the astronomical community and public in Swift.

  19. The Cosmic Gamma-Ray Bursts

    CERN Document Server

    Djorgovski, S G; Kulkarni, S R; Sari, R; Bloom, J S; Galama, T J; Harrison, F A; Price, P A; Fox, D; Reichart, D; Yost, S; Berger, E; Diercks, A H; Goodrich, R; Chaffee, F H

    2001-01-01

    Cosmic gamma-ray bursts are one of the great frontiers of astrophysics today. They are a playground of relativists and observers alike. They may teach us about the death of stars and the birth of black holes, the physics in extreme conditions, and help us probe star formation in the distant and obscured universe. In this review we summarise some of the remarkable progress in this field over the past few years. While the nature of the GRB progenitors is still unsettled, it now appears likely that at least some bursts originate in explosions of very massive stars, or at least occur in or near the regions of massive star formation. The physics of the burst afterglows is reasonably well understood, and has been tested and confirmed very well by the observations. Bursts are found to be beamed, but with a broad range of jet opening angles; the mean gamma-ray energies after the beaming corrections are ~ 10^51 erg. Bursts are associated with faint ~ 25 mag) galaxies at cosmological redshifts, with ~ 1. The host gal...

  20. X-ray bursts observed with JEM-X

    DEFF Research Database (Denmark)

    Brandt, Søren Kristian; Chenevez, Jérôme; Lund, Niels; Budtz-Jørgensen, Carl; Westergaard, Niels Jørgen Stenfeldt

    We report on the search for X-ray bursts in the JEM-X X-ray monitor on INTEGRAL during the first two years of operations. More than 350 bursts from 25 different type-I X-ray burst sources were found.......We report on the search for X-ray bursts in the JEM-X X-ray monitor on INTEGRAL during the first two years of operations. More than 350 bursts from 25 different type-I X-ray burst sources were found....