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Sample records for action potential bias

  1. Perceptual and performance biases in action selection

    A. Wilson; E. van Bergen; L. van Swieten; S. Kent; M. Mon-Williams

    2008-01-01

    When we see an object in the world, there may be a large number of different ways to interact with that object. This large 'visuomotor space' can be constrained through affordances (perceptually available object properties defining potential uses), task demands and the actor's intentions. The effect

  2. Perfect Actions with Chemical Potential

    Bietenholz, W

    1998-01-01

    We show how to include a chemical potential \\mu in perfect lattice actions. It turns out that the standard procedure of multiplying the quark fields \\Psi, an example, the case of free fermions with chemical potential is worked out explicitly. Even after truncation, cut-off effects in the pressure and the baryon density are small. Using a (quasi-)perfect action, numerical QCD simulations for non-zero chemical potential become more powerful, because coarse lattices are sufficient for extracting continuum physics.

  3. Vacuum and sheath potential measurements with current biased emissive probes

    Data are presented which show that an electron emitting (''emissive'') probe with proper current bias can make accurate vacuum potential measurements. Data show that a probe which is current biased to make accurate vacuum potential measurements also makes accurate sheath potential measurements. The accuracy and time response of this ''current bias method'' is compared with the accuracy and time response of two other emissive probe techniques, the inflection point in the limit of zero emission technique and the floating potential of a strongly heated probe technique. In a vacuum, finite current biased emissive probes are shown to be more accurate and have better time response than zero current biased (floating) emissive probes. The measurements were made in DOLI I, a triple plasma device (length 0.5 m, radius 0.25 m). Base pressure was 5 x 10/sup -6/ torr. For the sheath potential measurements, the plasma density was approximately 10/sup 8/ cm/sup -3/, T ≅ 1 - 2eV and the operating Argon pressure was 5 x 10/sup -5/ torr. The proper current bias for accurate vacuum potential measurements was determined in an empty, grounded vacuum chamber. The proper current bias for any particular probe was determined by strongly heating the probe and then varying its current bias until its voltage was ground

  4. Assessing atmospheric bias correction for dynamical consistency using potential vorticity

    Correcting biases in atmospheric variables prior to impact studies or dynamical downscaling can lead to new biases as dynamical consistency between the ‘corrected’ fields is not maintained. Use of these bias corrected fields for subsequent impact studies and dynamical downscaling provides input conditions that do not appropriately represent intervariable relationships in atmospheric fields. Here we investigate the consequences of the lack of dynamical consistency in bias correction using a measure of model consistency—the potential vorticity (PV). This paper presents an assessment of the biases present in PV using two alternative correction techniques—an approach where bias correction is performed individually on each atmospheric variable, thereby ignoring the physical relationships that exists between the multiple variables that are corrected, and a second approach where bias correction is performed directly on the PV field, thereby keeping the system dynamically coherent throughout the correction process. In this paper we show that bias correcting variables independently results in increased errors above the tropopause in the mean and standard deviation of the PV field, which are improved when using the alternative proposed. Furthermore, patterns of spatial variability are improved over nearly all vertical levels when applying the alternative approach. Results point to a need for a dynamically consistent atmospheric bias correction technique which results in fields that can be used as dynamically consistent lateral boundaries in follow-up downscaling applications. (letter)

  5. Estimating Production Potentials: Expert Bias in Applied Decision Making

    A study was conducted to evaluate how workers predict manufacturing production potentials given positively and negatively framed information. Findings indicate the existence of a bias toward positive information and suggest that this bias may be reduced with experience but is never the less maintained. Experts err in the same way non experts do in differentially processing negative and positive information. Additionally, both experts and non experts tend to overestimate production potentials in a positive direction. The authors propose that these biases should be addressed with further research including cross domain analyses and consideration in training, workplace design, and human performance modeling

  6. Action Principle for Potential Flows

    Frønsdal, Christian

    2014-01-01

    The restriction of hydrodynamics to non-viscous, potential (gradient, irrotational) flows is a theory both simple and elegant; a favorite topic of introductory textbooks. It is known that this theory (under the stated limitations) can be formulated as an action principle. It finds its principle application to adiabatic systems and cannot account for viscosity or dissipation. However, it can be generalized to include non-potential flows, as this paper shows. The new theory is a combination of Eulerian and Lagrangian hydrodynamics, with an extension to thermodynamics. It describes adiabatic phenomena but does not account for viscosity or dissipation. Nevertheless, it is an approach within which quasi-static processes can be described. In the adiabatic context it appears to be an improvement of the Navier-Stokes equation, the principal advantage being a natural concept of energy in the form of a first integral of the motion, conserved by virtue of the Euler-Lagrange equations.

  7. Potential bias in ophthalmic pharmaceutical clinical trials

    Paul Varner

    2008-01-01

    Paul VarnerJohn J Pershing Veterans’ Administration Medical Center, Poplar Bluff, Missouri, USAAbstract: To make clinicians aware of potential sources of error in ophthalmic pharmaceutical clinical trials that can lead to erroneous interpretation of results, a critical review of the study design of various pharmaceutical ophthalmic clinical trials was completed. Discrepancies as a result of study shortcomings may explain observed differences between reported ophthalmic trial data an...

  8. Light-triggered action potentials in plants

    Kazimierz Trębacz

    2014-01-01

    Special attention is paid in this paper to the criteria of the light-triggered action potential, namely the all-or-none law, propagation, the occurrence of refractory periods. Such action potentials have been recorded in Acetabularia mediterranea, Asplenium trichomanes, Bryum pseudotriquetrum, Eremosphaera viridis and Concephalum conicum. In Acetabularia, action potentials are generated after sudden cessation of light stimuli of sufficient intensity. The depolarization phase of the action pot...

  9. Improved Lattice Actions with Chemical Potential

    Bietenholz, W

    1998-01-01

    We give a prescription how to include a chemical potential \\mu into a general lattice action. This inclusion does not cause any lattice artifacts. Hence its application to an improved - or even perfect - action at \\mu =0 yields an improved resp. perfect action at arbitrary \\mu. For short-ranged improved actions, a good scaling behavior holds over a wide region, and the upper bound for the baryon density - which is known for the standard lattice actions - can be exceeded.

  10. Abstract Action Potential Models for Toxin Recognition

    Peterson, James; Khan, Taufiquar

    2005-01-01

    In this paper, we present a robust methodology using mathematical pattern recognition schemes to detect and classify events in action potentials for recognizing toxins in biological cells. We focus on event detection in action potential via abstraction of information content into a low dimensional feature vector within the constrained computational environment of a biosensor. We use generated families of action potentials from a classic Hodgkin–Huxley model to verify our methodology and build...

  11. Motherhood: a potential source of bias in employment decisions.

    Heilman, Madeline E; Okimoto, Tyler G

    2008-01-01

    Results of 2 experimental studies in which job incumbents were said to be applying for promotions to traditionally male positions demonstrated bias against mothers in competence expectations and in screening recommendations. This bias occurred regardless of whether the research participants were students (Study 1) or working people (Study 2). Although anticipated job commitment, achievement striving, and dependability were rated as generally lower for parents than for nonparents, anticipated competence was uniquely low for mothers. Mediational analyses indicated that, as predicted, negativity in competence expectations, not anticipated job commitment or achievement striving, promoted the motherhood bias in screening recommendations; expected deficits in agentic behaviors, not in dependability, were found to fuel these competence expectations. These findings suggest that motherhood can indeed hinder the career advancement of women and that it is the heightened association with gender stereotypes that occurs when women are mothers that is the source of motherhood's potentially adverse consequences. PMID:18211144

  12. Emotion biases voluntary vertical action only with visible cues.

    Sasaki, Kyoshiro; Yamada, Yuki; Miura, Kayo

    2016-01-01

    Emotional information influences our bodily experiences according to the space-valence metaphor (positive/negative is up/down). In the present study, we examined whether visible and invisible emotional stimuli could also modulate voluntary action. After observing an emotional image (e.g., positive, neutral, or negative), participants used a joystick to arbitrarily position a dot stimulus in a display. The emotional image was either masked (masked condition) or not (unmasked condition) via a continuous flash suppression technique, i.e., dynamic interocular masking. We found that in the unmasked condition, the placed position of the dot was significantly higher after observing the positive image compared with the negative image, but this difference was not present in the masked condition. Our findings suggest that conscious emotional information is necessary for activating sensorimotor representations of vertical directions, and voluntary action is performed based on these activations. PMID:26637931

  13. The precision of experienced action video-game players: line bisection reveals reduced leftward response bias.

    Latham, Andrew J; Patston, Lucy L M; Tippett, Lynette J

    2014-11-01

    Twenty-two experienced action video-game players (AVGPs) and 18 non-VGPs were tested on a pen-and-paper line bisection task that was untimed. Typically, right-handers bisect lines 2 % to the left of true centre, a bias thought to reflect the dominance of the right-hemisphere for visuospatial attention. Expertise may affect this bias, with expert musicians showing no bias in line bisection performance. Our results show that experienced-AVGPs also bisect lines with no bias with their right hand and a significantly reduced bias with their left hand compared to non-AVGPs. Bisections by experienced-AVGPs were also more precise than those of non-AVGPs. These findings show the cognitive proficiencies of experienced-AVGPs can generalize beyond computer based tasks, which resemble their training environment. PMID:25341651

  14. Screening action potentials: The power of light

    Lars eKaestner

    2011-07-01

    Full Text Available Action potentials reflect the concerted activity of all electrogenic constituents in the plasma membrane during the excitation of a cell. Therefore, the action potential is an integrated readout and a promising parameter to detect electrophysiological failures or modifications thereof in diagnosis as well as in drug screens. Cellular action potentials can be recorded by optical approaches. To fulfill the pre-requirements to scale up for e.g. pharmacological screens the following preparatory work has to be provided: (i model cells under investigation need to represent target cells in the best possible manner; (ii optical sensors that can be either small molecule dyes or genetically encoded potential probes need to provide a reliable readout with minimal interaction with the naive behavior of the cells and (iii devices need to be capable to stimulate the cells, read out the signals with the appropriate speed as well as provide the capacity for a sufficient throughput. Here we discuss several scenarios for all three categories in the field of cardiac physiology and pharmacology and provide a perspective to use the power of light in screening cardiac action potentials.

  15. Introducing the Action Potential to Psychology Students

    Simon-Dack, Stephanie L.

    2014-01-01

    For this simple active learning technique for teaching, students are assigned "roles" and act out the process of the action potential (AP), including the firing threshold, ion-specific channels for ions to enter and leave the cell, diffusion, and the refractory period. Pre-post test results indicated that students demonstrated increased…

  16. expression, physiological actions and therapeutic potential

    Steckelings, Ulrike

    2012-01-01

    Angiotensin II mediates its action via 2 receptor subtypes: the AT1- and AT2-receptor. The existence of more than one receptor for angiotensin II has been discovered not earlier than 1989. This "Habilitationsschrift" is based on six publications which represent mosaic stones within the growing picture of AT2-receptor expression, regulation of expression, physiological and patho-physiological function as well as potential therapeutic use. The first part is dealing with tissue specific ex...

  17. Publication Bias in Laboratory Animal Research: A Survey on Magnitude, Drivers, Consequences and Potential Solutions

    Gerben ter Riet; Daniel A Korevaar; Marlies Leenaars; Sterk, Peter J.; van Noorden, Cornelis J. F.; Bouter, Lex M; René Lutter; Ronald P Oude Elferink; Lotty Hooft

    2012-01-01

    CONTEXT: Publication bias jeopardizes evidence-based medicine, mainly through biased literature syntheses. Publication bias may also affect laboratory animal research, but evidence is scarce. OBJECTIVES: To assess the opinion of laboratory animal researchers on the magnitude, drivers, consequences and potential solutions for publication bias. And to explore the impact of size of the animals used, seniority of the respondent, working in a for-profit organization and type of research (fundament...

  18. Multilinear Biased Discriminant Analysis: A Novel Method for Facial Action Unit Representation

    Khademi, Mahmoud; Manzuri-Shalmani, Mohammad T

    2010-01-01

    In this paper a novel efficient method for representation of facial action units by encoding an image sequence as a fourth-order tensor is presented. The multilinear tensor-based extension of the biased discriminant analysis (BDA) algorithm, called multilinear biased discriminant analysis (MBDA), is first proposed. Then, we apply the MBDA and two-dimensional BDA (2DBDA) algorithms, as the dimensionality reduction techniques, to Gabor representations and the geometric features of the input image sequence respectively. The proposed scheme can deal with the asymmetry between positive and negative samples as well as curse of dimensionality dilemma. Extensive experiments on Cohn-Kanade database show the superiority of the proposed method for representation of the subtle changes and the temporal information involved in formation of the facial expressions. As an accurate tool, this representation can be applied to many areas such as recognition of spontaneous and deliberate facial expressions, multi modal/media huma...

  19. Bias-corrected estimation in potentially mildly explosive autoregressive models

    Haufmann, Hendrik; Kruse, Robinson

    This paper provides a comprehensive Monte Carlo comparison of different finite-sample bias-correction methods for autoregressive processes. We consider classic situations where the process is either stationary or exhibits a unit root. Importantly, the case of mildly explosive behaviour is studied...... indirect inference approach oers a valuable alternative to other existing techniques. Its performance (measured by its bias and root mean squared error) is balanced and highly competitive across many different settings. A clear advantage is its applicability for mildly explosive processes. In an empirical...... application to a long annual US Debt/GDP series we consider rolling window estimation of autoregressive models. We find substantial evidence for time-varying persistence and periods of explosiveness during the Civil War and World War II. During the recent years, the series is nearly explosive again. Further...

  20. Potential Biases in Service Research - Opportunity and Pitfall

    Bellm, Tilo

    2014-01-01

    People are not always rational, rely on heuristics and are influenced by situational factors being conducive to biased decisions. Hence, the decision outcome cannot be explained by consumers’ preferences exclusively. This offers opportunities to service managers to steer the decision outcome into a desirable direction by a beneficial design of situational factors. In contrast to the discussed opportunities, situational factors can also become a pitfall for researchers and managers. I show tha...

  1. The Potential of Deweyan-Inspired Action Research

    Stark, Jody L.

    2014-01-01

    In its broadest sense, pragmatism could be said to be the philosophical orientation of all action research. Action research is characterized by research, action, and participation grounded in democratic principles and guided by the aim of social improvement. Furthermore, action research is an active process of inquiry that does not admit separation between action and reflection or theory and practice. This paper considers the potential of action research informed specifically by Deweyan pragm...

  2. Examining Event-Related Potential (ERP correlates of decision bias in recognition memory judgments.

    Holger Hill

    Full Text Available Memory judgments can be based on accurate memory information or on decision bias (the tendency to report that an event is part of episodic memory when one is in fact unsure. Event related potentials (ERP correlates are important research tools for elucidating the dynamics underlying memory judgments but so far have been established only for investigations of accurate old/new discrimination. To identify the ERP correlates of bias, and observe how these interact with ERP correlates of memory, we conducted three experiments that manipulated decision bias within participants via instructions during recognition memory tests while their ERPs were recorded. In Experiment 1, the bias manipulation was performed between blocks of trials (automatized bias and compared to trial-by-trial shifts of bias in accord with an external cue (flexibly controlled bias. In Experiment 2, the bias manipulation was performed at two different levels of accurate old/new discrimination as the memory strength of old (studied items was varied. In Experiment 3, the bias manipulation was added to another, bottom-up driven manipulation of bias induced via familiarity. In the first two Experiments, and in the low familiarity condition of Experiment 3, we found evidence of an early frontocentral ERP component at 320 ms poststimulus (the FN320 that was sensitive to the manipulation of bias via instruction, with more negative amplitudes indexing more liberal bias. By contrast, later during the trial (500-700 ms poststimulus, bias effects interacted with old/new effects across all three experiments. Results suggest that the decision criterion is typically activated early during recognition memory trials, and is integrated with retrieved memory signals and task-specific processing demands later during the trial. More generally, the findings demonstrate how ERPs can help to specify the dynamics of recognition memory processes under top-down and bottom-up controlled retrieval conditions.

  3. Action potential broadening in a presynaptic channelopathy

    Begum, Rahima; Bakiri, Yamina; Volynski, Kirill E.; Kullmann, Dimitri M.

    2016-07-01

    Brain development and interictal function are unaffected in many paroxysmal neurological channelopathies, possibly explained by homoeostatic plasticity of synaptic transmission. Episodic ataxia type 1 is caused by missense mutations of the potassium channel Kv1.1, which is abundantly expressed in the terminals of cerebellar basket cells. Presynaptic action potentials of small inhibitory terminals have not been characterized, and it is not known whether developmental plasticity compensates for the effects of Kv1.1 dysfunction. Here we use visually targeted patch-clamp recordings from basket cell terminals of mice harbouring an ataxia-associated mutation and their wild-type littermates. Presynaptic spikes are followed by a pronounced afterdepolarization, and are broadened by pharmacological blockade of Kv1.1 or by a dominant ataxia-associated mutation. Somatic recordings fail to detect such changes. Spike broadening leads to increased Ca2+ influx and GABA release, and decreased spontaneous Purkinje cell firing. We find no evidence for developmental compensation for inherited Kv1.1 dysfunction.

  4. Teachers in Action Research: Assumptions and Potentials

    Li, Yuen-Ling

    2008-01-01

    Research literature has long indicated that action research may stimulate practitioners themselves to actively evaluate the quality of their practice. This study is designed to report the use of action research for the development of early years professional practice by analyzing the pre-project and the post-project video-filmed teaching events.…

  5. Action potential initiation in the hodgkin-huxley model.

    Colwell, Lucy J; Brenner, Michael P.

    2009-01-01

    A recent paper of B. Naundorf et al. described an intriguing negative correlation between variability of the onset potential at which an action potential occurs (the onset span) and the rapidity of action potential initiation (the onset rapidity). This correlation was demonstrated in numerical simulations of the Hodgkin-Huxley model. Due to this antagonism, it is argued that Hodgkin-Huxley-type models are unable to explain action potential initiation observed in cortical neurons in vivo or in...

  6. Spectral action, Weyl anomaly and the Higgs-Dilaton potential

    Andrianov, A.A.(V.A. Fock Department of Theoretical Physics, Saint-Petersburg State University, 1 ul. Ulyanovskaya, St. Petersburg, 198504, Russia); Kurkov, M.A.; Lizzi, Fedele

    2011-01-01

    We show how the bosonic spectral action emerges from the fermionic action by the renormalization group flow in the presence of a dilaton and the Weyl anomaly. The induced action comes out to be basically the Chamseddine-Connes spectral action introduced in the context of noncommutative geometry. The entire spectral action describes gauge and Higgs fields coupled with gravity. We then consider the effective potential and show, that it has the desired features of a broken and an unbroken phase,...

  7. Pattern-induced expectation bias in visual anticipation of action outcomes.

    Loffing, Florian; Stern, Ricarda; Hagemann, Norbert

    2015-10-01

    When anticipating an opponent's action intention, athletes may rely on both kinematic and contextual cues. Here we show that patterns of previous action outcomes (i.e., a contextual cue) bias visual anticipation of action outcome in subsequent trials. In two video-based experiments, skilled players and novices were presented with volleyball attacks stopping 360ms (Exp. 1) or 280ms (Exp. 2) before an attacker's hand-ball-contact and they were asked to predict the type of attack (smash or lob). Attacks were presented block-wise with six attacks per block. The fifth trial served as target trial where we presented identical attacks to control kinematic cues. We varied the outcomes of the preceding four attacks under three conditions: lobs only, smashes only or an alternating pattern of attack outcomes. In Exp. 1, skilled players but not novices were less accurate and responded later in target trials that were incongruent vs. congruent with preceding patterns. In Exp. 2, where the task was easier, another group of novices demonstrated a similar congruence effect for accuracy but not response time. Collectively, findings indicate that participants tended to preferentially expect the continuation of an attack pattern, while possibly attaching less importance to kinematic cues. Thus, overreliance on pattern continuation may be detrimental to anticipation in situations an action's outcome does not correspond to the pattern. From a methodological viewpoint, comparison of novices' performance in Exp. 1 and 2 suggests that task difficulty may be critical as to whether contextual cue effects can be identified in novices. PMID:26310873

  8. Testosterone biases automatic memory processes in women towards potential mates

    Wingen, G.A. van; Mattern, C.; Verkes, R.J.; Buitelaar, J.K.; Fernandez, G.S.E.

    2008-01-01

    Female mate choice involves the comparative evaluation of potential mates. Females use a pooled comparison of sampled males to maximize the perceived reproductive fitness of their partner, implying the memorization of sampled males. However, hormonal and reproductive states influence female choosine

  9. Testosterone biases automatic memory processes in women towards potential mates.

    Wingen, G van; Mattern, C.; Verkes, R.J.; Buitelaar, J.K.; Fernandez, G.S.E.

    2008-01-01

    Female mate choice involves the comparative evaluation of potential mates. Females use a pooled comparison of sampled males to maximize the perceived reproductive fitness of their partner, implying the memorization of sampled males. However, hormonal and reproductive states influence female choosine

  10. Action potentials reliably invade axonal arbors of rat neocortical neurons

    Cox, Charles L.; Denk, Winfried; Tank, David W.; Svoboda, Karel

    2000-01-01

    Neocortical pyramidal neurons have extensive axonal arborizations that make thousands of synapses. Action potentials can invade these arbors and cause calcium influx that is required for neurotransmitter release and excitation of postsynaptic targets. Thus, the regulation of action potential invasion in axonal branches might shape the spread of excitation in cortical neural networks. To measure the reliability and extent of action potential invasion into axonal arbors, we have used two-photon...

  11. Effect sizes and standardization in neighbourhood models of forest stands: potential biases and misinterpretations

    P. Stoll; Murrell, D. J.; Newbery, D. M.

    2015-01-01

    1. Effects of conspecific neighbours on survival and growth of trees have been found to be related to species abundance. Both positive and negative relationships may explain observed abundance patterns. Surprisingly, it is rarely tested whether such relationships could be biased or even spurious due to transforming neighbourhood variables or influences of spatial aggregation, distance decay of neighbour effects and standardization of effect sizes. 2. To investigate potential biases, co...

  12. Effective bias and potentials in steady-state quantum transport: A NEGF reverse-engineering study

    Karlsson, Daniel; Verdozzi, Claudio

    2016-03-01

    Using non-equilibrium Green's functions combined with many-body perturbation theory, we have calculated steady-state densities and currents through short interacting chains subject to a finite electric bias. By using a steady-state reverse-engineering procedure, the effective potential and bias which reproduce such densities and currents in a non-interacting system have been determined. The role of the effective bias is characterised with the aid of the so-called exchange-correlation bias, recently introduced in a steady-state density-functional- theory formulation for partitioned systems. We find that the effective bias (or, equivalently, the exchange-correlation bias) depends strongly on the interaction strength and the length of the central (chain) region. Moreover, it is rather sensitive to the level of many-body approximation used. Our study shows the importance of the effective/exchange-correlation bias out of equilibrium, thereby offering hints on how to improve the description of density- functional-theory based approaches to quantum transport.

  13. Critical Utopian Action Research: The Potential of Action Research in the Democratization of Society

    Nielsen, Birger Steen; Nielsen, Kurt Aagaard

    The specific concept of critical utopian action research is presented and discussed, as to its origin, use and potentials. The inspiration from Robert Jungk and his future creating workshops is elaborated.......The specific concept of critical utopian action research is presented and discussed, as to its origin, use and potentials. The inspiration from Robert Jungk and his future creating workshops is elaborated....

  14. Are Managed Futures Indices Telling Truth? Biases in CTA Databases and Proposals of Potential Enhancements

    Adam Zaremba

    2011-07-01

    Full Text Available Managed futures are an alternative asset class which has recently became considerably popular among investment industry. However, due to its characteristics, access to managed futures historical performance statistics is relatively confined. All available information originates from commercial and academic databases, reporting to which is entirely voluntary. This situation results in series of biases which distort the managed futures performance in the eyes of investors. The paper consists of two parts. First, the author reviews and describes various biases that influence the reliability of the managed futures indices and databases. The second section encompasses author’s proposals of potential enhancements, which aim to reduce the impact of the biases in order to derive a benchmark that could better reflect characteristics of managed futures investment from the point of view of a potential investor.

  15. Assessing the potential for outcome reporting bias in a review: a tutorial

    Powell Colin

    2010-05-01

    Full Text Available Abstract Background Outcome reporting bias (ORB occurs when variables are selected for publication based on their results. This can impact upon the results of a meta-analysis, biasing the pooled treatment effect estimate. The aim of this paper is to show how to assess a systematic review and corresponding trial reports for ORB using an example review of intravenous and nebulised magnesium in the treatment of asthma. Methods The review was assessed for ORB by 1 checking the reasons, when available, for excluding studies to ensure that no studies were excluded because they did not report the outcomes of interest in the review; 2 assessing the eligible studies as to whether the review outcomes of interest were reported. Each study was classified using a system developed in the ORBIT (Outcome Reporting Bias In Trials project to indicate whether ORB was suspected and a reason for the suspicion. Authors of trials that did not report the outcomes of interest were contacted for information. A sensitivity analysis was performed to assess the robustness of the conclusions of the review to this potential source of bias. Results Twenty-four studies were included in the review; two studies had been excluded for not reporting either of the two outcomes of interest. Six included studies did not report hospital admission and two did not report pulmonary function. There was high suspicion of outcome reporting bias in four studies. Results from the sensitivity analysis indicate that review conclusions were not overturned. Conclusion This paper demonstrates, with the example of the magnesium review, how to assess a review for outcome reporting bias. A review should not exclude studies if they have not reported the outcomes of interest and should consider the potential for outcome reporting bias in all included studies.

  16. [Individualised medicine - potentials and need for action].

    Hüsing, Bärbel

    2010-01-01

    Individualised medicine aims to classify seemingly homogenous patient groups into smaller clinically relevant subgroups (stratification) in order to be able to treat them differently, thus contributing to the improvement of health care services, to the prevention of inappropriate treatments and to the reduction of adverse effects. This article summarises a report to the Office of Technology Assessment at the German Bundestag and points out the need for action for transferring individualised medicine from research to clinical application: significant incentives are required in order to prove the clinical validity of newly identified biomarkers of complex diseases. Sustainable business models for the joint development of new applications by research institutions, biotechnology companies, pharmaceuticals and medical devices companies are required. Instruments for transferring knowledge from bench to bedside (translational research) and the existing regulatory framework should be further developed in order to strike an appropriate balance between incentives for accelerating the transfer of innovative technology to the health care sector while, at the same time, ensuring patient safety, high quality and clinical utility. PMID:21147435

  17. Angle-action estimation in a general axisymmetric potential

    Sanders, Jason

    2012-01-01

    The usefulness of angle-action variables in galaxy dynamics is well known, but their use is limited due to the difficulty of their calculation in realistic galaxy potentials. Here we present a method for estimating angle-action variables in a realistic Milky Way axisymmetric potential by locally fitting a St\\"ackel potential over the region an orbit probes. The quality of the method is assessed by comparison with other known methods for estimating angle-action variables of a range of disc and...

  18. Radial propagation of muscle action potential along the tubular system examined by potential-sensitive dyes

    Nakajima, S.; Gilai, A.

    1980-01-01

    Isolated single (Xenopus) muscle fibers were stained with a non-permeant potential-probing dye, merocyanine rhodanine (WW375) or merocyanine oxazolone (NK2367). When the fiber was massively stimulated, an absorption change (wave a), which seemed to reflect the action potential, occurred. Simultaneous recording of optical changes and intracellular action potentials revealed that the time-course of wave a was slower than the action potential: the peak of wave a was attained at 1 ms, and the pea...

  19. Kondo time scales for quantum dots: Response to pulsed bias potentials

    The response of a quantum dot in the Kondo regime to rectangular pulsed bias potentials of various strengths and durations is studied theoretically. It is found that the rise time is faster than the fall time, and also faster than time scales normally associated with the Kondo problem. For larger values of the pulsed bias, one can induce dramatic oscillations in the induced current with a frequency approximating the splitting between the Kondo peaks that would be present in steady state. The effect persists in the total charge transported per pulse, which should facilitate the experimental observation of the phenomenon. (c) 2000 The American Physical Society

  20. Pandemic influenza vaccine & narcolepsy: simulations on the potential impact of bias.

    Wijnans, Leonoor; Dodd, Caitlin; de Ridder, Maria; Romio, Silvana; Weibel, Daniel; Overeem, Sebastiaan; Lammers, Gert Jan; Bonhoeffer, Jan; Black, Steve; Sturkenboom, Miriam

    2016-05-01

    Several studies have identified an association between Pandemrix(TM), an AS03 adjuvanted pandemic influenza A(H1N1) vaccine, and narcolepsy, a rare and under-diagnosed sleep disorder with a median onset-to-diagnosis interval of ten years. This paper reviews potential sources of bias in published studies and aims to provide, through simulation, methodological recommendations for assessment of vaccine safety signals. Our simulation study showed that in the absence of an association between the vaccine and the outcome, presence of detection bias and differential exposure misclassification could account for elevated risk estimates. These may play a major role, particularly in alert situations when observation times are limited and the disease has a long latency period. Estimates from the case-control design were less inflated than those from the cohort design when these biases were present. Overall, these simulations provide useful insights for the design and interpretation of future studies. PMID:26967200

  1. Optogenetic stimulation in a computational model of the basal ganglia biases action selection and reward prediction error.

