Effect of expectation on pain assessment of lower- and higher-intensity stimuli.

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Ružić, Valentina; Ivanec, Dragutin; Modić Stanke, Koraljka

2017-01-01

Pain modulation via expectation is a well-documented phenomenon. So far it has been shown that expectations about effectiveness of a certain treatment enhance the effectiveness of different analgesics and of drug-free pain treatments. Also, studies demonstrate that people assess same-intensity stimuli differently, depending on the experimentally induced expectations regarding the characteristics of the stimuli. Prolonged effect of expectation on pain perception and possible symmetry in conditions of lower- and higher-intensity stimuli is yet to be studied. Aim of this study is to determine the effect of expectation on the perception of pain experimentally induced by the series of higher- and lower-intensity stimuli. 192 healthy participants were assigned to four experimental groups differing by expectations regarding the intensity of painful stimuli series. Expectations of two groups were congruent with actual stimuli; one group expected and received lower-intensity stimuli and the other expected and received higher-intensity stimuli. Expectations of the remaining two groups were not congruent with actual stimuli; one group expected higher-intensity stimuli, but actually received lower-intensity stimuli while the other group expected lower-intensity stimuli, but in fact received higher-intensity ones. Each group received a series of 24 varied-intensity electrical stimuli rated by the participants on a 30° intensity scale. Expectation manipulation had statistically significant effect on pain intensity assessment. When expecting lower-intensity stimuli, the participants underestimated pain intensity and when expecting higher-intensity stimuli, they overestimated pain intensity. The effect size of expectations upon pain intensity assessment was equal for both lower- and higher-intensity stimuli. The obtained results imply that expectation manipulation can achieve the desired effect of decreasing or increasing both slight and more severe pain for a longer period of

Common brain activations for painful and non-painful aversive stimuli

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Hayes Dave J

2012-06-01

Full Text Available Abstract Background Identification of potentially harmful stimuli is necessary for the well-being and self-preservation of all organisms. However, the neural substrates involved in the processing of aversive stimuli are not well understood. For instance, painful and non-painful aversive stimuli are largely thought to activate different neural networks. However, it is presently unclear whether there is a common aversion-related network of brain regions responsible for the basic processing of aversive stimuli. To help clarify this issue, this report used a cross-species translational approach in humans (i.e. meta-analysis and rodents (i.e. systematic review of functional neuroanatomy. Results Animal and human data combined to show a core aversion-related network, consisting of similar cortical (i.e. MCC, PCC, AI, DMPFC, RTG, SMA, VLOFC; see results section or abbreviation section for full names and subcortical (i.e. Amyg, BNST, DS, Hab, Hipp/Parahipp, Hyp, NAc, NTS, PAG, PBN, raphe, septal nuclei, Thal, LC, midbrain regions. In addition, a number of regions appeared to be more involved in pain-related (e.g. sensory cortex or non-pain-related (e.g. amygdala aversive processing. Conclusions This investigation suggests that aversive processing, at the most basic level, relies on similar neural substrates, and that differential responses may be due, in part, to the recruitment of additional structures as well as the spatio-temporal dynamic activity of the network. This network perspective may provide a clearer understanding of why components of this circuit appear dysfunctional in some psychiatric and pain-related disorders.

Long-latency auditory evoked potentials with verbal and nonverbal stimuli.

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Oppitz, Sheila Jacques; Didoné, Dayane Domeneghini; Silva, Débora Durigon da; Gois, Marjana; Folgearini, Jordana; Ferreira, Geise Corrêa; Garcia, Michele Vargas

2015-01-01

Long-latency auditory evoked potentials represent the cortical activity related to attention, memory, and auditory discrimination skills. Acoustic signal processing occurs differently between verbal and nonverbal stimuli, influencing the latency and amplitude patterns. To describe the latencies of the cortical potentials P1, N1, P2, N2, and P3, as well as P3 amplitude, with different speech stimuli and tone bursts, and to classify them in the presence and absence of these data. A total of 30 subjects with normal hearing were assessed, aged 18-32 years old, matched by gender. Nonverbal stimuli were used (tone burst; 1000Hz - frequent and 4000Hz - rare); and verbal (/ba/ - frequent; /ga/, /da/, and /di/ - rare). Considering the component N2 for tone burst, the lowest latency found was 217.45ms for the BA/DI stimulus; the highest latency found was 256.5ms. For the P3 component, the shortest latency with tone burst stimuli was 298.7 with BA/GA stimuli, the highest, was 340ms. For the P3 amplitude, there was no statistically significant difference among the different stimuli. For latencies of components P1, N1, P2, N2, P3, there were no statistical differences among them, regardless of the stimuli used. There was a difference in the latency of potentials N2 and P3 among the stimuli employed but no difference was observed for the P3 amplitude. Copyright © 2015 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Published by Elsevier Editora Ltda. All rights reserved.

Long-latency auditory evoked potentials with verbal and nonverbal stimuli,

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Sheila Jacques Oppitz

2015-12-01

Full Text Available ABSTRACT INTRODUCTION: Long-latency auditory evoked potentials represent the cortical activity related to attention, memory, and auditory discrimination skills. Acoustic signal processing occurs differently between verbal and nonverbal stimuli, influencing the latency and amplitude patterns. OBJECTIVE: To describe the latencies of the cortical potentials P1, N1, P2, N2, and P3, as well as P3 amplitude, with different speech stimuli and tone bursts, and to classify them in the presence and absence of these data. METHODS: A total of 30 subjects with normal hearing were assessed, aged 18-32 years old, matched by gender. Nonverbal stimuli were used (tone burst; 1000 Hz - frequent and 4000 Hz - rare; and verbal (/ba/ - frequent; /ga/, /da/, and /di/ - rare. RESULTS: Considering the component N2 for tone burst, the lowest latency found was 217.45 ms for the BA/DI stimulus; the highest latency found was 256.5 ms. For the P3 component, the shortest latency with tone burst stimuli was 298.7 with BA/GA stimuli, the highest, was 340 ms. For the P3 amplitude, there was no statistically significant difference among the different stimuli. For latencies of components P1, N1, P2, N2, P3, there were no statistical differences among them, regardless of the stimuli used. CONCLUSION: There was a difference in the latency of potentials N2 and P3 among the stimuli employed but no difference was observed for the P3 amplitude.

Clinical and evoked pain, personality traits, and emotional states: can familial confounding explain the associations?

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Strachan, Eric; Poeschla, Brian; Dansie, Elizabeth; Succop, Annemarie; Chopko, Laura; Afari, Niloofar

2015-01-01

Pain is a complex phenomenon influenced by context and person-specific factors. Affective dimensions of pain involve both enduring personality traits and fleeting emotional states. We examined how personality traits and emotional states are linked with clinical and evoked pain in a twin sample. 99 female twin pairs were evaluated for clinical and evoked pain using the McGill Pain Questionnaire (MPQ) and dolorimetry, and completed the 120-item International Personality Item Pool (IPIP), the Positive and Negative Affect Scale (PANAS), and ratings of stress and mood. Using a co-twin control design we examined a) the relationship of personality traits and emotional states with clinical and evoked pain and b) whether genetics and common environment (i.e. familial factors) may account for the associations. Neuroticism was associated with the sensory component of the MPQ; this relationship was not confounded by familial factors. None of the emotional state measures was associated with the MPQ. PANAS negative affect was associated with lower evoked pressure pain threshold and tolerance; these associations were confounded by familial factors. There were no associations between IPIP traits and evoked pain. A relationship exists between neuroticism and clinical pain that is not confounded by familial factors. There is no similar relationship between negative emotional states and clinical pain. In contrast, the relationship between negative emotional states and evoked pain is strong while the relationship with enduring personality traits is weak. The relationship between negative emotional states and evoked pain appears to be non-causal and due to familial factors. Copyright © 2014 Elsevier Inc. All rights reserved.

Methodology for self-report of rest pain (or spontaneous pain) vs evoked pain in chronic neuropathic conditions: a prospective observational pilot study

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He, David; Grant, Brian; Holden, Ronald R.; Gilron, Ian

2017-01-01

Abstract. Introduction:. The distinction between pain at rest and pain evoked by touch or movement has important clinical implications and may be associated with different mechanisms. However, current methods of clinical pain assessment pay little attention to directly distinguishing between these contrasting components of symptom burden. Objectives:. We developed the 10-item “Functional Impact of Neuropathic Evoked and Spontaneous Symptom Evaluation” questionnaire designed to distinguish ...

Psychophysical examination in patients with post-mastectomy pain

DEFF Research Database (Denmark)

Gottrup, Hanne; Andersen, Jørn; Arendt-Nielsen, Lars

2000-01-01

and contralateral sides in 15 women with spontaneous pain and sensory abnormalities and 11 pain-free women. Testing included the VAS score of spontaneous pain, detection and pain threshold to thermal and mechanical stimuli, temporal summation to repetitive heat and pinprick stimuli, and assessment of skin blood...... to side difference was seen in pressure pain threshold in the pain-free group. Evoked pain intensity to repetitive stimuli at 0.2 and 2.0 Hz was significantly higher on the operated side in pain patients compared to the control area while no such difference was seen in pain-free patients. Cutaneous blood...

Modulation of Itch by Conditioning Itch and Pain Stimulation in Healthy Humans.

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Andersen, Hjalte H; van Laarhoven, Antoinette I M; Elberling, Jesper; Arendt-Nielsen, Lars

2017-12-01

Little is known about endogenous descending control of itch. In chronic pain, descending pain inhibition is reduced as signified by lowered conditioned pain modulation. There are indications that patients with chronic itch may also exhibit reduced endogenous descending inhibition of itch and pain. This study aimed to investigate whether and the extent to which itch can be modulated by conditioning itch and pain stimuli. Twenty-six healthy volunteers participated. The study consisted of 5 conditions designed to systematically assess endogenous modulation of itch or pain: 1) itch-induced modulation of contralateral itch, 2) pain-induced modulation of contralateral itch, 3) pain-induced modulation of ipsilateral itch, 4) pain-induced modulation of contralateral pain, and 5) itch-induced modulation of contralateral pain. Conditioning stimuli were cold pressor-induced pain and histamine-evoked itch, whereas the test stimuli were electrical stimulation paradigms designed to evoke itch or pain. Pain was significantly reduced (conditioned pain modulation-effect) by the conditioning pain stimulus (P modulation-effect) by contra- as well as ipsilateral applied conditioning pain (both P modulation of itch as well as pain in humans. Future studies addressing potential aberrations in pain-evoked descending modulation of itch in chronic itch patients are warranted. Copyright © 2017 American Pain Society. Published by Elsevier Inc. All rights reserved.

Measures of spontaneous and movement-evoked pain are associated with disability in patients with whiplash injuries.

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Mankovsky-Arnold, Tsipora; Wideman, Timothy H; Larivière, Christian; Sullivan, Michael J L

2014-09-01

This study examined the degree to which measures of spontaneous and movement-evoked pain accounted for shared or unique variance in functional disability associated with whiplash injury. The study also addressed the role of fear of movement as a mediator or moderator of the relation between different indices of pain and functional disability. Measures of spontaneous pain, single-point movement-evoked pain, repetition-induced summation of activity-related pain (RISP), and fear of movement and disability were obtained on a sample of 142 individuals who had sustained whiplash injuries. Participants' pain ratings, provided after lifting a weighted canister, were used as the index of single-point movement-evoked pain. RISP was computed as the increase in pain reported by participants over successive lifts of 18 weighted canisters. Measures of functional disability included physical lift tolerance and self-reported disability. Hierarchical regression analyses revealed that measures of single-point movement-evoked pain and RISP accounted for significant unique variance in self-reported disability, beyond the variance accounted for by the measure of spontaneous pain. Only RISP accounted for significant unique variance in lift tolerance. The results suggest that measures of movement-evoked pain represent a disability-relevant dimension of pain that is not captured by measures of spontaneous pain. The clinical and conceptual implications of the findings are discussed. This study examined the degree to which measures of spontaneous and movement-evoked pain accounted for shared or unique variance in functional disability associated with whiplash injury. The findings suggest that approaches to the clinical evaluation of pain would benefit from the inclusion of measures of movement-evoked pain. Copyright © 2014 American Pain Society. Published by Elsevier Inc. All rights reserved.

Intramuscular temperature modulates glutamate-evoked masseter muscle pain intensity in humans.

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Sato, Hitoshi; Castrillon, Eduardo E; Cairns, Brian E; Bendixen, Karina H; Wang, Kelun; Nakagawa, Taneaki; Wajima, Koichi; Svensson, Peter

2015-01-01

To determine whether glutamate-evoked jaw muscle pain is altered by the temperature of the solution injected. Sixteen healthy volunteers participated and received injections of hot (48°C), neutral (36°C), or cold (3°C) solutions (0.5 mL) of glutamate or isotonic saline into the masseter muscle. Pain intensity was assessed with an electronic visual analog scale (eVAS). Numeric rating scale (NRS) scores of unpleasantness and temperature perception, pain-drawing areas, and pressure pain thresholds (PPTs) were also measured. Participants filled out the McGill Pain Questionnaire (MPQ). Two-way or three-way repeated measures ANOVA were used for data analyses. Injection of hot glutamate and cold glutamate solutions significantly increased and decreased, respectively, the peak pain intensity compared with injection of neutral glutamate solution. The duration of glutamate-evoked pain was significantly longer when hot glutamate was injected than when cold glutamate was injected. No significant effect of temperature on pain intensity was observed when isotonic saline was injected. No effect of solution temperature was detected on unpleasantness, heat perception, cold perception, area of pain drawings, or PPTs. There was a significantly greater use of the "numb" term in the MPQ to describe the injection of cold solutions compared to the injection of both neutral and hot solutions. Glutamate-evoked jaw muscle pain was significantly altered by the temperature of the injection solution. Although temperature perception in the jaw muscle is poor, pain intensity is increased when the muscle tissue temperature is elevated.

Pupil responses and pain ratings to heat stimuli: Reliability and effects of expectations and a conditioning pain stimulus.

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Eisenach, James C; Curry, Regina; Aschenbrenner, Carol A; Coghill, Robert C; Houle, Timothy T

2017-03-01

The locus coeruleus (LC) signals salience to sensory stimuli and these responses can modulate the experience of pain stimuli. The pupil dilation response (PDR) to noxious stimuli is thought to be a surrogate for LC responses, but PDR response to Peltier-controlled noxious heat stimuli, the most commonly used method in experimental pain research, has not been described. Healthy volunteers were presented with randomly presented heat stimuli of 5 sec duration and provided pain intensity ratings to each stimulus. Pupillometry was performed and a method developed to quantify the PDR relevant to these stimuli. The stimulus response, reliability, and effect of commonly used manipulations on pain experience were explored. A method of artifact removal and adjusting for lag from stimulus initiation to PDR response was developed, resulting in a close correlation between pain intensity rating and PDR across a large range of heat stimuli. A reliable assessment of PDR within an individual was achieved with fewer presentations as heat stimulus intensity increased. The correlation between pain rating and PDR was disrupted when cognitive load is increased by manipulating expectations or presenting a second pain stimulus. The PDR began later after skin heating than electrical stimuli and this is the first examination of the PDR using standard nociceptive testing and manipulations of expectations and competing noxious stimulation. A method is described applying PDR to standard heat nociceptive testing, demonstrating stimulus response, reliability, and disruption by cognitive manipulation. Copyright © 2017 Elsevier B.V. All rights reserved.