    Pierre Berthet

    Full Text Available Optogenetic stimulation of specific types of medium spiny neurons (MSNs in the striatum has been shown to bias the selection of mice in a two choices task. This shift is dependent on the localisation and on the intensity of the stimulation but also on the recent reward history. We have implemented a way to simulate this increased activity produced by the optical flash in our computational model of the basal ganglia (BG. This abstract model features the direct and indirect pathways commonly described in biology, and a reward prediction pathway (RP. The framework is similar to Actor-Critic methods and to the ventral/dorsal distinction in the striatum. We thus investigated the impact on the selection caused by an added stimulation in each of the three pathways. We were able to reproduce in our model the bias in action selection observed in mice. Our results also showed that biasing the reward prediction is sufficient to create a modification in the action selection. However, we had to increase the percentage of trials with stimulation relative to that in experiments in order to impact the selection. We found that increasing only the reward prediction had a different effect if the stimulation in RP was action dependent (only for a specific action or not. We further looked at the evolution of the change in the weights depending on the stage of learning within a block. A bias in RP impacts the plasticity differently depending on that stage but also on the outcome. It remains to experimentally test how the dopaminergic neurons are affected by specific stimulations of neurons in the striatum and to relate data to predictions of our model.

  2. Optogenetic stimulation in a computational model of the basal ganglia biases action selection and reward prediction error.

    Berthet, Pierre; Lansner, Anders

    2014-01-01

    Optogenetic stimulation of specific types of medium spiny neurons (MSNs) in the striatum has been shown to bias the selection of mice in a two choices task. This shift is dependent on the localisation and on the intensity of the stimulation but also on the recent reward history. We have implemented a way to simulate this increased activity produced by the optical flash in our computational model of the basal ganglia (BG). This abstract model features the direct and indirect pathways commonly described in biology, and a reward prediction pathway (RP). The framework is similar to Actor-Critic methods and to the ventral/dorsal distinction in the striatum. We thus investigated the impact on the selection caused by an added stimulation in each of the three pathways. We were able to reproduce in our model the bias in action selection observed in mice. Our results also showed that biasing the reward prediction is sufficient to create a modification in the action selection. However, we had to increase the percentage of trials with stimulation relative to that in experiments in order to impact the selection. We found that increasing only the reward prediction had a different effect if the stimulation in RP was action dependent (only for a specific action) or not. We further looked at the evolution of the change in the weights depending on the stage of learning within a block. A bias in RP impacts the plasticity differently depending on that stage but also on the outcome. It remains to experimentally test how the dopaminergic neurons are affected by specific stimulations of neurons in the striatum and to relate data to predictions of our model. PMID:24614169

  3. Prejudiced interactions: implicit racial bias reduces predictive simulation during joint action with an out-group avatar.

    Sacheli, Lucia Maria; Christensen, Andrea; Giese, Martin A; Taubert, Nick; Pavone, Enea Francesco; Aglioti, Salvatore Maria; Candidi, Matteo

    2015-01-01

    During social interactions people automatically apply stereotypes in order to rapidly categorize others. Racial differences are among the most powerful cues that drive these categorizations and modulate our emotional and cognitive reactivity to others. We investigated whether implicit racial bias may also shape hand kinematics during the execution of realistic joint actions with virtual in- and out-group partners. Caucasian participants were required to perform synchronous imitative or complementary reach-to-grasp movements with avatars that had different skin color (white and black) but showed identical action kinematics. Results demonstrate that stronger visuo-motor interference (indexed here as hand kinematics differences between complementary and imitative actions) emerged: i) when participants were required to predict the partner's action goal in order to on-line adapt their own movements accordingly; ii) during interactions with the in-group partner, indicating the partner's racial membership modulates interactive behaviors. Importantly, the in-group/out-group effect positively correlated with the implicit racial bias of each participant. Thus visuo-motor interference during joint action, likely reflecting predictive embodied simulation of the partner's movements, is affected by cultural inter-individual differences. PMID:25687636

  4. Intracellular recording of action potentials by nanopillar electroporation

    Xie, Chong; Lin, Ziliang; Hanson, Lindsey; Cui, Yi; Cui, Bianxiao

    2012-03-01

    Action potentials have a central role in the nervous system and in many cellular processes, notably those involving ion channels. The accurate measurement of action potentials requires efficient coupling between the cell membrane and the measuring electrodes. Intracellular recording methods such as patch clamping involve measuring the voltage or current across the cell membrane by accessing the cell interior with an electrode, allowing both the amplitude and shape of the action potentials to be recorded faithfully with high signal-to-noise ratios. However, the invasive nature of intracellular methods usually limits the recording time to a few hours, and their complexity makes it difficult to simultaneously record more than a few cells. Extracellular recording methods, such as multielectrode arrays and multitransistor arrays, are non-invasive and allow long-term and multiplexed measurements. However, extracellular recording sacrifices the one-to-one correspondence between the cells and electrodes, and also suffers from significantly reduced signal strength and quality. Extracellular techniques are not, therefore, able to record action potentials with the accuracy needed to explore the properties of ion channels. As a result, the pharmacological screening of ion-channel drugs is usually performed by low-throughput intracellular recording methods. The use of nanowire transistors, nanotube-coupled transistors and micro gold-spine and related electrodes can significantly improve the signal strength of recorded action potentials. Here, we show that vertical nanopillar electrodes can record both the extracellular and intracellular action potentials of cultured cardiomyocytes over a long period of time with excellent signal strength and quality. Moreover, it is possible to repeatedly switch between extracellular and intracellular recording by nanoscale electroporation and resealing processes. Furthermore, vertical nanopillar electrodes can detect subtle changes in action

  5. Compound sensory action potential in normal and pathological human nerves

    Krarup, Christian

    2004-01-01

    The compound sensory nerve action potential (SNAP) is the result of phase summation and cancellation of single fiber potentials (SFAPs) with amplitudes that depend on fiber diameter, and the amplitude and shape of the SNAP is determined by the distribution of fiber diameters. Conduction velocitie...

  6. Contamination, potential bias and humidity effects on electrical performance and corrosion reliability of electronic devices

    Piotrowska, Kamila; Verdingovas, Vadimas; Jellesen, Morten S.; Ambat, Rajan

    2015-01-01

    This paper describes the interactions between flux contamination, humidity and po-tential bias and their effect on corrosion reliability. Water layer formation on laminate surfaces and behavior of different solder flux chemistries with humid conditions have been studied, together with their influence on electrical performance of electronics. The effect of the type of laminate’s solder mask on the formation of water film and droplets was investigated for two different types: smooth glossy and ...

  7. Contamination, potential bias and humidity effects on electrical performance and corrosion reliability of electronic devices

    Piotrowska, Kamila; Verdingovas, Vadimas; Jellesen, Morten S.;

    2015-01-01

    This paper describes the interactions between flux contamination, humidity and po-tential bias and their effect on corrosion reliability. Water layer formation on laminate surfaces and behavior of different solder flux chemistries with humid conditions have been studied, together with their......-sponse of electronics is estimated as a function of contamination type under cycling humid conditions. The results show the correlation between the ionic contamination type and water layer formation on surfaces in the presence of the flux residue....

  8. Membrane, action, and oscillatory potentials in simulated protocells

    Syren, R. M.; Fox, S. W.; Przybylski, A. T.; Stratten, W. P.

    1982-01-01

    Electrical membrane potentials, oscillations, and action potentials are observed in proteinoid microspheres impaled with (3 M KCl) microelectrodes. Although effects are of greater magnitude when the vesicles contain glycerol and natural or synthetic lecithin, the results in the purely synthetic thermal protein structures are substantial, attaining 20 mV amplitude in some cases. The results add the property of electrical potential to the other known properties of proteinoid microspheres, in their role as models for protocells.

  9. Theophylline-induced potentiation of the antinociceptive action of baclofen.

    Sawynok, J

    1983-01-01

    1--Theophylline (35, 50 mg/kg) potentiated the antinociceptive action of intraperitoneally administered baclofen in the tail flick and hot plate tests. Potentiation was most marked when the pretreatment time was 1 h, but some potentiation was still apparent following a 2 h pretreatment. 2--Theophylline alone (50 mg/kg) produced only slight alterations in reaction latency in the two tests. 3--When baclofen was applied directly into the spinal subarachnoid space, a 1 h pretreatment with theophy...

  10. Membrane, action, and oscillatory potentials in simulated protocells

    Przybylski, Aleksander T.; Stratten, Wilford P.; Syren, Robert M.; Fox, Sidney W.

    1982-12-01

    Electrical membrane potentials, oscillations, and action potentials are observed in proteinoid microspheres impaled with (3 M KCl) microelectrodes. Although effects are of greater magnitude when the vesicles contain glycerol and natural or synthetic lecithin, the results in the purely synthetic thermal protein structures are substantial, attaining 20 mV amplitude in some cases. The results add the property of electrical potential to the other known properties of proteinoid microspheres, in their role as models for protocells.

  11. Numerical investigation of action potential transmission in plants

    Mariusz Pietruszka

    2014-02-01

    Full Text Available In context of a fairly concise review of recent literature and well established experimental results we reconsider the problem of action potential propagating steadily down the plant cell(s. Having adopted slightly modified Hodgkin-Huxley set of differential equations for the action potential we carried out the numerical investigation of these equations in the course of time. We argue that the Hodgkin-Huxley-Katz model for the nerve impulse can be used to describe the phenomena which take place in plants - this point of view seems to be plausible since the mechanisms involving active ionic transport across membranes from the mathematical point of view are similar. Besides, we compare in a qualitative way our theoretical outcomes with typical experimental results for the action potentials which arise as the reaction of plants to electrical, mechanical and light stimuli. Moreover, we point out the relevance of the sequence of events during the pulse with the appropriate ionic fluxes.

  12. ITS as an environmental DNA barcode for fungi: an in silico approach reveals potential PCR biases

    Taberlet Pierre

    2010-07-01

    Full Text Available Abstract Background During the last 15 years the internal transcribed spacer (ITS of nuclear DNA has been used as a target for analyzing fungal diversity in environmental samples, and has recently been selected as the standard marker for fungal DNA barcoding. In this study we explored the potential amplification biases that various commonly utilized ITS primers might introduce during amplification of different parts of the ITS region in samples containing mixed templates ('environmental barcoding'. We performed in silico PCR analyses with commonly used primer combinations using various ITS datasets obtained from public databases as templates. Results Some of the ITS primers, such as ITS1-F, were hampered with a high proportion of mismatches relative to the target sequences, and most of them appeared to introduce taxonomic biases during PCR. Some primers, e.g. ITS1-F, ITS1 and ITS5, were biased towards amplification of basidiomycetes, whereas others, e.g. ITS2, ITS3 and ITS4, were biased towards ascomycetes. The assumed basidiomycete-specific primer ITS4-B only amplified a minor proportion of basidiomycete ITS sequences, even under relaxed PCR conditions. Due to systematic length differences in the ITS2 region as well as the entire ITS, we found that ascomycetes will more easily amplify than basidiomycetes using these regions as targets. This bias can be avoided by using primers amplifying ITS1 only, but this would imply preferential amplification of 'non-dikarya' fungi. Conclusions We conclude that ITS primers have to be selected carefully, especially when used for high-throughput sequencing of environmental samples. We suggest that different primer combinations or different parts of the ITS region should be analyzed in parallel, or that alternative ITS primers should be searched for.

  13. Far-field potentials recorded from action potentials and from a tripole in a hemicylindrical volume.

    Jewett, D L; Deupree, D L

    1989-05-01

    There is growing evidence in support of the hypothesis that far-field potentials are recorded when action potentials encounter discontinuities in the surrounding volume. The present study found further support for this hypothesis using two methods of experimentation. The first method recorded potentials when the action potential from an isolated bullfrog sciatic nerve in a hemicylindrical volume (i) encountered a change in the shape of the surrounding volume, (ii) crossed a boundary between 2 volumes of differing resistivities, (iii) reached a bend in the nerve, or (iv) reached the functional end of the nerve. In the second method, potentials were recorded when an electrical tripole, constructed in a way to produce the electrical equivalent of an action potential, encountered the same discontinuities as well as when it was configured to simulate a curved nerve. These results are consistent with the hypothesis that dipole components of an action potential predominant in far-field recordings. PMID:2469568

  14. Imaging when acting: picture but not word cues induce action-related biases of visual attention

    Agnieszka Wykowska

    2012-10-01

    Full Text Available In line with the Theory of Event Coding (Hommel et al., 2001, action planning has been shown to affect perceptual processing—an effect that has been attributed to a so-called intentional weighting mechanism (Memelink & Hommel, in press; Wykowska, Schubö, & Hommel, 2009, whose functional role is to provide information for open parameters of online action adjustment (Hommel, 2010. The aim of this study was to test whether different types of action representations induce intentional weighting to various degrees. To meet this aim, we introduced a paradigm in which participants performed a visual search task while preparing to grasp or to point. The to-be performed movement was signaled either by a picture of a required action or a word cue. We reasoned that picture cues might trigger a more concrete action representation that would be more likely to activate the intentional weighting of perceptual dimensions that provide information for online action control. In contrast, word cues were expected to trigger a more abstract action representation that would be less likely to induce intentional weighting. In two experiments, preparing for an action facilitated the processing of targets in an unrelated search task if they differed from distractors on a dimension that provided information for online action control. As predicted, however, this effect was observed only if action preparation was signaled by picture cues but not if it was signaled by word cues. We conclude that picture cues are more efficient than word cues in activating the intentional weighting of perceptual dimensions, presumably by specifying not only invariant characteristics of the planned action but also the dimensions of action-specific parameters.

  15. Imaging When Acting: Picture but Not Word Cues Induce Action-Related Biases of Visual Attention

    AgnieszkaWykowska; BernhardHommel; AnnaSchubö

    2012-01-01

    In line with the Theory of Event Coding (Hommel et al., 2001), action planning has been shown to affect perceptual processing—an effect that has been attributed to a so-called intentional weighting mechanism (Memelink & Hommel, in press; Wykowska, Schubö, & Hommel, 2009), whose functional role is to provide information for open parameters of online action adjustment (Hommel, 2010). The aim of this study was to test whether different types of action representations induce intentio...

  16. How You Move Is What You See: Action Planning Biases Selection in Visual Search

    Wykowska, Agnieszka; Schubo, Anna; Hommel, Bernhard

    2009-01-01

    Three experiments investigated the impact of planning and preparing a manual grasping or pointing movement on feature detection in a visual search task. The authors hypothesized that action planning may prime perceptual dimensions that provide information for the open parameters of that action. Indeed, preparing for grasping facilitated detection…

  17. Action Alters Object Identification: Wielding a Gun Increases the Bias to See Guns

    Witt, Jessica K.; Brockmole, James R.

    2012-01-01

    Stereotypes, expectations, and emotions influence an observer's ability to detect and categorize objects as guns. In light of recent work in action-perception interactions, however, there is another unexplored factor that may be critical: The action choices available to the perceiver. In five experiments, participants determined whether another…

  18. Explaining the discrepancy between intentions and actions: the case of hypothetical bias in contingent valuation.

    Ajzen, Icek; Brown, Thomas C; Carvajal, Franklin

    2004-09-01

    An experiment was designed to account for intention-behavior discrepancies by applying the theory of planned behavior to contingent valuation. College students (N = 160) voted in hypothetical and real payment referenda to contribute $8 to a scholarship fund. Overestimates of willingness to pay in the hypothetical referendum could not be attributed to moderately favorable latent dispositions. Instead, this hypothetical bias was explained by activation of more favorable beliefs and attitudes in the context of a hypothetical rather than a real referendum. A corrective entreaty was found to eliminate this bias by bringing beliefs, attitudes, and intentions in line with those in the real payment situation. As a result, the theory of planned behavior produced more accurate prediction of real payment when participants were exposed to the corrective entreaty. PMID:15359015

  19. Action prediction based on anticipatory brain potentials during simulated driving

    Khaliliardali, Zahra; Chavarriaga, Ricardo; Gheorghe, Lucian Andrei; Millán, José del R.

    2015-12-01

    Objective. The ability of an automobile to infer the driver’s upcoming actions directly from neural signals could enrich the interaction of the car with its driver. Intelligent vehicles fitted with an on-board brain-computer interface able to decode the driver’s intentions can use this information to improve the driving experience. In this study we investigate the neural signatures of anticipation of specific actions, namely braking and accelerating. Approach. We investigated anticipatory slow cortical potentials in electroencephalogram recorded from 18 healthy participants in a driving simulator using a variant of the contingent negative variation (CNV) paradigm with Go and No-go conditions: count-down numbers followed by ‘Start’/‘Stop’ cue. We report decoding performance before the action onset using a quadratic discriminant analysis classifier based on temporal features. Main results. (i) Despite the visual and driving related cognitive distractions, we show the presence of anticipatory event related potentials locked to the stimuli onset similar to the widely reported CNV signal (with an average peak value of -8 μV at electrode Cz). (ii) We demonstrate the discrimination between cases requiring to perform an action upon imperative subsequent stimulus (Go condition, e.g. a ‘Red’ traffic light) versus events that do not require such action (No-go condition; e.g. a ‘Yellow’ light); with an average single trial classification performance of 0.83 ± 0.13 for braking and 0.79 ± 0.12 for accelerating (area under the curve). (iii) We show that the centro-medial anticipatory potentials are observed as early as 320 ± 200 ms before the action with a detection rate of 0.77 ± 0.12 in offline analysis. Significance. We show for the first time the feasibility of predicting the driver’s intention through decoding anticipatory related potentials during simulated car driving with high recognition rates.

  20. Propagation of Action Potentials: An Active Participation Exercise.

    Felsten, Gary

    1998-01-01

    Describes an active participation exercise that demonstrates the propagation of action potentials (the ability to transmit information through the neural network, dependent upon chemical interactions in the brain). Students assume the structure and function of the network by lining up around the room and communicating through hand signals and…

  1. Compound muscle action potentials in newborn infants with spina bifida.

    Geerdink, N.; Pasman, J.W.; Rotteveel, J.J.; Roeleveld, N.; Mullaart, R.A.

    2008-01-01

    The aim of this study was to investigate the relationship between compound muscle action potentials (CMAPs) and neurological impairment in newborn infants with spina bifida. Thirty-one newborn infants (17 males, 14 females, mean gestational age 39 wks [SD 2]; mean birthweight 3336 g [SD 496]) with s

  2. Sodium and potassium conductance changes during a membrane action potential.

    Bezanilla, F; Rojas, E; Taylor, R E

    1970-12-01

    1. A method for turning a membrane potential control system on and off in less than 10 musec is described. This method was used to record membrane currents in perfused giant axons from Dosidicus gigas and Loligo forbesi after turning on the voltage clamp system at various times during the course of a membrane action potential.2. The membrane current measured just after the capacity charging transient was found to have an almost linear relation to the controlled membrane potential.3. The total membrane conductance taken from these current-voltage curves was found to have a time course during the action potential similar to that found by Cole & Curtis (1939).4. The instantaneous current voltage curves were linear enough to make it possible to obtain a good estimate of the individual sodium and potassium channel conductances, either algebraically or by clamping to the sodium, or potassium, reversal potentials. Good general agreement was obtained with the predictions of the Hodgkin-Huxley equations.5. We consider these results to constitute the first direct experimental demonstration of the conductance changes to sodium and potassium during the course of an action potential. PMID:5505231

  3. An investigation of a potential low bias in the MODIS aerosol products over Asia

    McHardy, T. M.; Shi, Y.; Zhang, J.; Reid, J. S.; Campbell, J. R.; Hsu, N. Y. C.

    2015-12-01

    Heavy aerosol plumes can be misidentified as clouds in passive satellite-based aerosol retrievals due to their relatively high visible reflectivity. Thus, over regions such as China, where a higher frequency of heavy aerosol plumes is expected, regional aerosol optical depth analyses reported from passive satellite-based aerosol products may biased low. This fundamental error can be suppressed under certain conditions. In this study, with a synergistic use of satellite observations from MODIS, OMI and CALIOP, a low bias in the MODIS Dark Target (DT) and Deep Blue (DB) aerosol products is studied over Asia for the influence of dense aerosol plume undersampling. A new scheme has been developed for detecting heavy aerosol plumes by coupling OMI aerosol index retrievals with available CALIOP level 1B and cloud and aerosol profile data. Collocated CALIOP, MODIS and OMI data are then used to further investigate the potential low bias in the MODIS DT and DB aerosol products, in an attempt to quantify the measure of undersampling in the regional DT and DB archive. Our preliminary results show that DT and DB aerosol algorithms detect about half heavy aerosol loading when CALIPSO and OMI AI believe there are heavy absorbing aerosols.

  4. Sex differences in event-related potentials and attentional biases to emotional facial stimuli

    Daniela M. Pfabigan

    2014-12-01

    Full Text Available Attentional processes play an important role in the processing of emotional information. Previous research reported attentional biases during stimulus processing in anxiety and depression. However, sex differences in the processing of emotional stimuli and higher prevalence rates of anxiety disorders among women, compared to men, suggest that attentional biases may also differ between the two sexes. The present study used a modified version of the dot probe task with happy, angry, and neutral facial stimuli to investigate the time course of attentional biases in healthy volunteers. Moreover, associations of attentional biases with alexithymia were examined on the behavioral and physiological level. Event-related potentials were measured while 21 participants (11 women performed the task, utilizing also for the first time a difference wave approach in the analysis to highlight emotion-specific aspects. Women showed overall enhanced probe P1 amplitudes compared to men, in particular after rewarding facial stimuli. Under the difference wave approach, probe P1 amplitudes appeared specifically enhanced with regard to congruently presented happy facial stimuli among women, compared to men. Both methods yielded enhanced probe P1 amplitudes after presentation of the emotional stimulus in the left compared to the right visual hemifield. Probe P1 amplitudes correlated negatively with self-reported alexithymia, most of these correlations were only observable in women. Our results suggest that women orient their attention to a greater extent to facial stimuli than men and corroborate that alexithymia is a correlate of reduced emotional reactivity on a neuronal level. We recommend using a difference wave approach when addressing attentional processes of orientation and disengagement also in future studies.

  5. Action potential initiation in the hodgkin-huxley model.

    Lucy J Colwell

    2009-01-01

    Full Text Available A recent paper of B. Naundorf et al. described an intriguing negative correlation between variability of the onset potential at which an action potential occurs (the onset span and the rapidity of action potential initiation (the onset rapidity. This correlation was demonstrated in numerical simulations of the Hodgkin-Huxley model. Due to this antagonism, it is argued that Hodgkin-Huxley-type models are unable to explain action potential initiation observed in cortical neurons in vivo or in vitro. Here we apply a method from theoretical physics to derive an analytical characterization of this problem. We analytically compute the probability distribution of onset potentials and analytically derive the inverse relationship between onset span and onset rapidity. We find that the relationship between onset span and onset rapidity depends on the level of synaptic background activity. Hence we are able to elucidate the regions of parameter space for which the Hodgkin-Huxley model is able to accurately describe the behavior of this system.

  6. Tuning an rf-SQUID flux qubit system's potential with magnetic flux bias

    At an extremely low temperature of 20 mK, we measured the loop current in a tunable rf superconducting quantum interference device (SQUID) with a dc-SQUID. By adjusting the magnetic flux applied to the rf-SQUID loop (Φf) and the small dc-SQUID (Φfcjj), respectively, the potential shape of the system can be fully controlled in situ. Variation in the transition step and overlap size in the switching current with a barrier flux bias are analyzed, from which we can obtain some relevant device parameters and build a model to explain the experimental phenomenon

  7. Virtual Cathodes near small electrodes biased near the plasma potential and its effects on Langmuir probes

    Yip, Chi-Shung; Hershkowitz, Noah; Severn, Greg

    2015-09-01

    Movable small (3cm x 3.8cm) plates biased near the plasma potential are immersed in a filament discharge in a multi-dipole chamber. The plates are small (Aplate /Achamber collection of an electrode in the presence of the virtual cathode, and was experimentally investigated by comparing I-V characteristics of the small plate and a 0.6cm diameter Langmuir probe. This work is supported by U.S. DOE under the Grant and Contract No. DE-FG02-97ER54437.

  8. Spatially periodic domain wall pinning potentials: Asymmetric pinning and dipolar biasing

    Metaxas, P. J.; Zermatten, P.-J.; Novak, R. L.; Rohart, S.; Jamet, J.-P.; Weil, R.; Ferré, J.; Mougin, A.; Stamps, R. L.; Gaudin, G.; Baltz, V.; Rodmacq, B.

    2013-02-01

    Domain wall propagation has been measured in continuous, weakly disordered, quasi-two-dimensional, Ising-like magnetic layers that are subject to spatially periodic domain wall pinning potentials. The potentials are generated non-destructively using the stray magnetic field of ordered arrays of magnetically hard [Co/Pt]m nanoplatelets, which are patterned above and are physically separated from the continuous magnetic layer. The effect of the periodic pinning potentials on thermally activated domain wall creep dynamics is shown to be equivalent, at first approximation, to that of a uniform, effective retardation field, Hret, which acts against the applied field, H. We show that Hret depends not only on the array geometry but also on the relative orientation of H and the magnetization of the nanoplatelets. A result of the latter dependence is that wall-mediated hysteresis loops obtained for a set nanoplatelet magnetization exhibit many properties that are normally associated with ferromagnet/antiferromagnet exchange bias systems. These include a switchable bias, coercivity enhancement, and domain wall roughness that is dependent on the applied field polarity.

  9. First-principles modeling of Pt/LaAlO3/SrTiO3 capacitors under an external bias potential

    Cazorla, Claudio; Stengel, Massimiliano

    2012-01-01

    We study the electrical properties of Pt/LaAlO3/SrTiO3 capacitors under the action of an external bias potential, using first-principles simulations performed at constrained electric displacement field. A complete set of band diagrams, together with the relevant electrical characteristics (capacitance and built-in fields), are determined as a function of LaAlO3 thickness and the applied potential.We find that the internal field in LaAlO3 monotonically decreases with increasing thickness; henc...

  10. Social Class and Social Action: The Middle-Class Bias of Democratic Theory in Education

    Schutz, Aaron

    2008-01-01

    Background: This article examines the emergence of the middle and working classes in America and describes key characteristics of these cultures as they manifest themselves today. It then explores the effects of social class on our conceptions of democracy. Purpose: To help educators understand the relationship between social action strategies and…

  11. Click- and chirp-evoked human compound action potentials

    Chertoff, Mark; Lichtenhan, Jeffery; Willis, Marie

    2010-01-01

    In the experiments reported here, the amplitude and the latency of human compound action potentials (CAPs) evoked from a chirp stimulus are compared to those evoked from a traditional click stimulus. The chirp stimulus was created with a frequency sweep to compensate for basilar membrane traveling wave delay using the O-Chirp equations from Fobel and Dau [(2004). J. Acoust. Soc. Am. 116, 2213–2222] derived from otoacoustic emission data. Human cochlear traveling wave delay estimates were obta...

  12. Robotic action acquisition with cognitive biases in coarse-grained state space.

    Uragami, Daisuke; Kohno, Yu; Takahashi, Tatsuji

    2016-07-01

    Some of the authors have previously proposed a cognitively inspired reinforcement learning architecture (LS-Q) that mimics cognitive biases in humans. LS-Q adaptively learns under uniform, coarse-grained state division and performs well without parameter tuning in a giant-swing robot task. However, these results were shown only in simulations. In this study, we test the validity of the LS-Q implemented in a robot in a real environment. In addition, we analyze the learning process to elucidate the mechanism by which the LS-Q adaptively learns under the partially observable environment. We argue that the LS-Q may be a versatile reinforcement learning architecture, which is, despite its simplicity, easily applicable and does not require well-prepared settings. PMID:27195484

  13. Action potentials of curved nerves in finite limbs.

    Xiao, S; McGill, K C; Hentz, V R

    1995-06-01

    Previous simulations of volume-conducted nerve-fiber action-potentials have modeled the limb as semi-infinite or circularly cylindrical, and the fibers as straight lines parallel to the limb surface. The geometry of actual nerves and limbs, however, can be considerably more complicated. This paper presents a general method for computing the potentials of fibers with arbitrary paths in arbitrary finite limbs. It involves computing the propagating point-source response (PPSR), which is the potential arising from a single point source (dipole or tripole) travelling along the fiber. The PPSR can be applied to fibers of different conduction velocities by simple dilation or compression. The method is illustrated for oblique and spiralling nerve fibers. Potentials from oblique fibers are shown to be different for orthodromic and antidromic propagation. Such results show that the straight-line models are not always adequate for nerves with anatomical amounts of curvature. PMID:7790016

  14. Unconscious bias when experts are invited - and the results of conscious action

    Stadmark, Johanna; Conley, Daniel J.

    2016-04-01

    Visibility of different kinds is important in academic work. We publish papers, present results at conferences and are invited to give seminars and write contributions and reviews about other scientists' work. A few years back we reacted on the invitation-only sections in two of the leading scientific journals. We asked: "Who are invited to write about other researchers' newly published results?" The short answer could be: Experts in the field. However, we found that it was mainly male experts in the field when we reviewed/categorized the authors of the invitation-only sections News & Views and Perspective in Nature and Science, respectively, during the years 2010 and 2011 (in total 1663 authors). The proportion of female authors was compared to the proportion of female scientists within their respective fields within academia. We found that female scientists were invited less often than their male colleagues. We notified the two journals about the mismatch (Nature 2012: 488) and their encouraging reply was that they needed to improve how they reflect women's contributions to science (Nature 2012: 491). In 2013 and 2014 the invitation-only sections (with in total 1845 authors) had reached parity (compared to the pool of available scientists) for contributions regarding Earth and Environmental Science, and made steps forward for Medical/Biological/Chemical sciences and Physical sciences. By raising awareness about the unconscious biases we all have, e.g. both men and women, we can act to make progress towards parity in science.

  15. Beyond Bias and Barriers: Fulfilling the Potential of Women in Academic Science and Engineering

    Agogino, Alice

    2007-04-01

    Review of the report by the National Academies, with a focus on action strategies in the physical sciences. Women face barriers to hiring and promotion in research universities in many fields of science and engineering; a situation that deprives the United States of an important source of talent as the country faces increasingly stiff global competition in higher education, science and technology, and the marketplace. Eliminating gender bias in universities requires immediate, overarching reform and decisive action by university administrators, professional societies, government agencies, and Congress. Forty years ago, women made up only 3 percent of America's scientific and technical workers, but by 2003 they accounted for nearly one-fifth. In addition, women have earned more than half of the bachelor's degrees awarded in science and engineering since 2000. However, their representation on university and college faculties fails to reflect these gains. Among science and engineering Ph.D.s, four times more men than women hold full-time faculty positions. And minority women with doctorates are less likely than white women or men of any racial or ethnic group to be in tenure positions. The report urges higher education organizations and professional societies to form collaborative, self-monitoring body that would recommend standards for faculty recruitment, retention, and promotion; collect data; and track compliance across institutions. A ``report card'' template is provided in the report. To read the report online, add a comment, or purchase hard copy, go to: http://www.engineeringpathway.com/ep/learningresource/summary/index.jhtml?id=94A4929D-F1B2-432E-8167-63335569CB4E.

  16. Multiple Scattering of Laser Pulses in Snow Over Ice: Modeling the Potential Bias in ICESat Altimetry

    Davis, A. B.; Varnai, T.; Marshak, A.

    2010-01-01

    The primary goal of NASA's current ICESat and future ICESat2 missions is to map the altitude of the Earth's land ice with high accuracy using laser altimetry technology, and to measure sea ice freeboard. Ice however is a highly transparent optical medium with variable scattering and absorption properties. Moreover, it is often covered by a layer of snow with varying depth and optical properties largely dependent on its age. We describe a modeling framework for estimating the potential altimetry bias caused by multiple scattering in the layered medium. We use both a Monte Carlo technique and an analytical diffusion model valid for optically thick media. Our preliminary numerical results are consistent with estimates of the multiple scattering delay from laboratory measurements using snow harvested in Greenland, namely, a few cm. Planned refinements of the models are described.

  17. Numerical simulation of antiarrhythmic drugs effects on cardiac action potential

    Převorovská, Světlana; Maršík, František

    Brno : Brno University of Technology, 2006 - (Burša, J.; Fuis, V.), s. 170-171 ISBN 80-214-3232-2. [ Human Biomechanics 2006. Hrotovice (CZ), 13.11.2006-16.11.2006] R&D Projects: GA ČR(CZ) GA106/03/1073; GA ČR(CZ) GA106/03/0958 Institutional research plan: CEZ:AV0Z20760514 Keywords : human cardiovascular system * cardiac action potential * antiarrhytmmic drugs-cell channel interaction Subject RIV: BK - Fluid Dynamics

  18. Systematic biases on galaxy haloes parameters from Yukawa-like gravitational potentials

    Cardone, V F

    2011-01-01

    A viable alternative to the dark energy as a solution of the cosmic speed up problem is represented by Extended Theories of Gravity. Should this be indeed the case, there will be an impact not only on cosmological scales, but also at any scale, from the Solar System to extragalactic ones. In particular, the gravitational potential can be different from the Newtonian one commonly adopted when computing the circular velocity fitted to spiral galaxies rotation curves. Phenomenologically modelling the modified point mass potential as the sum of a Newtonian and a Yukawa like correction, we simulate observed rotation curves for a spiral galaxy described as the sum of an exponential disc and a NFW dark matter halo. We then fit these curves assuming parameterized halo models (either with an inner cusp or a core) and using the Newtonian potential to estimate the theoretical rotation curve. Such a study allows us to investigate the bias on the disc and halo model parameters induced by the systematic error induced by fo...

  19. Flexible graphene transistors for recording cell action potentials

    Blaschke, Benno M.; Lottner, Martin; Drieschner, Simon; Bonaccini Calia, Andrea; Stoiber, Karolina; Rousseau, Lionel; Lissourges, Gaëlle; Garrido, Jose A.

    2016-06-01

    Graphene solution-gated field-effect transistors (SGFETs) are a promising platform for the recording of cell action potentials due to the intrinsic high signal amplification of graphene transistors. In addition, graphene technology fulfills important key requirements for in-vivo applications, such as biocompability, mechanical flexibility, as well as ease of high density integration. In this paper we demonstrate the fabrication of flexible arrays of graphene SGFETs on polyimide, a biocompatible polymeric substrate. We investigate the transistor’s transconductance and intrinsic electronic noise which are key parameters for the device sensitivity, confirming that the obtained values are comparable to those of rigid graphene SGFETs. Furthermore, we show that the devices do not degrade during repeated bending and the transconductance, governed by the electronic properties of graphene, is unaffected by bending. After cell culture, we demonstrate the recording of cell action potentials from cardiomyocyte-like cells with a high signal-to-noise ratio that is higher or comparable to competing state of the art technologies. Our results highlight the great capabilities of flexible graphene SGFETs in bioelectronics, providing a solid foundation for in-vivo experiments and, eventually, for graphene-based neuroprosthetics.

  20. Bootstrapping Structural VARs: Avoiding a Potential Bias in Confidence Intervals for Impulse Response Functions

    Phillips, Kerk L.; David E. Spencer

    2010-01-01

    Constructing bootstrap confidence intervals for impulse response functions (IRFs) from structural vector autoregression (SVAR) models has become standard practice in empirical macroeconomic research. The accuracy of such confidence intervals can deteriorate severely, however, if the bootstrap IRFs are biased. We document an apparently common source of bias in the estimation of the VAR error covariance matrix which can be easily reduced by a scale adjustment. This bias is generally unrecogn...

  1. Metabolic syndrome potentiates the cardiac action potential-prolonging action of drugs: a possible 'anti-proarrhythmic' role for amlodipine.

    Caillier, Bertrand; Pilote, Sylvie; Patoine, Dany; Levac, Xavier; Couture, Christian; Daleau, Pascal; Simard, Chantale; Drolet, Benoit

    2012-03-01

    Type II diabetes was shown to prolong the QT interval on the ECG and to promote cardiac arrhythmias. This is not so clear for metabolic syndrome, a precursor state of type II diabetes. The objectives of the present study were to generate a guinea pig model of metabolic syndrome by long-term exposure to diabetogenic diets, and to evaluate the monophasic action potential duration (MAPD)-modulating effects of drugs in these animals. Male Hartley guinea pigs were fed with either the control, the High Fat High Sucrose (HFHS) or the High Fat High Fructose (HFHF) diet for 150 days. Evolution of weight, blood cholesterol, triglycerides, urea and glucose tolerance were regularly monitored. Histopathological evolution was also evaluated in target organs such as pancreas, heart, liver and kidneys. Ex vivo experiments using the Langendorff retroperfusion technique, isolated hearts from guinea pigs either fed with the control, the HFHS or the HFHF diet were exposed to dofetilide 20 nM (D), chromanol 293B 10 μM (C) and amlodipine 100 nM (A) in different drug combinations and monophasic action potential duration was measured at 90% repolarization (MAPD₉₀). Our data show that it is possible to generate a guinea pig model of metabolic syndrome by chronic exposure to diabetogenic diets. Minor histopathological abnormalities were observed, mainly in the pancreas and the liver. Metabolic syndrome potentiates the MAPD-prolonging actions of I(Kr)-blocking (dofetilide) and I(Ks)-blocking (chromanol 293B) drugs, an effect that is reversible upon administration of the calcium channel blocker amlodipine. PMID:22154802

  2. Influence of the substrate bias potential on the properties of ta-C coatings deposited using Venetian blind plasma filter

    Zavaleyev, V., E-mail: viktor.zavaleyev@tu.koszalin.pl; Walkowicz, J.

    2015-04-30

    The paper presents the research results on the formation of amorphous ta-C films with a minimum amount of defects, deposited by pulsed vacuum-arc method with the use of a water-cooled electromagnetic Venetian blind plasma filter. The subject of the research was the influence of the substrate bias voltage, in the range of − 25 to − 200 V, on the structural and mechanical properties of ta-C coatings. Dependence of the microstructure and phase composition of ta-C films on the substrate bias voltage were analyzed by Raman and X-ray photoelectron spectroscopy. The results of the structural analysis of coatings showed characteristic changes in the content of the diamond-like sp{sup 3} fraction on the substrate potential. Mechanical properties of ta-C films — roughness, adhesion, hardness and Young's modulus were investigated using a profilometer, the scratch tester and a nanoindenter. The highest content of sp{sup 3} bonds, of about 63%, was obtained in the coating deposited at the substrate bias potential of − 100 V, which also showed the minimum surface roughness and maximum hardness and Young's modulus of 50 GPa and 371 GPa respectively. The ta-C coating synthesized at this bias potential had excellent adhesion — complete film delamination occurs at the load of 41 N. Our preliminary studies and the results described in this work enable the use of electromagnetic Venetian blind plasma filter for deposition of thin ta-C coatings with a minimum amount of defects. - Highlights: • ta-C films were deposited by pulsed arc method using a Venetian blind plasma filter. • Dependence of the film properties on the substrate bias potential was studied. • Substrate bias determines the content ratio of sp{sup 3} and sp{sup 2} phases in the ta-C films. • Substrate bias influences the roughness, microhardness, and adhesion of the films.

  3. Influence of the substrate bias potential on the properties of ta-C coatings deposited using Venetian blind plasma filter

    The paper presents the research results on the formation of amorphous ta-C films with a minimum amount of defects, deposited by pulsed vacuum-arc method with the use of a water-cooled electromagnetic Venetian blind plasma filter. The subject of the research was the influence of the substrate bias voltage, in the range of − 25 to − 200 V, on the structural and mechanical properties of ta-C coatings. Dependence of the microstructure and phase composition of ta-C films on the substrate bias voltage were analyzed by Raman and X-ray photoelectron spectroscopy. The results of the structural analysis of coatings showed characteristic changes in the content of the diamond-like sp3 fraction on the substrate potential. Mechanical properties of ta-C films — roughness, adhesion, hardness and Young's modulus were investigated using a profilometer, the scratch tester and a nanoindenter. The highest content of sp3 bonds, of about 63%, was obtained in the coating deposited at the substrate bias potential of − 100 V, which also showed the minimum surface roughness and maximum hardness and Young's modulus of 50 GPa and 371 GPa respectively. The ta-C coating synthesized at this bias potential had excellent adhesion — complete film delamination occurs at the load of 41 N. Our preliminary studies and the results described in this work enable the use of electromagnetic Venetian blind plasma filter for deposition of thin ta-C coatings with a minimum amount of defects. - Highlights: • ta-C films were deposited by pulsed arc method using a Venetian blind plasma filter. • Dependence of the film properties on the substrate bias potential was studied. • Substrate bias determines the content ratio of sp3 and sp2 phases in the ta-C films. • Substrate bias influences the roughness, microhardness, and adhesion of the films

  4. Electronic transport and shot noise in a Thue-Morse bilayer graphene superlattice with interlayer potential bias

    Li, Yuanqiao; Zhang, Hongmei; Liu, De

    2016-06-01

    In this paper, we evaluate the transport properties of a Thue-Morse AB-stacked bilayer graphene superlattice with different interlayer potential biases. Based on the transfer matrix method, the transmission coefficient, the conductance, and the Fano factor are numerically calculated and discussed. We find that the symmetry of the transmission coefficient with respect to normal incidence depends on the structural symmetry of the system and the new transmission peak appears in the energy band gap opening region. The conductance and the Fano factor can be greatly modulated not only by the Fermi energy and the interlayer potential bias but also by the generation number. Interestingly, the conductance exhibits the plateau of almost zero conductance and the Fano factor plateaus with Poisson value occur in the energy band gap opening region for large interlayer potential bias.

  5. The Potential of Deweyan-Inspired Action Research

    Stark, Jody L.

    2014-01-01

    In its broadest sense, pragmatism could be said to be the philosophical orientation of all action research. Action research is characterized by research, action, and participation grounded in democratic principles and guided by the aim of social improvement. Furthermore, action research is an active process of inquiry that does not admit…

  6. Pressure wave model for action potential propagation in excitable cells

    Rvachev, M M

    2003-01-01

    Speed of propagation of small-amplitude pressure waves through the cytoplasmic interior of myelinated and unmyelinated axons of different diameters is theoretically estimated and is found to generally agree with the action potential (AP) conduction velocities. This remarkable coincidence allows to surmise a model in which AP spread along axon is propelled not by straggling ionic currents as in the widely accepted local circuit theory, but by mechanoactivation of the membrane ion channels by a traveling pressure pulse. Hydraulic pulses propagating in the viscous axoplasm are calculated to decay over ~1 mm distances, and it is further hypothesized that it is the role of influxing during the AP calcium ions to activate membrane skeletal protein network attached to the membrane cytoplasmic side for a brief radial contraction amplifying the pressure pulse and preventing its decay. The model correctly predicts that the AP conduction velocity should vary as the one-half power of axon diameter for large unmyelinated ...

  7. Map-based model of the cardiac action potential

    A simple computationally efficient model which is capable of replicating the basic features of cardiac cell action potential is proposed. The model is a four-dimensional map and demonstrates good correspondence with real cardiac cells. Various regimes of cardiac activity, which can be reproduced by the proposed model, are shown. Bifurcation mechanisms of these regimes transitions are explained using phase space analysis. The dynamics of 1D and 2D lattices of coupled maps which model the behavior of electrically connected cells is discussed in the context of synchronization theory. -- Highlights: → Recent experimental-data based models are complicated for analysis and simulation. → The simplified map-based model of the cardiac cell is constructed. → The model is capable for replication of different types of cardiac activity. → The spatio-temporal dynamics of ensembles of coupled maps are investigated. → Received data are analyzed in context of biophysical processes in the myocardium.

  8. Compound sensory action potential in normal and pathological human nerves

    Krarup, Christian

    2004-01-01

    at different conduction distances are determined by summation of SFAPs of varying fiber diameters, and differ in this respect, also, from the compound muscle action potential (CMAP) for which conduction velocities are determined by the very fastest fibers in the nerve. The effect and extent of temporal...... dispersion over increasing conduction distance is greater for the SNAP than CMAP, and demonstration of conduction block is therefore difficult. In addition, the effect of temporal dispersion on amplitude and shape is strongly dependent on the number of conducting fibers and their distribution, and...... in different polyneuropathies. In this review, different factors that characterize sensory fibers and set the SNAP apart from the CMAP are discussed to emphasize the supplementary and complementary information that can be obtained from sensory conduction studies. Sensory conduction studies require particular...

  9. Influence of positive bias potential in plasma surface interactions and its application for simulation of radiolytic corrosion

    A simulation and acceleration test apparatus with helicon plasma for the radiolytic corrosion were arranged to investigate the corrosion phenomena of the metal surface under the heavy irradiation environment. The oxidation of 304 stainless steel by contact with the oxygen plasma was investigated. It was confirmed that the plasma oxidation phenomenon is enhanced by biasing the positive potential. (author)

  10. Attentional Bias in Patients with Decompensated Tinnitus: Prima Facie Evidence from Event-Related Potentials.

    Li, Zhicheng; Gu, Ruolei; Zeng, Xiangli; Zhong, Weifang; Qi, Min; Cen, Jintian

    2016-01-01

    Tinnitus refers to the auditory perception of sound in the absence of external sound or electric stimuli. The influence of tinnitus on cognitive processing is at the cutting edge of ongoing tinnitus research. In this study, we adopted an objective indicator of attentional processing, i.e. the mismatch negativity (MMN), to assess the attentional bias in patients with decompensated tinnitus. Three kinds of pure tones, D1 (8,000 Hz), S (8,500 Hz) and D2 (9,000 Hz), were used to induce event-related potentials (ERPs) in the normal ear. Employing the oddball paradigm, the task was divided into two blocks in which D1 and D2 were set as deviation stimuli, respectively. Only D2 induced a significant MMN in the tinnitus group, while neither D1 nor D2 was able to induce MMN in the control group. In addition, the ERPs in the left hemisphere, which were recorded within the time window of 90-150 ms (ERP90-150 ms), were significantly higher than those in the right hemisphere in the tinnitus group, while no significant difference was observed in the control group. Lastly, the amplitude of ERP90-150 ms in the tinnitus group was significantly higher than that in the control group. These findings suggest that patients with decompensated tinnitus showed automatic processing of acoustic stimuli, thereby indicating that these patients allocated more cognitive resources to acoustic stimulus processing. We suggest that the difficulty in disengaging or facilitated attention of patients might underlie this phenomenon. The limitations of the current study are discussed. PMID:26800229

  11. Short latency compound action potentials from mammalian gravity receptor organs

    Jones, T. A.; Jones, S. M.

    1999-01-01

    Gravity receptor function was characterized in four mammalian species using far-field vestibular evoked potentials (VsEPs). VsEPs are compound action potentials of the vestibular nerve and central relays that are elicited by linear acceleration ramps applied to the cranium. Rats, mice, guinea pigs, and gerbils were studied. In all species, response onset occurred within 1.5 ms of the stimulus onset. Responses persisted during intense (116 dBSPL) wide-band (50 to 50 inverted question mark omitted inverted question mark000 Hz) forward masking, whereas auditory responses to intense clicks (112 dBpeSPL) were eliminated under the same conditions. VsEPs remained after cochlear extirpation but were eliminated following bilateral labyrinthectomy. Responses included a series of positive and negative peaks that occurred within 8 ms of stimulus onset (range of means at +6 dBre: 1.0 g/ms: P1=908 to 1062 micros, N1=1342 to 1475 micros, P2=1632 to 1952 micros, N2=2038 to 2387 micros). Mean response amplitudes at +6 dBre: 1.0 g/ms ranged from 0.14 to 0.99 microV. VsEP input/output functions revealed latency slopes that varied across peaks and species ranging from -19 to -51 micros/dB. Amplitude-intensity slopes also varied ranging from 0.04 to 0.08 microV/dB for rats and mice. Latency values were comparable to those of birds although amplitudes were substantially smaller in mammals. VsEP threshold values were considerably higher in mammals compared to birds and ranged from -8.1 to -10.5 dBre 1.0 g/ms across species. These results support the hypothesis that mammalian gravity receptors are less sensitive to dynamic stimuli than are those of birds.

  12. Modelling Action Potential Generation and Propagation in Fibroblastic Cells

    Torres, J. J.; Cornelisse, L. N.; Harks, E. G. A.; Theuvenet, A. P. R.; Ypey, D. L.

    2003-04-01

    Using a standard Hodgkin-Huxley (HH) formalism, we present a mathematical model for action potential (AP) generation and intercellular AP propagation in quiescent (serum-deprived) normal rat kidney (NRK) fibroblasts [1], based on the recent experimental identification of the ion channels involved [2]. The principal ion channels described are those of an inwardly rectifying K+ conductance (GKIR), an L-type calcium conductance (GCaL), an intracellular calcium activated Cl- conductance (GCl(Ca)), a residual leak conductance Gleak, and gap junctional channels between the cells (Ggj). The role of each one of these components in the particular shape of the AP wave-form has been analyzed and compared with experimental observations. In addition, we have studied the role of subcellular processes like intracellular calcium dynamics and calcium buffering in AP generation. AP propagation between cells was reconstructed in a hexagonal model of cells coupled by Ggj with physiological conductance values. The model revealed an excitability mechanism of quiescent NRK cells with a particular role of intracellular calcium dynamics. It allows further explorations of the mechanism of signal generation and transmission in NRK cell cultures and its dependence on growth conditions.

  13. Pharmacological actions of statins: potential utility in COPD

    T. E. Eaton

    2009-12-01

    Full Text Available Chronic obstructive pulmonary disease (COPD is characterised by minimally reversible airflow limitation and features of systemic inflammation. Current therapies for COPD have been shown to reduce symptoms and infective exacerbations and to improve quality of life. However, these drugs have little effect on the natural history of the disease (progressive decline in lung function and exercise tolerance and do not improve mortality. The anti-inflammatory effects of statins on both pulmonary and systemic inflammation through inhibition of guanosine triphosphatase and nuclear factor-B mediated activation of inflammatory and matrix remodelling pathways could have substantial benefits in patients with COPD due to the following. 1 Inhibition of cytokine production (tumour necrosis factor-, interleukin (IL-6 and IL-8 and neutrophil infiltration into the lung; 2 inhibition of the fibrotic activity in the lung leading to small airways fibrosis and irreversible airflow limitation; 3 antioxidant and anti-inflammatory (IL-6 mediated effects on skeletal muscle; 4 reduced inflammatory response to pulmonary infection; and 5 inhibition of the development (or reversal of epithelial-mesenchymal transition, a precursor event to lung cancer. This review examines the pleiotropic pharmacological action of statins which inhibit key inflammatory and remodelling pathways in COPD and concludes that statins have considerable potential as adjunct therapy in COPD.

  14. Pharmacological actions of statins: potential utility in COPD.

    Young, R P; Hopkins, R; Eaton, T E

    2009-12-01

    Chronic obstructive pulmonary disease (COPD) is characterised by minimally reversible airflow limitation and features of systemic inflammation. Current therapies for COPD have been shown to reduce symptoms and infective exacerbations and to improve quality of life. However, these drugs have little effect on the natural history of the disease (progressive decline in lung function and exercise tolerance) and do not improve mortality. The anti-inflammatory effects of statins on both pulmonary and systemic inflammation through inhibition of guanosine triphosphatase and nuclear factor-κB mediated activation of inflammatory and matrix remodelling pathways could have substantial benefits in patients with COPD due to the following. 1) Inhibition of cytokine production (tumour necrosis factor-α, interleukin (IL)-6 and IL-8) and neutrophil infiltration into the lung; 2) inhibition of the fibrotic activity in the lung leading to small airways fibrosis and irreversible airflow limitation; 3) antioxidant and anti-inflammatory (IL-6 mediated) effects on skeletal muscle; 4) reduced inflammatory response to pulmonary infection; and 5) inhibition of the development (or reversal) of epithelial-mesenchymal transition, a precursor event to lung cancer. This review examines the pleiotropic pharmacological action of statins which inhibit key inflammatory and remodelling pathways in COPD and concludes that statins have considerable potential as adjunct therapy in COPD. PMID:20956147

  15. Potential fitting biases resulting from grouping data into variable width bins

    When reading peer-reviewed scientific literature describing any analysis of empirical data, it is natural and correct to proceed with the underlying assumption that experiments have made good faith efforts to ensure that their analyses yield unbiased results. However, particle physics experiments are expensive and time consuming to carry out, thus if an analysis has inherent bias (even if unintentional), much money and effort can be wasted trying to replicate or understand the results, particularly if the analysis is fundamental to our understanding of the universe. In this note we discuss the significant biases that can result from data binning schemes. As we will show, if data are binned such that they provide the best comparison to a particular (but incorrect) model, the resulting model parameter estimates when fitting to the binned data can be significantly biased, leading us to too often accept the model hypothesis when it is not in fact true. When using binned likelihood or least squares methods there is of course no a priori requirement that data bin sizes need to be constant, but we show that fitting to data grouped into variable width bins is particularly prone to produce biased results if the bin boundaries are chosen to optimize the comparison of the binned data to a wrong model. The degree of bias that can be achieved simply with variable binning can be surprisingly large. Fitting the data with an unbinned likelihood method, when possible to do so, is the best way for researchers to show that their analyses are not biased by binning effects. Failing that, equal bin widths should be employed as a cross-check of the fitting analysis whenever possible

  16. Potential biases in colorectal cancer screening using faecal occult blood test

    Riboe, Dea Grip; Dogan, Tilde Steen; Brodersen, John

    2013-01-01

    BACKGROUND: Colorectal cancer (CRC) is one of the most common types of cancer in European countries and associated with a high mortality rate. A 16% relative risk reduction (RRR) of mortality was found in a meta-analysis based on four randomized controlled trials (RCT) on CRC screening. The aim...... in their study. Data were collected from The Danish Data Archives. Authors of the Cochrane review were contacted. RESULTS: Six biases were identified, of which five favour screening. Three of the biases identified were specific to CRC screening: type of diagnostic method, place of surgery and diagnostic delay...

  17. Dynamics of the inward rectifier K+ current during the action potential of guinea pig ventricular myocytes.

    Ibarra, J; Morley, G E; Delmar, M

    1991-01-01

    The potassium selective, inward rectifier current (IK1) is known to be responsible for maintaining the resting membrane potential of quiescent ventricular myocytes. However, the contribution of this current to the different phases of the cardiac action potential has not been adequately established. In the present study, we have used the action potential clamp (APC) technique to characterize the dynamic changes of a cesium-sensitive (i.e., Ik1) current which occur during the action potential. ...

  18. High prevalence of potential biases threatens the interpretation of trials in patients with chronic disease

    Boyd Cynthia M

    2011-06-01

    Full Text Available Abstract Background The complexity of chronic diseases is a challenge for investigators conducting randomized trials. The causes for this include the often difficult control for confounding, the selection of outcomes from many potentially important outcomes, the risk of missing data with long follow-up and the detection of heterogeneity of treatment effects. Our aim was to assess such aspects of trial design and analysis for four prevalent chronic diseases. Methods We included 161 randomized trials on drug and non-drug treatments for chronic obstructive pulmonary disease, type 2 diabetes mellitus, stroke and heart failure, which were included in current Cochrane reviews. We assessed whether these trials defined a single outcome or several primary outcomes, statistically compared baseline characteristics to assess comparability of treatment groups, reported on between-group comparisons, and we also assessed how they handled missing data and whether appropriate methods for subgroups effects were used. Results We found that only 21% of all chronic disease trials had a single primary outcome, whereas 33% reported one or more primary outcomes. Two of the fifty-one trials that tested for statistical significance of baseline characteristics adjusted the comparison for a characteristic that was significantly different. Of the 161 trials, 10% reported a within-group comparison only; 17% (n = 28 of trials reported how missing data were handled (50% (n = 14 carried forward last values, 27% (n = 8 performed a complete case analysis, 13% (n = 4 used a fixed value imputation and 10% (n = 3 used more advanced methods; and 27% of trials performed a subgroup analysis but only 23% of them (n = 10 reported an interaction test. Drug trials, trials published after wide adoption of the CONSORT (CONsolidated Standards of Reporting Trials statement (2001 or later and trials in journals with higher impact factors were more likely to report on some of these aspects of

  19. Acute nerve compression and the compound muscle action potential

    Baylor Kelly

    2008-01-01

    Full Text Available Abstract Detecting acute nerve compression using neurophysiologic studies is an important part of the practice of clinical intra-operative neurophysiology. The goal of this paper was to study the changes in the compound muscle action potential (CMAP during acute mechanical compression. This is the type of injury most likely to occur during surgery. Thus, understanding the changes in the CMAP during this type of injury will be useful in the detection and prevention using intra-operative neurophysiologic monitoring. The model involved compression of the hamster sciatic nerve over a region of 1.3 mm with pressures up to 2000 mmHg for times on the order of 3 minutes. In this model CMAP amplitude dropped to 50% of its baseline value when a pressure of roughly 1000 mmHg is applied while, at the same time, nerve conduction velocities decline by only 5%. The ability to detect statistically significant changes in the CMAP at low force levels using other descriptors of the CMAP including duration, latency variation, etc alone or in conjunction with amplitude and velocity measures was investigated. However, these other parameters did not allow for earlier detection of significant changes. This study focused on a model in which nerve injury on a short time scale is purely mechanical in origin. It demonstrated that a pure compression injury produced large changes in CMAP amplitude prior to large changes in conduction velocity. On the other hand, ischemic and stretch injuries are associated with larger changes in conduction velocity for a given value of CMAP amplitude reduction.

  20. Increased Event-Related Potentials and Alpha-, Beta-, and Gamma-Activity Associated with Intentional Actions

    Karch, Susanne; Loy, Fabian; Krause, Daniela; Schwarz, Sandra; Kiesewetter, Jan; Segmiller, Felix; Chrobok, Agnieszka I.; Keeser, Daniel; Pogarell, Oliver

    2016-01-01

    Objective: Internally guided actions are defined as being purposeful, self-generated and offering choices between alternatives. Intentional actions are essential to reach individual goals. In previous empirical studies, internally guided actions were predominantly related to functional responses in frontal and parietal areas. The aim of the present study was to distinguish event-related potentials and oscillatory responses of intentional actions and externally guided actions. In addition, we ...

  1. The membrane actions of estrogens can potentiate their lordosis behavior-facilitating genomic actions

    Kow, Lee-Ming; Pfaff, Donald W.

    2004-01-01

    The membrane actions of estrogens can facilitate their genomic actions. To determine whether this facilitation bears on CNS mechanisms for estrogen-dependent behaviors, ovariectomized rats were subjected to a two-pulse treatment of estrogen directly in the hypothalamic ventromedial nucleus. Two days later, each rat was given progesterone and then tested for lordosis behavior, the induction of which requires the genomic actions of estrogen. When estrogen was given in both pulses (15 min to 2 h...

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

    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. Scaling of the quark-antiquark potential and improved actions in SU(2) lattice gauge theory

    The scaling behaviour of the quark-antiquark potential is investigated by a high statistics Monte Carlo calculation in SU(2) lattice gauge theory. Besides the standard one-plaquette action we also use Symanzik's tree-level improved action and Wilson's block-spin improved action. No significant differences between Symanzik's action and the standard action have been observed. For small β Wilson's action scales differently. The string tension value chi extracted from the data corresponds to Λsub(latt) = (0.018 +- 0.001) √chi for the one-plaquette action. (orig.)