Increased Evoked Potentials and Behavioral Indices in Response to Pain Among Individuals with Intellectual Disability.

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Benromano, Tali; Pick, Chaim G; Granovsky, Yelena; Defrin, Ruth

2017-09-01

Previous studies on the sensitivity and reactivity to pain of individuals with intellectual disability (ID) are inconsistent. The inconsistency may result from the reliance on self-reports and facial expressions of pain that are subject to internal and external biases. The aim was therefore to evaluate the reactivity to pain of individuals with ID by recording pain-evoked potentials (EPs), here for the first time, and testing their association with behavioral pain indices. Forty-one healthy adults, 16 with mild-moderate ID and 25 controls. Subjects received series of phasic heat stimuli and rated their pain on self-report scales. Changes in facial expressions and in pain EPs were recorded and analyzed offline. Pain self-reports, facial expressions, and the N2P2 amplitudes of the EPs exhibited stimulus-response relationship with stimulation intensity in both groups. The facial expressions and N2P2 amplitudes of individuals with ID were increased and N2P2 latency prolonged compared with controls. N2P2 amplitudes correlated with self-reports only in controls. Individuals with ID are hypersensitive/reactive to pain, a finding bearing clinical implications. Although pain EPs may reflect a somewhat different aspect of pain than the behavioral indices do, there is evidence to support their use to record pain in noncommunicative individuals, pending further validation. © 2017 American Academy of Pain Medicine. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com

Modulation of itch by conditioning itch and pain stimulation in healthy humans

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Andersen, Hjalte Holm; van Laarhoven, Antoinette I. M.; Elberling, Jesper

2017-01-01

Little is known about endogenous descending control of itch. In chronic pain, descending pain inhibition is reduced as signified by lowered conditioned pain modulation (CPM). There are indications that patients with chronic itch may also exhibit reduced endogenous descending inhibition of itch......-evoked itch, while the test stimuli were electrical stimulation paradigms designed to evoke itch or pain. Pain was significantly reduced (CPM-effect) by the conditioning pain stimulus (p

Differences in cortical coding of heat evoked pain beyond the perceived intensity: an fMRI and EEG study.

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Haefeli, Jenny; Freund, Patrick; Kramer, John L K; Blum, Julia; Luechinger, Roger; Curt, Armin

2014-04-01

Imaging studies have identified a wide network of brain areas activated by nociceptive stimuli and revealed differences in somatotopic representation of highly distinct stimulation sites (foot vs. hand) in the primary (S1) and secondary (S2) somatosensory cortices. Somatotopic organization between adjacent dermatomes and differences in cortical coding of similarly perceived nociceptive stimulation are less well studied. Here, cortical processing following contact heat nociceptive stimulation of cervical (C4, C6, and C8) and trunk (T10) dermatomes were recorded in 20 healthy subjects using functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). Stimulation of T10 compared with the C6 and C8 revealed significant higher response intensity in the left S1 (contralateral) and the right S2 (ipsilateral) even when the perceived pain was equal between stimulation sites. Accordingly, contact heat evoked potentials following stimulation of T10 showed significantly higher N2P2 amplitudes compared to C6 and C8. Adjacent dermatomes did not reveal a distinct somatotopical representation. Within the assessed cervical and trunk dermatomes, nociceptive cortical processing to heat differs significantly in magnitude even when controlling for pain perception. This study provides evidence that controlling for pain perception is not sufficient to compare directly the magnitude of cortical processing [blood oxygen level dependence (BOLD) response and amplitude of evoked potentials] between body sites. Copyright © 2013 Wiley Periodicals, Inc.

Neuronal responses to tactile stimuli and tactile sensations evoked by microstimulation in the human thalamic principal somatic sensory nucleus (ventral caudal).

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Schmid, Anne-Christine; Chien, Jui-Hong; Greenspan, Joel D; Garonzik, Ira; Weiss, Nirit; Ohara, Shinji; Lenz, Frederick Arthur

2016-06-01

The normal organization and plasticity of the cutaneous core of the thalamic principal somatosensory nucleus (ventral caudal, Vc) have been studied by single-neuron recordings and microstimulation in patients undergoing awake stereotactic operations for essential tremor (ET) without apparent somatic sensory abnormality and in patients with dystonia or chronic pain secondary to major nervous system injury. In patients with ET, most Vc neurons responded to one of the four stimuli, each of which optimally activates one mechanoreceptor type. Sensations evoked by microstimulation were similar to those evoked by the optimal stimulus only among rapidly adapting neurons. In patients with ET, Vc was highly segmented somatotopically, and vibration, movement, pressure, and sharp sensations were usually evoked by microstimulation at separate sites in Vc. In patients with conditions including spinal cord transection, amputation, or dystonia, RFs were mismatched with projected fields more commonly than in patients with ET. The representation of the border of the anesthetic area (e.g., stump) or of the dystonic limb was much larger than that of the same part of the body in patients with ET. This review describes the organization and reorganization of human Vc neuronal activity in nervous system injury and dystonia and then proposes basic mechanisms. Copyright © 2016 the American Physiological Society.

Stress-evoked opioid release inhibits pain in major depressive disorder.

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Frew, Ashley K; Drummond, Peter D

2008-10-15

To determine whether stress-evoked release of endogenous opioids might account for hypoalgesia in major depressive disorder (MDD), the mu-opioid antagonist naltrexone (50mg) or placebo was administered double-blind to 24 participants with MDD and to 31 non-depressed controls. Eighty minutes later participants completed a painful foot cold pressor test and, after a 5-min interval, began a 25-min arithmetic task interspersed with painful electric shocks. Ten minutes later participants completed a second cold pressor test. Negative affect was greater in participants with MDD than in non-depressed controls throughout the experiment, and increased significantly in both groups during mental arithmetic. Before the math task, naltrexone unmasked direct linear relationships between severity of depression, negative affect while resting quietly, and cold-induced pain in participants with MDD. In contrast, facilitatory effects of naltrexone on cold- and shock-induced pain were greatest in controls with the lowest depression scores. Naltrexone strengthened the relationship between negative affect and shock-induced pain during the math task, particularly in the depressed group, and heightened anxiety in both groups toward the end of the task. Thus, mu-opioid activity apparently masked a positive association between negative affect and pain in the most distressed participants. These findings suggest that psychological distress inhibits pain via stress-evoked release of opioid peptides in severe cases of MDD. In addition, tonic endogenous opioid neurotransmission could inhibit depressive symptoms and pain in people with low depression scores.

Physical activity, pain responses to heat stimuli, and conditioned pain modulation in postmenopausal women.

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Adrian, Amanda L; O'Connor, Patrick J; Ward-Ritacco, Christie L; Evans, Ellen M

2015-08-01

Postmenopausal women (PMW) are at high risk for disabling pain and physical inactivity. This study sought to enhance the understanding of relationships between physical activity (PA) and pain among PMW using heat pain sensitivity test and conditioned pain modulation test. We hypothesized that, compared with active women, (i) inactive women would report higher pain intensity and pain unpleasantness ratings; (ii) inactive women in disabling pain would report higher pain intensity and pain unpleasantness at high, but not low, stimulus intensities; and (iii) inactive women would have less modulation. Sixty-eight PMW rated the pain intensity and pain unpleasantness of hot stimuli presented to the thenar eminence of the hand. A subset of 31 women rated the pain intensity of a test stimulus (noxious heat) and a conditioning stimulus (cold water) as part of the conditioned pain modulation task. PA was assessed objectively with accelerometry. Mixed-model analysis of variance (2 × 4 × 2; PA × Temperature × Pain Status) showed that inactive women in disabling pain rated pain unpleasantness higher than active women in disabling pain (F3,192 = 3.526, ∂η = 0.052, P = 0.016). Significantly lower pain unpleasantness ratings were found at the highest stimulus intensity (49°C) only for active women in disabling pain compared with inactive women in disabling pain (t11 = 2.523, P = 0.028). The other hypotheses were not supported. PA is associated with a reduced sensitivity to the unpleasantness of painful high-intensity heat stimuli among women in disabling pain.

EEG and EMG responses to emotion-evoking stimuli processed without conscious awareness.

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Wexler, B E; Warrenburg, S; Schwartz, G E; Janer, L D

1992-12-01

Dichotic stimulus pairs were constructed with one word that was emotionally neutral and another that evoked either negative or positive feelings. Temporal and spectral overlap between the members of each pair was so great that the two words fused into a single auditory percept. Subjects were consciously aware of hearing only one word from most pairs; sometimes the emotion-evoking word was heard consciously, other times the neutral word was heard consciously. Subjects were instructed to let their thoughts wander in response to the word they heard, during which time EEG alpha activity over left and right frontal regions, and muscle activity (EMG) in the corrugator ("frowning") and zygomatic ("smiling") regions were recorded. Both EEG and EMG provided evidence of emotion-specific responses to stimuli that were processed without conscious awareness. Moreover both suggested relatively greater right hemisphere activity with unconscious rather than conscious processing.

The influence of pain-related expectations on intensity perception of non-painful somatosensory stimuli.

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Zaman, Jonas; Wiech, Katja; Claes, Nathalie; Van Oudenhove, Lukas; Van Diest, Ilse; Vlaeyen, Johan W S

2018-04-03

The extent to which pain-related expectations, known to affect pain perception, also affect perception of non-painful sensations remains unclear, as well as the potential role of unpredictability in this context. In a proprioceptive fear conditioning paradigm, various arm extension movements were associated with predictable and unpredictable electrocutaneous pain or its absence. During a subsequent test phase non-painful electrocutaneous stimuli with a high or low intensity were presented during movement execution. We used hierarchical drift diffusion modeling to examine the influence of expecting pain on the perceptual decision-making process underlying intensity perception of non-painful sensations. In the first experiment (n=36), the pain stimulus was never presented during the test phase after conditioning. In the second experiment (n=39), partial reinforcement was adopted to prevent extinction of pain expectations. In both experiments, movements that were associated with (un)predictable pain led to higher pain-expectancy, self-reported fear, unpleasantness and arousal, as compared to movements that were never paired with pain (effect sizes ηp ranging from .119 - .557; all p-values threat of the pain US remained present - we found that the expectation of pain affected decision-making. Compared to the no pain condition, an a priori decision-making bias towards the high intensity decision threshold was found with the strongest bias during unpredictable pain (effect sizes ηp ranging from .469 - .504; all p-values affects inferential processes for subsequent painful but also for non-painful bodily stimuli, with unpredictability moderating these effects, and only when the threat of pain remains present due to partial reinforcement.

Do Tonic Itch and Pain Stimuli Draw Attention towards Their Location?

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Antoinette I. M. van Laarhoven

2017-01-01

Full Text Available Background. Although itch and pain are distinct experiences, both are unpleasant, may demand attention, and interfere with daily activities. Research investigating the role of attention in tonic itch and pain stimuli, particularly whether attention is drawn to the stimulus location, is scarce. Methods. In the somatosensory attention task, fifty-three healthy participants were exposed to 35-second electrical itch or pain stimuli on either the left or right wrist. Participants responded as quickly as possible to visual targets appearing at the stimulated location (ipsilateral trials or the arm without stimulation (contralateral trials. During control blocks, participants performed the visual task without stimulation. Attention allocation at the itch and pain location is inferred when responses are faster ipsilaterally than contralaterally. Results. Results did not indicate that attention was directed towards or away from the itch and pain location. Notwithstanding, participants were slower during itch and pain than during control blocks. Conclusions. In contrast with our hypotheses, no indications were found for spatial attention allocation towards the somatosensory stimuli. This may relate to dynamic shifts in attention over the time course of the tonic sensations. Our secondary finding that itch and pain interfere with task performance is in-line with attention theories of bodily perception.

Functional deficits in peripheral nerve mitochondria in rats with paclitaxel- and oxaliplatin-evoked painful peripheral neuropathy

OpenAIRE

Zheng, Huaien; Xiao, Wen Hua; Bennett, Gary J.

2011-01-01

Cancer chemotherapeutics like paclitaxel and oxaliplatin produce a dose-limiting chronic sensory peripheral neuropathy that is often accompanied by neuropathic pain. The cause of the neuropathy and pain is unknown. In animal models, paclitaxel-evoked and oxaliplatin-evoked painful peripheral neuropathies are accompanied by an increase in the incidence of swollen and vacuolated mitochondria in peripheral nerve axons. It has been proposed that mitochondrial swelling and vacuolation are indicati...

Exposure to Virtual Social Stimuli Modulates Subjective Pain Reports

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Jacob M Vigil

2014-01-01

Full Text Available BACKGROUND: Contextual factors, including the gender of researchers, influence experimental and patient pain reports. It is currently not known how social stimuli influence pain percepts, nor which types of sensory modalities of communication, such as auditory, visual or olfactory cues associated with person perception and gender processing, produce these effects.

Biomarkers of neuropathic pain in skin nerve degeneration neuropathy: contact heat-evoked potentials as a physiological signature.

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Wu, Shao-Wei; Wang, Yi-Chia; Hsieh, Paul-Chen; Tseng, Ming-Tsung; Chiang, Ming-Chang; Chu, Chih-Pang; Feng, Fang-Ping; Lin, Yea-Huey; Hsieh, Sung-Tsang; Chao, Chi-Chao

2017-03-01

Contact heat-evoked potentials (CHEPs) have become an established method of assessing small-fiber sensory nerves; however, their potential as a physiological signature of neuropathic pain symptoms has not been fully explored. To investigate the diagnostic efficacy in examining small-fiber sensory nerve degeneration, the relationship with skin innervations, and clinical correlates with sensory symptoms, we recruited 188 patients (115 men) with length-dependent sensory symptoms and reduced intraepidermal nerve fiber (IENF) density at the distal leg to perform CHEP, quantitative sensory testing, and nerve conduction study. Fifty-seven age- and sex-matched controls were enrolled for comparison of CHEP and skin innervation. Among patients with neuropathy, 144 patients had neuropathic pain and 64 cases had evoked pain. Compared with quantitative sensory testing and nerve conduction study parameters, CHEP amplitudes showed the highest sensitivity for diagnosing small-fiber sensory nerve degeneration and exhibited the strongest correlation with IENF density in multiple linear regression. Contact heat-evoked potential amplitudes were strongly correlated with the degree of skin innervation in both patients with neuropathy and controls, and the slope of the regression line between CHEP amplitude and IENF density was higher in patients with neuropathy than in controls. Patients with evoked pain had higher CHEP amplitude than those without evoked pain, independent of IENF density. Receiver operating characteristic analysis showed that CHEP had better performance in diagnosing small-fiber sensory nerve degeneration than thermal thresholds. Furthermore, CHEPs showed superior classification accuracy with respect to evoked pain. In conclusion, CHEP is a sensitive tool to evaluate pathophysiology of small-fiber sensory nerve and serves as a physiological signature of neuropathic pain symptoms.

Thermoreceptive innervation of human glabrous and hairy skin: a contact heat evoked potential analysis.

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Granovsky, Yelena; Matre, Dagfinn; Sokolik, Alexander; Lorenz, Jürgen; Casey, Kenneth L

2005-06-01

The human palm has a lower heat detection threshold and a higher heat pain threshold than hairy skin. Neurophysiological studies of monkeys suggest that glabrous skin has fewer low threshold heat nociceptors (AMH type 2) than hairy skin. Accordingly, we used a temperature-controlled contact heat evoked potential (CHEP) stimulator to excite selectively heat receptors with C fibers or Adelta-innervated AMH type 2 receptors in humans. On the dorsal hand, 51 degrees C stimulation produced painful pinprick sensations and 41 degrees C stimuli evoked warmth. On the glabrous thenar, 41 degrees C stimulation produced mild warmth and 51 degrees C evoked strong but painless heat sensations. We used CHEP responses to estimate the conduction velocities (CV) of peripheral fibers mediating these sensations. On hairy skin, 41 degrees C stimuli evoked an ultra-late potential (mean, SD; N wave latency: 455 (118) ms) mediated by C fibers (CV by regression analysis: 1.28 m/s, N=15) whereas 51 degrees C stimuli evoked a late potential (N latency: 267 (33) ms) mediated by Adelta afferents (CV by within-subject analysis: 12.9 m/s, N=6). In contrast, thenar responses to 41 and 51 degrees C were mediated by C fibers (average N wave latencies 485 (100) and 433 (73) ms, respectively; CVs 0.95-1.35 m/s by regression analysis, N=15; average CV=1.7 (0.41) m/s calculated from distal glabrous and proximal hairy skin stimulation, N=6). The exploratory range of the human and monkey palm is enhanced by the abundance of low threshold, C-innervated heat receptors and the paucity of low threshold AMH type 2 heat nociceptors.

Musical Brains. A study of evoked musical sensations without external auditory stimuli. Preliminary report of three cases

International Nuclear Information System (INIS)

Goycoolea, Marcos V; Mena, Ismael; Neubauer, Sonia G; Levy, Raquel G.; Fernandez Grez, Margarita; Berger, Claudia G

2006-01-01

Background: There are individuals, usually musicians, who are seemingly able to evoke musical sensations without external auditory stimuli. However, to date there is no available evidence to determine if it is feasible to have musical sensations without using external sensory receptors nor if there is a biological substrate to these sensations. Study design: Two single photon emission computerized tomography (SPECT) evaluations with [99mTc]-HMPAO were conducted in each of three female musicians. One was done under basal conditions (without evoking) and the other one while evoking these sensations. Results: In the NeuroSPECT studies of the musicians who were tested while evoking a musical composition, there was a significant increase in perfusion above the normal mean in the right and left hemispheres in Brodmann's areas 9 and 8 (frontal executive area) and in areas 40 on the left side (auditory center). However, under basal conditions there was no hyper perfusion of areas 9, 8, 39 and 40. In one case hyper perfusion was found under basal conditions in area 45, however it was less than when she was evoking. Conclusions: These findings are suggestive of a biological substrate to the process of evoking musical sensations (au)

Effects of insomnia disorder and knee osteoarthritis on resting and pain-evoked inflammatory markers.

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Quartana, Phillip J; Finan, Patrick H; Page, Gayle G; Smith, Michael T

2015-07-01

Osteoarthritis is the most prevalent arthritic condition. Systemic inflammatory cytokines appear to have an important role in the onset and maintenance of the disease. Sleep disturbances are prevalent in osteoarthritis and associated with alterations in systemic inflammatory cytokines, suggesting a common pathophysiology across these conditions. A comparative investigation of the effects of insomnia disorder and osteoarthritis on pain-evoked cytokine responses has yet to be undertaken. We examined the influence of symptomatic knee osteoarthritis and insomnia disorder on resting C-reactive protein (CRP), interleukin (IL)-6, and IL-10 levels, and pain-evoked IL-6 and IL-10 responses. Participants were N=117 older adults (mean age=59.7years; 61.8% women) rigorously evaluated for knee osteoarthritis and insomnia disorder using established diagnostic guidelines. Results revealed no association of osteoarthritis or insomnia disorder with CRP. Resting IL-6 was greater in osteoarthritis participants versus those without osteoarthritis, although this association was largely attributable to BMI. IL-10 was highest among participants with osteoarthritis or insomnia disorder. Growth curve modeling revealed that participants with insomnia disorder had greater pain-evoked IL-6 responses than participants without insomnia disorder or osteoarthritis. These findings highlight the utility of laboratory pain testing methods for understanding individual differences in inflammatory cytokines. Moreover, our findings provide evidence for amplified pain-evoked pro-inflammatory cytokine reactivity among older adults with clinically diagnosed insomnia disorder, even after controlling for individual differences in BMI and age. Additional research will be required determine whether an amplified pain-related cytokine response contributes to OA, and possibly other age-related disease, associated with insomnia disorder. Published by Elsevier Inc.

Effects of gabapentin on experimental somatic pain and temporal summation

DEFF Research Database (Denmark)

Arendt-Nielsen, Lars; Frøkjaer, Jens Brøndum; Staahl, Camilla

2007-01-01

at 2 Hz); (2) stimulus-response function relating pain intensity scores (visual analog scale, VAS) to increasing current intensities for electrical skin and muscle stimuli (single and repeated, determined at baseline); and (3) the pain intensity (VAS) and pain areas after intramuscular injection......, was to examine the effect of a single dose of 1200 mg gabapentin on multi-modal experimental cutaneous and muscle pain models. METHODS: The following pain models were applied: (1) pain thresholds to single and repeated cutaneous and intramuscular electrical stimulation (temporal summation to 5 stimuli delivered...... reduced the area under the pain intensity curve to hypertonic saline injections in the muscle (P = .02); and (3) significantly reduced the area of pain evoked by hypertonic saline (P = .03). CONCLUSIONS: Gabapentin reduces temporal summation of skin stimuli at pain threshold intensities; this may have...

Assessment of pain sensitivity in patients with deep bite and sex- and age-matched controls

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Sonnesen, Ane Liselotte; Svensson, Peter

2011-01-01

AIMS: To compare pain sensitivity between deep bite patients and a sex- and age-matched control group with normal occlusion. METHODS: Pain sensitivity was assessed by injections of the excitatory amino acid glutamate into the masseter and brachioradialis muscles. Intensity of glutamate-evoked pai...... of gender-related differences in somatosensory sensitivity and for the first time indicate that subjects with deep bite may be more sensitive to glutamate-evoked pain and thermal stimuli.......AIMS: To compare pain sensitivity between deep bite patients and a sex- and age-matched control group with normal occlusion. METHODS: Pain sensitivity was assessed by injections of the excitatory amino acid glutamate into the masseter and brachioradialis muscles. Intensity of glutamate-evoked pain...

Normative data for Aδ contact heat evoked potentials in adult population: a multicenter study.

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Granovsky, Yelena; Anand, Praveen; Nakae, Aya; Nascimento, Osvaldo; Smith, Benn; Sprecher, Elliot; Valls-Solé, Josep

2016-05-01

There has been a significant increase over recent years in the use of contact heat evoked potentials (CHEPs) for the evaluation of small nerve fiber function. Measuring CHEP amplitude and latency has clinical utility for the diagnosis and assessment of conditions with neuropathic pain. This international multicenter study aimed to provide reference values for CHEPs to stimuli at 5 commonly examined body sites. Contact heat evoked potentials were recorded from 226 subjects (114 females), distributed per age decade between 20 and 79 years. Temperature stimuli were delivered by a thermode (32°C-51°C at a rate of 70°C/s). In phase I of the study, we investigated side-to-side differences and reported the maximum normal side-to-side difference in Aδ CHEP peak latency and amplitude for leg, forearm, and face. In phase II, we obtained normative data for 3 CHEP parameters (N2P2 amplitude, N2 latency, and P2 latency), stratified for gender and age decades from face, upper and lower limbs, and overlying cervical and lumbar spine. In general, larger CHEP amplitudes were associated with higher evoked pain scores. Females had CHEPs of larger amplitude and shorter latency than males. This substantive data set of normative values will facilitate the clinical use of CHEPs as a rapid, noninvasive, and objective technique for the assessment of patients presenting with neuropathic pain.

Peripheral and central components of habituation of heat pain perception and evoked potentials in humans.

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Greffrath, Wolfgang; Baumgärtner, Ulf; Treede, Rolf-Detlef

2007-12-05

For the neurophysiological examination of nociceptive pathways, contact-heat evoked potentials (contact-heat EPs) are elicited by repetitive brief noxious heat stimuli. Suppression of heat responses in primary nociceptive neurons during repetitive stimulation has been shown in animal models in vivo and in vitro. We now investigated whether heat pain and contact-heat EPs in humans display equivalent signs of habituation. Heat pain and EPs were elicited in 16 volunteers with a contact thermode (30 degrees Cs(-1)). Heat pulses at three intensities (pain threshold, moderate noxious and maximum available) were applied to the right forearm either by moving the thermode after each pulse to variable locations or when fixed to one location (inter-stimulus intervals 8-10s). Contact-heat EPs consisted of an early negativity in temporal leads (N1), followed by a biphasic response at the vertex (N2-P2). Pain ratings and contact-heat EPs (N1 and N2-P2 components) displayed significant temperature dependence. N2-P2 correlated positively with ratings. With stimulation at variable locations, both measures slowly decreased with time constants tau of 2 min (ratings) and 12 min (EPs). With stimulation at a fixed location, habituation was much faster for both, ratings (tau=10s) and EPs (tau=33 s). As a consequence, both measures were significantly reduced (pheat pain perception and contact-heat EPs display signs of rapid habituation when stimulation is restricted to a fixed location and thus, reflect fatigue of peripheral nociceptive neurons. Habituation within the central nervous system is slower and less pronounced.

Differential effect of intravenous S-ketamine and fentanyl on atypical odontalgia and capsaicin-evoked pain

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Baad-Hansen, Lene; Juhl, Gitte Irene; Jensen, Troels Staehelin

2007-01-01

temporal summation were compared between groups and sides. Both drugs failed to produce an analgesic effect on spontaneous AO pain, but fentanyl effectively reduced capsaicin-evoked pain. AO patients showed increased sensitivity to capsaicin and heat pain, but no significant differences in cold......Atypical odontalgia (AO) is an intraoral pain condition of currently unknown mechanisms. In 10 AO patients and 10 matched healthy controls, we examined the effect of intravenous infusion of an N-methyl-D-aspartate (NMDA) receptor antagonist S-ketamine and a mu-opioid agonist fentanyl on spontaneous...... AO pain and on an acute intraoral nociceptive input evoked by topical application of capsaicin. The drugs were administered in a randomized, placebo-controlled, cross-over manner. Furthermore, measures of intraoral sensitivity to mechanical and thermal quantitative sensory testing (QST) including...

[Intraoperative pain stimuli change somatosensory evoked potentials, but not auditory evoked potentials during isoflurane/nitrous oxide anesthesia].

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Rundshagen, I; Kochs, E; Bischoff, P; Schulte am Esch, J

1997-10-01

Evoked potentials are used for intraoperative monitoring to assess changes of cerebral function. This prospective randomised study assesses the influence of surgical stimulation on midlatency components of somatosensory (SEPs) and auditory evoked potentials (AEPs) in anaesthetised patients. After approval of the Ethics Committee and written informed consent 36 orthopaedic patients (34 +/- 15 y, 73 +/- 14 kg. 1.71 +/- 0.07 m, ASA I-II) were randomly included in the study. Anaesthesia was induced with 1.5 micrograms/kg fentanyl, 0.3 mg/kg etomidate and 0.1 mg/kg vecuronium. The lungs were intubated and patients normoventilated in steady state anaesthesia with isoflurane (end-tidal 0.6%) and 66% nitrous oxide. 18 patients (group 1) were assigned to the SEP group: median nerve stimulation, recording at Erb, C 6 and the contralateral somatosensory cortex (N20, P25, N35) vs Fz. AEPs were recorded in group 2 (n = 18): binaural stimulation, recording at Cz versus linked mastoid (V, Na, Pa, Nb). Recordings were performed during 30 min before the start of surgery (baseline: BL), at skin incision (SURG1) and at the preparation of the periost (SURG2). Heart rate, mean arterial blood pressure, oxygen saturation, endtidal pCO2 and isoflurane (PetISO) concentrations were registered simultaneously. Data were analysed by one-way analysis of variance. Post hoc comparison were made by Mann-Whitney U-Wilcoxon Rank Sum Test with p beats/min) to SURG2 (76 +/- 12 beats/min). Increases of amplitudes of midlatency SEP amplitudes indicate increased nociceptive signal transmission which is not blunted by isoflurane-nitrous oxide anaesthesia. In contrast, unchanged AEPs indicate adequate levels of the hypnotic components of anaesthesia.

Heightened eating drive and visual food stimuli attenuate central nociceptive processing.

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Wright, Hazel; Li, Xiaoyun; Fallon, Nicholas B; Giesbrecht, Timo; Thomas, Anna; Harrold, Joanne A; Halford, Jason C G; Stancak, Andrej

2015-03-01

Hunger and pain are basic drives that compete for a behavioral response when experienced together. To investigate the cortical processes underlying hunger-pain interactions, we manipulated participants' hunger and presented photographs of appetizing food or inedible objects in combination with painful laser stimuli. Fourteen healthy participants completed two EEG sessions: one after an overnight fast, the other following a large breakfast. Spatio-temporal patterns of cortical activation underlying the hunger-pain competition were explored with 128-channel EEG recordings and source dipole analysis of laser-evoked potentials (LEPs). We found that initial pain ratings were temporarily reduced when participants were hungry compared with fed. Source activity in parahippocampal gyrus was weaker when participants were hungry, and activations of operculo-insular cortex, anterior cingulate cortex, parahippocampal gyrus, and cerebellum were smaller in the context of appetitive food photographs than in that of inedible object photographs. Cortical processing of noxious stimuli in pain-related brain structures is reduced and pain temporarily attenuated when people are hungry or passively viewing food photographs, suggesting a possible interaction between the opposing motivational forces of the eating drive and pain. Copyright © 2015 the American Physiological Society.

Sex Differences in How Erotic and Painful Stimuli Impair Inhibitory Control

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Yu, Jiaxin; Hung, Daisy L.; Tseng, Philip; Tzeng, Ovid J. L.; Muggleton, Neil G.; Juan, Chi-Hung

2012-01-01

Witnessing emotional events such as arousal or pain may impair ongoing cognitive processes such as inhibitory control. We found that this may be true only half of the time. Erotic images and painful video clips were shown to men and women shortly before a stop signal task, which measures cognitive inhibitory control. These stimuli impaired…

Hyperalgesia and temporal summation of pain after heat injury in man

DEFF Research Database (Denmark)

Pedersen, J L; Andersen, O K; Arendt-Nielsen, L

1998-01-01

of pain in normal skin with summation of pain in skin with primary and secondary hyperalgesia evoked by a heat injury. A heat injury was produced on the crus of 12 volunteers with a 50 x 25 mm thermode (47 degrees C, 7 min). Measurements were made before, and 0, 1, 2, and 4 h after the heat injury......, in three areas: primary and secondary mechanical hyperalgesia induced by the heat injury, and in a mirror image of the injury on the opposite leg. Temporal summation of pain was induced by repeated electrical stimuli (five stimuli at 2 Hz) and assessed by visual analog scale (VAS). Primary hyperalgesia...... was evaluated by von Frey hairs and electrical stimuli, and the areas of secondary hyperalgesia with a rigid von Frey hair (314 mN). Significant primary (P heat injury. The pain threshold to single electrical stimuli was reduced...