  4. Understanding the Electrical Behavior of the Action Potential in Terms of Elementary Electrical Sources

    Rodriguez-Falces, Javier

    2015-01-01

    A concept of major importance in human electrophysiology studies is the process by which activation of an excitable cell results in a rapid rise and fall of the electrical membrane potential, the so-called action potential. Hodgkin and Huxley proposed a model to explain the ionic mechanisms underlying the formation of action potentials. However,…

  5. Ontogeny of vestibular compound action potentials in the domestic chicken

    Jones, S. M.; Jones, T. A.

    2000-01-01

    Compound action potentials of the vestibular nerve were measured from the surface of the scalp in 148 chickens (Gallus domesticus). Ages ranged from incubation day 18 (E18) to 22 days posthatch (P22). Responses were elicited using linear acceleration cranial pulses. Response thresholds decreased at an average rate of -0.45 dB/day. The decrease was best fit by an exponential model with half-maturity time constant of 5.1 days and asymptote of approximately -25.9 dB re:1.0 g/ms. Mean threshold approached within 3 dB of the asymptote by ages P6-P9. Similarly, response latencies decreased exponentially to within 3% of mature values at ages beyond P9. The half-maturity time constant for peripheral response peak latencies P1, N1, and P2 was comparable to thresholds and ranged from approximately 4.6 to 6.2 days, whereas central peaks (N2, P3, and N3) ranged from 2.9 to 3.4 days. Latency-intensity slopes for P1, N1, and P2 tended to decrease with age, reaching mature values within approximately 100 hours of hatching. Amplitudes increased as a function of age with average growth rates for response peaks ranging from 0.04 to 0.09 microV/day. There was no obvious asymptote to the growth of amplitudes over the ages studied. Amplitude-intensity slopes also increased modestly with age. The results show that gravity receptors are responsive to transient cranial stimuli as early as E19 in the chicken embryo. The functional response of gravity receptors continues to develop for many days after all major morphological structures are in place. Distinct maturational processes can be identified in central and peripheral neural relays. Functional improvements during maturation may result from refinements in the receptor epithelia, improvements in central and peripheral synaptic transmission, increased neural myelination, as well as changes in the mechanical coupling between the cranium and receptor organ.

  6. Mathematical Distinction in Action Potential between Primo-Vessels and Smooth Muscle

    Seong-Jin Cho; Sang-Hun Lee; Wenji Zhang; Sae-Bhom Lee; Kwang-Ho Choi; Sun-Mi Choi; Yeon-Hee Ryu

    2012-01-01

    We studied the action potential of Primo-vessels in rats to determine the electrophysiological characteristics of these structures. We introduced a mathematical analysis method, a normalized Fourier transform that displays the sine and cosine components separately, to compare the action potentials of Primo-vessels with those for the smooth muscle. We found that Primo-vessels generated two types of action potential pulses that differed from those of smooth muscle: (1) Type I pulse had rapid de...

  7. Distribution of Action Potential Duration and T-wave Morphology: a Simulation Study

    Ryzhii, Elena; Ryzhii, Maxim; Wei, Daming

    2009-01-01

    The results of a simulation study of the action potential duration (APD) distribution and T-wave morphology taking into account the midmyocardial cells (M-cells) concept are described. To investigate the effect of M-cells we present a computer model in which ion channel action potential formulations are incorporated into three-dimensional whole heart model. We implemented inhomogeneous continuous action potential duration distribution based on different distributions of maximal slow delayed r...

  8. A Rabbit Ventricular Action Potential Model Replicating Cardiac Dynamics at Rapid Heart Rates

    Mahajan, Aman; Shiferaw, Yohannes; Sato, Daisuke; Baher, Ali; Olcese, Riccardo; Xie, Lai-Hua; Yang, Ming-Jim; Chen, Peng-Sheng; Restrepo, Juan G.; Karma, Alain; Garfinkel, Alan; Qu, Zhilin; Weiss, James N.

    2008-01-01

    Mathematical modeling of the cardiac action potential has proven to be a powerful tool for illuminating various aspects of cardiac function, including cardiac arrhythmias. However, no currently available detailed action potential model accurately reproduces the dynamics of the cardiac action potential and intracellular calcium (Cai) cycling at rapid heart rates relevant to ventricular tachycardia and fibrillation. The aim of this study was to develop such a model. Using an existing rabbit ven...

  9. On the excitation of action potentials by protons and its potential implications for cholinergic transmission

    Fillafer, Christian

    2014-01-01

    One of the most conserved mechanisms for transmission of a nerve pulse across a synapse relies on acetylcholine. Ever since the Nobel-prize winning works of Dale and Loewi, it has been assumed that acetylcholine - subsequent to its action on a postsynaptic cell - is split into inactive by-products by acetylcholinesterase. Herein, this widespread assumption is falsified. Excitable cells (Chara australis internodes), which had previously been unresponsive to acetylcholine, became acetylcholine-sensitive in presence of acetylcholinesterase. The latter was evidenced by a striking difference in cell membrane depolarisation upon exposure to 10 mM intact acetylcholine (deltaV=-2plus/minus5 mV) and its hydrolysate respectively (deltaV=81plus/minus19 mV) for 60 sec. This pronounced depolarization, which also triggered action potentials, was clearly attributed to one of the hydrolysis products: acetic acid (deltaV=87plus/minus9 mV at pH 4.0; choline ineffective in range 1-10 mM). In agreement with our findings, numerou...

  10. Dynamics of action potential initiation in the GABAergic thalamic reticular nucleus in vivo.

    Fabián Muñoz

    Full Text Available Understanding the neural mechanisms of action potential generation is critical to establish the way neural circuits generate and coordinate activity. Accordingly, we investigated the dynamics of action potential initiation in the GABAergic thalamic reticular nucleus (TRN using in vivo intracellular recordings in cats in order to preserve anatomically-intact axo-dendritic distributions and naturally-occurring spatiotemporal patterns of synaptic activity in this structure that regulates the thalamic relay to neocortex. We found a wide operational range of voltage thresholds for action potentials, mostly due to intrinsic voltage-gated conductances and not synaptic activity driven by network oscillations. Varying levels of synchronous synaptic inputs produced fast rates of membrane potential depolarization preceding the action potential onset that were associated with lower thresholds and increased excitability, consistent with TRN neurons performing as coincidence detectors. On the other hand the presence of action potentials preceding any given spike was associated with more depolarized thresholds. The phase-plane trajectory of the action potential showed somato-dendritic propagation, but no obvious axon initial segment component, prominent in other neuronal classes and allegedly responsible for the high onset speed. Overall, our results suggest that TRN neurons could flexibly integrate synaptic inputs to discharge action potentials over wide voltage ranges, and perform as coincidence detectors and temporal integrators, supported by a dynamic action potential threshold.

  11. Potential involvement of serotonergic signaling in ketamine's antidepressant actions

    du Jardin, Kristian Gaarn; Müller, Heidi Kaastrup; Elfving, Betina;

    2016-01-01

    A single i.v. infusion of ketamine, classified as an N-methyl-D-aspartate (NMDA) receptor antagonist, may alleviate depressive symptoms within hours of administration in treatment resistant depressed patients, and the antidepressant effect may last for several weeks. These unique therapeutic...... properties have prompted researchers to explore the mechanisms mediating the antidepressant effects of ketamine, but despite many efforts, no consensus on its antidepressant mechanism of action has been reached. Recent preclinical reports have associated the neurotransmitter serotonin (5-hydroxytryptamine; 5......-HT) with the antidepressant-like action of ketamine. Here, we review the current evidence for a serotonergic role in ketamine's antidepressant effects. The pharmacological profile of ketamine may include equipotent activity on several non-NMDA targets, and the current hypotheses for the mechanisms...

  12. Characteristics of action potentials and their underlying outward currents in rat taste receptor cells.

    Chen, Y; Sun, X D; Herness, S

    1996-02-01

    1. Taste receptor cells produce action potentials as a result of transduction mechanisms that occur when these cells are stimulated with tastants. These action potentials are thought to be key signaling events in relaying information to the central nervous system. We explored the ionic basis of action potentials from dissociated posterior rat taste cells using the patch-clamp recording technique in both voltage-clamp and current-clamp modes. 2. Action potentials were evoked by intracellular injection of depolarizing current pulses from a holding potential of -80 mV. The threshold potential for firing of action potentials was approximately -35 mV; the input resistance of these cells averaged 6.9 G omega. With long depolarizing pulses, two or three action potentials could be elicited with successive attenuation of the spike height. Afterhyperpolarizations were observed often. 3. Both sodium and calcium currents contribute to depolarizing phases of the action potential. Action potentials were blocked completely in the presence of the sodium channel blocker tetrodotoxin. Calcium contributions could be visualized as prolonged calcium plateaus when repolarizing potassium currents were blocked and barium was used as a charge carrier. 4. Outward currents were composed of sustained delayed rectifier current, transient potassium current, and calcium-activated potassium current. Transient and sustained potassium currents activated close to -30 mV and increased monotonically with further depolarization. Up to half the outward current inactivated with decay constants on the order of seconds. Sustained and transient currents displayed steep voltage dependence in conductance and inactivation curves. Half inactivation occurred at -20 +/- 3.1 mV (mean +/- SE) with a decrease of 11.2 +/- 0.5 mV per e-fold. Half maximal conductance occurred at 3.6 +/- 1.8 mV and increased 12.2 +/- 0.6 mV per e-fold. Calcium-activated potassium current was evidenced by application of apamin and the

  13. Analysis of toxin induced changes in action potential shape for drug development

    Akanda, Nesar; Molnar, Peter; Stancescu, Maria; Hickman, James J.

    2009-01-01

    The generation of an action potential is a complex process in excitable cells which involves the temporal opening and closing of several voltage-dependent ion channels in the cell membrane. The shape of an action potential can carry information concerning the state of the involved ion channels and their relationship to cellular processes. Alteration of these ion channels by the administration of toxins, drugs, and biochemicals can change the action potential’s shape in a specific way which ca...

  14. Fish oil curtails the human action potential dome in a heterogeneous manner: Implication for arrhythmogenesis

    A.O. Verkerk; H.M. den Ruijter; N. de Jonge; R. Coronel

    2009-01-01

    Omega-3 polyunsaturated fatty acids (omega3-PUFAs) from fish oil modulate various ion channels, including the L-type calcium current (I(Ca,L)). As a result, fish oil shortens the cardiac action potential and may cause a loss of the dome of the action potential (AP). Under conditions of increased pre

  15. Potential for bias in 21st century semiempirical sea level projections

    Jevrejeva, S.; Moore, J. C.; Grinsted, A.

    2012-01-01

    We examine the limitations of a semiempirical model characterized by a sea level projection of 73 cm with RCP4.5 scenario by 2100. Calibrating the model with data to 1990 and then simulating the period 1993-2009 produces sea level in close agreement with acceleration in sea level rise observed by...... satellite altimetry. Nonradiative forcing contributors, such as long-term adjustment of Greenland and Antarctica ice sheets since Last Glacial Maximum, abyssal ocean warming, and terrestrial water storage, may bias model calibration which, if corrected for, tend to reduce median sea level projections at...... 2100 by 2-10 cm, though this is within the confidence interval. We apply the semiempirical approach to simulate individual contributions from thermal expansion and small glacier melting. Steric sea level projections agree within 3 cm of output from process-based climate models. In contrast...

  16. Triangulation of the monophasic action potential causes flattening of the electrocardiographic T-wave

    Bhuiyan, Tanveer Ahmed; Graff, Claus; Thomsen, Morten Bækgaard;

    2012-01-01

    It has been proposed that triangulation on the cardiac action potential manifests as a broadened, more flat and notched T-wave on the ECG but to what extent such morphology characteristics are indicative of triangulation is more unclear. In this paper, we have analyzed the morphological changes of...... the action potential under the effect of the IKr blocker sertindole and associated these changes to concurrent changes in the morphology of electrocardiographic T-waves in dogs. We show that, under the effect of sertindole, the peak changes in the morphology of action potentials occur at time points...... similar to those observed for the peak changes in T-wave morphology on the ECG. We further show that the association between action potential shape and ECG shape is dose-dependent and most prominent at the time corresponding to phase 3 of the action potential. © 2012 CCAL....

  17. Consumer-Related Food Waste: Causes and Potential for Action

    Jessica Aschemann-Witzel

    2015-05-01

    Full Text Available In the past decade, food waste has received increased attention on both academic and societal levels. As a cause of negative economic, environmental and social effects, food waste is considered to be one of the sustainability issues that needs to be addressed. In developed countries, consumers are one of the biggest sources of food waste. To successfully reduce consumer-related food waste, it is necessary to have a clear understanding of the factors influencing food waste-related consumer perceptions and behaviors. The present paper presents the results of a literature review and expert interviews on factors causing consumer-related food waste in households and supply chains. Results show that consumers’ motivation to avoid food waste, their management skills of food provisioning and food handling and their trade-offs between priorities have an extensive influence on their food waste behaviors. We identify actions that governments, societal stakeholders and retailers can undertake to reduce consumer-related food waste, highlighting that synergistic actions between all parties are most promising. Further research should focus on exploring specific food waste contexts and interactions more in-depth. Experiments and interventions in particular can contribute to a shift from analysis to solutions.

  18. Time-Dependent Action in φ~6 Potential

    Hatem Widyan; Mashhoor Al-Wardat

    2012-01-01

    The false vacuum decay in field theory from a coherently oscillating initial state is studied for φ6 potential. An oscillating bubble solution is obtained. The instantaneous bubble nucleation rate is calculated.

  19. Spatially periodic domain wall pinning potentials: Asymmetric pinning and dipolar biasing

    Metaxas, P. J.; Zermatten, P. -J.; Novak, R. L.; Rohart, S.; Jamet, J. -P.; Weil, R.; Ferré, J.; Mougin, A.; Stamps, R. L.; Gaudin, G.; Baltz, V.; Rodmacq, B.

    2013-01-01

    Domain wall propagation has been measured in continuous, weakly disordered, quasi-two-dimensional, Ising-like magnetic layers that are subject to spatially periodic domain wall pinning potentials. The potentials are generated non-destructively using the stray magnetic field of ordered arrays of magnetically hard [Co/Pt]$_m$ nanoplatelets which are patterned above and are physically separated from the continuous magnetic layer. The effect of the periodic pinning potentials on thermally activat...

  20. Alteration of neural action potential patterns by axonal stimulation: the importance of stimulus location

    Crago, Patrick E.; Makowski, Nathaniel S.

    2014-10-01

    Objective. Stimulation of peripheral nerves is often superimposed on ongoing motor and sensory activity in the same axons, without a quantitative model of the net action potential train at the axon endpoint. Approach. We develop a model of action potential patterns elicited by superimposing constant frequency axonal stimulation on the action potentials arriving from a physiologically activated neural source. The model includes interactions due to collision block, resetting of the neural impulse generator, and the refractory period of the axon at the point of stimulation. Main results. Both the mean endpoint firing rate and the probability distribution of the action potential firing periods depend strongly on the relative firing rates of the two sources and the intersite conduction time between them. When the stimulus rate exceeds the neural rate, neural action potentials do not reach the endpoint and the rate of endpoint action potentials is the same as the stimulus rate, regardless of the intersite conduction time. However, when the stimulus rate is less than the neural rate, and the intersite conduction time is short, the two rates partially sum. Increases in stimulus rate produce non-monotonic increases in endpoint rate and continuously increasing block of neurally generated action potentials. Rate summation is reduced and more neural action potentials are blocked as the intersite conduction time increases. At long intersite conduction times, the endpoint rate simplifies to being the maximum of either the neural or the stimulus rate. Significance. This study highlights the potential of increasing the endpoint action potential rate and preserving neural information transmission by low rate stimulation with short intersite conduction times. Intersite conduction times can be decreased with proximal stimulation sites for muscles and distal stimulation sites for sensory endings. The model provides a basis for optimizing experiments and designing neuroprosthetic

  1. A model for thermal exchange in axons during action potential propagation.

    Masson, Jean-Baptiste; Gallot, Guilhem

    2008-01-01

    International audience Several experiments have shown that during propagation of the action potential in axons, thermal energy is locally exchanged. In this paper, we use a simple model based on statistical physics to show that an important part of this exchange comes from the physics of the effusion. We evaluate, during the action potential propagation, the variation of internal energy and of the energy associated with the chemical potential of the effusion of water and ions to extract th...

  2. Potential Bias in Projecting Future Regional Megadrought Risk: Insights From A Global Data-Model Framework

    Overpeck, J. T.; Ault, T.; Cole, J. E.; Fasullo, J.; Loope, G. R.; Parsons, L. A.; Stevenson, S.

    2015-12-01

    Megadrought is one of the most significant and costly climate extremes, and one that stakeholders (e.g., water and other resource managers) the world over wish to understand better; in particular, they need estimates of the risk of severe droughts as a function of drought frequency, severity, duration, and atmospheric greenhouse gas concentration. In many dry-climate regions of the globe, megadrought is synonymous with multi-decadal drought. However, in other regions, megadrought can be defined as extended drought, mostly not seen in the period of instrumental observations, and that would have large impacts if it were to occur in the future. New and published paleoclimatic observations allow us to understand the spectrum of drought in many regions of the globe; droughts exceeding 50 years have occurred in recent Earth history in southwestern North America, sub-Saharan Africa, the Mediterranean and Australia, whereas shorter megadroughts have occurred in Monsoon Asia, Amazonia and elsewhere. Data-model comparisons for regions with sufficiently long (e.g., 1000-2000 years) records of observed hydroclimatic variability suggest that state-of-the-art models can provide realistic estimates of interannual to decadal drought risk, but underestimate the risk of megadrought. Likely reasons for this shortcoming are the lack of sufficient multi-decadal variability in simulations of the past and future, plus an underappreciated understanding about how temperature variability and land-surface feedbacks interact with hydrological and ecological drought, as well as the roles played by unusually wet hydroclimatic extremes (e.g., ENSO related) in ending droughts of long duration. Paleoclimatic records also provide the opportunity to estimate how much models underestimate megadrought risk as a function of locale, frequency, severity, duration, and atmospheric greenhouse gas concentration; they also aid in providing stakeholders with bias-corrected estimates of megadrought risk.

  3. Biased Motion in a Symmetric Periodic Potential by Breaking Temporal Symmetry

    ZHENG Zhi-Gang; LI Xiao-Wen

    2001-01-01

    Unidirectional transport of a particle in a spatially periodic and symmetric potential under a periodic force with broken temporal symmetry is studied. With a collaboration of the potential field and the asymmetric ac force, a dc current can be observed. Resonant current steps are found for a finite period of the ac force. A phase diagram of these resonant steps is given. Stochastic-resonance-like directional transport induced by thermal noises is revealed.

  4. Fishery induces sperm depletion and reduction in male reproductive potential for crab species under male-biased harvest strategy.

    Pardo, Luis Miguel; Rosas, Yenifer; Fuentes, Juan Pablo; Riveros, Marcela Paz; Chaparro, Oscar Roberto

    2015-01-01

    Sperm depletion in males can occur when polygynous species are intensively exploited under a male-biased management strategy. In fisheries involving crabs species, the effects of this type of management on the reproductive potential is far from being understood. This study tests whether male-biased management of the principal Chilean crab fishery is able to affect the potential capacity of Metacarcinus edwardsii males to transfer sperm to females. Five localities in southern Chile, recording contrasting crab fishery landing, were selected to assess the potential of sperm depletion triggered by fishery. Seasonally, male crabs from each locality were obtained. Dry weight and histological condition of vasa deferentia and the Vaso-Somatic Index (VSI) were determined in order to use them as proxies for sperm depletion and male reproductive condition. A manipulative experiment was performed in the laboratory to estimate vasa deferentia weight and VSI from just-mated males in order to obtain a reference point for the potential effects of the fishery on sperm reserves. Sperm storage capacity is significantly affected by fisheries; during the mating season vasa deferentia from localities with low fishery intensity were heavier than those from high intensity fisheries, and these differences were even more evident in large males. Histological section showed that this disparity in vasa deferentia weight was explained principally by differences in the quantity of spermatophores rather than other seminal material. VSI was always higher in males from localities with low fishery intensity. Males from localities with high fishery intensity showed little capacity to recover sperm reserves and the VSI of these males remained below the values of the just-mated males. Detriment in the capacity of males to transfer sperm is the first step to sperm limitation in an exploited population, thus detection of sperm depletion can be an alert to introduce changes in the current management of

  5. Action potentials in retinal ganglion cells are initiated at the site of maximal curvature of the extracellular potential

    Eickenscheidt, Max; Zeck, Günther

    2014-06-01

    Objective. The initiation of an action potential by extracellular stimulation occurs after local depolarization of the neuronal membrane above threshold. Although the technique shows remarkable clinical success, the site of action and the relevant stimulation parameters are not completely understood. Approach. Here we identify the site of action potential initiation in rabbit retinal ganglion cells (RGCs) interfaced to an array of extracellular capacitive stimulation electrodes. We determine which feature of the extracellular potential governs action potential initiation by simultaneous stimulation and recording RGCs interfaced in epiretinal configuration. Stimulation electrodes were combined to areas of different size and were presented at different positions with respect to the RGC. Main results. Based on stimulation by electrodes beneath the RGC soma and simultaneous sub-millisecond latency measurement we infer axonal initiation at the site of maximal curvature of the extracellular potential. Stimulation by electrodes at different positions along the axon reveals a nearly constant threshold current density except for a narrow region close to the cell soma. These findings are explained by the concept of the activating function modified to consider a region of lower excitability close to the cell soma. Significance. We present a framework how to estimate the site of action potential initiation and the stimulus required to cross threshold in neurons tightly interfaced to capacitive stimulation electrodes. Our results underscore the necessity of rigorous electrical characterization of the stimulation electrodes and of the interfaced neural tissue.

  6. Action Research’s Potential to Foster Institutional Change for Urban Water Management

    Dimitrios Zikos; Andreas Thiel

    2013-01-01

    The paper discusses the potential of action research to meet the challenges entailed in institutional design for urban water management. Our overall aim is to briefly present action research and discuss its methodological merits with regard to the challenges posed by the different conceptual bases for extrapolating the effects of institutional design on institutional change. Thus, our aim is to explore how Action Research meets the challenge of scoping the field in an open fashion for determi...

  7. The electrostatic potential profile along a biased molecular wire A model quantum mechanical calculation

    Pleutin, S; Ingold, G L; Nitzan, A; Pleutin, St\\'ephane; Grabert, Hermann; Ingold, Gert-Ludwig; Nitzan, Abraham

    2003-01-01

    We study the electrostatic potential of a molecular wire bridging two metallic electrodes in the limit of weak contacts. With the use of a tight-binding model including a fully three-dimensional treatment of the electrostatics of the molecular junction, the potential is shown to be poorly screened, dropping mostly along the entire molecule. In addition, we observe pronounced Friedel oscillations that can be related to the breaking of electron-hole symmetry. Our results are in semi-quantitative agreement with recent state-of-the-art ab initio calculations and point to the need of a three-dimensional treatment to properly capture the behavior of the electrostatic potential. Based on these results, current-voltage curves are calculated within the Landauer formalism. It is shown that Coulomb interaction partially compensates the localization of the charges induced by the electric field and consequently tends to suppress zones of negative differential resistance.

  8. Neuronal oscillations enhance stimulus discrimination by ensuring action potential precision

    Schaefer, Andreas T; Angelo, Kamilla; Spors, Hartwig;

    2006-01-01

    Although oscillations in membrane potential are a prominent feature of sensory, motor, and cognitive function, their precise role in signal processing remains elusive. Here we show, using a combination of in vivo, in vitro, and theoretical approaches, that both synaptically and intrinsically......--permitted accurate discernment of up to 1,000 different stimuli. At low oscillation frequencies, stimulus discrimination showed a clear phase dependence whereby inputs arriving during the trough and the early rising phase of an oscillation cycle were most robustly discriminated. Thus, by ensuring AP precision...

  9. More evidence for a refined Gribov-Zwanziger action based on an effective potential approach

    Vandersickel, N.; Dudal, D.; Sorella, S.P.

    2011-01-01

    The purpose of this proceeding is twofold. Firstly, we shall make the refining of the Gribov-Zwanziger action more complete by taking into account more condensates than considered so far. Secondly, we shall provide more evidence for the refined Gribov-Zwanziger action based on an effective potential approach.

  10. Synaptically evoked dendritic action potentials in rat neocortical pyramidal neurons.

    Schwindt, P C; Crill, W E

    1998-05-01

    In a previous study iontophoresis of glutamate on the apical dendrite of layer 5 pyramidal neurons from rat neocortex was used to identify sites at which dendritic depolarization evoked small, prolonged Ca2+ spikes and/or low-threshold Na+ spikes recorded by an intracellular microelectrode in the soma. These spikes were identified as originating in the dendrite. Here we evoke similar dendritic responses by electrical stimulation of presynaptic elements near the tip of the iontophoretic electrode with the use of a second extracellular electrode. In 9 of 12 recorded cells, electrically evoked excitatory postsynaptic potentials (EPSPs) above a minimum size triggered all-or-none postsynaptic responses similar to those evoked by dendritic glutamate iontophoresis at the same site. Both the synaptically evoked and the iontophoretically evoked depolarizations were abolished reversibly by blockade of glutamate receptors. In all recorded cells, the combination of iontophoresis and an EPSP, each of which was subthreshold for the dendritic spike when given alone, evoked a dendritic spike similar to that evoked by a sufficiently large iontophoresis. In one cell tested, dendritic spikes could be evoked by the summation of two independent subthreshold EPSPs evoked by stimulation at two different locations. We conclude that the dendritic spikes are not unique to the use of glutamate iontophoresis because similar spikes can be evoked by EPSPs. We discuss the implications of these results for synaptic integration and for the interpretation of recorded synaptic potentials. PMID:9582218

  11. Distinct electrophysiological potentials for intention in action and prior intention for action

    Vinding, Mikkel Christoffer; Jensen, Mads; Overgaard, Morten

    2014-01-01

    The role of conscious intention in relation to motoric movements has become a major topic of investigation in neuroscience. Traditionally, reports of conscious intention have been compared to various features of the readiness-potential (RP) – an electrophysiological signal that appears before...... electrophysiological “intention potential” above the mid-frontal areas at the time participants formed a distal intention. This potential was only found when the distal intention was self-paced and not when the intention was formed in response to an external cue....

  12. Action potential detection by non-linear microscopy

    Sacconi, Leonardo; Lotti, Jacopo; O'Connor, Rodney P.; Mapelli, Jonathan; Gandolfi, Daniela; D'Angelo, Egidio; Pavone, Francesco S.

    2009-02-01

    In this work, we combined the advantages of second-harmonic generation (SHG) with a random access (RA) excitation scheme to realize a new microscope (RA-SHG) capable of optically recording fast membrane potential events occurring in a wide-field configuration. The RA-SHG microscope in combination with a bulk staining method with FM4-64 was used to simultaneously record electrical activity from clusters of Purkinje cells (PCs) in acute cerebellar slices. Spontaneous electrical activity was also monitored simultaneously in pairs of neurons, where APs were recorded in a single trial without averaging. These results show the strength of this technique to describe the temporal dynamics of neuronal assemblies.

  13. Control of Secretion by Encodes of Action Potentials in Neuronal Cells

    Kailai Duan; Zhuan Zhou

    2003-01-01

    @@ Action potentials (APs) are principle physiological stimuli of neurotransmitter secretion or synaptic transmis sion. Most studies on stimulus-secretion-coupling have been performed under voltage clamp using artificial electric stimulations.

  14. NeuroGrid: recording action potentials from the surface of the brain

    Khodagholy, Dion; Gelinas, Jennifer N.; Thesen, Thomas; Doyle, Werner; Devinsky, Orrin; Malliaras, George G.; Buzsáki, György

    2014-01-01

    Recording from neural networks at the resolution of action potentials is critical for understanding how information is processed in the brain. Here, we address this challenge by developing an organic material-based, ultra-conformable, biocompatible and scalable neural interface array (the ‘NeuroGrid’) that can record both LFP and action potentials from superficial cortical neurons without penetrating the brain surface. Spikes with features of interneurons and pyramidal cells were simultaneous...

  15. Dynamics of Action Potential Initiation in the GABAergic Thalamic Reticular Nucleus In Vivo

    Fabián Muñoz; Pablo Fuentealba

    2012-01-01

    Understanding the neural mechanisms of action potential generation is critical to establish the way neural circuits generate and coordinate activity. Accordingly, we investigated the dynamics of action potential initiation in the GABAergic thalamic reticular nucleus (TRN) using in vivo intracellular recordings in cats in order to preserve anatomically-intact axo-dendritic distributions and naturally-occurring spatiotemporal patterns of synaptic activity in this structure that regulates the th...

  16. Cortical Action Potential Backpropagation Explains Spike Threshold Variability and Rapid-Onset Kinetics

    Yu, Yuguo; Shu, Yousheng; McCormick, David A.

    2008-01-01

    Neocortical action potential responses in vivo are characterized by considerable threshold variability, and thus timing and rate variability, even under seemingly identical conditions. This finding suggests that cortical ensembles are required for accurate sensorimotor integration and processing. Intracellularly, trial-to-trial variability results not only from variation in synaptic activities, but also in the transformation of these into patterns of action potentials. Through simultaneous ax...

  17. Pharmacological actions and potential uses of Momordica charantia: a review.

    Grover, J K; Yadav, S P

    2004-07-01

    Since ancient times, plants and herbal preparations have been used as medicine. Research carried out in last few decades has certified several such claims of use of several plants of traditional medicine. Popularity of Momordica charantia (MC) in various systems of traditional medicine for several ailments (antidiabetic, abortifacient, anthelmintic, contraceptive, dysmenorrhea, eczema, emmenagogue, antimalarial, galactagogue, gout, jaundice, abdominal pain, kidney (stone), laxative, leprosy, leucorrhea, piles, pneumonia, psoriasis, purgative, rheumatism, fever and scabies) focused the investigator's attention on this plant. Over 100 studies using modern techniques have authenticated its use in diabetes and its complications (nephropathy, cataract, insulin resistance), as antibacterial as well as antiviral agent (including HIV infection), as anthelmintic and abortifacient. Traditionally it has also been used in treating peptic ulcers, interestingly in a recent experimental studies have exhibited its potential against Helicobacter pylori. Most importantly, the studies have shown its efficacy in various cancers (lymphoid leukemia, lymphoma, choriocarcinoma, melanoma, breast cancer, skin tumor, prostatic cancer, squamous carcinoma of tongue and larynx, human bladder carcinomas and Hodgkin's disease). There are few reports available on clinical use of MC in diabetes and cancer patients that have shown promising results. PMID:15182917

  18. Detection of Variability of the Motor Unit Action Potential Shape by Means of the Firing Patterns

    Krarup, Christian; Nikolic, Mile; Dahl, Kristian;

    1997-01-01

    The motor unit action potential is a summation of the potentials of the individual muscle fibers from the same motor unit.By using a newly developed automatic EMG decomposition system, variability of the firing patterns of the muscle fibers are analyzed.......The motor unit action potential is a summation of the potentials of the individual muscle fibers from the same motor unit.By using a newly developed automatic EMG decomposition system, variability of the firing patterns of the muscle fibers are analyzed....

  19. Measurements of distribution of self-bias potential on an RF-plane electrode in plasma etching devices

    The self-bias potential (Vdc) induced on an RF-powdered electrode (153 mm diameter) in a plasma is measured using electrical probes which are buried in, dc-insulated from, and RF-connected to the electrode. The configuration of the probes allows to study the distribution of Vdc discretely on the electrode. The potential is homogeneous in the absence of external magnetic field. In the presence of a homogeneous magnetic field parallel to the electrode, it is reduced and a monotonous gradient takes place in its distribution due to the plasma shift induced by ExB drift. When the magnetic field is rotated along the axis of the RF-electrode at a frequency less than 50 Hz, the distribution, which is almost identical to the one in a static field, rotates with the magnetic field. On the coordinate system rotating with the magnetic field, the probes are regarded to be rotating. The potential distribution is obtained as a continuous function of the azimuthal angle. Thus the rotation of the field provides information for the experimental interpolation. (orig.)

  20. 76 FR 21938 - Potential Environmental Impacts of the Proposed Runway 13 Extension and Associated Actions for...

    2011-04-19

    ... Federal Aviation Administration Potential Environmental Impacts of the Proposed Runway 13 Extension and... Administration (FAA), Department of Transportation (DOT). ACTION: Notice of availability of a final EA and FONSI/ROD for the evaluation of the potential environmental impacts associated with the proposed Runway...

  1. 7 CFR 1945.19 - Reporting potential natural disasters and initial actions.

    2010-01-01

    ... assessment of agricultural production losses resulting from a potential natural disaster. These councils are...) Actions to be taken. Immediately after the occurrence of a potential natural disaster: (1) When physical... Administrator will decide whether a natural disaster has occurred. If it has, the Administrator will make...

  2. Perturbation analysis of spontaneous action potential initiation by stochastic ion channels

    Keener, James P.

    2011-07-01

    A stochastic interpretation of spontaneous action potential initiation is developed for the Morris-Lecar equations. Initiation of a spontaneous action potential can be interpreted as the escape from one of the wells of a double well potential, and we develop an asymptotic approximation of the mean exit time using a recently developed quasistationary perturbation method. Using the fact that the activating ionic channel\\'s random openings and closings are fast relative to other processes, we derive an accurate estimate for the mean time to fire an action potential (MFT), which is valid for a below-threshold applied current. Previous studies have found that for above-threshold applied current, where there is only a single stable fixed point, a diffusion approximation can be used. We also explore why different diffusion approximation techniques fail to estimate the MFT. © 2011 American Physical Society.

  3. An Examination of Potential Racial and Gender Bias in the Principal Version of the Interactive Computer Interview System

    DiPonio, Joseph M.

    2010-01-01

    The primary object of this study was to determine whether racial and/or gender bias were evidenced in the use of the ICIS-Principal. Specifically, will the use of the ICIS-Principal result in biased scores at a statistically significant level when rating current practicing administrators of varying gender and race. The study involved simulated…

  4. Phase lagging model of brain response to external stimuli - modeling of single action potential

    Seetharaman, Karthik; Kulish, Vladimir V

    2012-01-01

    In this paper we detail a phase lagging model of brain response to external stimuli. The model is derived using the basic laws of physics like conservation of energy law. This model eliminates the paradox of instantaneous propagation of the action potential in the brain. The solution of this model is then presented. The model is further applied in the case of a single neuron and is verified by simulating a single action potential. The results of this modeling are useful not only for the fundamental understanding of single action potential generation, but also they can be applied in case of neuronal interactions where the results can be verified against the real EEG signal.

  5. Initiation and blocking of the action potential in the axon in a weak ultrasonic field

    Shneider, M N

    2013-01-01

    It is shown that the longitudinal standing ultrasonic wave of low intensity leads to the lateral drift and to redistribution of the transmembrane ion channels in the initial segment of the myelinated axon of a neuron. The analysis is based on the Hodgkin - Huxley model of an axon. Redistribution of the density of transmembrane sodium channels, caused by ultrasound, may reduce the threshold of the action potential, up to its spontaneous initiation. At significant redistribution of sodium channels in membrane, the zones of rarefaction of the transmembrane channels density are formed blocking the propagation of the action potential. After switching the ultrasound off, the unperturbed uniform distribution of transmembrane channels in the axon recovers due to lateral diffusion. The blocking effect of the action potential can be used in anesthesia.

  6. DBI potential, DBI inflation action and general Lagrangian relative to phantom, K-essence and quintessence

    We derive a Dirac-Born-Infeld (DBI) potential and DBI inflation action by rescaling the metric. The determinant of the induced metric naturally includes the kinetic energy and the potential energy. In particular, the potential energy and kinetic energy can convert into each other in any order, which is in agreement with the limit of classical physics. This is quite different from the usual DBI action. We show that the Taylor expansion of the DBI action can be reduced into the form in the non-linear classical physics. These investigations are the support for the statement that the results of string theory are consistent with quantum mechanics and classical physics. We deduce the Phantom, K-essence, Quintessence and Generalized Klein-Gordon Equation from the DBI model

  7. Modeling and simulation of ion channels and action potentials in taste receptor cells

    2009-01-01

    Based on patch clamp data on the ionic currents of rat taste receptor cells, a mathematical model of mammalian taste receptor cells was constructed to simulate the action potentials of taste receptor cells and their corresponding ionic components, including voltage-gated Na+ currents and outward delayed rectifier K+ currents. Our simulations reproduced the action potentials of taste receptor cells in response to electrical stimuli or sour tastants. The kinetics of ion channels and their roles in action potentials of taste receptor cells were also analyzed. Our prototype model of single taste receptor cell and simulation results presented in this paper provide the basis for the further study of taste information processing in the gustatory system.

  8. Modeling and simulation of ion channels and action potentials in taste receptor cells

    CHEN PeiHua; LIU Xiaodong; ZHANG Wei; ZHOU Jun; WANG Ping; YANG Wei; LUO JianHong

    2009-01-01

    Based on patch clamp data on the ionic currents of rat taste receptor cells,a mathematical model of mammalian taste receptor cells was constructed to simulate the action potentials of taste receptor cells and their corresponding ionic components,including voltage-gated Na~+ currents and outward delayed rectifier K~+ currents.Our simulations reproduced the action potentials of taste receptor cells in response to electrical stimuli or sour tastants.The kinetics of ion channels and their roles in action potentials of taste receptor cells were also analyzed.Our prototype model of single taste receptor cell and simulation results presented in this paper provide the basis for the further study of taste information processing in the gustatory system.

  9. RXP-E: a connexin43-binding peptide that prevents action potential propagation block

    Lewandowski, Rebecca; Procida, Kristina; Vaidyanathan, Ravi;

    2008-01-01

    . Separately, RXP-E was concatenated to a cytoplasmic transduction peptide (CTP) for cytoplasmic translocation (CTP-RXP-E). The effect of RXP-E on action potential propagation was assessed by high-resolution optical mapping in monolayers of neonatal rat ventricular myocytes, containing approximately 20% of...... randomly distributed myofibroblasts. In contrast to control experiments, when heptanol (2 mmol/L) was added to the superfusate of monolayers loaded with CTP-RXP-E, action potential propagation was maintained, albeit at a slower velocity. Similarly, intracellular acidification (pH(i) 6.2) caused a loss of...... action potential propagation in control monolayers; however, propagation was maintained in CTP-RXP-E-treated cells, although at a slower rate. Patch-clamp experiments revealed that RXP-E did not prevent heptanol-induced block of sodium currents, nor did it alter voltage dependence or amplitude of Kir2...

  10. Optical magnetic detection of single-neuron action potentials using NV-diamond

    Turner, Matthew; Barry, John; Schloss, Jennifer; Glenn, David; Walsworth, Ron

    2016-05-01

    A key challenge for neuroscience is noninvasive, label-free sensing of action potential dynamics in whole organisms with single-neuron resolution. Here, we report a new approach to this problem: using nitrogen-vacancy (NV) color centers in diamond to measure the time-dependent magnetic fields produced by single-neuron action potentials. We demonstrate our method using excised single neurons from two invertebrate species, marine worm and squid; and then by single-neuron action potential magnetic sensing exterior to whole, live, opaque marine worms for extended periods with no adverse effect. The results lay the groundwork for real-time, noninvasive 3D magnetic mapping of functional mammalian neuronal networks.

  11. A phantom axon setup for validating models of action potential recordings.

    Rossel, Olivier; Soulier, Fabien; Bernard, Serge; Guiraud, David; Cathébras, Guy

    2016-08-01

    Electrode designs and strategies for electroneurogram recordings are often tested first by computer simulations and then by animal models, but they are rarely implanted for long-term evaluation in humans. The models show that the amplitude of the potential at the surface of an axon is higher in front of the nodes of Ranvier than at the internodes; however, this has not been investigated through in vivo measurements. An original experimental method is presented to emulate a single fiber action potential in an infinite conductive volume, allowing the potential of an axon to be recorded at both the nodes of Ranvier and the internodes, for a wide range of electrode-to-fiber radial distances. The paper particularly investigates the differences in the action potential amplitude along the longitudinal axis of an axon. At a short radial distance, the action potential amplitude measured in front of a node of Ranvier is two times larger than in the middle of two nodes. Moreover, farther from the phantom axon, the measured action potential amplitude is almost constant along the longitudinal axis. The results of this new method confirm the computer simulations, with a correlation of 97.6 %. PMID:27016364

  12. Incorporated fish oil fatty acids prevent action potential shortening induced by circulating fish oil fatty acids

    Hester M Den Ruijter

    2010-11-01

    Full Text Available Increased consumption of fatty fish, rich in omega-3 polyunsaturated fatty acids (3-PUFAs reduces the severity and number of arrhythmias. Long term 3-PUFA-intake modulates the activity of several cardiac ion channels leading to cardiac action potential shortening. Circulating 3-PUFAs in the bloodstream and incorporated 3-PUFAs in the cardiac membrane have a different mechanism to shorten the action potential. It is, however, unknown whether circulating 3-PUFAs in the bloodstream enhance or diminish the effects of incorporated 3-PUFAs. In the present study, we address this issue. Rabbits were fed a diet rich in fish oil (3 or sunflower oil (9, as control for 3 weeks. Ventricular myocytes were isolated by enzymatic dissociation and action potentials were measured using the perforated patch clamp technique in the absence and presence of acutely administered 3-PUFAs. Plasma of 3 fed rabbits contained more free eicosapentaenoic acid (EPA and isolated myocytes of 3 fed rabbits contained higher amounts of both EPA and docosahexaenoic acid (DHA in their sarcolemma compared to control. In the absence of acutely administered fatty acids, 3 myocytes had a shorter action potential with a more negative plateau than 9 myocytes. In the 9 myocytes, but not in the 3 myocytes, acute administration of a mixture of EPA+DHA shortened the action potential significantly. From these data we conclude that incorporated 3-PUFAs into the sarcolemma and acutely administered 3 fatty acids do not have a cumulative effect on action potential duration and morphology. As a consequence, patients with a high cardiac 3-PUFA status will probably not benefit from short term 3 supplementation as an antiarrhythmic therapy.

  13. Differential effects of thioridazine enantiomers on action potential duration in rabbit papillary muscle

    Jensen, Ask Schou; Pennisi, Cristian Pablo; Sevcencu, Cristian;

    2015-01-01

    (+)-thioridazine. In this study we for the first time investigate the cardiotoxicity of the isolated thioridazine enantiomers and show their effects on ventricular repolarization. The effects of (+)-thioridazine, (-)-thioridazine, and racemate on the rabbit ventricular action potential duration (APD) were...... investigated in a randomized controlled blinded experiment. Action potentials were measured in papillary muscles isolated from 21 female rabbits, and the drug effect on 90% APD in comparison with control (DeltaDelta-APD90) was evaluated. Increasing concentrations of (+)-thioridazine and the racemate caused...

  14. A potential gender bias in assessing quality of life – a standard gamble experiment among university students

    Al Obaidi L

    2015-04-01

    Full Text Available Leath Al Obaidi,1 Jörg Mahlich2,3 1University of Nottingham, School of Economics, Nottingham, UK; 2Health Economics, Janssen KK, Tokyo, Japan; 3Düsseldorf Institute for Competition Economics (DICE, University of Düsseldorf, Düsseldorf, Germany Background: There are several methodologies that can be used for evaluating patients' perception of their quality of life. Most commonly, utilities are directly elicited by means of either the time-trade-off or the standard-gamble method. In both methods, risk attitudes determine the quality of life values. Methods: Quality of life values among 31 Austrian undergraduate students were elicited by means of the standard gamble approach. The impact of several variables such as gender, side job, length of study, and living arrangements on the quality of life were identified using different types of regression techniques (ordinary least squares, generalized linear model, Betafit. Results: Significant evidence was found that females are associated with a higher quality of life in all specifications of our estimations. Discussion: The observed gender differences in quality of life can be attributed to a higher degree of risk aversion of women. A higher risk aversion leads to a higher valuation of given health states and a potential gender bias in health economic evaluations. This result could have implications for health policy planners when it comes to budget allocation decisions. Keywords: quality of life, gender, risk aversion, standard gamble, students 

  15. Wogonin potentiates the antitumor action of etoposide and ameliorates its adverse effects.

    Enomoto, Riyo; Koshiba, Chika; Suzuki, Chie; Lee, Eibai

    2011-05-01

    Wogonin, a flavone in the roots of Scutellaria baicalensis, reduced etoposide-induced apoptotic cell death in normal cells, such as bone marrow cells and thymocytes. On the other hand, wogonin potentiated the proapoptotic or cytotoxic action of etoposide in tumor cells, such as Jurkat, HL-60, A549, and NCI-H226. These contradictory actions of wogonin on apoptosis are distinguished by normal or cancer cell types. Wogonin had no effect on apoptosis induced by other anticancer agents in the tumor cells. Thus, the potentiation effect of wogonin was observed only in etoposide-induced apoptosis in tumor cells. In a functional assay for P-glycoprotein (P-gp), wogonin suppressed excretion of calcein, a substrate for P-gp, in these tumor cells. Moreover, wogonin decreased the excretion of radiolabeled etoposide and accordingly increased intracellular content of this agent in the cells. P-gp inhibitors showed a similar potentiation effect on etoposide-induced apoptosis in these tumor cells. Thus, wogonin is likely to potentiate the anticancer action of etoposide due to P-gp inhibition and accumulation of this agent. These findings suggest that wogonin may be a useful chemotherapeutic adjuvant to potentiate the pharmacological action of etoposide and ameliorate its adverse effects. PMID:20658136

  16. Investigating a Potential Auxin-Related Mode of Hormetic/Inhibitory Action of the Phytotoxin Parthenin.

    Belz, Regina G

    2016-01-01

    Parthenin is a metabolite of Parthenium hysterophorus and is believed to contribute to the weed's invasiveness via allelopathy. Despite the potential of parthenin to suppress competitors, low doses stimulate plant growth. This biphasic action was hypothesized to be auxin-like and, therefore, an auxin-related mode of parthenin action was investigated using two approaches: joint action experiments with Lactuca sativa, and dose-response experiments with auxin/antiauxin-resistant Arabidopsis thaliana genotypes. The joint action approach comprised binary mixtures of subinhibitory doses of the auxin 3-indoleacetic acid (IAA) mixed with parthenin or one of three reference compounds [indole-3-butyric acid (IBA), 2,3,5-triiodobenzoic acid (TIBA), 2-(p-chlorophenoxy)-2-methylpropionic acid (PCIB)]. The reference compounds significantly interacted with IAA at all doses, but parthenin interacted only at low doses indicating that parthenin hormesis may be auxin-related, in contrast to its inhibitory action. The genetic approach investigated the response of four auxin/antiauxin-resistant mutants and a wildtype to parthenin or two reference compounds (IAA, PCIB). The responses of mutant plants to the reference compounds confirmed previous reports, but differed from the responses observed for parthenin. Parthenin stimulated and inhibited all mutants independent of resistance. This provided no indication for an auxin-related action of parthenin. Therefore, the hypothesis of an auxin-related inhibitory action of parthenin was rejected in two independent experimental approaches, while the hypothesis of an auxin-related stimulatory effect could not be rejected. PMID:26686984

  17. Inhibition by TRPA1 agonists of compound action potentials in the frog sciatic nerve

    Highlights: •TRPA1 agonists inhibited compound action potentials in frog sciatic nerves. •This inhibition was not mediated by TRPA1 channels. •This efficacy was comparable to those of lidocaine and cocaine. •We found for the first time an ability of TRPA1 agonists to inhibit nerve conduction. -- Abstract: Although TRPV1 and TRPM8 agonists (vanilloid capsaicin and menthol, respectively) at high concentrations inhibit action potential conduction, it remains to be unknown whether TRPA1 agonists have a similar action. The present study examined the actions of TRPA1 agonists, cinnamaldehyde (CA) and allyl isothiocyanate (AITC), which differ in chemical structure from each other, on compound action potentials (CAPs) recorded from the frog sciatic nerve by using the air-gap method. CA and AITC concentration-dependently reduced the peak amplitude of the CAP with the IC50 values of 1.2 and 1.5 mM, respectively; these activities were resistant to a non-selective TRP antagonist ruthenium red or a selective TRPA1 antagonist HC-030031. The CA and AITC actions were distinct in property; the latter but not former action was delayed in onset and partially reversible, and CA but not AITC increased thresholds to elicit CAPs. A CAP inhibition was seen by hydroxy-α-sanshool (by 60% at 0.05 mM), which activates both TRPA1 and TRPV1 channels, a non-vanilloid TRPV1 agonist piperine (by 20% at 0.07 mM) and tetrahydrolavandulol (where the six-membered ring of menthol is opened; IC50 = 0.38 mM). It is suggested that TRPA1 agonists as well as TRPV1 and TRPM8 agonists have an ability to inhibit nerve conduction without TRP activation, although their agonists are quite different in chemical structure from each other

  18. Inhibition by TRPA1 agonists of compound action potentials in the frog sciatic nerve

    Matsushita, Akitomo; Ohtsubo, Sena; Fujita, Tsugumi; Kumamoto, Eiichi, E-mail: kumamote@cc.saga-u.ac.jp

    2013-04-26

    Highlights: •TRPA1 agonists inhibited compound action potentials in frog sciatic nerves. •This inhibition was not mediated by TRPA1 channels. •This efficacy was comparable to those of lidocaine and cocaine. •We found for the first time an ability of TRPA1 agonists to inhibit nerve conduction. -- Abstract: Although TRPV1 and TRPM8 agonists (vanilloid capsaicin and menthol, respectively) at high concentrations inhibit action potential conduction, it remains to be unknown whether TRPA1 agonists have a similar action. The present study examined the actions of TRPA1 agonists, cinnamaldehyde (CA) and allyl isothiocyanate (AITC), which differ in chemical structure from each other, on compound action potentials (CAPs) recorded from the frog sciatic nerve by using the air-gap method. CA and AITC concentration-dependently reduced the peak amplitude of the CAP with the IC{sub 50} values of 1.2 and 1.5 mM, respectively; these activities were resistant to a non-selective TRP antagonist ruthenium red or a selective TRPA1 antagonist HC-030031. The CA and AITC actions were distinct in property; the latter but not former action was delayed in onset and partially reversible, and CA but not AITC increased thresholds to elicit CAPs. A CAP inhibition was seen by hydroxy-α-sanshool (by 60% at 0.05 mM), which activates both TRPA1 and TRPV1 channels, a non-vanilloid TRPV1 agonist piperine (by 20% at 0.07 mM) and tetrahydrolavandulol (where the six-membered ring of menthol is opened; IC{sub 50} = 0.38 mM). It is suggested that TRPA1 agonists as well as TRPV1 and TRPM8 agonists have an ability to inhibit nerve conduction without TRP activation, although their agonists are quite different in chemical structure from each other.

  19. Examining the Potential for Gender Bias in the Prediction of Symptom Validity Test Failure by MMPI-2 Symptom Validity Scale Scores

    Lee, Tayla T. C.; Graham, John R.; Sellbom, Martin; Gervais, Roger O.

    2012-01-01

    Using a sample of individuals undergoing medico-legal evaluations (690 men, 519 women), the present study extended past research on potential gender biases for scores of the Symptom Validity (FBS) scale of the Minnesota Multiphasic Personality Inventory-2 by examining score- and item-level differences between men and women and determining the…

  20. A dual potassium channel activator improves repolarization reserve and normalizes ventricular action potentials

    Calloe, Kirstine; Di Diego, José M; Hansen, Rie Schultz;

    2016-01-01

    cultured canine cardiac myocytes and determined whether a dual K(+) current activator can normalize K(+) currents and restore action potential (AP) configuration. METHODS AND RESULTS: Ventricular myocytes were isolated and cultured for up to 48h. Current and voltage clamp recordings were made using patch...... of EADs. Our results suggest a potential benefit of K(+) current activators under conditions of reduced repolarization reserve including heart failure....

  1. Youth Participatory Action Research and Educational Transformation: The Potential of Intertextuality as a Methodological Tool

    Bertrand, Melanie

    2016-01-01

    In this article, Melanie Bertrand explores the potential of using the concept of intertextuality--which captures the way snippets of written or spoken text from one source become incorporated into other sources--in the study and practice of youth participatory action research (YPAR). Though this collective and youth-centered form of research…

  2. Quantitative analysis of single muscle fibre action potentials recorded at known distances

    Albers, B.A.; Put, J.H.M.; Wallinga, W.; Wirtz, P.

    1989-01-01

    In vivo records of single fibre action potentials (SFAPs) have always been obtained at unknown distance from the active muscle fibre. A new experimental method has been developed enabling the derivation of the recording distance in animal experiments. A single fibre is stimulated with an intracellu

  3. ACTION OF PROGESTERONE ON THE DEPOLARIZATION OF THE MEMBRANE POTENTIAL IN TOAD OOCYTES INDUCED BY LEUCINE

    WANGYu-Feng

    1989-01-01

    The depolarization of the membrane potential in toad oocytes induced by leucine was found in our previous experiment. In this paper, a possible action or progesterone in the process was further investigated. After oocytes had been incubated for 16 to 24 hours with

  4. Preservation of cardiac function by prolonged action potentials in mice deficient of KChIP2

    Grubb, Søren Jahn; Aistrup, Gary L; Koivumäki, Jussi T;

    2015-01-01

    Inherited ion channelopathies and electrical remodeling in heart disease alter the cardiac action potential with important consequences for excitation-contraction coupling. Potassium channel-interacting protein 2 (KChIP2) is reduced in heart failure and interacts under physiological conditions with...

  5. Effect of ethanol on action potential in ventricular cardiomyocytes: experimental and computational approach

    Pásek, Michal; Bébarová, M.; Christé, G.; Šimurdová, M.; Šimurda, J.

    London: The Physiological Society, 2014. 208P. [Physiology 2014. 30.06.2014-02.07.2014, London] R&D Projects: GA MZd(CZ) NT14301-3/2013 Institutional support: RVO:61388998 Keywords : rat ventricular cardiomyocyte * action potential * ethanol * rat ventricular cell model Subject RIV: BO - Biophysics

  6. Effects of benactyzine on action potentials and contractile force of guinea pig papillary muscles

    2000-01-01

    Aim:To explore the effects of benactyzine (BEN) on the action potential and contractile force in guinea pig papillary muscles.Methods:Conventional microelectrode technique was used to record the fast action potentials (FAP) and slow action potentials (SAP) of guinea pig papillary muscles.Results:Benactyzine 5,10,50 μmol·L-1 suppressed the maximal upstroke velocity (vmax) of FAP and contractile force (Fc) concentration-dependently while prolonged the action potential duration at 50%,90% repolarization (APD50,APD90) and effective refractory period (ERP) of FAP.The suppression on the vmax was frequency-dependent.Benactyzine 5,10,50μmol·L-1 lengthened the APD50,APD90 of SAP induced by isoprenaline or histamine when perfused with KCl 22 mmol·L-1 Tyrode's solution.The vmax of the SAP was not decreased by benactyzine 5,10 μmol·L-1 but by 50 μmol·L-1.The effects on the SAP were antagonized by elevation of the extracellular calcium from 2.0 to 5.6 mmol·L-1.The effects of benactyzine on SAP elicited by tetrodotoxin resembled that by isoprenaline or histamine except the more pronounced suppression on vmax and action potential amplitude (APA).The persistent rapid spontaneous activity and triggered tachyarrhythmia induced by ouabain were also abolished immediately by benactyzine 5 μmol·L-1.Conclusion:Benactyzine can inhibit Na+,K+,Ca2+ transmembrane movement and intracellular Ca2+ mobilization in the myocardium,and this may be the electrophysiological basis of its effects against experimental arrhythmias.

  7. Axonal sodium channel distribution shapes the depolarized action potential threshold of dentate granule neurons.

    Kress, Geraldine J; Dowling, Margaret J; Eisenman, Lawrence N; Mennerick, Steven

    2010-04-01

    Intrinsic excitability is a key feature dictating neuronal response to synaptic input. Here we investigate the recent observation that dentate granule neurons exhibit a more depolarized voltage threshold for action potential initiation than CA3 pyramidal neurons. We find no evidence that tonic GABA currents, leak or voltage-gated potassium conductances, or the expression of sodium channel isoform differences can explain this depolarized threshold. Axonal initial segment voltage-gated sodium channels, which are dominated by the Na(V)1.6 isoform in both cell types, distribute more proximally and exhibit lower overall density in granule neurons than in CA3 neurons. To test possible contributions of sodium channel distributions to voltage threshold and to test whether morphological differences participate, we performed simulations of dentate granule neurons and of CA3 pyramidal neurons. These simulations revealed that cell morphology and sodium channel distribution combine to yield the characteristic granule neuron action potential upswing and voltage threshold. Proximal axon sodium channel distribution strongly contributes to the higher voltage threshold of dentate granule neurons for two reasons. First, action potential initiation closer to the somatodendritic current sink causes the threshold of the initiating axon compartment to rise. Second, the proximity of the action potential initiation site to the recording site causes somatic recordings to more faithfully reflect the depolarized threshold of the axon than in cells like CA3 neurons, with distally initiating action potentials. Our results suggest that the proximal location of axon sodium channels in dentate granule neurons contributes to the intrinsic excitability differences between DG and CA3 neurons and may participate in the low-pass filtering function of dentate granule neurons. PMID:19603521

  8. The DBI action, higher-derivative supergravity, and flattening inflaton potentials

    Bielleman, Sjoerd; Ibáñez, Luis E.; Pedro, Francisco G.; Valenzuela, Irene; Wieck, Clemens

    2016-05-01

    In string theory compactifications it is common to find an effective Lagrangian for the scalar fields with a non-canonical kinetic term. We study the effective action of the scalar position moduli of Type II D p-branes. In many instances the kinetic terms are in fact modified by a term proportional to the scalar potential itself. This can be linked to the appearance of higher-dimensional supersymmetric operators correcting the Kähler potential. We identify the supersymmetric dimension-eight operators describing the α' corrections captured by the D-brane Dirac-Born-Infeld action. Our analysis then allows an embedding of the D-brane moduli effective action into an {N}=1 supergravity formulation. The effects of the potential-dependent kinetic terms may be very important if one of the scalars is the inflaton, since they lead to a flattening of the scalar potential. We analyze this flattening effect in detail and compute its impact on the CMB observables for single-field inflation with monomial potentials.

  9. Acute NMDA receptor antagonism disrupts synchronization of action potential firing in rat prefrontal cortex.

    Leonardo A Molina

    Full Text Available Antagonists of N-methyl-D-aspartate receptors (NMDAR have psychotomimetic effects in humans and are used to model schizophrenia in animals. We used high-density electrophysiological recordings to assess the effects of acute systemic injection of an NMDAR antagonist (MK-801 on ensemble neural processing in the medial prefrontal cortex of freely moving rats. Although MK-801 increased neuron firing rates and the amplitude of gamma-frequency oscillations in field potentials, the synchronization of action potential firing decreased and spike trains became more Poisson-like. This disorganization of action potential firing following MK-801 administration is consistent with changes in simulated cortical networks as the functional connections among pyramidal neurons become less clustered. Such loss of functional heterogeneity of the cortical microcircuit may disrupt information processing dependent on spike timing or the activation of discrete cortical neural ensembles, and thereby contribute to hallucinations and other features of psychosis induced by NMDAR antagonists.