Effects of temperature on heat pain adaptation and habituation in men and women.

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Hashmi, Javeria A; Davis, Karen D

2010-12-01

We recently reported that women report greater pain adaptation and habituation to moderately painful heat stimuli than men (Hashmi and Davis [16]); but slightly lower temperatures were needed to evoke moderate pain in the women. Hardy et al (1962) and LaMotte (1979) suggested that pain adaptation is most prominent at modest noxious heat temperatures and may occur at temperatures close to pain thresholds. Thus, as a follow-up to our previous study, we examined the role of absolute temperature in pain adaptation and habituation in men and women and assessed whether pain threshold impacts these findings. We hypothesised that pain adaptation and habituation would be more prominent at low and moderate temperatures, and that higher temperatures would induce pain adaptation and habituation in women but not in men. We further hypothesized that pain adaptation would not be correlated with pain thresholds. To test this, we obtained continuous ratings of pain evoked by 44.5-47.5°C stimuli applied to the dorsal foot of men and women. Each run consisted of three 30s stimuli at the same temperature with a 60s inter-stimulus interval. Women showed within-stimulus adaptation of total pain at all temperatures, but men showed significant adaptation to temperatures less than 47°C. There were no sex differences in inter-stimulus habituation and both men and women reported habituation to temperatures less than 46°C. Pain thresholds did not correlate with pain adaptation. These data highlight the temperature-sensitivity and sex differences of pain adaptation and habituation. Copyright © 2010 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

CORTICAL RESPONSES TO SALIENT NOCICEPTIVE AND NOT NOCICEPTIVE STIMULI IN VEGETATIVE AND MINIMAL CONSCIOUS STATE

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MARINA eDE TOMMASO

2015-01-01

Full Text Available Aims Questions regarding perception of pain in non-communicating patients and the management of pain continue to raise controversy both at a clinical and ethical level. The aim of this study was to examine the cortical response to salient multimodal visual, acoustic, somatosensory electric non nociceptive and nociceptive laser stimuli and their correlation with the clinical evaluation.Methods: Five Vegetative State (VS, 4 Minimally Conscious State (MCS patients and 11 age- and sex-matched controls were examined. Evoked responses were obtained by 64 scalp electrodes, while delivering auditory, visual, non-noxious electrical and noxious laser stimulation, which were randomly presented every 10 sec. Laser, somatosensory, auditory and visual evoked responses were identified as a negative-positive (N2-P2 vertex complex in the 500 msec post-stimulus time. We used Nociception Coma Scale-Revised (NCS-R and Coma Recovery Scale (CRS-R for clinical evaluation of pain perception and consciousness impairment.Results: The laser evoked potentials (LEPs were recognizable in all cases. Only one MCS patient showed a reliable cortical response to all the employed stimulus modalities. One VS patient did not present cortical responses to any other stimulus modality. In the remaining participants, auditory, visual and electrical related potentials were inconstantly present. Significant N2 and P2 latency prolongation occurred in both VS and MCS patients. The presence of a reliable cortical response to auditory, visual and electric stimuli was able to correctly classify VS and MCS patients with 90% accuracy. Laser P2 and N2 amplitudes were not correlated with the CRS-R and NCS-R scores, while auditory and electric related potentials amplitude were associated with the motor response to pain and consciousness recovery. Discussion: pain arousal may be a primary function also in vegetative state patients while the relevance of other stimulus modalities may indicate the

Medication overuse reinstates conditioned pain modulation in women with migraine.

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Guy, Nathalie; Voisin, Daniel; Mulliez, Aurélien; Clavelou, Pierre; Dallel, Radhouane

2018-05-01

Background This study investigated the effects of medication overuse and withdrawal on modulation of pain processing in women with migraine. Temporal summation of laser-evoked thermal pain was used to measure the effects of conditioned pain modulation. Methods 36 female participants (12 healthy volunteers, 12 with episodic migraine and 12 with medication overuse headache) were included in a two session protocol. Medication overuse headache subjects were also tested three weeks after medication overuse headache withdrawal. Mechanical and laser-evoked thermal pain thresholds were measured on the back of the non-dominant hand where, later, temporal summation of laser-evoked thermal pain to repetitive thermal stimuli was elicited for 30 min, at an intensity producing moderate pain. Between the 10 th and 20 th minutes, the contralateral foot was immersed into a water bath at a not painful (30℃) or painfully cold (8℃; conditioned pain modulation) temperature. Results Episodic migraine, medication overuse headache and medication overuse headache withdrawal were associated with an increase in extracephalic temporal summation of laser-evoked thermal pain as compared to healthy volunteer subjects, while there was no alteration of laser-evoked thermal and mechanical extracephalic pain thresholds in these subjects. Conditioned pain modulation was highly efficient in temporal summation of laser-evoked thermal pain in healthy volunteer subjects, with a solid post-effect (reduction of pain). Conditioned pain modulation was still present, but reduced, in episodic migraine. By contrast, conditioned pain modulation was normal in medication overuse headache and strongly reduced in medication overuse headache withdrawal. Furthermore, in medication overuse headache withdrawal, the post-effect was no longer a decrease, but a facilitation of pain. Conclusions These data show that a decrease in conditioned pain modulation does not underlie medication overuse headache in women. On

Early life vincristine exposure evokes mechanical pain hypersensitivity in the developing rat.

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Schappacher, Katie A; Styczynski, Lauren; Baccei, Mark L

2017-09-01

Vincristine (VNC) is commonly used to treat pediatric cancers, including the most prevalent childhood malignancy, acute lymphoblastic leukemia. Although clinical evidence suggests that VNC causes peripheral neuropathy in children, the degree to which pediatric chemotherapeutic regimens influence pain sensitivity throughout life remains unclear, in part because of the lack of an established animal model of chemotherapy-induced neuropathic pain during early life. Therefore, this study investigated the effects of VNC exposure between postnatal days (P) 11 and 21 on mechanical and thermal pain sensitivity in the developing rat. Low doses of VNC (15 or 30 μg/kg) failed to alter nociceptive withdrawal reflexes at any age examined compared with vehicle-injected littermate controls. Meanwhile, high dose VNC (60 μg/kg) evoked mechanical hypersensitivity in both sexes beginning at P26 that persisted until adulthood and included both static and dynamic mechanical allodynia. Hind paw withdrawal latencies to noxious heat and cold were unaffected by high doses of VNC, suggesting a selective effect of neonatal VNC on mechanical pain sensitivity. Gross and fine motor function appeared normal after VNC treatment, although a small decrease in weight gain was observed. The VNC regimen also produced a significant decrease in intraepidermal nerve fiber density in the hind paw skin by P33. Overall, the present results demonstrate that high-dose administration of VNC during the early postnatal period selectively evokes a mechanical hypersensitivity that is slow to emerge during adolescence, providing further evidence that aberrant sensory input during early life can have prolonged consequences for pain processing.

Prey capture behaviour evoked by simple visual stimuli in larval zebrafish

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Isaac Henry Bianco

2011-12-01

Full Text Available Understanding how the nervous system recognises salient stimuli in the environ- ment and selects and executes the appropriate behavioural responses is a fundamen- tal question in systems neuroscience. To facilitate the neuroethological study of visually-guided behaviour in larval zebrafish, we developed virtual reality assays in which precisely controlled visual cues can be presented to larvae whilst their behaviour is automatically monitored using machine-vision algorithms. Freely swimming larvae responded to moving stimuli in a size-dependent manner: they directed multiple low amplitude orienting turns (∼ 20◦ towards small moving spots (1◦ but reacted to larger spots (10◦ with high-amplitude aversive turns (∼ 60◦. The tracking of small spots led us to examine how larvae respond to prey during hunting routines. By analysing movie sequences of larvae hunting parame- cia, we discovered that all prey capture routines commence with eye convergence and larvae maintain their eyes in a highly converged position for the duration of the prey-tracking and capture swim phases. We adapted our virtual reality assay to deliver artificial visual cues to partially restrained larvae and found that small moving spots evoked convergent eye movements and J-turns of the tail, which are defining features of natural hunting. We propose that eye convergence represents the engagement of a predatory mode of behaviour in larval fish and serves to increase the region of binocular visual space to enable stereoscopic targeting of prey.

Evoked related potentials correlates of empathy for pain from adolescence through adulthood

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Nathalie eMella

2012-11-01

Full Text Available Affective and cognitive empathy are traditionally differentiated, the affective component being concerned with resonating with another’s emotional state, whereas the cognitive component reflects regulation of the resulting distress and understanding of another’s mental states (see Decety and Jackson, 2004 for a review. Adolescence is a critical period for the development of cognitive control processes necessary to regulate affective processes: it is only in young adulthood that these control processes achieve maturity (Steinberg, 2005. Thus, one should expect adolescents to show greater automatic empathy than young adults. The present study aimed at exploring the neural correlates of affective (automatic and cognitive empathy for pain from adolescence to young adulthood. With this aim, Event Related Potentials (ERPs were recorded in 32 participants (aged 11 to 39 in a task designed to dissociate these components. ERPs results showed an early automatic frontocentral response to pain (that was not modulated by task demand and a late parietal response to painful stimuli modulated by attention to pain cues. Adolescents exhibited earlier automatic responses to painful situations than young adults did and showed greater activity in the late cognitive component even when viewing neutral stimuli. Results are discussed in the context of the development of regulatory abilities during adolescence.

Premature infants display increased noxious-evoked neuronal activity in the brain compared to healthy age-matched term-born infants.

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Slater, Rebeccah; Fabrizi, Lorenzo; Worley, Alan; Meek, Judith; Boyd, Stewart; Fitzgerald, Maria

2010-08-15

This study demonstrates that infants who are born prematurely and who have experienced at least 40days of intensive or special care have increased brain neuronal responses to noxious stimuli compared to healthy newborns at the same postmenstrual age. We have measured evoked potentials generated by noxious clinically-essential heel lances in infants born at term (8 infants; born 37-40weeks) and in infants born prematurely (7 infants; born 24-32weeks) who had reached the same postmenstrual age (mean age at time of heel lance 39.2+/-1.2weeks). These noxious-evoked potentials are clearly distinguishable from shorter latency potentials evoked by non-noxious tactile sensory stimulation. While the shorter latency touch potentials are not dependent on the age of the infant at birth, the noxious-evoked potentials are significantly larger in prematurely-born infants. This enhancement is not associated with specific brain lesions but reflects a functional change in pain processing in the brain that is likely to underlie previously reported changes in pain sensitivity in older ex-preterm children. Our ability to quantify and measure experience-dependent changes in infant cortical pain processing will allow us to develop a more rational approach to pain management in neonatal intensive care. Copyright (c) 2010 Elsevier Inc. All rights reserved.

Blocking proteinase-activated receptor 2 alleviated neuropathic pain evoked by spinal cord injury.

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Wei, H; Wei, Y; Tian, F; Niu, T; Yi, G

2016-01-01

Spinal cord injury (SCI) is an extremely serious type of physical trauma observed in clinics. Especially, neuropathic pain resulting from SCI has a lasting and significant impact on most aspects of daily life. Thus, a better understanding of the molecular pathways responsible for the cause of neuropathic pain observed in SCI is important to develop effectively therapeutic agents and treatment strategies. Proteinase-activated receptors (PARs) are a family member of G-protein-coupled receptors and are activated by a proteolytic mechanism. One of its subtypes PAR2 has been reported to be engaged in mechanical and thermal hyperalgesia. Thus, in this study we specifically examined the underlying mechanisms responsible for SCI evoked-neuropathic pain in a rat model. Overall, we demonstrated that SCI increases PAR2 and its downstream pathways TRPV1 and TRPA1 expression in the superficial dorsal horn of the spinal cord. Also, we showed that blocking spinal PAR2 by intrathecal injection of FSLLRY-NH2 significantly inhibits neuropathic pain responses induced by mechanical and thermal stimulation whereas FSLLRY-NH2 decreases the protein expression of TRPV1 and TRPA1 as well as the levels of substance P and calcitonin gene-related peptide. Results of this study have important implications, i.e. targeting one or more of these signaling molecules involved in activation of PAR2 and TRPV1/TRPA1 evoked by SCI may present new opportunities for treatment and management of neuropathic pain often observed in patients with SCI.

Pain relief by touch: a quantitative approach.

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Mancini, Flavia; Nash, Thomas; Iannetti, Gian Domenico; Haggard, Patrick

2014-03-01

Pain relief by touch has been studied for decades in pain neuroscience. Human perceptual studies revealed analgesic effects of segmental tactile stimulation, as compared to extrasegmental touch. However, the spatial organisation of touch-pain interactions within a single human dermatome has not been investigated yet. In 2 experiments we tested whether, how, and where within a dermatome touch modulates the perception of laser-evoked pain. We measured pain perception using intensity ratings, qualitative descriptors, and signal detection measures of sensitivity and response bias. Touch concurrent with laser pulses produced a significant analgesia, and reduced the sensitivity in detecting the energy of laser stimulation, implying a functional loss of information within the ascending Aδ pathway. Touch also produced a bias to judge laser stimuli as less painful. This bias decreased linearly when the distance between the laser and tactile stimuli increased. Thus, our study provides evidence for a spatial organisation of intrasegmental touch-pain interactions. Copyright © 2013 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Functional MRI brain imaging studies using the Contact Heat Evoked Potential Stimulator (CHEPS in a human volunteer topical capsaicin pain model

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Shenoy R

2011-10-01

Full Text Available Ravikiran Shenoy1, Katherine Roberts1, Anastasia Papadaki2, Donald McRobbie2, Maarten Timmers3, Theo Meert3, Praveen Anand11Peripheral Neuropathy Unit, Hammersmith Hospital, Imperial College London; 2Imaging Sciences Department, Charing Cross Hospital, London, United Kingdom; 3Johnson and Johnson Pharmaceutical Research and Development, Beerse, BelgiumAbstract: Acute application of topical capsaicin produces spontaneous burning and stinging pain similar to that seen in some neuropathic states, with local hyperalgesia. Use of capsaicin applied topically or injected intradermally has been described as a model for neuropathic pain, with patterns of activation in brain regions assessed using functional magnetic resonance imaging (fMRI and positron emission tomography. The Contact Heat Evoked Potential Stimulator (CHEPS is a noninvasive clinically practical method of stimulating cutaneous A-delta nociceptors. In this study, topical capsaicin (1% was applied to the left volar forearm for 15 minutes of twelve adult healthy human volunteers. fMRI scans and a visual analog pain score were recorded during CHEPS stimulation precapsaicin and postcapsaicin application. Following capsaicin application there was a significant increase in visual analog scale (mean ± standard error of the mean; precapsaicin 26.4 ± 5.3; postcapsaicin 48.9 ± 6.0; P < 0.0001. fMRI demonstrated an overall increase in areas of activation, with a significant increase in the contralateral insular signal (mean ± standard error of the mean; precapsaicin 0.434 ± 0.03; postcapsaicin 0.561 ± 0.07; P = 0.047. The authors of this paper recently published a study in which CHEPS-evoked A-delta cerebral potential amplitudes were found to be decreased postcapsaicin application. In patients with neuropathic pain, evoked pain and fMRI brain responses are typically increased, while A-delta evoked potential amplitudes are decreased. The protocol of recording fMRI following CHEPS stimulation

Synaptic responses evoked by tactile stimuli in Purkinje cells in mouse cerebellar cortex Crus II in vivo.