  10. Voltage-gated sodium channel expression and action potential generation in differentiated NG108-15 cells

    Liu Jinxu; Tu Huiyin; Zhang Dongze; Zheng Hong; Li Yu-Long

    2012-01-01

    Abstract Background The generation of action potential is required for stimulus-evoked neurotransmitter release in most neurons. Although various voltage-gated ion channels are involved in action potential production, the initiation of the action potential is mainly mediated by voltage-gated Na+ channels. In the present study, differentiation-induced changes of mRNA and protein expression of Na+ channels, Na+ currents, and cell membrane excitability were investigated in NG108-15 cells. Result...

  11. Simulation and calculation of the contribution of hyperpolarization-activated cyclic nucleotide-gated channels to action potentials

    Liao Liping; Lin Xianguang; Hu Jielin; Wu Xin; Yang Xiaofei; Wang Wei; Li Chenhong

    2016-01-01

    The hyperpolarization-activated cyclic nucleotide-gated (HCN) channel, which mediates the influx of cations, has an important role in action potential generation. In this article, we describe the contribution of the HCN channel to action potential generation. We simulated several common ion channels in neuron membranes based on data from rat dorsal root ganglion cells and modeled the action potential. The ion channel models employed in this paper were based...

  12. The DBI Action, Higher-derivative Supergravity, and Flattening Inflaton Potentials

    Bielleman, Sjoerd; Pedro, Francisco G; Valenzuela, Irene; Wieck, Clemens

    2016-01-01

    In string theory compactifications it is common to find an effective Lagrangian for the scalar fields with a non-canonical kinetic term. We study the effective action of the scalar position moduli of Type II D$p$-branes. In many instances the kinetic terms are in fact modified by a term proportional to the scalar potential itself. This can be linked to the appearance of higher-dimensional supersymmetric operators correcting the K\\"ahler potential. We identify the supersymmetric dimension-eight operators describing the $\\alpha'$ corrections captured by the D-brane Dirac-Born-Infeld action. Our analysis then allows an embedding of the D-brane moduli effective action into an $\\mathcal N = 1$ supergravity formulation. The effects of the potential-dependent kinetic terms may be very important if one of the scalars is the inflaton, since they lead to a flattening of the scalar potential. We analyze this flattening effect in detail and compute its impact on the CMB observables for single-field inflation with monomia...

  13. The potential for regional-scale bias in top-down CO2 flux estimates due to atmospheric transport errors

    S. M. Miller

    2014-09-01

    Full Text Available Estimates of CO2 fluxes that are based on atmospheric data rely upon a meteorological model to simulate atmospheric CO2 transport. These models provide a quantitative link between surface fluxes of CO2 and atmospheric measurements taken downwind. Therefore, any errors in the meteorological model can propagate into atmospheric CO2 transport and ultimately bias the estimated CO2 fluxes. These errors, however, have traditionally been difficult to characterize. To examine the effects of CO2 transport errors on estimated CO2 fluxes, we use a global meteorological model-data assimilation system known as "CAM–LETKF" to quantify two aspects of the transport errors: error variances (standard deviations and temporal error correlations. Furthermore, we develop two case studies. In the first case study, we examine the extent to which CO2 transport uncertainties can bias CO2 flux estimates. In particular, we use a common flux estimate known as CarbonTracker to discover the minimum hypothetical bias that can be detected above the CO2 transport uncertainties. In the second case study, we then investigate which meteorological conditions may contribute to month-long biases in modeled atmospheric transport. We estimate 6 hourly CO2 transport uncertainties in the model surface layer that range from 0.15 to 9.6 ppm (standard deviation, depending on location, and we estimate an average error decorrelation time of ∼2.3 days at existing CO2 observation sites. As a consequence of these uncertainties, we find that CarbonTracker CO2 fluxes would need to be biased by at least 29%, on average, before that bias were detectable at existing non-marine atmospheric CO2 observation sites. Furthermore, we find that persistent, bias-type errors in atmospheric transport are associated with consistent low net radiation, low energy boundary layer conditions. The meteorological model is not necessarily more uncertain in these conditions. Rather, the extent to which meteorological

  14. Potentiators of Defective ΔF508-CFTR Gating that Do Not Interfere with Corrector Action.

    Phuan, Puay-Wah; Veit, Guido; Tan, Joseph A; Finkbeiner, Walter E; Lukacs, Gergely L; Verkman, A S

    2015-10-01

    Combination drug therapies under development for cystic fibrosis caused by the ∆F508 mutation in cystic fibrosis transmembrane conductance regulator (CFTR) include a "corrector" to improve its cellular processing and a "potentiator" to improve its chloride channel function. Recently, it was reported that the approved potentiator N-(2,4-di-tert-butyl-5-hydroxyphenyl)-4-oxo-1,4-dihydroquinoline-3-carboxamide (Ivacaftor) reduces ∆F508-CFTR cellular stability and the efficacy of investigational correctors, including 3-(6-[([1-(2,2-difluoro-1,3-benzodioxol-5-yl)cyclopropyl]carbonyl) amino]-3-methyl-2-pyridinyl)-benzoic acid and 1-(2,2-difluoro-1,3-benzodioxol-5-yl)-N-(1-[(2R)-2,3-dihydroxypropyl]-6-fluoro-2-(2-hydroxy-1,1-dimethylethyl)-1H-indol-5-yl), which might contribute to the modest reported efficacy of combination therapy in clinical trials. Here, we report the identification and characterization of potentiators that do not interfere with ∆F508-CFTR stability or corrector action. High-throughput screening and structure-activity analysis identified several classes of potentiators that do not impair corrector action, including tetrahydrobenzothiophenes, thiooxoaminothiazoles, and pyrazole-pyrrole-isoxazoles. The most potent compounds have an EC(50) for ∆F508-CFTR potentiation down to 18 nM and do not reduce corrector efficacy in heterologous ∆F508-CFTR-expressing cells or primary cultures of ∆F508/∆F508 human bronchial epithelia. The ΔF508-CFTR potentiators also activated wild-type and G551D CFTR, albeit weakly. The efficacy of combination therapy for cystic fibrosis caused by the ∆F508 mutation may be improved by replacement of Ivacaftor with a potentiator that does not interfere with corrector action. PMID:26245207

  15. Spatial and frequency domain ring source models for the single muscle fiber action potential

    Henneberg, Kaj-åge; R., Plonsey

    1994-01-01

    In the paper, single-fibre models for the extracellular action potential are developed that will allow the potential to the evaluated at an arbitrary field point in the extracellular space. Fourier-domain models are restricted in that they evaluate potentials at equidistant points along a line...... parallel to the fibre axis. Consequently, they cannot easily evaluate the potential at the boundary nodes of a boundary-element electrode model. The Fourier-domain models employ axial-symmetric ring source models, and thereby provide higher accuracy that the line source model, where the source is lumped...... examples including anisotropy show that the spatial models require extreme care in the integration procedure owing to the singularity in the weighting functions. With adequate sampling, the spatial models can evaluate extracellular potentials with high accuracy....

  16. Application of Emergency Action Levels from Potential Release at Research Reactor HANARO

    Execution of the protective action promptly is possible that Emergency Action Levels (EALs) must be established for a radiological release from nuclear facility. The EALs for electric power reactor are already developed and applied to recognize an emergency situation rapidly. Recently the IAEA published the safety report including the EALs for research reactor. This paper describes the EALs to apply for a potential release pathway at the research reactor HANARO. The results of table 1 and 2 will be higher than actual because the weather condition in real situation is difference. However, the EALs applying the potential stack release, ground release and site can be useful for research reactor HANARO making the emergency declaration. The EALs at the site boundary of the table 3 can be applied to protect the off-site public

  17. Real-time imaging of action potentials in nerves using changes in birefringence.

    Badreddine, Ali H; Jordan, Tomas; Bigio, Irving J

    2016-05-01

    Polarized light can be used to measure the electrical activity associated with action potential propagation in nerves, as manifested in simultaneous dynamic changes in their intrinsic optical birefringence. These signals may serve as a tool for minimally invasive neuroimaging in various types of neuroscience research, including the study of neuronal activation patterns with high spatiotemporal resolution. A fast linear photodiode array was used to image propagating action potentials in an excised portion of the lobster walking leg nerve. We show that the crossed-polarized signal (XPS) can be reliably imaged over a ≥2 cm span in our custom nerve chamber, by averaging multiple-stimulation signals, and also in single-scan real-time "movies". This demonstration paves the way toward utilizing changes in the optical birefringence to image more complex neuronal activity in nerve fibers and other organized neuronal tissue. PMID:27231635

  18. Application of Emergency Action Levels from Potential Release at Research Reactor HANARO

    Kim, Jongsoo; Lee, Goan Yub; Lee, Hae Choi; Kim, Bong Suk [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-05-15

    Execution of the protective action promptly is possible that Emergency Action Levels (EALs) must be established for a radiological release from nuclear facility. The EALs for electric power reactor are already developed and applied to recognize an emergency situation rapidly. Recently the IAEA published the safety report including the EALs for research reactor. This paper describes the EALs to apply for a potential release pathway at the research reactor HANARO. The results of table 1 and 2 will be higher than actual because the weather condition in real situation is difference. However, the EALs applying the potential stack release, ground release and site can be useful for research reactor HANARO making the emergency declaration. The EALs at the site boundary of the table 3 can be applied to protect the off-site public.

  19. Bimodal action of menthol on the transient receptor potential channel TRPA1

    Karashima, Yuji; Damann, Nils; Prenen, Jean; Talavera Pérez, Karel; Segal Stanciu, Andrei; Voets, Thomas; Nilius, Bernd

    2007-01-01

    TRPA1 is a calcium-permeable nonselective cation transient receptor potential (TRP) channel that functions as an excitatory ionotropic receptor in nociceptive neurons. TRPA1 is robustly activated by pungent substances in mustard oil, cinnamon, and garlic and mediates the inflammatory actions of environmental irritants and proalgesic agents. Here, we demonstrate a bimodal sensitivity of TRPA1 to menthol, a widely used cooling agent and known activator of the related cold receptor TRPM8. In who...

  20. Variability of Action Potentials Within and Among Cardiac Cell Clusters Derived from Human Embryonic Stem Cells

    Renjun Zhu; Millrod, Michal A.; Zambidis, Elias T.; Leslie Tung

    2016-01-01

    Electrophysiological variability in cardiomyocytes derived from pluripotent stem cells continues to be an impediment for their scientific and translational applications. We studied the variability of action potentials (APs) recorded from clusters of human embryonic stem cell-derived cardiomyocytes (hESC-CMs) using high-resolution optical mapping. Over 23,000 APs were analyzed through four parameters: APD30, APD80, triangulation and fractional repolarization. Although measures were taken to re...

  1. Action Potential Energy Efficiency Varies Among Neuron Types in Vertebrates and Invertebrates

    Biswa Sengupta; Martin Stemmler; Simon B Laughlin; Niven, Jeremy E.

    2010-01-01

    The initiation and propagation of action potentials (APs) places high demands on the energetic resources of neural tissue. Each AP forces ATP-driven ion pumps to work harder to restore the ionic concentration gradients, thus consuming more energy. Here, we ask whether the ionic currents underlying the AP can be predicted theoretically from the principle of minimum energy consumption. A long-held supposition that APs are energetically wasteful, based on theoretical analysis of the squid giant ...

  2. Correlation of compound action potential and electromyography with facial muscle tension

    Goodnight, J W; Dulguerov, Pavel; Berke, G S; Lesavoy, M; Hoffman, L. F.

    1995-01-01

    Functional electric stimulation is a new method for dynamic rehabilitation of paralyzed muscles. The output of such prosthetic devices needs to be modulated by some index of the muscle movement. In facial paralysis a measure of the muscle contractions of the normal contralateral side seems to be an appropriate input. In the rabbit, we simultaneously measured the compound action potential of the buccal branch of the facial nerve, the electromyogram of the zygomaticus major muscle, and the musc...

  3. Depth-Resolved Measurement of Transient Structural Changes during Action Potential Propagation

    Akkin, T.; Joo, C.; Boer

    2007-01-01

    We report noncontact optical measurement of fast transient structural changes in the crustacean nerve during action potential propagation without the need for exogenous chemicals or reflection coatings. The technique, spectral domain optical coherence tomography, provides real-time cross-sectional images of the nerve with micron-scale resolution to select a specific region for functional assessment and interferometric phase sensitivity for subnanometer-scale motion detection. Noncontact optic...

  4. Variety of the Wave Change in Compound Muscle Action Potential in an Animal Model

    ITO, ZENYA; Imagama, Shiro; Ando, Kei; Muramoto, Akio; Kobayashi, Kazuyoshi; Hida, Tetsuro; Ito, Kenyu; Ishikawa, Yoshimoto; Tsushima, Mikito; Matsumoto, Akiyuki; Tanaka, Satoshi; Morozumi, Masayoshi; Matsuyama, Yukihiro; Ishiguro, Naoki

    2015-01-01

    Study Design Animal study. Purpose To review the present warning point criteria of the compound muscle action potential (CMAP) and investigate new criteria for spinal surgery safety using an animal model. Overview of Literature Little is known about correlation palesis and amplitude of spinal cord monitoring. Methods After laminectomy of the tenth thoracic spinal lamina, 2-140 g force was delivered to the spinal cord with a tension gage to create a bilateral contusion injury. The study morpho...

  5. Action Potential Morphology Influences Intracellular Calcium Handling Stability and the Occurrence of Alternans

    Jordan, Peter N; Christini, David J

    2005-01-01

    Instability in the intracellular Ca2+ handling system leading to Ca2+ alternans is hypothesized to be an underlying cause of electrical alternans. The highly coupled nature of membrane voltage and Ca2+ regulation suggests that there should be reciprocal effects of membrane voltage on the stability of the Ca2+ handling system. We investigated such effects using a mathematical model of the cardiac intracellular Ca2+ handling system. We found that the morphology of the action potential has a sig...

  6. Relation of recurrent laryngeal nerve compound action potential to laryngeal biomechanics

    Nasri, S.; Dulguerov, Pavel; Damrose, E J; Ye, M.; Kreiman, J; Berke, G S

    1995-01-01

    This study was designed to investigate the compound action potential (CAP) of the recurrent laryngeal nerve (RLN) and to correlate this electrophysiologic signal to laryngeal biomechanics and phonatory function. Four adult mongrel canines were anesthetized. The RLN was isolated and stimulated, and recording electrodes were applied. The electromyographic (EMG) electrode was placed in the thyroarytenoid (TA) muscle. The RLN CAP and the EMG of the TA muscle were recorded and compared to the stim...

  7. Human sensory nerve compound action potential amplitude: variation with sex and finger circumference.

    Bolton, C F; Carter, K M

    1980-01-01

    The amplitude of human, antidromic, sensory compound action potentials (CAP) recorded from median and ulnar digital nerves is greater in females than males. This sex difference is probably due entirely to females having digits of smaller circumference, resulting in digital nerves being closer to the recording ring electrode enclosing the digit. The negative linear correlation between CAP amplitude and circumference holds true for persons of the same sex.

  8. Effect of ethanol on action potential and ionic membrane currents in rat ventricular myocytes

    Bébarová, M.; Matejovič, P.; Pásek, Michal; Ohlídalová, D.; Jansová, D.; Šimurdová, M.; Šimurda, J.

    2010-01-01

    Roč. 200, č. 4 (2010), s. 301-314. ISSN 1748-1708 Institutional research plan: CEZ:AV0Z20760514 Keywords : action potential * ethanol * rat ventricular myocyte Subject RIV: BO - Biophysics Impact factor: 3.138, year: 2010 http:// apps .isiknowledge.com/full_record.do?product=UA&search_mode=GeneralSearch&qid=15&SID=Y1pmpi@7k2HPEc8ehEE&page=1&doc=1&colname=WOS

  9. Experimental determination of compound action potential direction and propagation velocity from multi-electrode nerve cuffs.

    Rieger, R; Taylor, J; Comi, E; Donaldson, N; Russold, M; Mahony, C M O; McLaughlin, J A; McAdams, E; Demosthenous, A; Jarvis, J C

    2004-07-01

    Information extracted from whole-nerve electroneurograms, recorded using electrode cuffs, can provide signals to neuroprostheses. However, the amount of information that can be extracted from a single tripole is limited. This communication demonstrates how previously unavailable information about the direction of action potential propagation and velocity can be obtained using a multi-electrode cuff and that the arrangement acts as a velocity-selective filter. Results from in vitro experiments on frog nerves are presented. PMID:15234689

  10. Axonal sodium channel distribution shapes the depolarized action potential threshold of dentate granule neurons

    Kress, Geraldine J.; Dowling, Margaret; Eisenman, Lawrence N.; Mennerick, Steven

    2010-01-01

    Intrinsic excitability is a key feature dictating neuronal response to synaptic input. Here we investigate the recent observation that dentate granule neurons exhibit a more depolarized voltage threshold for action potential initiation than CA3 pyramidal neurons. We find no evidence that tonic GABA currents, leak or voltage-gated potassium conductances, or the expression of sodium channel isoform differences can explain this depolarized threshold. Axonal initial segment voltage-gated sodium c...

  11. Comparative investigations of manual action representations: evidence that chimpanzees represent the costs of potential future actions involving tools

    Frey, Scott H.; POVINELLI, DANIEL J.

    2012-01-01

    The ability to adjust one's ongoing actions in the anticipation of forthcoming task demands is considered as strong evidence for the existence of internal action representations. Studies of action selection in tool use reveal that the behaviours that we choose in the present moment differ depending on what we intend to do next. Further, they point to a specialized role for mechanisms within the human cerebellum and dominant left cerebral hemisphere in representing the likely sensory costs of ...

  12. Is the cultural transmission of irrelevant tool actions in adult humans (Homo sapiens best explained as the result of an evolved conformist bias?

    Nicola McGuigan

    Full Text Available BACKGROUND: Recent studies of social learning have revealed that adult humans are "over-imitators" who frequently reproduce a model's causally irrelevant tool actions to the detriment of task efficiency. At present our knowledge of adult over-imitation is limited to the fact that adults do over-imitate, we know very little about the causes of this behavior. The current study aimed to provide novel insights into adult over-imitation by extending a paradigm recently used with human children to explore social aspects of over-imitation. In the child study observers saw two models demonstrate a tool-use task using the same inefficient approach, or two models demonstrate different approaches to the task (one inefficient and one efficient. The manipulation of social influence came in the testing phase where the observer completed the task in the presence of either an inefficient model or an efficient model. METHODOLOGY/PRINCIPAL FINDINGS: We adapted the paradigm used in the child study to provide the first systematic exploration of factors which may lead to adult over-imitation including: 1 the presence of the model(s during testing, 2 the presence of a competing efficient task demonstration, 3 the presence of a majority displaying the inefficient approach, and 4 the 'removal' of the experimental context during task completion. We show that the adult participants only over-imitated in conditions where the inefficient strategy was the majority approach witnessed. This tendency towards over-imitation was almost entirely eliminated when the participants interacted with the task when they believed the experiment to be complete. CONCLUSIONS: Our results suggest that adult over-imitation is best explained as a result of an evolved 'conformist bias' argued to be crucial to the transmission of human cultural behavior and one which may be unique in the animal kingdom.

  13. Intergroup bias.

    Hewstone, Miles; Rubin, Mark; Willis, Hazel

    2002-01-01

    This chapter reviews the extensive literature on bias in favor of in-groups at the expense of out-groups. We focus on five issues and identify areas for future research: (a) measurement and conceptual issues (especially in-group favoritism vs. out-group derogation, and explicit vs. implicit measures of bias); (b) modern theories of bias highlighting motivational explanations (social identity, optimal distinctiveness, uncertainty reduction, social dominance, terror management); (c) key moderators of bias, especially those that exacerbate bias (identification, group size, status and power, threat, positive-negative asymmetry, personality and individual differences); (d) reduction of bias (individual vs. intergroup approaches, especially models of social categorization); and (e) the link between intergroup bias and more corrosive forms of social hostility. PMID:11752497

  14. Action Research’s Potential to Foster Institutional Change for Urban Water Management

    Dimitrios Zikos

    2013-04-01

    Full Text Available The paper discusses the potential of action research to meet the challenges entailed in institutional design for urban water management. Our overall aim is to briefly present action research and discuss its methodological merits with regard to the challenges posed by the different conceptual bases for extrapolating the effects of institutional design on institutional change. Thus, our aim is to explore how Action Research meets the challenge of scoping the field in an open fashion for determining the appropriate mechanisms of institutional change and supporting the emerging of new water institutions. To accomplish this aim, we select the Water Framework Directive (WFD as an illustrative driving force requiring changes in water management practices and implying the need for the emergence of new institutions. We employ a case of urban water management in the Volos Metropolitan Area, part of the Thessaly region in Greece, where a Pilot River Basin Plan was implemented. By applying action research and being involved in a long process of interaction between stakeholders, we examine the emergence of new institutions dealing with urban water management under the general principles of the major driving force for change: the WFD.

  15. Optimistic bias and Facebook use: self-other discrepancies about potential risks and benefits of Facebook use.

    Kim, Sunny Jung; Hancock, Jeffrey T

    2015-04-01

    Despite the accumulating evidence on the positive and negative outcomes of Facebook use, how people perceive themselves to be subject to these outcomes as well as the consequences and mechanisms of these perceptions are underexplored. According to optimistic bias, Facebook users may perceive that bad things are more likely to happen to others than to themselves, while good things are more likely to happen to them than to others. The findings from an online survey among Facebook users indicate that the negative psychological and social outcomes of using Facebook were perceived to be more likely to happen to other Facebook users than to themselves, pInternet regulation, Sobel z=2.49, p=0.01. For positive outcomes of Facebook use, the direction of optimistic bias was reversed, t(235) = -5.52, pbenefits of Facebook use. PMID:25879379

  16. Reply to Cohen's letter on 'The potential for bias in Cohen's ecological analysis of lung cancer and residential radon'

    Dear Sir, In the above letter, Cohen repeats arguments that he as made in the past; however, the thrust of those comments indicates a fundamental misunderstanding of the point of my article and indeed of my prior articles on this topic. It was not and has never been my goal to identify a specific factor (or several factors) that induced the negative correlation between the estimates of county-level mean radon concentration and county lung cancer mortality rates. Other investigators have offered powerful examples, both theoretical and practical, that Cohen's results are indeed an artifact of ecological regression. The primary purpose of my contributions to this topic has been to demonstrate the fundamental deficiencies of the methodology itself, in particular the unboundedness of the bias. The current article demonstrates that the ecological fallacy always applies, that the addition of county-level adjustment variables does not reduce bias and increase validity, and that an observed ecological risk pattern can differ markedly from the true risk pattern. Because of these deficiencies, epidemiologists have never used ecological regression as a tool for confirmatory analysis. For radon and lung cancer, results of 25-30 analytic studies of individuals clearly prove the deficiency of the method. There are numerous risks factors for lung cancer, including smoking, age, various occupational exposures, air pollution, previous lung diseases, and so on. I take an extremely simplified model for lung cancer in radon and smoking status, and demonstrate that the induced county-level model is non-linear. A more realistic, and complex, model for lung cancer would include all principal risk factors, and would also generate a non-linear model at the county level. Cohen's claims, which are based on his linear (or linear-quadratic) model for county lung cancer rates, are therefore built on a false premise, and his continual reference to the 'scientific method' is fatuous. One could

  17. A critical examination of spatial biases between MODIS and MISR aerosol products – application for potential AERONET deployment

    T. F. Eck

    2011-12-01

    Full Text Available AErosol RObotic NETwork (AERONET data are the primary benchmark for evaluating satellite-retrieved aerosol properties. However, despite its extensive coverage, the representativeness of the AERONET data is rarely discussed. Indeed, many studies have shown that satellite retrieval biases have a significant degree of spatial correlation that may be problematic for higher-level processes or inverse-emissions-modeling studies. To consider these issues and evaluate relative performance in regions of few surface observations, cross-comparisons between the Aerosol Optical Depth (AOD products of operational MODIS Collection 5.1 Dark Target (DT and operational MODIS Collection 5.1 Deep Blue (DB with MISR version 22 were conducted. Through such comparisons, we can observe coherent spatial features of the AOD bias while sidestepping the full analysis required for determining when or where either retrieval is more correct. We identify regions where MODIS to MISR AOD ratios were found to be above 1.4 and below 0.7. Regions where lower boundary condition uncertainty is likely to be a dominant factor include portions of Western North America, the Andes mountains, Saharan Africa, the Arabian Peninsula, and Central Asia. Similarly, microphysical biases may be an issue in South America, and specific parts of Southern Africa, India Asia, East Asia, and Indonesia. These results help identify high-priority locations for possible future deployments of both in situ and ground based remote sensing measurements. The Supplement includes a kml file.

  18. A Critical Examination of Spatial Biases Between MODIS and MISR Aerosol Products - Application for Potential AERONET Deployment

    Shi, Y.; Zhang, J.; Reid, J. S.; Hyer, E. J.; Eck, T. F.; Holben, B. N.; Kahn, R. A.

    2011-01-01

    AErosol RObotic NETwork (AERONET) data are the primary benchmark for evaluating satellite-retrieved aerosol properties. However, despite its extensive coverage, the representativeness of the AERONET data is rarely discussed. Indeed, many studies have shown that satellite retrieval biases have a significant degree of spatial correlation that may be problematic for higher-level processes or inverse-emissions-modeling studies. To consider these issues and evaluate relative performance in regions of few surface observations, cross-comparisons between the Aerosol Optical Depth (AOD) products of operational MODIS Collection 5.1 Dark Target (DT) and operational MODIS Collection 5.1 Deep Blue (DB) with MISR version 22 were conducted. Through such comparisons, we can observe coherent spatial features of the AOD bias while side-stepping the full analysis required for determining when or where either retrieval is more correct. We identify regions where MODIS to MISR AOD ratios were found to be above 1.4 and below 0.7. Regions where lower boundary condition uncertainty is likely to be a dominant factor include portions of Western North America, the Andes mountains, Saharan Africa, the Arabian Peninsula, and Central Asia. Similarly, microphysical biases may be an issue in South America, and specific parts of Southern Africa, India Asia, East Asia, and Indonesia. These results help identify high-priority locations for possible future deployments of both in situ and ground based remote sensing measurements. The Supplement includes a km1 file.

  19. The use of interim data and Data Monitoring Committee recommendations in randomized controlled trial reports: frequency, implications and potential sources of bias

    Hampton John

    2008-03-01

    Full Text Available Abstract Background Interim analysis of accumulating trial data is important to protect participant safety during randomized controlled trials (RCTs. Data Monitoring Committees (DMCs often undertake such analyses, but their widening role may lead to extended use of interim analysis or recommendations that could potentially bias trial results. Methods Systematic search of eight major publications: Annals of Internal Medicine, BMJ, Circulation, CID, JAMA, JCO, Lancet and NEJM, including all randomised controlled trials (RCTs between June 2000 and May 2005 to identify RCTs that reported use of interim analysis, with or without DMC involvement. Recommendations made by the DMC or based on interim analysis were identified and potential sources of bias assessed. Independent double data extraction was performed on all included trials. Results We identified 1772 RCTs, of which 470 (27%; 470/1772 reported the use of a DMC and a further 116 (7%; 116/1772 trials reported some form of interim analysis without explicit mention of a DMC. There were 28 trials (24 with a formal DMC, randomizing a total of 79396 participants, identified as recommending changes to the trial that may have lead to biased results. In most of these, some form of sample size re-estimation was recommended with four trials also reporting changes to trial endpoints. The review relied on information reported in the primary publications and methods papers relating to the trials, higher rates of use may have occurred but not been reported. Conclusion The reported use of interim analysis and DMCs in clinical trials has been increasing in recent years. It is reassuring that in most cases recommendations were made in the interest of participant safety. However, in practice, recommendations that may lead to potentially biased trial results are being made.

  20. Possibilities of structural engineering in multilayer vacuum-arc ZrN/CrN coatings by varying the nanolayer thickness and application of a bias potential

    Sobol', O. V.; Andreev, A. A.; Gorban', V. F.; Stolbovoy, V. A.; Melekhov, A. A.; Postelnyk, A. A.

    2016-07-01

    The possibility of attaining an superhard state in multilayer vacuum-arc ZrN/CrN coatings with a layer thickness of about 20 nm has been established. It has been shown that the application of a constant negative potential for structural engineering during deposition leads to the formation of solid solutions due to mixing of interfaces. The hardness of these systems exceeds 30 GPa. The application of a pulsed high-voltage bias potential at which the ordering of atoms stimulated by elevated mobility is observed makes it possible to suppress the mixing of the interfaces and to attain elevated hardness (up to 42 GPa) for nanometer layer thicknesses.

  1. Population of Computational Rabbit-Specific Ventricular Action Potential Models for Investigating Sources of Variability in Cellular Repolarisation

    Philip Gemmell; Kevin Burrage; Blanca Rodriguez; T Alexander Quinn

    2014-01-01

    Variability is observed at all levels of cardiac electrophysiology. Yet, the underlying causes and importance of this variability are generally unknown, and difficult to investigate with current experimental techniques. The aim of the present study was to generate populations of computational ventricular action potential models that reproduce experimentally observed intercellular variability of repolarisation (represented by action potential duration) and to identify its potential causes. A s...