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Chun-Ping Chu

Full Text Available Sensory stimuli evoke responses in cerebellar Purkinje cells (PCs via the mossy fiber-granule cell pathway. However, the properties of synaptic responses evoked by tactile stimulation in cerebellar PCs are unknown. The present study investigated the synaptic responses of PCs in response to an air-puff stimulation on the ipsilateral whisker pad in urethane-anesthetized mice.Thirty-three PCs were recorded from 48 urethane-anesthetized adult (6-8-week-old HA/ICR mice by somatic or dendritic patch-clamp recording and pharmacological methods. Tactile stimulation to the ipsilateral whisker pad was delivered by an air-puff through a 12-gauge stainless steel tube connected with a pressurized injection system. Under current-clamp conditions (I = 0, the air-puff stimulation evoked strong inhibitory postsynaptic potentials (IPSPs in the somata of PCs. Application of SR95531, a specific GABA(A receptor antagonist, blocked IPSPs and revealed stimulation-evoked simple spike firing. Under voltage-clamp conditions, tactile stimulation evoked a sequence of transient inward currents followed by strong outward currents in the somata and dendrites in PCs. Application of SR95531 blocked outward currents and revealed excitatory postsynaptic currents (EPSCs in somata and a temporal summation of parallel fiber EPSCs in PC dendrites. We also demonstrated that PCs respond to both the onset and offset of the air-puff stimulation.These findings indicated that tactile stimulation induced asynchronous parallel fiber excitatory inputs onto the dendrites of PCs, and failed to evoke strong EPSCs and spike firing in PCs, but induced the rapid activation of strong GABA(A receptor-mediated inhibitory postsynaptic currents in the somata and dendrites of PCs in the cerebellar cortex Crus II in urethane-anesthetized mice.

Cortical responses to salient nociceptive and not nociceptive stimuli in vegetative and minimal conscious state

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de Tommaso, Marina; Navarro, Jorge; Lanzillotti, Crocifissa; Ricci, Katia; Buonocunto, Francesca; Livrea, Paolo; Lancioni, Giulio E.

2015-01-01

Aims: Questions regarding perception of pain in non-communicating patients and the management of pain continue to raise controversy both at a clinical and ethical level. The aim of this study was to examine the cortical response to salient visual, acoustic, somatosensory electric non-nociceptive and nociceptive laser stimuli and their correlation with the clinical evaluation. Methods: Five Vegetative State (VS), 4 Minimally Conscious State (MCS) patients and 11 age- and sex-matched controls were examined. Evoked responses were obtained by 64 scalp electrodes, while delivering auditory, visual, non-noxious electrical and noxious laser stimulation, which were randomly presented every 10 s. Laser, somatosensory, auditory and visual evoked responses were identified as a negative-positive (N2-P2) vertex complex in the 500 ms post-stimulus time. We used Nociception Coma Scale-Revised (NCS-R) and Coma Recovery Scale (CRS-R) for clinical evaluation of pain perception and consciousness impairment. Results: The laser evoked potentials (LEPs) were recognizable in all cases. Only one MCS patient showed a reliable cortical response to all the employed stimulus modalities. One VS patient did not present cortical responses to any other stimulus modality. In the remaining participants, auditory, visual and electrical related potentials were inconstantly present. Significant N2 and P2 latency prolongation occurred in both VS and MCS patients. The presence of a reliable cortical response to auditory, visual and electric stimuli was able to correctly classify VS and MCS patients with 90% accuracy. Laser P2 and N2 amplitudes were not correlated with the CRS-R and NCS-R scores, while auditory and electric related potentials amplitude were associated with the motor response to pain and consciousness recovery. Discussion: pain arousal may be a primary function also in vegetative state patients while the relevance of other stimulus modalities may indicate the degree of cognitive and motor

Abnormal brain processing of pain in migraine without aura

DEFF Research Database (Denmark)

Buchgreitz, L.; Egsgaard, Line Lindhardt; Jensen, R.

2010-01-01

and somatosensory-evoked potentials were recorded with 128-channel EEG with and without concurrent induced tonic neck/shoulder muscle pain. At baseline, the calculated P300 dipole for single stimuli was localized in the cingulate cortex. In patients, but not in controls, the dipole changed position from baseline...

Effect profile of paracetamol, Δ9-THC and promethazine using an evoked pain test battery in healthy subjects.

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van Amerongen, G; Siebenga, P; de Kam, M L; Hay, J L; Groeneveld, G J

2018-04-10

A battery of evoked pain tasks (PainCart) was developed to investigate the pharmacodynamic properties of novel analgesics in early-phase clinical research. As part of its clinical validation, compounds with different pharmacological mechanisms of actions are investigated. The aim was to investigate the analgesic effects of classic and nonclassic analgesics compared to a sedating negative control in a randomized placebo-controlled crossover study in 24 healthy volunteers using the PainCart. The PainCart consisted of pain tasks eliciting electrical, pressure, heat, cold and inflammatory pain. Subjective scales for cognitive functioning and psychotomimetic effects were included. Subjects were administered each of the following oral treatments: paracetamol (1000 mg), Δ9-THC (10 mg), promethazine (50 mg) or matching placebo. Pharmacodynamic measurements were performed at baseline and repeated up to 10 h postdose. Paracetamol did not show a significant reduction in pain sensation or subjective cognitive functioning compared to placebo. Promethazine induced a statistically significant reduction in PTT for cold pressor and pressure stimulation. Furthermore, reduced subjective alertness was observed. Δ9-THC showed a statistically significant decrease in PTT for electrical and pressure stimulation. Δ9-THC also demonstrated subjective effects, including changes in alertness and calmness, as well as feeling high and psychotomimetic effects. This study found a decreased pain tolerance due to Δ9-THC and promethazine, or lack thereof, using an evoked pain task battery. Pain thresholds following paracetamol administration remained unchanged, which may be due to insufficient statistical power. We showed that pain thresholds determined using this pain test battery are not driven by sedation. The multimodal battery of evoked pain tasks utilized in this study may play an important role in early-phase clinical drug development. This battery of pain tasks is not sensitive to the

Enhanced pain and autonomic responses to ambiguous visual stimuli in chronic Complex Regional Pain Syndrome (CRPS) type I.

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Cohen, H E; Hall, J; Harris, N; McCabe, C S; Blake, D R; Jänig, W

2012-02-01

Cortical reorganisation of sensory, motor and autonomic systems can lead to dysfunctional central integrative control. This may contribute to signs and symptoms of Complex Regional Pain Syndrome (CRPS), including pain. It has been hypothesised that central neuroplastic changes may cause afferent sensory feedback conflicts and produce pain. We investigated autonomic responses produced by ambiguous visual stimuli (AVS) in CRPS, and their relationship to pain. Thirty CRPS patients with upper limb involvement and 30 age and sex matched healthy controls had sympathetic autonomic function assessed using laser Doppler flowmetry of the finger pulp at baseline and while viewing a control figure or AVS. Compared to controls, there were diminished vasoconstrictor responses and a significant difference in the ratio of response between affected and unaffected limbs (symmetry ratio) to a deep breath and viewing AVS. While viewing visual stimuli, 33.5% of patients had asymmetric vasomotor responses and all healthy controls had a homologous symmetric pattern of response. Nineteen (61%) CRPS patients had enhanced pain within seconds of viewing the AVS. All the asymmetric vasomotor responses were in this group, and were not predictable from baseline autonomic function. Ten patients had accompanying dystonic reactions in their affected limb: 50% were in the asymmetric sub-group. In conclusion, there is a group of CRPS patients that demonstrate abnormal pain networks interacting with central somatomotor and autonomic integrational pathways. © 2011 European Federation of International Association for the Study of Pain Chapters.

Modulation of laser-evoked potentials and pain perception by transcutaneous electrical nerve stimulation (TENS): a placebo-controlled study in healthy volunteers.

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Vassal, François; Créac'h, C; Convers, Ph; Laurent, B; Garcia-Larrea, L; Peyron, R

2013-09-01

To investigate the effects of transcutaneous electrical nerve stimulation (TENS) on brain nociceptive responses (laser-evoked potentials, LEPs) and pain perception. Twenty healthy subjects were included. Nociceptive CO(2)-laser pulses were sequentially delivered to the dorsum of both feet. The amplitude of LEPs and nociceptive thresholds were collected in three consecutive conditions: T1: "sham" TENS (2 Hz/low-intensity) positioned heterotopically, over the left thigh; T2: "active" TENS (120 Hz/low-intensity) applied homotopically, over the left common peroneal nerve; and T3: "sham" TENS (replication of condition T1). Compared with "sham" TENS, "active" TENS significantly decreased the LEPs amplitude. This effect was observed exclusively when "active" TENS was applied ipsilaterally to the painful stimulus. Nociceptive thresholds increased with sessions in both limbs, but the increase observed during the "active" condition of TENS (T2) exceeded significantly that observed during the condition T3 only on the foot ipsilateral to TENS. Compared with a credible placebo TENS, high-frequency TENS induced a significant attenuation of both the acute pain and LEPs induced by noxious stimuli applied on the same dermatome. This modulation of subjective and objective concomitants of pain processing reflects a real neurophysiological TENS-related effect on nociceptive transmission. Copyright © 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Characterization of music-evoked autobiographical memories.

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Janata, Petr; Tomic, Stefan T; Rakowski, Sonja K

2007-11-01

Despite music's prominence in Western society and its importance to individuals in their daily lives, very little is known about the memories and emotions that are often evoked when hearing a piece of music from one's past. We examined the content of music-evoked autobiographical memories (MEAMs) using a novel approach for selecting stimuli from a large corpus of popular music, in both laboratory and online settings. A set of questionnaires probed the cognitive and affective properties of the evoked memories. On average, 30% of the song presentations evoked autobiographical memories, and the majority of songs also evoked various emotions, primarily positive, that were felt strongly. The third most common emotion was nostalgia. Analyses of written memory reports found both general and specific levels of autobiographical knowledge to be represented, and several social and situational contexts for memory formation were common across many memories. The findings indicate that excerpts of popular music serve as potent stimuli for studying the structure of autobiographical memories.

A crossmodal crossover: opposite effects of visual and auditory perceptual load on steady-state evoked potentials to irrelevant visual stimuli.

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Jacoby, Oscar; Hall, Sarah E; Mattingley, Jason B

2012-07-16

Mechanisms of attention are required to prioritise goal-relevant sensory events under conditions of stimulus competition. According to the perceptual load model of attention, the extent to which task-irrelevant inputs are processed is determined by the relative demands of discriminating the target: the more perceptually demanding the target task, the less unattended stimuli will be processed. Although much evidence supports the perceptual load model for competing stimuli within a single sensory modality, the effects of perceptual load in one modality on distractor processing in another is less clear. Here we used steady-state evoked potentials (SSEPs) to measure neural responses to irrelevant visual checkerboard stimuli while participants performed either a visual or auditory task that varied in perceptual load. Consistent with perceptual load theory, increasing visual task load suppressed SSEPs to the ignored visual checkerboards. In contrast, increasing auditory task load enhanced SSEPs to the ignored visual checkerboards. This enhanced neural response to irrelevant visual stimuli under auditory load suggests that exhausting capacity within one modality selectively compromises inhibitory processes required for filtering stimuli in another. Copyright © 2012 Elsevier Inc. All rights reserved.

Thoughts of death modulate psychophysical and cortical responses to threatening stimuli.

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Elia Valentini

Full Text Available Existential social psychology studies show that awareness of one's eventual death profoundly influences human cognition and behaviour by inducing defensive reactions against end-of-life related anxiety. Much less is known about the impact of reminders of mortality on brain activity. Therefore we explored whether reminders of mortality influence subjective ratings of intensity and threat of auditory and painful thermal stimuli and the associated electroencephalographic activity. Moreover, we explored whether personality and demographics modulate psychophysical and neural changes related to mortality salience (MS. Following MS induction, a specific increase in ratings of intensity and threat was found for both nociceptive and auditory stimuli. While MS did not have any specific effect on nociceptive and auditory evoked potentials, larger amplitude of theta oscillatory activity related to thermal nociceptive activity was found after thoughts of death were induced. MS thus exerted a top-down modulation on theta electroencephalographic oscillatory amplitude, specifically for brain activity triggered by painful thermal stimuli. This effect was higher in participants reporting higher threat perception, suggesting that inducing a death-related mind-set may have an influence on body-defence related somatosensory representations.

Skin-transmitted pathogens and the heebie jeebies: evidence for a subclass of disgust stimuli that evoke a qualitatively unique emotional response.

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Blake, Khandis R; Yih, Jennifer; Zhao, Kun; Sung, Billy; Harmon-Jones, Cindy

2017-09-01

Skin-transmitted pathogens have threatened humans since ancient times. We investigated whether skin-transmitted pathogens were a subclass of disgust stimuli that evoked an emotional response that was related to, but distinct from, disgust and fear. We labelled this response "the heebie jeebies". In Study 1, coding of 76 participants' experiences of disgust, fear, and the heebie jeebies showed that the heebie jeebies was elicited by unique stimuli which produced skin-crawling sensations and an urge to protect the skin. In Experiment 2,350 participants' responses to skin-transmitted pathogen, fear-inducing, and disgust-inducing vignettes showed that the vignettes elicited sensations and urges which loaded onto heebie jeebies, fear, and disgust factors, respectively. Experiment 3 largely replicated findings from Experiment 2 using video stimuli (178 participants). Results are consistent with the notion that skin-transmitted pathogens are a subclass of disgust stimuli which motivate behaviours that are functionally consistent with disgust yet qualitatively distinct.

Potencial evocado miogênico vestibular a baixas frequências de estimulação Vestibular evoked myogenic potentials using low frequency stimuli

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Aline Cabral de Oliveira

2011-12-01

Full Text Available Os potenciais evocados miogênicos vestibulares são reflexos vestíbulo-cervicais, decorrentes da estimulação do sáculo com sons de forte intensidade. São necessários parâmetros de normalidade para indivíduos jovens normais, utilizando-se estímulos a baixas frequências, as quais configuram a região de maior sensibilidade desse órgão sensorial. OBJETIVO: Realizar normatização do potencial evocado miogênico vestibular para baixas frequências de estimulação. MATERIAL E MÉTODO: Captou-se o potencial evocado miogênico vestibular em 160 orelhas, no músculo esternocleidomastoideo, de forma ipsilateral, por meio da promediação de 200 tone bursts, frequência de 250 Hz, intensidade de 95 dB NAn. FORMA DE ESTUDO: Estudo de coorte contemporânea com corte transversal. RESULTADOS: Aplicando-se o teste T de Student ou o Teste de Mann-Whitney, não foi constatada diferença significativa para parâmetros do potencial evocado miogênico vestibular entre os gêneros, para p Vestibular evoked myogenic potentials are vestibulocervical reflexes resulting from sacculus stimulation with strong intensity sounds. Normality parameters are necessary for young normal individuals, using low frequency stimuli, which configure the most sensitive region of this sensory organ. AIM: To establish vestibular evoked myogenic potential standards for low frequency stimulation. MATERIAL AND METHOD: Vestibular evoked myogenic potential was captured from 160 ears, in the ipsilateral sternocleidomastoid muscle, using 200 averaged tone-burst stimuli, at 250 Hz, with an intensity of 95 dB NAn. CASE STUDY: Clinical observational cross-sectional. RESULTS: Neither the student's t-test nor the Mann-Whitney test showed a significant difference in latency or vestibular evoked myogenic potential amplitudes, for p <; 0.05. Irrespective of gender, we found latencies of p13-n23 and p13-n23 interpeaks of 13.84 ms (± 1.41, 23.81 ms (±1.99 and 10.62 ms (± 6.56, respectively

Chronic Widespread Back Pain is Distinct From Chronic Local Back Pain: Evidence From Quantitative Sensory Testing, Pain Drawings, and Psychometrics.