  2. Effects of Potassium Currents upon Action Potential of Cardiac Cells Exposed to External Electric fields

    An-Ying Zhang; Xiao-Feng Pang

    2008-01-01

    Previous studies show that exposure to high-voltage electric fields would influence the electro cardiogram both in experimental animate and human beings. The effects of the external electric fields upon action potential of cardiac cells are studied in this paper based on the dynamical model, LR91. Fourth order Runger-Kuta is used to analyze the change of potassium ion channels exposed to external electric fields in detail. Results indicate that external electric fields could influence the current of potassium ion by adding an induced component voltage on membrane. This phenomenon might be one of the reasons of heart rate anomaly under the high-voltage electric fields.

  3. On modelling of physical effects accompanying the propagation of action potentials in nerve fibres

    Engelbrecht, Jüri; Tamm, Kert; Laasmaa, Martin; Vendelin, Marko

    2016-01-01

    The recent theoretical and experimental studies have revealed many details of signal propagation in nervous systems. In this paper an attempt is made to unify various mathematical models which describe the signal propagation in nerve fibres. The analysis of existing single models permits to select the leading physiological effects. As a result, a more general mathematical model is described based on the coupling of action potentials with mechanical waves in a nerve fibre. The crucial issue is how to model coupling effects which are strongly linked to the ion currents through biomembranes.

  4. Effects of terpineol on the compound action potential of the rat sciatic nerve

    M.R. Moreira; G.M.P. Cruz; Lopes, M S; A.A.C. Albuquerque; J.H. Leal-Cardoso

    2001-01-01

    Terpineol, a volatile terpenoid alcohol of low toxicity, is widely used in the perfumery industry. It is an important chemical constituent of the essential oil of many plants with widespread applications in folk medicine and in aromatherapy. The effects of terpineol on the compound action potential (CAP) of rat sciatic nerve were studied. Terpineol induced a dose-dependent blockade of the CAP. At 100 µM, terpineol had no demonstrable effect. At 300 µM terpineol, peak-to-peak amplitude and con...

  5. Ranolazine inhibits shear sensitivity of endogenous Na+ current and spontaneous action potentials in HL-1 cells

    Strege, Peter; Beyder, Arthur; Bernard, Cheryl; Crespo-Diaz, Ruben; Behfar, Atta; Terzic, Andre; Ackerman, Michael; Farrugia, Gianrico

    2012-01-01

    NaV1.5 is a mechanosensitive voltage-gated Na+ channel encoded by the gene SCN5A, expressed in cardiac myocytes and required for phase 0 of the cardiac action potential (AP). In the cardiomyocyte, ranolazine inhibits depolarizing Na+ current and delayed rectifier (IKr) currents. Recently, ranolazine was also shown to be an inhibitor of NaV1.5 mechanosensitivity. Stretch also accelerates the firing frequency of the SA node, and fluid shear stress increases the beating rate of cultured cardiomy...

  6. The optimal distance between two electrode tips during recording of compound nerve action potentials in the rat median nerve

    Yongping Li; Jie Lao; Xin Zhao; Dong Tian; Yi Zhu; Xiaochun Wei

    2014-01-01

    The distance between the two electrode tips can greatly inlfuence the parameters used for record-ing compound nerve action potentials. To investigate the optimal parameters for these recordings in the rat median nerve, we dissociated the nerve using different methods and compound nerve action potentials were orthodromically or antidromically recorded with different electrode spac-ings. Compound nerve action potentials could be consistently recorded using a method in which the middle part of the median nerve was intact, with both ends dissociated from the surrounding fascia and a ground wire inserted into the muscle close to the intact part. When the distance be-tween two stimulating electrode tips was increased, the threshold and supramaximal stimulating intensity of compound nerve action potentials were gradually decreased, but the amplitude was not changed signiifcantly. When the distance between two recording electrode tips was increased, the amplitude was gradually increased, but the threshold and supramaximal stimulating intensity exhibited no signiifcant change. Different distances between recording and stimulating sites did not produce signiifcant effects on the aforementioned parameters. A distance of 5 mm between recording and stimulating electrodes and a distance of 10 mm between recording and stimulating sites were found to be optimal for compound nerve action potential recording in the rat median nerve. In addition, the orthodromic compound action potential, with a biphasic waveform that was more stable and displayed less interference (however also required a higher threshold and higher supramaximal stimulus), was found to be superior to the antidromic compound action potential.

  7. Toward a Better Understanding of the Relationship between Belief in the Paranormal and Statistical Bias: The Potential Role of Schizotypy.

    Dagnall, Neil; Denovan, Andrew; Drinkwater, Kenneth; Parker, Andrew; Clough, Peter

    2016-01-01

    The present paper examined relationships between schizotypy (measured by the Oxford-Liverpool Inventory of Feelings and Experience; O-LIFE scale brief), belief in the paranormal (assessed via the Revised Paranormal Belief Scale; RPBS) and proneness to statistical bias (i.e., perception of randomness and susceptibility to conjunction fallacy). Participants were 254 volunteers recruited via convenience sampling. Probabilistic reasoning problems appeared framed within both standard and paranormal contexts. Analysis revealed positive correlations between the Unusual Experience (UnExp) subscale of O-LIFE and paranormal belief measures [RPBS full scale, traditional paranormal beliefs (TPB) and new age philosophy]. Performance on standard problems correlated negatively with UnExp and belief in the paranormal (particularly the TPB dimension of the RPBS). Consideration of specific problem types revealed that perception of randomness associated more strongly with belief in the paranormal than conjunction; both problem types related similarly to UnExp. Structural equation modeling specified that belief in the paranormal mediated the indirect relationship between UnExp and statistical bias. For problems presented in a paranormal context a framing effect occurred. Whilst UnExp correlated positively with conjunction proneness (controlling for perception of randomness), there was no association between UnExp and perception of randomness (controlling for conjunction). PMID:27471481

  8. Non-destructive generation of nano-scale periodic pinning potentials for magnetic domain walls: a way to bias domain wall propagation

    Metaxas, Peter; Zermatten, Pierre-Jean; Novak, Rafael; Jamet, Jean-Pierre; Weil, Raphael; Rohart, Stanislas; Ferre, Jacques; Mougin, Alexandra; Stamps, Robert; Baltz, Vincent; Rodmacq, Bernard; Gaudin, Gilles

    2012-02-01

    The stray magnetic field of an array of ferromagnetic nanodots is used to generate a spatially periodic pinning potential for domain walls moving through a physically separate, weakly disordered, magnetic layer lying beneath the array. This technique represents a non-destructive method to create tunable and localised pinning sites for domain walls which are consequently subject to co-existing (but independent) periodic and disordered pinning potentials. Beyond the fundamentally attractive application of creating a model experimental system to study interface motion through multiple co-existing pinning potentials, our system interestingly exhibits many characteristics that are normally associated with exchange bias. This is a direct result of the fact that pinning effects induced by the periodic pinning potential depend upon the polarity of the applied magnetic field which drives the domain wall motion, a phenomenon which manifests itself in field-polarity-dependent domain wall mobilities and profiles.

  9. Characterization of action potential-triggered [Ca2+]i transients in single smooth muscle cells of guinea-pig ileum

    Kohda, M.; Komori, S.; Unno, T; Ohashi, H

    1997-01-01

    To characterize increases in cytosolic free Ca2+ concentration ([Ca2+]i) associated with discharge of action potentials, membrane potential and [Ca2+]i were simultaneously recorded from single smooth muscle cells of guinea-pig ileum by use of a combination of nystatin-perforated patch clamp and fura-2 fluorimetry techniques.A single action potential in response to a depolarizing current pulse elicited a transient rise in [Ca2+]i. When the duration of the current pulse was prolonged, action po...

  10. Action of hallucinogens on raphe-evoked dorsal root potentials (DRPs) in the cat.

    Larson, A A; Anderson, E G

    1986-02-01

    The dorsal root potential (DRP) evoked by stimulation of the inferior central nucleus (ICN) of the cat is affected by administration of a variety of hallucinogenic agents. It has been previously shown that a single low dose of LSD is unique in that it potentiates this DRP, while injections of 5-methoxy-N,N- dimethyltryptamine (5-MeODMT), ketamine or phencyclidine (PCP) inhibit its production. Tolerance develops to the facilitatory effect of low doses of LSD on the DRP, but not to the inhibitory action of 5-MeODMT. Repeated injections of ketamine every 30 minutes also fail to produce tachyphylaxis to the inhibitory effect of this dissociative anesthetic. The raphe-evoked DRP is a long latency potential that is inhibited by a wide variety of putative serotonin antagonists and has therefore been traditionally thought to be mediated by serotonin. However, in light of the inability of either tryptophan or fluoxetine to potentiate this DRP, and the resistance of this DRP to blockade by parachlorophenylalanine, reserpine or intrathecally administered 5,7-dihydroxytryptamine, it appears that this potential may in fact be mediated, at least in part, by a non-serotonergic transmitter. PMID:3952125

  11. Quantitative assessment of the distributions of membrane conductances involved in action potential backpropagation along basal dendrites.

    Acker, Corey D; Antic, Srdjan D

    2009-03-01

    Basal dendrites of prefrontal cortical neurons receive strong synaptic drive from recurrent excitatory synaptic inputs. Synaptic integration within basal dendrites is therefore likely to play an important role in cortical information processing. Both synaptic integration and synaptic plasticity depend crucially on dendritic membrane excitability and the backpropagation of action potentials. We carried out multisite voltage-sensitive dye imaging of membrane potential transients from thin basal branches of prefrontal cortical pyramidal neurons before and after application of channel blockers. We found that backpropagating action potentials (bAPs) are predominantly controlled by voltage-gated sodium and A-type potassium channels. In contrast, pharmacologically blocking the delayed rectifier potassium, voltage-gated calcium, or I(h) conductance had little effect on dendritic AP propagation. Optically recorded bAP waveforms were quantified and multicompartmental modeling was used to link the observed behavior with the underlying biophysical properties. The best-fit model included a nonuniform sodium channel distribution with decreasing conductance with distance from the soma, together with a nonuniform (increasing) A-type potassium conductance. AP amplitudes decline with distance in this model, but to a lesser extent than previously thought. We used this model to explore the mechanisms underlying two sets of published data involving high-frequency trains of APs and the local generation of sodium spikelets. We also explored the conditions under which I(A) down-regulation would produce branch strength potentiation in the proposed model. Finally, we discuss the hypothesis that a fraction of basal branches may have different membrane properties compared with sister branches in the same dendritic tree. PMID:19118105

  12. The characteristics of action potential and nonselective cation current of cardiomyocytes in rabbit superior vena cava

    WANG Pan; YANG XinChun; LIU XiuLan; BAO RongFeng; LIU TaiFeng

    2008-01-01

    As s special focus in initiating and maintaining atrial fibrillation (AF), cardiomyocytes in superior vena cavs (SVC) have distinctive electrophysiological characters. In this study, we found that comparing with the right atrial (RA) cardiomyoctyes, the SVC cardiomyoctyes had longer APD90 at the different basic cycle lengths; the conduction block could be observed on both RA and SVC cardiomyoctyes. A few of SVC cardiomyoctyes showed slow response action potentials with automatic activity and some others showed early afterdepolarization (EAD) spontaneously. Further more, we found that there are nonselective cation current (INs) in both SVC and RA cardiomyocytes. The peak density of INs in SVC cardiomyocytes was smaller than that in RA cardiomyocytes. Removal of extracellular divalent cation and glucose could increase INs in SVC cardiomyocytes. The agonist or the antagonist of INs may increase or decrease APD. To sum up, some SVC cardiomyocytes possess the ability of spontaneous activity; the difference of transmembrane action potentials between SVC and RA cardiomyocytes is partly because of the different density of INs between them; the agonist or the antagonist of INs can increase or decrease APD leading to the enhancement or reduction of EAD genesis in SVC cardiomyocytes. INs in rabbit myocytes is fairly similar to TRPC3 current in electrophysiological property, which might play an important role in the mechanisms of AF.

  13. Biophysical foundations for the study of the electrical excitability and action potential propagation in myocardium

    The electric current flow in the heterogeneous and anysotropic volume conductor of the myocardium is studied. The equations of bidomain theory are derived using an approach framed in the theory of averaged fields, introducing microscopic, mesoscopic and macroscopic spatial scales. However, the procedure, compatible with the histological and the anatomical details of the organ, is different from the multiple scale asymptotic expansions usually applied in homogeneization problems. A probabilistic approach framed in large numbers theorems is used to derive the equation for membrane ionic current from the stochastic activity of the channels at the microscopic level. An operational procedure suitable to define a sharp bidomain boundary from the fuzzy distribution of structural details and physical properties at the histological level is given. The problem of threshold is studied. The sizes and shapes of critical masses of cardiac cells that must be depolarized above threshold in order to produce a propagated action potential are determined by an approximate analytical procedure. The concept of family of threshold patterns for the emergence of action potentials in the heart is introduced. This concept is applied to discuss the conditions of emergence of ectopic focus. Analytical formulae are derived, for the time constant and the rheobase for electrical stimulation of the myocardium. These formulae are in good agreement with known experimental results. New experiments that could be done to confirm or reject them are suggested

  14. Ventricular filling slows epicardial conduction and increases action potential duration in an optical mapping study of the isolated rabbit heart

    Sung, Derrick; Mills, Robert W.; Schettler, Jan; Narayan, Sanjiv M.; Omens, Jeffrey H.; McCulloch, Andrew D.; McCullough, A. D. (Principal Investigator)

    2003-01-01

    INTRODUCTION: Mechanical stimulation can induce electrophysiologic changes in cardiac myocytes, but how mechanoelectric feedback in the intact heart affects action potential propagation remains unclear. METHODS AND RESULTS: Changes in action potential propagation and repolarization with increased left ventricular end-diastolic pressure from 0 to 30 mmHg were investigated using optical mapping in isolated perfused rabbit hearts. With respect to 0 mmHg, epicardial strain at 30 mmHg in the anterior left ventricle averaged 0.040 +/- 0.004 in the muscle fiber direction and 0.032 +/- 0.006 in the cross-fiber direction. An increase in ventricular loading increased average epicardial activation time by 25%+/- 3% (P action potential duration at 20% repolarization (APD20) but did at 80% repolarization (APD80), from 179 +/- 7 msec to 207 +/- 5 msec (P action potential duration by a load-dependent mechanism that may not involve stretch-activated channels.

  15. The Belem Framework for Action: Harnessing the Power and Potential of Adult Learning and Education for a Viable Future

    Adult Learning, 2012

    2012-01-01

    This article presents the Belem Framework for Action. This framework focuses on harnessing the power and potential of adult learning and education for a viable future. This framework begins with a preamble on adult education and towards lifelong learning.

  16. Regulation of action potential waveforms by axonal GABAA receptors in cortical pyramidal neurons.

    Yang Xia

    Full Text Available GABAA receptors distributed in somatodendritic compartments play critical roles in regulating neuronal activities, including spike timing and firing pattern; however, the properties and functions of GABAA receptors at the axon are still poorly understood. By recording from the cut end (bleb of the main axon trunk of layer -5 pyramidal neurons in prefrontal cortical slices, we found that currents evoked by GABA iontophoresis could be blocked by picrotoxin, indicating the expression of GABAA receptors in axons. Stationary noise analysis revealed that single-channel properties of axonal GABAA receptors were similar to those of somatic receptors. Perforated patch recording with gramicidin revealed that the reversal potential of the GABA response was more negative than the resting membrane potential at the axon trunk, suggesting that GABA may hyperpolarize the axonal membrane potential. Further experiments demonstrated that the activation of axonal GABAA receptors regulated the amplitude and duration of action potentials (APs and decreased the AP-induced Ca2+ transients at the axon. Together, our results indicate that the waveform of axonal APs and the downstream Ca2+ signals are modulated by axonal GABAA receptors.

  17. Action potential-simulated weak electric fields can directly initiate myelination

    Lei Liu; Shifu Zhao; Haiming Wang

    2008-01-01

    BACKGROUND: Myelination is a process whereby glial cells identify, adhere, wrap and enclose axons to form a spiral myelin sheath.OBJECTIVE: To investigate the effects of action potential-simulated weak electric fields on myelination in the central nervous system.DESIGN AND SETTING: This single-sample observation study was performed at the 324 Hospital of Chinese PLA.MATERIALS: Two 5 μm carbon fibers were provided by the Institute of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences. One Sprague Dawley rat, aged 1 day, was used.METHODS: Cerebral cortex was harvested from the rat to prepare a suspension [(1-2)×105/mL] containing neurons and glial cells. To simulate the axon, carbon fibers were placed at the bottom of the neuron-glial cell coculture dish, and were electrified with a single phase square wave current, 1×10-2, 1×10-3, 1×10-4, and 1×10-5 seconds, 1 Hz, 40 mV, and 10 μA, 30 minutes each, once aday for 10 consecutive days to simulate weak negative electric fields during action potential conduction.MAIN OUTCOME MEASURES: Glial cell growth and wrapping of carbon fibers were observed by phase contrast microscopy and immunohistochemistry.RESULTS: On culture day 7, cell groups were found to adhere to negative carbon fibers in the 1×10-3 seconds square wave group. Cell membrane-like substances grew out of cell groups, wrapped the carbon fibers, and stretched to the ends of carbon fibers. Only some small and round cells close to negative carbon fibers were found on culture day 12. In the 1×10-4 and 1×10-3 seconds square wave groups, the negative carbon fibers were wrapped by oligodendrocytes or their progenitor cells.CONCLUSION: The local negative electric field which is generated by action potentials at 1×(10-4-10-3)seconds, 40 mV can directly initiate and participate in myelination in the central nervous system.

  18. Hindsight Bias.

    Roese, Neal J; Vohs, Kathleen D

    2012-09-01

    Hindsight bias occurs when people feel that they "knew it all along," that is, when they believe that an event is more predictable after it becomes known than it was before it became known. Hindsight bias embodies any combination of three aspects: memory distortion, beliefs about events' objective likelihoods, or subjective beliefs about one's own prediction abilities. Hindsight bias stems from (a) cognitive inputs (people selectively recall information consistent with what they now know to be true and engage in sensemaking to impose meaning on their own knowledge), (b) metacognitive inputs (the ease with which a past outcome is understood may be misattributed to its assumed prior likelihood), and (c) motivational inputs (people have a need to see the world as orderly and predictable and to avoid being blamed for problems). Consequences of hindsight bias include myopic attention to a single causal understanding of the past (to the neglect of other reasonable explanations) as well as general overconfidence in the certainty of one's judgments. New technologies for visualizing and understanding data sets may have the unintended consequence of heightening hindsight bias, but an intervention that encourages people to consider alternative causal explanations for a given outcome can reduce hindsight bias. PMID:26168501

  19. Intracellular recordings of action potentials by an extracellular nanoscale field-effect transistor

    Duan, Xiaojie; Gao, Ruixuan; Xie, Ping; Cohen-Karni, Tzahi; Qing, Quan; Choe, Hwan Sung; Tian, Bozhi; Jiang, Xiaocheng; Lieber, Charles M.

    2012-03-01

    The ability to make electrical measurements inside cells has led to many important advances in electrophysiology. The patch clamp technique, in which a glass micropipette filled with electrolyte is inserted into a cell, offers both high signal-to-noise ratio and temporal resolution. Ideally, the micropipette should be as small as possible to increase the spatial resolution and reduce the invasiveness of the measurement, but the overall performance of the technique depends on the impedance of the interface between the micropipette and the cell interior, which limits how small the micropipette can be. Techniques that involve inserting metal or carbon microelectrodes into cells are subject to similar constraints. Field-effect transistors (FETs) can also record electric potentials inside cells, and because their performance does not depend on impedance, they can be made much smaller than micropipettes and microelectrodes. Moreover, FET arrays are better suited for multiplexed measurements. Previously, we have demonstrated FET-based intracellular recording with kinked nanowire structures, but the kink configuration and device design places limits on the probe size and the potential for multiplexing. Here, we report a new approach in which a SiO2 nanotube is synthetically integrated on top of a nanoscale FET. This nanotube penetrates the cell membrane, bringing the cell cytosol into contact with the FET, which is then able to record the intracellular transmembrane potential. Simulations show that the bandwidth of this branched intracellular nanotube FET (BIT-FET) is high enough for it to record fast action potentials even when the nanotube diameter is decreased to 3 nm, a length scale well below that accessible with other methods. Studies of cardiomyocyte cells demonstrate that when phospholipid-modified BIT-FETs are brought close to cells, the nanotubes can spontaneously penetrate the cell membrane to allow the full-amplitude intracellular action potential to be

  20. Cancer Driver Log (CanDL): Catalog of Potentially Actionable Cancer Mutations.

    Damodaran, Senthilkumar; Miya, Jharna; Kautto, Esko; Zhu, Eliot; Samorodnitsky, Eric; Datta, Jharna; Reeser, Julie W; Roychowdhury, Sameek

    2015-09-01

    Massively parallel sequencing technologies have enabled characterization of genomic alterations across multiple tumor types. Efforts have focused on identifying driver mutations because they represent potential targets for therapy. However, because of the presence of driver and passenger mutations, it is often challenging to assign the clinical relevance of specific mutations observed in patients. Currently, there are multiple databases and tools that provide in silico assessment for potential drivers; however, there is no comprehensive resource for mutations with functional characterization. Therefore, we created an expert-curated database of potentially actionable driver mutations for molecular pathologists to facilitate annotation of cancer genomic testing. We reviewed scientific literature to identify variants that have been functionally characterized in vitro or in vivo as driver mutations. We obtained the chromosome location and all possible nucleotide positions for each amino acid change and uploaded them to the Cancer Driver Log (CanDL) database with associated literature reference indicating functional driver evidence. In addition to a simple interface, the database allows users to download all or selected genes as a comma-separated values file for incorporation into their own analysis pipeline. Furthermore, the database includes a mechanism for third-party contributions to support updates for novel driver mutations. Overall, this freely available database will facilitate rapid annotation of cancer genomic testing in molecular pathology laboratories for mutations. PMID:26320871

  1. Electrophysiological Motor Unit Number Estimation (MUNE) Measuring Compound Muscle Action Potential (CMAP) in Mouse Hindlimb Muscles.

    Arnold, W David; Sheth, Kajri A; Wier, Christopher G; Kissel, John T; Burghes, Arthur H; Kolb, Stephen J

    2015-01-01

    Compound muscle action potential (CMAP) and motor unit number estimation (MUNE) are electrophysiological techniques that can be used to monitor the functional status of a motor unit pool in vivo. These measures can provide insight into the normal development and degeneration of the neuromuscular system. These measures have clear translational potential because they are routinely applied in diagnostic and clinical human studies. We present electrophysiological techniques similar to those employed in humans to allow recordings of mouse sciatic nerve function. The CMAP response represents the electrophysiological output from a muscle or group of muscles following supramaximal stimulation of a peripheral nerve. MUNE is an electrophysiological technique that is based on modifications of the CMAP response. MUNE is a calculated value that represents the estimated number of motor neurons or axons (motor control input) supplying the muscle or group of muscles being tested. We present methods for recording CMAP responses from the proximal leg muscles using surface recording electrodes following the stimulation of the sciatic nerve in mice. An incremental MUNE technique is described using submaximal stimuli to determine the average single motor unit potential (SMUP) size. MUNE is calculated by dividing the CMAP amplitude (peak-to-peak) by the SMUP amplitude (peak-to-peak). These electrophysiological techniques allow repeated measures in both neonatal and adult mice in such a manner that facilitates rapid analysis and data collection while reducing the number of animals required for experimental testing. Furthermore, these measures are similar to those recorded in human studies allowing more direct comparisons. PMID:26436455

  2. Optical magnetic detection of single-neuron action potentials using quantum defects in diamond

    Barry, J F; Schloss, J M; Glenn, D R; Song, Y; Lukin, M D; Park, H; Walsworth, R L

    2016-01-01

    A key challenge for neuroscience is noninvasive, label-free sensing of action potential (AP) dynamics in whole organisms with single-neuron resolution. Here, we present a new approach to this problem: using nitrogen-vacancy (NV) quantum defects in diamond to measure the time-dependent magnetic fields produced by single-neuron APs. Our technique has a unique combination of features: (i) it is noninvasive, as the light that probes the NV sensors stays within the biocompatible diamond chip and does not enter the organism, enabling activity monitoring over extended periods; (ii) it is label-free and should be widely applicable to most organisms; (iii) it provides high spatial and temporal resolution, allowing precise measurement of the AP waveforms and conduction velocities of individual neurons; (iv) it directly determines AP propagation direction through the inherent sensitivity of NVs to the associated AP magnetic field vector; (v) it is applicable to neurons located within optically opaque tissue or whole org...

  3. Anthropomorphizing the Mouse Cardiac Action Potential via a Novel Dynamic Clamp Method

    Ahrens-Nicklas, Rebecca C.; Christini, David J.

    2009-01-01

    Abstract Interspecies differences can limit the translational value of excitable cells isolated from model organisms. It can be difficult to extrapolate from a drug- or mutation-induced phenotype in mice to human pathophysiology because mouse and human cardiac electrodynamics differ greatly. We present a hybrid computational-experimental technique, the cell-type transforming clamp, which is designed to overcome such differences by using a calculated compensatory current to convert the macroscopic electrical behavior of an isolated cell into that of a different cell type. We demonstrate the technique's utility by evaluating drug arrhythmogenicity in murine cardiomyocytes that are transformed to behave like human myocytes. Whereas we use the cell-type transforming clamp in this work to convert between mouse and human electrodynamics, the technique could be adapted to convert between the action potential morphologies of any two cell types of interest. PMID:19917221

  4. Effect of sampling frequency on the measurement of phase-locked action potentials.

    Go eAshida

    2010-09-01

    Full Text Available Phase-locked spikes in various types of neurons encode temporal information. To quantify the degree of phase-locking, the metric called vector strength (VS has been most widely used. Since VS is derived from spike timing information, error in measurement of spike occurrence should result in errors in VS calculation. In electrophysiological experiments, the timing of an action potential is detected with finite temporal precision, which is determined by the sampling frequency. In order to evaluate the effects of the sampling frequency on the measurement of VS, we derive theoretical upper and lower bounds of VS from spikes collected with finite sampling rates. We next estimate errors in VS assuming random sampling effects, and show that our theoretical calculation agrees with data from electrophysiological recordings in vivo. Our results provide a practical guide for choosing the appropriate sampling frequency in measuring VS.

  5. BK channels regulate spontaneous action potential rhythmicity in the suprachiasmatic nucleus.

    Jack Kent

    Full Text Available BACKGROUND: Circadian ( approximately 24 hr rhythms are generated by the central pacemaker localized to the suprachiasmatic nucleus (SCN of the hypothalamus. Although the basis for intrinsic rhythmicity is generally understood to rely on transcription factors encoded by "clock genes", less is known about the daily regulation of SCN neuronal activity patterns that communicate a circadian time signal to downstream behaviors and physiological systems. Action potentials in the SCN are necessary for the circadian timing of behavior, and individual SCN neurons modulate their spontaneous firing rate (SFR over the daily cycle, suggesting that the circadian patterning of neuronal activity is necessary for normal behavioral rhythm expression. The BK K(+ channel plays an important role in suppressing spontaneous firing at night in SCN neurons. Deletion of the Kcnma1 gene, encoding the BK channel, causes degradation of circadian behavioral and physiological rhythms. METHODOLOGY/PRINCIPAL FINDINGS: To test the hypothesis that loss of robust behavioral rhythmicity in Kcnma1(-/- mice is due to the disruption of SFR rhythms in the SCN, we used multi-electrode arrays to record extracellular action potentials from acute wild-type (WT and Kcnma1(-/- slices. Patterns of activity in the SCN were tracked simultaneously for up to 3 days, and the phase, period, and synchronization of SFR rhythms were examined. Loss of BK channels increased arrhythmicity but also altered the amplitude and period of rhythmic activity. Unexpectedly, Kcnma1(-/- SCNs showed increased variability in the timing of the daily SFR peak. CONCLUSIONS/SIGNIFICANCE: These results suggest that BK channels regulate multiple aspects of the circadian patterning of neuronal activity in the SCN. In addition, these data illustrate the characteristics of a disrupted SCN rhythm downstream of clock gene-mediated timekeeping and its relationship to behavioral rhythms.