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Gerhardt, Andreas; Eich, Wolfgang; Janke, Susanne; Leisner, Sabine; Treede, Rolf-Detlef; Tesarz, Jonas

2016-07-01

Whether chronic localized pain (CLP) and chronic widespread pain (CWP) have different mechanisms or to what extent they overlap in their pathophysiology is controversial. The study compared quantitative sensory testing profiles of nonspecific chronic back pain patients with CLP (n=48) and CWP (n=29) with and fibromyalgia syndrome (FMS) patients (n=90) and pain-free controls (n = 40). The quantitative sensory testing protocol of the "German-Research-Network-on-Neuropathic-Pain" was used to measure evoked pain on the painful area in the lower back and the pain-free hand (thermal and mechanical detection and pain thresholds, vibration threshold, pain sensitivity to sharp and blunt mechanical stimuli). Ongoing pain and psychometrics were captured with pain drawings and questionnaires. CLP patients did not differ from pain-free controls, except for lower pressure pain threshold (PPT) on the back. CWP and FMS patients showed lower heat pain threshold and higher wind-up ratio on the back and lower heat pain threshold and cold pain threshold on the hand. FMS showed lower PPT on back and hand, and higher comorbidity of anxiety and depression and more functional impairment than all other groups. Even after long duration CLP presents with a local hypersensitivity for PPT, suggesting a somatotopically specific sensitization of nociceptive processing. However, CWP patients show widespread ongoing pain and hyperalgesia for different stimuli that is generalized in space, suggesting the involvement of descending control systems, as also suggested for FMS patients. Because mechanisms in nonspecific chronic back pain with CLP and CWP differ, these patients should be distinguished in future research and allocated to different treatments.

Some Words Hurt More Than Others: Semantic Activation of Pain Concepts in Memory and Subsequent Experiences of Pain.

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Swannell, Ellen R; Brown, Christopher A; Jones, Anthony K P; Brown, Richard J

2016-03-01

Theory suggests that as activation of pain concepts in memory increases, so too does subsequent pain perception. Previously, researchers have found that activating pain concepts in memory increases pain perception of subsequent painful stimuli, relative to neutral information. However, they have not attempted to quantify the nature of the association between information studied and ensuing pain perception. We subliminally presented words that had either a low or high degree of association to the word 'pain,' although this was only partially successful and some words were consciously perceived. Participants then received randomized laser heat stimuli, delivered at 1 of 3 intensity levels (low, moderate, high), and we measured the effect of this on behavioral and electrophysiological measures of pain. Participants (N = 27) rated moderate- and high-intensity laser stimuli as more painful after viewing high relative to low associates of pain; these effects remained present when we controlled for measures of mood, anxiety, and physical symptom reporting. Similar effects were observed physiologically, with higher stimulus negativity preceding after high relative to low associates and greater amplitudes for the N2 component of the laser-evoked potential after presentation of high associates in the moderate and high laser intensity conditions. These data support activation-based models of the effects of memory on pain perception. Consistent with current theories of memory and pain, we found that high, relative to low activation of pain concepts in memory increased psychological and physiological responses to laser-induced pain. The effect remained regardless of whether participants showed conscious awareness of activation. Theoretical and clinical implications are discussed. Copyright © 2016 American Pain Society. Published by Elsevier Inc. All rights reserved.

Proprioceptive evoked gamma oscillations

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Arnfred, S.M.; Hansen, Lars Kai; Parnas, J.

2007-01-01

A proprioceptive stimulus consisting of a weight change of a handheld load has recently been shown to elicit an evoked potential. Previously, somatosensory gamma oscillations have only been evoked by electrical stimuli. We conjectured that a natural proprioceptive stimulus also would be able...... to evoke gamma oscillations. EEG was recorded using 64 channels in 14 healthy subjects. In each of three runs a stimulus of 100 g load increment in each hand was presented in 120 trials. Data were wavelet transformed and runs collapsed. Inter-trial phase coherence (ITPC) was computed as the best measure...

Pharmacologic attenuation of cross-modal sensory augmentation within the chronic pain insula

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Harte, Steven E.; Ichesco, Eric; Hampson, Johnson P.; Peltier, Scott J.; Schmidt-Wilcke, Tobias; Clauw, Daniel J.; Harris, Richard E.

2016-01-01

Abstract Pain can be elicited through all mammalian sensory pathways yet cross-modal sensory integration, and its relationship to clinical pain, is largely unexplored. Centralized chronic pain conditions such as fibromyalgia are often associated with symptoms of multisensory hypersensitivity. In this study, female patients with fibromyalgia demonstrated cross-modal hypersensitivity to visual and pressure stimuli compared with age- and sex-matched healthy controls. Functional magnetic resonance imaging revealed that insular activity evoked by an aversive level of visual stimulation was associated with the intensity of fibromyalgia pain. Moreover, attenuation of this insular activity by the analgesic pregabalin was accompanied by concomitant reductions in clinical pain. A multivariate classification method using support vector machines (SVM) applied to visual-evoked brain activity distinguished patients with fibromyalgia from healthy controls with 82% accuracy. A separate SVM classification of treatment effects on visual-evoked activity reliably identified when patients were administered pregabalin as compared with placebo. Both SVM analyses identified significant weights within the insular cortex during aversive visual stimulation. These data suggest that abnormal integration of multisensory and pain pathways within the insula may represent a pathophysiological mechanism in some chronic pain conditions and that insular response to aversive visual stimulation may have utility as a marker for analgesic drug development. PMID:27101425

Light evokes melanopsin-dependent vocalization and neural activation associated with aversive experience in neonatal mice.

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Anton Delwig

Full Text Available Melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs are the only functional photoreceptive cells in the eye of newborn mice. Through postnatal day 9, in the absence of functional rods and cones, these ipRGCs mediate a robust avoidance behavior to a light source, termed negative phototaxis. To determine whether this behavior is associated with an aversive experience in neonatal mice, we characterized light-induced vocalizations and patterns of neuronal activation in regions of the brain involved in the processing of aversive and painful stimuli. Light evoked distinct melanopsin-dependent ultrasonic vocalizations identical to those emitted under stressful conditions, such as isolation from the litter. In contrast, light did not evoke the broad-spectrum calls elicited by acute mechanical pain. Using markers of neuronal activation, we found that light induced the immediate-early gene product Fos in the posterior thalamus, a brain region associated with the enhancement of responses to mechanical stimulation of the dura by light, and thought to be the basis for migrainous photophobia. Additionally, light induced the phosphorylation of extracellular-related kinase (pERK in neurons of the central amygdala, an intracellular signal associated with the processing of the aversive aspects of pain. However, light did not activate Fos expression in the spinal trigeminal nucleus caudalis, the primary receptive field for painful stimulation to the head. We conclude that these light-evoked vocalizations and the distinct pattern of brain activation in neonatal mice are consistent with a melanopsin-dependent neural pathway involved in processing light as an aversive but not acutely painful stimulus.

A Basic Study on P300 Event-Related Potentials Evoked by Simultaneous Presentation of Visual and Auditory Stimuli for the Communication Interface

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Masami Hashimoto

2011-10-01

Full Text Available We have been engaged in the development of a brain-computer interface (BCI based on the cognitive P300 event-related potentials (ERPs evoked by simultaneous presentation of visual and auditory stimuli in order to assist with the communication in severe physical limitation persons. The purpose of the simultaneous presentation of these stimuli is to give the user more choices as commands. First, we extracted P300 ERPs by either visual oddball paradigm or auditory oddball paradigm. Then amplitude and latency of the P300 ERPs were measured. Second, visual and auditory stimuli were presented simultaneously, we measured the P300 ERPs varying the condition of combinations of these stimuli. In this report, we used 3 colors as visual stimuli and 3 types of MIDI sounds as auditory stimuli. Two types of simultaneous presentations were examined. The one was conducted with random combination. The other was called group stimulation, combining one color, such as red, and one MIDI sound, such as piano, in order to make a group; three groups were made. Each group was presented to users randomly. We evaluated the possibility of BCI using these stimuli from the amplitudes and the latencies of P300 ERPs.

Central representation of muscle pain and mechanical hyperesthesia in the orofacial region: a positron emission tomography study

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Kupers, Rron; Svensson, Peter; Jensen, Troels Staehlin

2004-01-01

Functional neuroimaging studies of the human brain have revealed a network of brain regions involved in the processing of nociceptive information. However, little is known of the cerebral processing of pain originating from muscles. The aim of this study was to investigate the cerebral activation...... pattern evoked by experimental jaw-muscle pain and its interference by simultaneous mechanical stimuli, which has been shown to evoke hyperesthesia. Ten healthy subjects participated in a PET study and jaw-muscle pain was induced by bolus injections of 5% hypertonic saline into the right masseter muscle....... Repeated von Frey hair stimulation (0.5 Hz) of the skin above the masseter muscle was used as the mechanical stimulus. Hypertonic saline injections caused strong muscle pain spreading to adjacent areas. von Frey stimulation was rated as non-painful but produced hyperesthesia during jaw-muscle pain. Jaw...

Mast cell deficiency attenuates acupuncture analgesia for mechanical pain using c-kit gene mutant rats.

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Cui, Xiang; Liu, Kun; Xu, Dandan; Zhang, Youyou; He, Xun; Liu, Hao; Gao, Xinyan; Zhu, Bing

2018-01-01

Acupuncture therapy plays a pivotal role in pain relief, and increasing evidence demonstrates that mast cells (MCs) may mediate acupuncture analgesia. The present study aims to investigate the role of MCs in acupuncture analgesia using c-kit gene mutant-induced MC-deficient rats. WsRC-Ws/Ws rats and their wild-type (WT) littermates (WsRC-+/+) were used. The number of MCs in skin of ST36 area was compared in two rats after immunofluorescence labeling. Mechanical withdrawal latency (MWL), mechanical withdrawal threshold (MWT), and thermal withdrawal latency (TWL) were measured on bilateral plantar for pain threshold evaluation before and after each stimulus. Acupuncture- and moxibustion-like stimuli (43°C, 46°C heat, 1 mA electroacupuncture [EA], 3 mA EA, and manual acupuncture [MA]) were applied randomly on different days. Fewer MCs were observed in the skin of ST36 in mutant rats compared to WT rats ( P 0.05). Bilateral MWL and MWT in WsRC-+/+ rats increased significantly after each stimulus compared to baseline ( P <0.01, P <0.001). In WsRC-Ws/Ws rats, only noxious stimuli could produce anti-nociceptive effects for mechanical pain (46°C, 3 mA EA, MA) ( P <0.01, P <0.001). Additionally, the net increases in MWL and MWT induced by most stimuli were greater in WT than in mutant rats ( P <0.05). For thermal nociception, either high- or low-intensity stimuli could significantly augment TWL in two rats ( P <0.001), and the net increases of TWL evoked by most stimuli were to the same extent in two genetic variants. MCs influence the basic mechanical but not thermal pain threshold. MCs participate in acupuncture analgesia in mechanical but not in thermal nociception, in that MC deficiency may attenuate the mechanical analgesia evoked by high-intensity stimuli and eliminate analgesia provoked by low-intensity stimuli.

Vestibular Evoked Myogenic Potential Produced by Bone-Conducted Stimuli: A Study on its Basics and Clinical Applications in Patients with Conductive and Sensorineural Hearing Loss and a Group with Vestibular Schawannoma.

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Mahdi, Parvane; Amali, Amin; Pourbakht, Akram; Karimi Yazdi, Alireza; Bassam, Ali

2013-06-01

Vestibular evoked myogenic potential (VEMP) has recently been broadly studied in vestibular disorders. As it is evoked by loud sound stimulation, even mild conductive hearing loss may affect VEMP results. Bone-conducted (BC) stimulus is an alternative stimulation for evoking this response. This study aims to assess the characteristics of BC-VEMP in different groups of patients. We performed a cross sectional analysis on 20 healthy volunteers with normal pure-tone audiometry as a control group; and on a group of patients consisted of 20 participants with conductive hearing loss, five with bilateral sensorineural hearing loss and four with vestibular schawannoma. AC and BC-VEMP were performed in all participants. In control group the VEMP responses to both kinds of stimuli had an acceptable morphology and consisted of p13 and n23 waves. Latency value of these main components in each type of stimulus was not significantly different (P>0.05). However, the mean amplitude was larger in BC modality than AC stimulation (P=0.025). In the group with conductive hearing loss, the VEMP response was absent in fifteen (46.87%) of the 32 ears using the AC method, whereas all (100%) displayed positive elicitability of VEMP by BC method. Normal VEMP responses in both stimuli were evoked in all patients with sensorineural hearing loss. In patients with unilateral vestibular schwannomas (VS), 2 (50.00%) had neither AC-VEMP nor BC-VEMP. Auditory stimuli delivered by bone conduction can evoke VEMP response. These responses are of vestibular origin and can be used in vestibular evaluation of patients with conductive hearing loss.

Effect of sympathetic activity on capsaicin-evoked pain, hyperalgesia, and vasodilatation.

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Baron, R; Wasner, G; Borgstedt, R; Hastedt, E; Schulte, H; Binder, A; Kopper, F; Rowbotham, M; Levine, J D; Fields, H L

1999-03-23

Painful nerve and tissue injuries can be exacerbated by activity in sympathetic neurons. The mechanisms of sympathetically maintained pain (SMP) are unclear. To determine the effect of cutaneous sympathetic activity on pain induced by primary afferent C-nociceptor sensitization with capsaicin in humans. In healthy volunteers capsaicin was applied topically (n = 12) or injected into the forearm skin (n = 10) to induce spontaneous pain, dynamic and punctate mechanical hyperalgesia, and antidromic (axon reflex) vasodilatation (flare). Intensity of pain and hyperalgesia, axon reflex vasodilatation (laser Doppler), and flare size and area of hyperalgesia (planimetry) were assessed. The local skin temperature at the application and measurement sites was kept constant at 35 degrees C. In each individual the analyses were performed during the presence of high and low sympathetic skin activity induced by whole-body cooling and warming with a thermal suit. By this method sympathetic vasoconstrictor activity is modulated in the widest range that can be achieved physiologically. The degree of vasoconstrictor discharge was monitored by measuring skin blood flow (laser Doppler) and temperature (infrared thermometry) at the index finger. The intensity and spatial distribution of capsaicin-evoked spontaneous pain and dynamic and punctate mechanical hyperalgesia were identical during the presence of high and low sympathetic discharge. Antidromic vasodilatation and flare size were significantly diminished when sympathetic vasoconstrictor neurons were excited. Cutaneous sympathetic vasoconstrictor activity does not influence spontaneous pain and mechanical hyperalgesia after capsaicin-induced C-nociceptor sensitization. When using physiologic stimulation of sympathetic activity, the capsaicin model is not useful for elucidating mechanisms of SMP. In neuropathic pain states with SMP, different mechanisms may be present.