  6. Modulation of hERG potassium channel gating normalizes action potential duration prolonged by dysfunctional KCNQ1 potassium channel

    Zhang, Hongkang; Zou, Beiyan; Yu, Haibo; Moretti, Alessandra; Wang, Xiaoying; Yan, Wei; Babcock, Joseph J.; Bellin, Milena; McManus, Owen B.; Tomaselli, Gordon; Nan, Fajun; Laugwitz, Karl-Ludwig; Li, Min

    2012-01-01

    Long QT syndrome (LQTS) is a genetic disease characterized by a prolonged QT interval in an electrocardiogram (ECG), leading to higher risk of sudden cardiac death. Among the 12 identified genes causal to heritable LQTS, ∼90% of affected individuals harbor mutations in either KCNQ1 or human ether-a-go-go related genes (hERG), which encode two repolarizing potassium currents known as IKs and IKr. The ability to quantitatively assess contributions of different current components is therefore important for investigating disease phenotypes and testing effectiveness of pharmacological modulation. Here we report a quantitative analysis by simulating cardiac action potentials of cultured human cardiomyocytes to match the experimental waveforms of both healthy control and LQT syndrome type 1 (LQT1) action potentials. The quantitative evaluation suggests that elevation of IKr by reducing voltage sensitivity of inactivation, not via slowing of deactivation, could more effectively restore normal QT duration if IKs is reduced. Using a unique specific chemical activator for IKr that has a primary effect of causing a right shift of V1/2 for inactivation, we then examined the duration changes of autonomous action potentials from differentiated human cardiomyocytes. Indeed, this activator causes dose-dependent shortening of the action potential durations and is able to normalize action potentials of cells of patients with LQT1. In contrast, an IKr chemical activator of primary effects in slowing channel deactivation was not effective in modulating action potential durations. Our studies provide both the theoretical basis and experimental support for compensatory normalization of action potential duration by a pharmacological agent. PMID:22745159

  7. Variability of Action Potentials Within and Among Cardiac Cell Clusters Derived from Human Embryonic Stem Cells.

    Zhu, Renjun; Millrod, Michal A; Zambidis, Elias T; Tung, Leslie

    2016-01-01

    Electrophysiological variability in cardiomyocytes derived from pluripotent stem cells continues to be an impediment for their scientific and translational applications. We studied the variability of action potentials (APs) recorded from clusters of human embryonic stem cell-derived cardiomyocytes (hESC-CMs) using high-resolution optical mapping. Over 23,000 APs were analyzed through four parameters: APD30, APD80, triangulation and fractional repolarization. Although measures were taken to reduce variability due to cell culture conditions and rate-dependency of APs, we still observed significant variability in APs among and within the clusters. However, similar APs were found in spatial locations with close proximity, and in some clusters formed distinct regions having different AP characteristics that were reflected as separate peaks in the AP parameter distributions, suggesting multiple electrophysiological phenotypes. Using a recently developed automated method to group cells based on their entire AP shape, we identified distinct regions of different phenotypes within single clusters and common phenotypes across different clusters when separating APs into 2 or 3 subpopulations. The systematic analysis of the heterogeneity and potential phenotypes of large populations of hESC-CMs can be used to evaluate strategies to improve the quality of pluripotent stem cell-derived cardiomyocytes for use in diagnostic and therapeutic applications and in drug screening. PMID:26729331

  8. Calcium Transients Closely Reflect Prolonged Action Potentials in iPSC Models of Inherited Cardiac Arrhythmia

    C. Ian Spencer

    2014-08-01

    Full Text Available Long-QT syndrome mutations can cause syncope and sudden death by prolonging the cardiac action potential (AP. Ion channels affected by mutations are various, and the influences of cellular calcium cycling on LQTS cardiac events are unknown. To better understand LQTS arrhythmias, we performed current-clamp and intracellular calcium ([Ca2+]i measurements on cardiomyocytes differentiated from patient-derived induced pluripotent stem cells (iPS-CM. In myocytes carrying an LQT2 mutation (HERG-A422T, APs and [Ca2+]i transients were prolonged in parallel. APs were abbreviated by nifedipine exposure and further lengthened upon releasing intracellularly stored Ca2+. Validating this model, control iPS-CM treated with HERG-blocking drugs recapitulated the LQT2 phenotype. In LQT3 iPS-CM, expressing NaV1.5-N406K, APs and [Ca2+]i transients were markedly prolonged. AP prolongation was sensitive to tetrodotoxin and to inhibiting Na+-Ca2+ exchange. These results suggest that LQTS mutations act partly on cytosolic Ca2+ cycling, potentially providing a basis for functionally targeted interventions regardless of the specific mutation site.

  9. Optophysiological approach to resolve neuronal action potentials with high spatial and temporal resolution in cultured neurons

    Stephane ePages

    2011-10-01

    Full Text Available Cell to cell communication in the central nervous system is encoded into transient and local membrane potential changes (ΔVm. Deciphering the rules that govern synaptic transmission and plasticity entails to be able to perform Vm recordings throughout the entire neuronal arborization. Classical electrophysiology is, in most cases, not able to do so within small and fragile neuronal subcompartments. Thus, optical techniques based on the use of fluorescent voltage-sensitive dyes (VSDs have been developed. However, reporting spontaneous or small ΔVm from neuronal ramifications has been challenging, in part due to the limited sensitivity and phototoxicity of VSD-based optical measurements. Here we demonstrate the use of water soluble VSD, ANNINE-6plus, with laser scanning microscopy to optically record ΔVm in cultured neurons. We show that the sensitivity (> 10 % of fluorescence change for 100 mV depolarization and time response (submillisecond of the dye allows the robust detection of action potentials (APs even without averaging, allowing the measurement of spontaneous neuronal firing patterns. In addition, we show that back-propagating APs can be recorded, along distinct dendritic sites and within dendritic spines. Importantly, our approach does not induce any detectable phototoxic effect on cultured neurons. This optophysiological approach provides a simple, minimally invasive and versatile optical method to measure electrical activity in cultured neurons with high temporal (ms resolution and high spatial (µm resolution.

  10. Optimisation of Ionic Models to Fit Tissue Action Potentials: Application to 3D Atrial Modelling

    Amr Al Abed

    2013-01-01

    Full Text Available A 3D model of atrial electrical activity has been developed with spatially heterogeneous electrophysiological properties. The atrial geometry, reconstructed from the male Visible Human dataset, included gross anatomical features such as the central and peripheral sinoatrial node (SAN, intra-atrial connections, pulmonary veins, inferior and superior vena cava, and the coronary sinus. Membrane potentials of myocytes from spontaneously active or electrically paced in vitro rabbit cardiac tissue preparations were recorded using intracellular glass microelectrodes. Action potentials of central and peripheral SAN, right and left atrial, and pulmonary vein myocytes were each fitted using a generic ionic model having three phenomenological ionic current components: one time-dependent inward, one time-dependent outward, and one leakage current. To bridge the gap between the single-cell ionic models and the gross electrical behaviour of the 3D whole-atrial model, a simplified 2D tissue disc with heterogeneous regions was optimised to arrive at parameters for each cell type under electrotonic load. Parameters were then incorporated into the 3D atrial model, which as a result exhibited a spontaneously active SAN able to rhythmically excite the atria. The tissue-based optimisation of ionic models and the modelling process outlined are generic and applicable to image-based computer reconstruction and simulation of excitable tissue.

  11. Small-conductance calcium-activated potassium (SK) channels contribute to action potential repolarization in human atria

    Skibsbye, Lasse; Poulet, Claire; Diness, Jonas Goldin;

    2014-01-01

    (+) currents by ∼15% and prolonged action potential duration (APD), but no effect was observed in myocytes from AF patients. In trabeculae muscle strips from right atrial appendages of SR patients, both compounds increased APD and effective refractory period, and depolarized the resting membrane potential...

  12. Potential involvement of serotonergic signaling in ketamine's antidepressant actions: A critical review.

    du Jardin, Kristian Gaarn; Müller, Heidi Kaastrup; Elfving, Betina; Dale, Elena; Wegener, Gregers; Sanchez, Connie

    2016-11-01

    A single i.v. infusion of ketamine, classified as an N-methyl-d-aspartate (NMDA) receptor antagonist, may alleviate depressive symptoms within hours of administration in treatment resistant depressed patients, and the antidepressant effect may last for several weeks. These unique therapeutic properties have prompted researchers to explore the mechanisms mediating the antidepressant effects of ketamine, but despite many efforts, no consensus on its antidepressant mechanism of action has been reached. Recent preclinical reports have associated the neurotransmitter serotonin (5-hydroxytryptamine; 5-HT) with the antidepressant-like action of ketamine. Here, we review the current evidence for a serotonergic role in ketamine's antidepressant effects. The pharmacological profile of ketamine may include equipotent activity on several non-NMDA targets, and the current hypotheses for the mechanisms responsible for ketamine's antidepressant activity do not appear to preclude the possibility that non-glutamate neurotransmitters are involved in the antidepressant effects. At multiple levels, the serotonergic and glutamatergic systems interact, and such crosstalk could support the notion that changes in serotonergic neurotransmission may impact ketamine's antidepressant potential. In line with these prospects, ketamine may increase 5-HT levels in the prefrontal cortex of rats, plausibly via hippocampal NMDA receptor inhibition and activation of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors. In addition, a number of preclinical studies suggest that the antidepressant-like effects of ketamine may depend on endogenous activation of 5-HT receptors. Recent imaging and behavioral data predominantly support a role for 5-HT1A or 5-HT1B receptors, but the full range of 5-HT receptors has currently not been systematically investigated in this context. Furthermore, the nature of any 5-HT dependent mechanism in ketamine's antidepressant effect is currently not

  13. CLINICAL AND EXPERIMENTAL STUDIES OF LARGE AMPLITUDE ACTION POTENTIAL OF THE SUFFERED FACIAL MUSCLES IN INTRATEMPORAL FACIAL NERVE PARALYSIS

    1999-01-01

    Ojective. To testify the phenomenon that large amplitude action potential appears at the early stage of facial paralysis, and to search for the mechanism through clinical and experimental studies. Patients(animals) and methods. The action potentials of the orbicular ocular and oral muscles were recorded in 34 normal persons by electromyogram instruments. The normal range of amplitude percentage was found out according to he normal distribution. One hundred patients with facial paralysis were also studied. The action potentials of facial muscles were recorded in 17 guinea pigs before and after the facial nerve was compressed and the facial nerve was examined under electromicroscope before and after the compression.Results. The amplitude percentage of the suffered ide to the healthy side was more than 153 percent in 6 of the 100 patients. Lare amplitude action potential ocured in 35 per cent guinea pigs which were performed the experiment of facial nrve compression. Electromicroscopic examination revealed separation of the lammae of the facial nerve's myelin sheath in the guinea pigs which exhibited large amplitude action potential.Conclusion. The facial nerve exhibited a temporary over-exciability at the early stage of facial nerve injury in some patients and guinea pigs. If the injury waslimited in the myelin sheath, te prognosis was relatively good.

  14. CLINICAL AND EXPERIMENTAL STUDIES OF LARGE AMPLITUDE ACTION POTENTIAL OF THE SUFFERED FACIAL MUSCLES IN INTRATEMPORAL FACIAL NERVE PARALYSIS

    任重; 惠莲

    1999-01-01

    Objctive. To testify the phenomenon that large amplitude action potential appears at the early stage oil facial paralysis, and to search for the mechanism through clinical and experimental studies. Patients(aninmls) and methods. The action potentials of the orbicular ocular and oral museles were recorded in 34 normal persons by electromyogram instrtiments. The normal range of amplitude percentage was found out according to the normal distribution, One hundred patients with facial paralysis were also studied. The action potentials of facial muscles were recorded ia 17 guinea pigs before and after the facial nerve was comp~ and the facial nerve was examined under electromicroscope before and after the compression.Results. The amplitude percentage of the suffered side to the healthy side was more than 153 percent in 6 of the 100 patients. Large amplitude action potential occured in 35 per cent guinea pigs which were performed the experiment of facial nerve compression. Electromicroscopic examination revealed separation of the lammae of the facial nerve's myelin sheath in the guinea pigs which exhibited large amplitude action potential Conclusion. The facial nerve exhibited a temporary over-excitability at the early stage of facial nerve injury in scane patients and guinea pigs. If the injury was limited in the myelin sheath, the prognods was relatively good.

  15. Surface electrocardiogram and action potential in mice lacking urea transporter UT-B

    MENG Yan; ZHAO ChunYan; ZHANG XueXin; ZHAO HuaShan; GUO LiRong; Lü Bin; ZHAO XueJian; YANG BaoXue

    2009-01-01

    UT-B is a urea transporter protein expressed in the kidney and in many non-renal tissues including erythrocytes, brain, heart, bladder and the testis. The objective of this study was to determine the phenotype of UT-B deletion in the heart. UT-B expression in the heart was studied in wild-type mice vs UT-B null mice by utilizing RT-PCR and Western blot. A surface electrocardiogram (ECG) recording (lead Ⅱ) was measured in wild-type mice and UT-B null mice at the ages of 6, 16 and 52 weeks. For the action potential recording, the ventricular myocytes of 16 w mice were isolated and recorded by float-ing microelectrode method. The sodium current was recorded by the patch clamp technique. RT-PCR and Western blot showed the UT-B expression in the heart of wild-type mice. No UT-B transcript and protein was found in UT-B null mice. The ECG recording showed that the P-R interval was significantly prolonged in UT-B null mice ((43.5±4.2), (45.5±6.9) and (43.8±7.6) ms at ages of 6, 16 and 52 weeks) vs wild-type mice ((38.6±2.9), (38.7±5.6) and (38.2±7.3) ms, P<0.05). The atrial ventricular heart block type Ⅱ and Ⅲ only appeared in the aging UT-B null mice (52 w old). The amplitude of action potential and Vmax decreased significantly in UT-B null mice ((92.17±10.56) and (101.89±9.54) mV/s) vs those in wild-type mice (vs (110.51±10.38) and (109.53±10.64) mV/s, P<0.05). The action potential duration at 50% and 90% (APD50 and APD90) was significantly prolonged in UT-B null mice ((123.83±11.17) and (195.43±16.41) ms) vs that in wild-type mice ((108.27±10.85) and (171.00±15.53) ms, P<0.05). The maximal sodium current decreased significantly in UT-B null mice (-8.80±0.92) nA vs that in wild-type mice ((-5.98±1.07) nA, P<0.05). These results provide the first evidence that UT-B deletion causes progressive heart block in mice.

  16. Surface electrocardiogram and action potential in mice lacking urea transporter UT-B

    2009-01-01

    UT-B is a urea transporter protein expressed in the kidney and in many non-renal tissues including erythrocytes, brain, heart, bladder and the testis. The objective of this study was to determine the phenotype of UT-B deletion in the heart. UT-B expression in the heart was studied in wild-type mice vs UT-B null mice by utilizing RT-PCR and Western blot. A surface electrocardiogram (ECG) recording (lead II) was measured in wild-type mice and UT-B null mice at the ages of 6, 16 and 52 weeks. For the action potential recording, the ventricular myocytes of 16 w mice were isolated and recorded by floating microelectrode method. The sodium current was recorded by the patch clamp technique. RT-PCR and Western blot showed the UT-B expression in the heart of wild-type mice. No UT-B transcript and protein was found in UT-B null mice. The ECG recording showed that the P-R interval was significantly prolonged in UT-B null mice ((43.5 ± 4.2), (45.5 ± 6.9) and (43.8 ± 7.6) ms at ages of 6, 16 and 52 weeks) vs wild-type mice ((38.6 ± 2.9), (38.7 ± 5.6) and (38.2 ± 7.3) ms, P<0.05). The atrial ventricular heart block type II and III only appeared in the aging UT-B null mice (52 w old). The amplitude of action potential and Vmax decreased significantly in UT-B null mice ((92.17 ± 10.56) and (101.89 ± 9.54) mV/s) vs those in wild-type mice (vs (110.51 ± 10.38) and (109.53 ± 10.64) mV/s, P<0.05). The action potential duration at 50% and 90% (APD50 and APD90) was significantly prolonged in UT-B null mice ((123.83 ± 11.17) and (195.43 ± 16.41) ms) vs that in wild-type mice ((108.27 ± 10.85) and (171.00 ± 15.53) ms, P<0.05). The maximal sodium current decreased significantly in UT-B null mice (-8.80 ± 0.92) nA vs that in wild-type mice ((-5.98 ± 1.07) nA, P<0.05). These results provide the first evidence that UT-B deletion causes progressive heart block in mice.

  17. Intention seekers: conspiracist ideation and biased attributions of intentionality.

    Brotherton, Robert; French, Christopher C

    2015-01-01

    Conspiracist beliefs are widespread and potentially hazardous. A growing body of research suggests that cognitive biases may play a role in endorsement of conspiracy theories. The current research examines the novel hypothesis that individuals who are biased towards inferring intentional explanations for ambiguous actions are more likely to endorse conspiracy theories, which portray events as the exclusive product of intentional agency. Study 1 replicated a previously observed relationship between conspiracist ideation and individual differences in anthropomorphisation. Studies 2 and 3 report a relationship between conspiracism and inferences of intentionality for imagined ambiguous events. Additionally, Study 3 again found conspiracist ideation to be predicted by individual differences in anthropomorphism. Contrary to expectations, however, the relationship was not mediated by the intentionality bias. The findings are discussed in terms of a domain-general intentionality bias making conspiracy theories appear particularly plausible. Alternative explanations are suggested for the association between conspiracism and anthropomorphism. PMID:25970175

  18. Intention seekers: conspiracist ideation and biased attributions of intentionality.

    Robert Brotherton

    Full Text Available Conspiracist beliefs are widespread and potentially hazardous. A growing body of research suggests that cognitive biases may play a role in endorsement of conspiracy theories. The current research examines the novel hypothesis that individuals who are biased towards inferring intentional explanations for ambiguous actions are more likely to endorse conspiracy theories, which portray events as the exclusive product of intentional agency. Study 1 replicated a previously observed relationship between conspiracist ideation and individual differences in anthropomorphisation. Studies 2 and 3 report a relationship between conspiracism and inferences of intentionality for imagined ambiguous events. Additionally, Study 3 again found conspiracist ideation to be predicted by individual differences in anthropomorphism. Contrary to expectations, however, the relationship was not mediated by the intentionality bias. The findings are discussed in terms of a domain-general intentionality bias making conspiracy theories appear particularly plausible. Alternative explanations are suggested for the association between conspiracism and anthropomorphism.

  19. Potential bias in testing for hyperprolactinemia and pituitary tumors in risperidone-treated patients: a claims-based study

    Wu Jasmanda; Mahmoud Ramy; Pandina Gahan; Gianfrancesco Frank D; Wang Ruey H

    2009-01-01

    Abstract Background A reporting association of risperidone with pituitary tumors has been observed. Because such tumors are highly prevalent, there may be other reasons why they were revealed in association with risperidone treatment. We assessed two potential explanations: disproportionately more prolactin assessment and head/brain imaging in risperidone-treated patients vs patients treated with other antipsychotics. Methods Treatment episodes with risperidone, clozapine, olanzapine, quetiap...

  20. Cognitive Biases and Nonverbal Cue Availability in Detecting Deception

    Burgoon, Judee K.; Blair, J. Pete; Strom, Renee E.

    2008-01-01

    In potentially deceptive situations, people rely on mental shortcuts to help process information. These heuristic judgments are often biased and result in inaccurate assessments of sender veracity. Four such biases--truth bias, visual bias, demeanor bias, and expectancy violation bias--were examined in a judgment experiment that varied nonverbal…

  1. Spin chemical potential bias induced surface current evidenced by spin pumping into the topological insulator B i2T e3

    Abdulahad, Faris Basheer; Lin, Jin-Han; Liou, Yung; Chiu, Wen-Kai; Chang, Liang-Juan; Kao, Ming-Yi; Liang, Jun-Zhi; Hung, Dung-Shing; Lee, Shang-Fan

    2015-12-01

    A spin chemical potential bias can induce a spin-polarized current by the exchange interaction of a ferromagnet with the spin-momentum locking surface states of the topological insulators. We carried out our ferromagnetic resonance experiment in a NiFe /B i2T e3 heterostructure. Apart from the enhanced Gilbert damping constant, we observed strong enhancement of the effective magnetic field at low temperatures. The enhanced field decreased exponentially with increasing temperature at an energy scale of 2.5 meV, representing the strength of the exchange coupling. We attribute the enhanced field to the induced spin-polarized current in the surface states of B i2T e3 .

  2. Potential effects of bias and nitrogen pressure on structural-stress state and properties of nitride coatings, obtained by evaporation of high-entropy alloys by vacuum arc

    A study of the influence of the negative bias potential and pressure of the atmosphere of nitrogen on the structural properties of the stress state and vacuum-arc nitride coatings. The comparison data for the three groups of coatings: 1 - (Ti, V, Zr, Nb, Hf) N, 2 - (Ti, V, Zr, Nb, Hf, Ta) N , and 3 - TiN. Excluding the drop component, multielement nitride coatings deposited in nitrogen are single phase with cubic fcc lattice (structural type NaCl). At the level of substructure in these coatings increase the nitrogen pressure leads to an increase in the crystallite size and micro strain relaxation , and increase the capacity of displacement - the opposite effect. The absolute value of micro deformation in such coatings is higher and the size of crystallites - less than mononitrides. Maximum hardness of 70 GPa achieved nitride coatings deposited by vacuum arc evaporation (Ti, V, Zr, Nb, Hf) alloy at a nitrogen pressure of 0.35 Pa

  3. Unlearning Implicit Social Biases During Sleep **

    Hu, Xiaoqing; Antony, James W.; Creery, Jessica D.; Vargas, Iliana M.; Bodenhausen, Galen V.; Paller, Ken A.

    2015-01-01

    Although people may endorse egalitarianism and tolerance, social biases can remain operative and drive harmful actions in an unconscious manner. Here we investigated training to reduce implicit racial and gender bias. Forty participants processed counter-stereotype information paired with one sound for each type of bias. Biases were reduced immediately after training. During subsequent slow-wave sleep, one sound was unobtrusively presented to each participant, repeatedly, to reactivate one ty...

  4. Genetic structure and rabies spread potential in raccoons: the role of landscape barriers and sex-biased dispersal.

    Côté, Héloïse; Garant, Dany; Robert, Karine; Mainguy, Julien; Pelletier, Fanie

    2012-06-01

    Identifying natural barriers to movements of hosts associated with infectious diseases is essential for developing effective control strategies. Raccoon rabies variant (RRV) is a zoonosis of concern for humans because its main vector, the raccoon (Procyon lotor), is found near residential areas. In Québec, Canada, all cases of RRV found in raccoons since 2006 were detected on the eastern side of the Richelieu River, suggesting that this river acts as a barrier to gene flow and thus the potential for RRV to spread. The objectives of this study were to characterize the genetic structure of raccoon populations and assess the effect of the Richelieu River on the population structure in southern Québec, Canada. We also evaluated whether RRV spread potential differed between sex and at a larger spatial scale. Our analyses revealed a weak signal of genetic differentiation among individuals located on each side of the Richelieu River. At a larger spatial scale, genetic structuring was weak. Our results suggest that rivers might not always efficiently restrain raccoon movements and spread of RRV. We suggest that the difference in genetic structure found between sexes can be partly explained by male movements during the breeding season in winter, when ice bridges allow passage over most rivers in Québec. PMID:25568059

  5. MCH and apomorphine in combination enhance action potential firing of nucleus accumbens shell neurons in vitro

    F Woodward Hopf

    2013-04-01

    Full Text Available The MCH and dopamine receptor systems have been shown to modulate a number of behaviors related to reward processing, addiction, and neuropsychiatric conditions such as schizophrenia and depression. In addition, MCH and dopamine receptors can interact in a positive manner, for example in the expression of cocaine self-administration. A recent report (Chung et al., 2011a showed that the DA1/DA2 dopamine receptor activator apomorphine suppresses pre-pulse inhibition, a preclinical model for some aspects of schizophrenia. Importantly, MCH can enhance the effects of lower doses of apomorphine, suggesting that co-modulation of dopamine and MCH receptors might alleviate some symptoms of schizophrenia with a lower dose of dopamine receptor modulator and thus fewer potential side effects. Here, we investigated whether MCH and apomorphine could enhance action potential firing in vitro in the nucleus accumbens shell (NAshell, a region which has previously been shown to mediate some behavioral effects of MCH. Using whole-cell patch-clamp electrophysiology, we found that MCH, which has no effect on firing on its own, was able to increase NAshell firing when combined with a subthreshold dose of apomorphine. Further, this MCH/apomorphine increase in firing was prevented by an antagonist of either a DA1 or a DA2 receptor, suggesting that apomorphine acts through both receptor types to enhance NAshell firing. The MCH/apomorphine-mediated firing increase was also prevented by an MCH receptor antagonist or a PKA inhibitor. Taken together, our results suggest that MCH can interact with lower doses of apomorphine to enhance NAshell firing, and thus that MCH and apomorphine might interact in vivo within the NAshell to suppress pre-pulse inhibition.

  6. The Venus Flytrap Dionaea muscipula Counts Prey-Induced Action Potentials to Induce Sodium Uptake

    Böhm, Jennifer; Scherzer, Sönke; Krol, Elzbieta; Kreuzer, Ines; von Meyer, Katharina; Lorey, Christian; Mueller, Thomas D.; Shabala, Lana; Monte, Isabel; Solano, Roberto; Al-Rasheid, Khaled A.S.; Rennenberg, Heinz; Shabala, Sergey; Neher, Erwin; Hedrich, Rainer

    2016-01-01

    Summary Carnivorous plants, such as the Venus flytrap (Dionaea muscipula), depend on an animal diet when grown in nutrient-poor soils. When an insect visits the trap and tilts the mechanosensors on the inner surface, action potentials (APs) are fired. After a moving object elicits two APs, the trap snaps shut, encaging the victim. Panicking preys repeatedly touch the trigger hairs over the subsequent hours, leading to a hermetically closed trap, which via the gland-based endocrine system is flooded by a prey-decomposing acidic enzyme cocktail. Here, we asked the question as to how many times trigger hairs have to be stimulated (e.g., now many APs are required) for the flytrap to recognize an encaged object as potential food, thus making it worthwhile activating the glands. By applying a series of trigger-hair stimulations, we found that the touch hormone jasmonic acid (JA) signaling pathway is activated after the second stimulus, while more than three APs are required to trigger an expression of genes encoding prey-degrading hydrolases, and that this expression is proportional to the number of mechanical stimulations. A decomposing animal contains a sodium load, and we have found that these sodium ions enter the capture organ via glands. We identified a flytrap sodium channel DmHKT1 as responsible for this sodium acquisition, with the number of transcripts expressed being dependent on the number of mechano-electric stimulations. Hence, the number of APs a victim triggers while trying to break out of the trap identifies the moving prey as a struggling Na+-rich animal and nutrition for the plant. Video Abstract PMID:26804557

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

    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.

  8. The Venus Flytrap Dionaea muscipula Counts Prey-Induced Action Potentials to Induce Sodium Uptake.

    Böhm, Jennifer; Scherzer, Sönke; Krol, Elzbieta; Kreuzer, Ines; von Meyer, Katharina; Lorey, Christian; Mueller, Thomas D; Shabala, Lana; Monte, Isabel; Solano, Roberto; Al-Rasheid, Khaled A S; Rennenberg, Heinz; Shabala, Sergey; Neher, Erwin; Hedrich, Rainer

    2016-02-01

    Carnivorous plants, such as the Venus flytrap (Dionaea muscipula), depend on an animal diet when grown in nutrient-poor soils. When an insect visits the trap and tilts the mechanosensors on the inner surface, action potentials (APs) are fired. After a moving object elicits two APs, the trap snaps shut, encaging the victim. Panicking preys repeatedly touch the trigger hairs over the subsequent hours, leading to a hermetically closed trap, which via the gland-based endocrine system is flooded by a prey-decomposing acidic enzyme cocktail. Here, we asked the question as to how many times trigger hairs have to be stimulated (e.g., now many APs are required) for the flytrap to recognize an encaged object as potential food, thus making it worthwhile activating the glands. By applying a series of trigger-hair stimulations, we found that the touch hormone jasmonic acid (JA) signaling pathway is activated after the second stimulus, while more than three APs are required to trigger an expression of genes encoding prey-degrading hydrolases, and that this expression is proportional to the number of mechanical stimulations. A decomposing animal contains a sodium load, and we have found that these sodium ions enter the capture organ via glands. We identified a flytrap sodium channel DmHKT1 as responsible for this sodium acquisition, with the number of transcripts expressed being dependent on the number of mechano-electric stimulations. Hence, the number of APs a victim triggers while trying to break out of the trap identifies the moving prey as a struggling Na(+)-rich animal and nutrition for the plant. PMID:26804557

  9. Action potential energy efficiency varies among neuron types in vertebrates and invertebrates.

    Biswa Sengupta

    Full Text Available The initiation and propagation of action potentials (APs places high demands on the energetic resources of neural tissue. Each AP forces ATP-driven ion pumps to work harder to restore the ionic concentration gradients, thus consuming more energy. Here, we ask whether the ionic currents underlying the AP can be predicted theoretically from the principle of minimum energy consumption. A long-held supposition that APs are energetically wasteful, based on theoretical analysis of the squid giant axon AP, has recently been overturned by studies that measured the currents contributing to the AP in several mammalian neurons. In the single compartment models studied here, AP energy consumption varies greatly among vertebrate and invertebrate neurons, with several mammalian neuron models using close to the capacitive minimum of energy needed. Strikingly, energy consumption can increase by more than ten-fold simply by changing the overlap of the Na(+ and K(+ currents during the AP without changing the APs shape. As a consequence, the height and width of the AP are poor predictors of energy consumption. In the Hodgkin-Huxley model of the squid axon, optimizing the kinetics or number of Na(+ and K(+ channels can whittle down the number of ATP molecules needed for each AP by a factor of four. In contrast to the squid AP, the temporal profile of the currents underlying APs of some mammalian neurons are nearly perfectly matched to the optimized properties of ionic conductances so as to minimize the ATP cost.

  10. Sensitivity analysis of potential events affecting the double-shell tank system and fallback actions

    Knutson, B.J.

    1996-09-27

    Sensitivity analyses were performed for fall-back positions (i.e., management actions) to accommodate potential off-normal and programmatic change events overlaid on the waste volume projections and their uncertainties. These sensitivity analyses allowed determining and ranking tank system high-risk parameters and fall- back positions that will accommodate the respective impacts. This quantification of tank system impacts shows periods where tank capacity is sensitive to certain variables that must be carefully managed and/or evaluated. Identifying these sensitive variables and quantifying their impact will allow decision makers to prepare fall-back positions and focus available resources on the highest impact parameters where technical data are needed to reduce waste projection uncertainties. For noncomplexed waste, the period of capacity vulnerability occurs during the years of single-shell tank (SST) retrieval (after approximately 2009) due to the sensitivity to several variables. Ranked by importance these variables include the pretreatment rate and 200-East SST solids transfer volume. For complexed waste, the period of capacity vulnerability occurs during the period after approximately 2005 due to the sensitivity to several variables. Ranked by importance these variables include the pretreatment rate. 200-East SST solids transfer volume. complexed waste reduction factor using evaporation, and 200-west saltwell liquid porosity.