Visually Evoked Spiking Evolves While Spontaneous Ongoing Dynamics Persist

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Huys, Raoul; Jirsa, Viktor K.; Darokhan, Ziauddin; Valentiniene, Sonata; Roland, Per E.

2016-01-01

Neurons in the primary visual cortex spontaneously spike even when there are no visual stimuli. It is unknown whether the spiking evoked by visual stimuli is just a modification of the spontaneous ongoing cortical spiking dynamics or whether the spontaneous spiking state disappears and is replaced by evoked spiking. This study of laminar recordings of spontaneous spiking and visually evoked spiking of neurons in the ferret primary visual cortex shows that the spiking dynamics does not change: the spontaneous spiking as well as evoked spiking is controlled by a stable and persisting fixed point attractor. Its existence guarantees that evoked spiking return to the spontaneous state. However, the spontaneous ongoing spiking state and the visual evoked spiking states are qualitatively different and are separated by a threshold (separatrix). The functional advantage of this organization is that it avoids the need for a system reorganization following visual stimulation, and impedes the transition of spontaneous spiking to evoked spiking and the propagation of spontaneous spiking from layer 4 to layers 2–3. PMID:26778982

Vestibular Evoked Myogenic Potential Produced by Bone-Conducted Stimuli: A Study on its Basics and Clinical Applications in Patients With Conductive and Sensorineural Hearing Loss and a Group With Vestibular Schawannoma

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Parvane Mahdi

2013-06-01

Full Text Available Introduction: Vestibular evoked myogenic potential (VEMP has recently been broadly studied in vestibular disorders. As it is evoked by loud sound stimulation, even mild conductive hearing loss may affect VEMP results. Bone-conducted (BC stimulus is an alternative stimulation for evoking this response. This study aims to assess the characteristics of BC-VEMP in different groups of patients.   Materials and Methods: We performed a cross sectional analysis on 20 healthy volunteers with normal pure-tone audiometry as a control group; and on a group of patients consisted of 20 participants with conductive hearing loss, five with bilateral sensorineural hearing loss and four with vestibular schawannoma. AC and BC-VEMP were performed in all participants.   Results: In control group the VEMP responses to both kinds of stimuli had an acceptable morphology and consisted of p13 and n23 waves. Latency value of these main components in each type of stimulus was not significantly different (P>0.05. However, the mean amplitude was larger in BC modality than AC stimulation (P=0.025. In the group with conductive hearing loss, the VEMP response was absent in fifteen (46.87% of the 32 ears using the AC method, whereas all (100% displayed positive elicitability of VEMP by BC method. Normal VEMP responses in both stimuli were evoked in all patients with sensorineural hearing loss. In patients with unilateral vestibular schwannomas (VS, 2 (50.00% had neither AC-VEMP nor BC-VEMP. Conclusion:  Auditory stimuli delivered by bone conduction can evoke VEMP response. These responses are of vestibular origin and can be used in vestibular evaluation of patients with conductive hearing loss.

Discrepancy between perceived pain and cortical processing: A voxel-based morphometry and contact heat evoked potential study.

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Kramer, J L K; Jutzeler, C R; Haefeli, J; Curt, A; Freund, P

2016-01-01

The purpose of this study was to determine if local gray and white matter volume variations between subjects could account for variability in responses to CHEP stimulation. Structural magnetic resonance imaging was used to perform voxel-based morphometry (VBM) of gray and white matter in 30 neurologically healthy subjects. Contact heat stimulation was performed on the dorsum of the right hand at the base of the thumb. Evoked potentials were acquired from a vertex-recording electrode referenced to linked ears. Controlling for age, total intracranial volume, and skull/scalp thickness, CHEP amplitude and pain rating were not significantly correlated between subjects. A VBM region of interest approach demonstrated a significant interaction between pain rating and N2 amplitude in the right insular cortex (ppain rating. This finding suggests that the discrepancy between pain ratings and the amplitude of evoked potentials is not solely related to measurement artifact, but rather attributable, in part, to anatomical differences between subjects. Crown Copyright © 2015. Published by Elsevier Ireland Ltd. All rights reserved.

Increased sensitivity to supra-threshold painful stimuli in patients with multiple functional somatic symptoms (MFS)

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Kuzminskyte, Ruta; Kupers, Ronny Clement Florent; Videbech, Poul

2010-01-01

threshold and pain tolerance levels in patients with MFS. Twenty-two patients with MFS and 27 age- and sex-matched healthy control subjects volunteered for this study. The subjects received innocuous and noxious thermal stimuli to the volar forearm by means of a Peltier contact heat probe. We assessed pain...... threshold and pain tolerance with an ascending staircase method. Anxiety levels and hemodynamic (blood pressure, pulse rate) and endocrine (cortisol and prolactin release) responses were measured before and after pain testing. We found no group differences for any of the physiological or self...

Comparison of the influence of stimuli color on Steady-State Visual Evoked Potentials

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Richard Junior Manuel Godinez Tello

Full Text Available IntroductionThe main idea of a traditional Steady State Visually Evoked Potentials (SSVEP-BCI is the activation of commands through gaze control. For this purpose, the retina of the eye is excited by a stimulus at a certain frequency. Several studies have shown effects related to different kind of stimuli, frequencies, window lengths, techniques of feature extraction and even classification. So far, none of the previous studies has performed a comparison of performance of stimuli colors through LED technology. This study addresses precisely this important aspect and would be a great contribution to the topic of SSVEP-BCIs. Additionally, the performance of different colors at different frequencies and the visual comfort were evaluated in each case.MethodsLEDs of four different colors (red, green, blue and yellow flickering at four distinct frequencies (8, 11, 13 and 15 Hz were used. Twenty subjects were distributed in two groups performing different protocols. Multivariate Synchronization Index (MSI was the technique adopted as feature extractor.ResultsThe accuracy was gradually enhanced with the increase of the time window. From our observations, the red color provides, in most frequencies, both highest rates of accuracy and Information Transfer Rate (ITR for detection of SSVEP.ConclusionAlthough the red color has presented higher ITR, this color was turned in the less comfortable one and can even elicit epileptic responses according to the literature. For this reason, the green color is suggested as the best choice according to the proposed rules. In addition, this color has shown to be safe and accurate for an SSVEP-BCI.

Neural Habituation to Painful Stimuli Is Modulated by Dopamine: Evidence from a Pharmacological fMRI Study

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Eva M. Bauch

2017-12-01

Full Text Available In constantly changing environments, it is crucial to adaptively respond to threatening events. In particular, painful stimuli are not only processed in terms of their absolute intensity, but also with respect to their context. While contextual pain processing can simply entail the repeated processing of information (i.e., habituation, it can, in a more complex form, be expressed through predictions of magnitude before the delivery of nociceptive information (i.e., adaptive coding. Here, we investigated the brain regions involved in the adaptation to nociceptive electrical stimulation as well as their link to dopaminergic neurotransmission (placebo/haloperidol. The main finding is that haloperidol changed the habituation to the absolute pain intensity over time. More precisely, in the placebo condition, activity in left postcentral gyrus and midcingulate cortex increased linearly with pain intensity only in the beginning of the experiment and subsequently habituated. In contrast, when the dopaminergic system was blocked by haloperidol, a linear increase with pain intensity was present throughout the entire experiment. Finally, there were no adaptive coding effects in any brain regions. Together, our findings provide novel insights into the nature of pain processing by suggesting that dopaminergic neurotransmission plays a specific role for the habituation to painful stimuli over time.

Neuropathic Pain Causes Pyramidal Neuronal Hyperactivity in the Anterior Cingulate Cortex

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Ruohe Zhao

2018-04-01

Full Text Available The anterior cingulate cortex (ACC is thought to be important for acute pain perception as well as the development of chronic pain after peripheral nerve injury. Nevertheless, how ACC neurons respond to sensory stimulation under chronic pain states is not well understood. Here, we used an in vivo two-photon imaging technique to monitor the activity of individual neurons in the ACC of awake, head restrained mice. Calcium imaging in the dorsal ACC revealed robust somatic activity in layer 5 (L5 pyramidal neurons in response to peripheral noxious stimuli, and the degree of evoked activity was correlated with the intensity of noxious stimulation. Furthermore, the activation of ACC neurons occurred bilaterally upon noxious stimulation to either contralateral or ipsilateral hind paws. Notably, with nerve injury-induced neuropathic pain in one limb, L5 pyramidal neurons in both sides of the ACC showed enhanced activity in the absence or presence of pain stimuli. These results reveal hyperactivity of L5 pyramidal neurons in the bilateral ACC during the development of neuropathic pain.

Associative learning in humans--conditioning of sensory-evoked brain activity.

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Skrandies, W; Jedynak, A

2000-01-01

A classical conditioning paradigm was employed in two experiments performed on 35 human volunteers. In nine subjects, the presentation of Landolt rings (conditioned stimuli, CS + ) was paired with an electric stimulus (unconditioned stimuli, UCS) applied to the left median nerve. Neutral visual control stimuli were full circles (CS -) that were not paired with the UCS. The skin conductance response (SCR) was determined in a time interval of 5 s after onset of the visual stimuli, and it was measured in the acquisition and test phase. Associative learning was reflected by a SCR occurring selectively with CS +. The same experiment was repeated with another group of 26 adults while electroencephalogram (EEG) was recorded from 30 electrodes. For each subject, mean evoked potentials were computed. In 13 of the subjects, a conditioning paradigm was followed while the other subjects served as the control group (non-contingent stimulation). There were somatosensory and visual brain activity evoked by the stimuli. Conditioned components were identified by computing cross-correlation between evoked somatosensory components and the averaged EEG. In the visual evoked brain activity, three components with mean latencies of 105.4, 183.2, and 360.3 ms were analyzed. Somatosensory stimuli were followed by major components that occurred at mean latencies of 48.8, 132.5, 219.7, 294.8, and 374.2 ms latency after the shock. All components were analyzed in terms of latency, field strength, and topographic characteristics, and were compared between groups and experimental conditions. Both visual and somatosensory brain activity was significantly affected by classical conditioning. Our data illustrate how associative learning affects the topography of brain electrical activity elicited by presentation of conditioned visual stimuli.

Deficient conditioned pain modulation after spinal cord injury correlates with clinical spontaneous pain measures.

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Albu, Sergiu; Gómez-Soriano, Julio; Avila-Martin, Gerardo; Taylor, Julian

2015-02-01

The contribution of endogenous pain modulation dysfunction to clinical and sensory measures of neuropathic pain (NP) has not been fully explored. Habituation, temporal summation, and heterotopic noxious conditioning stimulus-induced modulation of tonic heat pain intensity were examined in healthy noninjured subjects (n = 10), and above the level of spinal cord injury (SCI) in individuals without (SCI-noNP, n = 10) and with NP (SCI-NP, n = 10). Thermoalgesic thresholds, Cz/AFz contact heat evoked potentials (CHEPs), and phasic or tonic (30 seconds) heat pain intensity were assessed within the C6 dermatome. Although habituation to tonic heat pain intensity (0-10) was reported by the noninjured (10 s: 3.5 ± 0.3 vs 30 s: 2.2 ± 0.5 numerical rating scale; P = 0.003), loss of habituation was identified in both the SCI-noNP (3.8 ± 0.3 vs 3.6 ± 0.5) and SCI-NP group (4.2 ± 0.4 vs 4.9 ± 0.8). Significant temporal summation of tonic heat pain intensity was not observed in the 3 groups. Inhibition of tonic heat pain intensity induced by heterotopic noxious conditioning stimulus was identified in the noninjured (-29.7% ± 9.7%) and SCI-noNP groups (-19.6% ± 7.0%), but not in subjects with SCI-NP (+1.1% ± 8.0%; P pain modulation response correlated positively with Cz/AFz CHEP amplitude (ρ = 0.8; P = 0.015) and evoked heat pain intensity (ρ = 0.8; P = 0.007) in the SCI-NP group. Stepwise regression analysis revealed that the mean conditioned pain modulation (R = 0.72) correlated with pain severity and pressing spontaneous pain in the SCI-NP group. Comprehensive assessment of sensory dysfunction above the level of injury with tonic thermal test and conditioning stimuli revealed less-efficient endogenous pain modulation in subjects with SCI-NP.

Blocking mammalian target of rapamycin (mTOR) improves neuropathic pain evoked by spinal cord injury.

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Wang, Xiaoping; Li, Xiaojia; Huang, Bin; Ma, Shuai

2016-01-01

Spinal cord injury (SCI) is an extremely serious type of physical trauma observed in clinics. Neuropathic pain resulting from SCI has a lasting and significant impact on most aspects of daily life. Thus, a better understanding of the molecular pathways responsible for the cause of neuropathic pain observed in SCI is important to develop effective therapeutic agents and treatment strategies. Mammalian target of rapamycin (mTOR) is a serine/threonine protein kinase that is well known for its critical roles in regulating protein synthesis and growth. Furthermore, compelling evidence supports the notion that widespread dysregulation of mTOR and its downstream pathways are involved in neuropathic pain. Thus, in this study we specifically examined the underlying mechanisms by which mTOR and its signaling pathways are involved in SCI-evoked neuropathic pain in a rat model. Overall, we demonstrated that SCI increased the protein expression of p-mTOR, and mTORmediated- phosphorylation of 4E-binding protein 4 (4E-BP1) and p70 ribosomal S6 protein kinase 1 (S6K1) in the superficial dorsal horn of the spinal cord. Also, we showed that blocking spinal mTOR by intrathecal injection of rapamycin significantly inhibited pain responses induced by mechanical and thermal stimulation. In addition, blocking spinal phosphatidylinositide 3-kinase (p-PI3K) pathway significantly attenuated activities of p-mTOR pathways as well as mechanical and thermal hyperalgesia in SCI rats. Moreover, blocking mTOR and PI3K decreased the enhanced levels of substance P and calcitonin gene-related peptide (CGRP) in the dorsal horn of SCI rats. We revealed specific signaling pathways leading to SCI-evoked neuropathic pain, including the activation of PI3K, mTOR and its downstream signaling pathways. Targeting one or more of these signaling molecules may present new opportunities for treatment and management of neuropathic pain often observed in patients with SCI.

Blocking mammalian target of rapamycin (mTOR improves neuropathic pain evoked by spinal cord injury

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Wang Xiaoping

2016-01-01

Full Text Available Spinal cord injury (SCI is an extremely serious type of physical trauma observed in clinics. Neuropathic pain resulting from SCI has a lasting and significant impact on most aspects of daily life. Thus, a better understanding of the molecular pathways responsible for the cause of neuropathic pain observed in SCI is important to develop effective therapeutic agents and treatment strategies. Mammalian target of rapamycin (mTOR is a serine/threonine protein kinase that is well known for its critical roles in regulating protein synthesis and growth. Furthermore, compelling evidence supports the notion that widespread dysregulation of mTOR and its downstream pathways are involved in neuropathic pain. Thus, in this study we specifically examined the underlying mechanisms by which mTOR and its signaling pathways are involved in SCI-evoked neuropathic pain in a rat model. Overall, we demonstrated that SCI increased the protein expression of p-mTOR, and mTORmediated- phosphorylation of 4E–binding protein 4 (4E-BP1 and p70 ribosomal S6 protein kinase 1 (S6K1 in the superficial dorsal horn of the spinal cord. Also, we showed that blocking spinal mTOR by intrathecal injection of rapamycin significantly inhibited pain responses induced by mechanical and thermal stimulation. In addition, blocking spinal phosphatidylinositide 3-kinase (p-PI3K pathway significantly attenuated activities of p-mTOR pathways as well as mechanical and thermal hyperalgesia in SCI rats. Moreover, blocking mTOR and PI3K decreased the enhanced levels of substance P and calcitonin gene-related peptide (CGRP in the dorsal horn of SCI rats. We revealed specific signaling pathways leading to SCI-evoked neuropathic pain, including the activation of PI3K, mTOR and its downstream signaling pathways. Targeting one or more of these signaling molecules may present new opportunities for treatment and management of neuropathic pain often observed in patients with SCI.

Assessment of Responsiveness to Everyday Non-Noxious Stimuli in Pain-Free Migraineurs With Versus Without Aura.

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Granovsky, Yelena; Shor, Merav; Shifrin, Alla; Sprecher, Elliot; Yarnitsky, David; Bar-Shalita, Tami

2018-03-27

Migraineurs with aura (MWA) express higher interictal response to non-noxious and noxious experimental sensory stimuli compared with migraineurs without aura (MWoA), but whether these differences also prevail in response to everyday non-noxious stimuli is not yet explored. This is a cross-sectional study testing 53 female migraineurs (30 MWA; 23 MWoA) who underwent a wide battery of noxious psychophysical testing at a pain-free phase, and completed a Sensory Responsiveness Questionnaire and pain-related psychological questionnaires. The MWA group showed higher questionnaire-based sensory over-responsiveness (P = .030), higher magnitude of pain temporal summation (P = .031) as well as higher monthly attack frequency (P = .027) compared with the MWoA group. Overall, 45% of migraineurs described abnormal sensory (hyper- or hypo-) responsiveness; its incidence was higher among MWA (19 of 30, 63%) versus MWoA (6 of 23, 27%, P = .012), with an odds ratio of 3.58 for MWA. Sensory responsiveness scores were positively correlated with attack frequency (r = .361, P = .008) and temporal summation magnitude (r = .390, P = .004), both regardless of migraine type. MWA express higher everyday sensory responsiveness than MWoA, in line with higher response to experimental noxious stimuli. Abnormal scores of sensory responsiveness characterize people with sensory modulation dysfunction, suggesting possible underlying mechanisms overlap, and possibly high incidence of both clinical entities. This article presents findings distinguishing MWA, showing enhanced pain amplification, monthly attack frequency, and over-responsiveness to everyday sensations, compared with MWoA. Further, migraine is characterized by a high incidence of abnormal responsiveness to everyday sensation, specifically sensory over-responsiveness, that was also found related to pain. Copyright © 2018 The American Pain Society. Published by Elsevier Inc. All rights reserved.

Evoked acoustic emission

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Elberling, C; Parbo, J; Johnsen, N J

1985-01-01

Stimulated acoustic emissions were recorded in response to tonal stimuli at 60 dB p.e. SPL in a small group of normal-hearing adults. Power spectral analysis reveals that the evoked activity from each ear contains energy in preferential frequency bands and the change of stimulus frequency has only...

Contact heat-evoked temporal summation: tonic versus repetitive-phasic stimulation.

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Granot, Michal; Granovsky, Yelena; Sprecher, Elliot; Nir, Rony-Reuven; Yarnitsky, David

2006-06-01

Temporal summation (TS) is usually evoked by repetitive mechanical or electrical stimuli, and less commonly by tonic heat pain. The present study aimed to examine the TS induction by repetitive-phasic versus tonic heat pain stimuli. Using 27 normal volunteers, we compared the extent of summation by three calculation methods: start-to-end pain rating difference, percent change, and double-logarithmic regression of successive ratings along the stimulation. Subjects were tested twice, and the reliability of each of the paradigms was obtained. In addition, personality factors related to pain catastrophizing and anxiety level were also correlated with the psychophysical results. Both paradigms induced significant TS, with similar increases for the repetitive-phasic and the tonic paradigms, as measured on 0-100 numerical pain scale (from 52.9+/-11.7 to 80.2+/-15.5, p<0.001; and from 38.5+/-13.3 to 75.8+/-18.3, p<0.001, respectively). The extent of summation was significantly correlated between the two paradigms, when calculated by absolute change (r=0.543, p=0.004) and by regression (r=0.438, p=0.025). Session-to-session variability was similar for both paradigms, relatively large, yet not biased. As with other psychophysical parameters, this poses some limitations on TS assessment in individual patients over time. The extent of TS induced by both paradigms was found to be associated with anxiety level and pain catastrophizing. Despite some dissimilarity between the repetitive-phasic and the tonic paradigms, the many similarities suggest that the two represent a similar physiological process, even if not precisely the same. Future clinical applications of these tests will determine the clinical relevance of the TS paradigms presented in this study.

Attentional Modulation of Somatosensory Processing During the Anticipation of Movements Accompanying Pain: An Event-Related Potential Study.

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Clauwaert, Amanda; Torta, Diana M; Danneels, Lieven; Van Damme, Stefaan

2018-02-01

Attending to pain-relevant information is crucial to protect us from physical harm. Behavioral studies have already suggested that during anticipation of pain somatosensory input at the body location under threat is prioritized. However, research using daily life cues for pain, especially movements, is lacking. Furthermore, to our knowledge, no studies have investigated cortical processing associated with somatosensory processing during threatened movements. The current study aims to investigate whether movements accompanying pain automatically steer attention toward somatosensory input at the threatened location, affecting somatosensory evoked potentials (SEPs). Healthy volunteers were cued to perform movements with the left or the right hand, and one of these movements could be accompanied by pain on the moving hand. During movement anticipation, a task-irrelevant tactile stimulus was presented to the threatened or pain-free hand to evoke SEPs. During anticipation of movements accompanying pain, the N120 component was increased for tactile stimuli at the threatened relative to the hand without pain. Moreover, the P200 SEP was enhanced during anticipation of movements accompanying pain relative to movements without pain, irrespective of which hand was stimulated. These findings show that the anticipation of pain-accompanying movements may affect the processing of somatosensory input, and that this is likely to be driven by attentional processes. This study shows that the anticipation of pain-related movements automatically biases attention toward stimuli at a pain-related location, measured according to SEPs. The present study provides important new insights in the interplay between pain and attention, and its consequences at the cortical level. Copyright © 2017 The American Pain Society. Published by Elsevier Inc. All rights reserved.

The sensory channel of presentation alters subjective ratings and autonomic responses towards disgusting stimuli -Blood pressure, heart rate and skin conductance in response to visual, auditory, haptic and olfactory presented disgusting stimuli-

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Ilona eCroy

2013-09-01

Full Text Available Disgust causes specific reaction patterns, observable in mimic responses and body reactions. Most research on disgust deals with visual stimuli. However, pictures may cause another disgust experience than sounds, odors or tactile stimuli. Therefore disgust experience evoked by four different sensory channels was compared.A total of 119 participants received 3 different disgusting and one control stimulus, each presented through the visual, auditory, tactile and olfactory channel. Ratings of evoked disgust as well as responses of the autonomic nervous system (heart rate, skin conductance level, systolic blood pressure were recorded and the effect of stimulus labeling and of repeated presentation was analyzed. Ratings suggested that disgust could be evoked through all senses; they were highest for visual stimuli. However, autonomic reaction towards disgusting stimuli differed according to the channel of presentation. In contrast to the other, olfactory disgust stimuli provoked a strong decrease of systolic blood pressure. Additionally, labeling enhanced disgust ratings and autonomic reaction for olfactory and tactile, but not for visual and auditory stimuli. Repeated presentation indicated that participant’s disgust rating diminishes to all but olfactory disgust stimuli. Taken together we argue that the sensory channel through which a disgust reaction is evoked matters.

Negative body image associated with changes in the visual body appearance increases pain perception.

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Michihiro Osumi

Full Text Available Changing the visual body appearance by use of as virtual reality system, funny mirror, or binocular glasses has been reported to be helpful in rehabilitation of pain. However, there are interindividual differences in the analgesic effect of changing the visual body image. We hypothesized that a negative body image associated with changing the visual body appearance causes interindividual differences in the analgesic effect although the relationship between the visual body appearance and analgesic effect has not been clarified. We investigated whether a negative body image associated with changes in the visual body appearance increased pain. Twenty-five healthy individuals participated in this study. To evoke a negative body image, we applied the method of rubber hand illusion. We created an "injured rubber hand" to evoke unpleasantness associated with pain, a "hairy rubber hand" to evoke unpleasantness associated with embarrassment, and a "twisted rubber hand" to evoke unpleasantness associated with deviation from the concept of normality. We also created a "normal rubber hand" as a control. The pain threshold was measured while the participant observed the rubber hand using a device that measured pain caused by thermal stimuli. Body ownership experiences were elicited by observation of the injured rubber hand and hairy rubber hand as well as the normal rubber hand. Participants felt more unpleasantness by observing the injured rubber hand and hairy rubber hand than the normal rubber hand and twisted rubber hand (p<0.001. The pain threshold was lower under the injured rubber hand condition than with the other conditions (p<0.001. We conclude that a negative body appearance associated with pain can increase pain sensitivity.

Effect of heat-induced pain stimuli on pulse transit time and pulse wave amplitude in healthy volunteers.

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van Velzen, Marit H N; Loeve, Arjo J; Kortekaas, Minke C; Niehof, Sjoerd P; Mik, Egbert G; Stolker, Robert J

2016-01-01

Pain is commonly assessed subjectively by interpretations of patient behaviour and/or reports from patients. When this is impossible the availability of a quantitative objective pain assessment tool based on objective physiological parameters would greatly benefit clinical practice and research beside the standard self-report tests. Vasoconstriction is one of the physiological responses to pain. The aim of this study was to investigate whether pulse transit time (PTT) and pulse wave amplitude (PWA) decrease in response to this vasoconstriction when caused by heat-induced pain. The PTT and PWA were measured in healthy volunteers, on both index fingers using photoplethysmography and electrocardiography. Each subject received 3 heat-induced pain stimuli using a Temperature-Sensory Analyzer thermode block to apply a controlled, increasing temperature from 32.0 °C to 50.0 °C to the skin. After reaching 50.0 °C, the thermode was immediately cooled down to 32.0 °C. The study population was divided into 2 groups with a time-interval between the stimuli 20s or 60s. The results showed a significant (p  Heat-induced pain causes a decrease of PTT and PWA. Consequently, it is expected that, in the future, PTT and PWA may be applied as objective indicators of pain, either beside the standard self-report test, or when self-report testing is impossible.

Enhanced pain expectation in migraine: EEG-based evidence for impaired prefrontal function.

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Lev, Rina; Granovsky, Yelena; Yarnitsky, David

2013-01-01

Dysexcitability characterizes the interictal migraineous brain. The main central expressions of this dysexcitability are decreased habituation and enhanced anticipation and attention to pain and other external sensory stimuli. This study evaluates the effects of anticipation on pain modulation and their neural correlates in migraine. In 39 migraineurs (20 migraine with aura [MWA] and 19 migraine without aura [MOA]) and 22 healthy controls, cortical responses to 2 successive trains of noxious contact-heat stimuli, presented in either predicted or unpredicted manner, were analyzed using standardized low-resolution electromagnetic tomography key. A lack of habituation to repeated predicted pain was associated with significantly increased pain-evoked potential amplitudes in MWAs (increase of 3.9 μV) and unchanged ones in MOAs (1.1 μV) but not in controls (decrease of 5 μV). Repeated unpredicted pain resulted in enhanced pain-evoked potential amplitudes in both MWA and MOA groups (increase of 5.5 μV and 4.4 μV, respectively) compared with controls (decrease of 0.2 μV). Source localization revealed reduced activations in the anterior-medial prefrontal cortices and subsequent increased somatosensory activity in migraineurs (P < .05). The prefrontal-somatosensory dysfunction positively correlated with lifetime headache duration (P < .05) and concern of upcoming migraine attacks (P < .05) in MWAs, and with frequency of migraine attacks in MOAs (P < .05). Our findings of impaired modulation of anticipated pain in migraine suggest a heightened state of anticipatory readiness combined with ineffective recruitment of prefrontal inhibitory pathways during experience of pain; the latter might account for the former, at least partially. In line, less efficient inhibitory capability is a plausible mechanistic explanation for patients' high concern about their upcoming migraine attacks. © 2012 American Headache Society.

Multiple sites and actions of gabapentin-induced relief of ongoing experimental neuropathic pain.

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Bannister, Kirsty; Qu, Chaoling; Navratilova, Edita; Oyarzo, Janice; Xie, Jennifer Yanhua; King, Tamara; Dickenson, Anthony H; Porreca, Frank

2017-12-01

Gabapentin (GBP) is a first-line therapy for neuropathic pain, but its mechanisms and sites of action remain uncertain. We investigated GBP-induced modulation of neuropathic pain following spinal nerve ligation (SNL) in rats. Intravenous or intrathecal GBP reversed evoked mechanical hypersensitivity and produced conditioned place preference (CPP) and dopamine (DA) release in the nucleus accumbens (NAc) selectively in SNL rats. Spinal GBP also significantly inhibited dorsal horn wide-dynamic-range neuronal responses to a range of evoked stimuli in SNL rats. By contrast, GBP microinjected bilaterally into the rostral anterior cingulate cortex (rACC), produced CPP, and elicited NAc DA release selectively in SNL rats but did not reverse tactile allodynia and had marginal effects on wide-dynamic-range neuronal activity. Moreover, blockade of endogenous opioid signaling in the rACC prevented intravenous GBP-induced CPP and NAc DA release but failed to block its inhibition of tactile allodynia. Gabapentin, therefore, can potentially act to produce its pain relieving effects by (a) inhibition of injury-induced spinal neuronal excitability, evoked hypersensitivity, and ongoing pain and (b) selective supraspinal modulation of affective qualities of pain, without alteration of reflexive behaviors. Consistent with previous findings of pain relief from nonopioid analgesics, GBP requires engagement of rACC endogenous opioid circuits and downstream activation of mesolimbic reward circuits reflected in learned pain-motivated behaviors. These findings support the partial separation of sensory and affective dimensions of pain in this experimental model and suggest that modulation of affective-motivational qualities of pain may be the preferential mechanism of GBP's analgesic effects in patients.

Temporal changes in cortical activation during conditioned pain modulation (CPM), a LORETA study.

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Moont, Ruth; Crispel, Yonatan; Lev, Rina; Pud, Dorit; Yarnitsky, David

2011-07-01

For most healthy subjects, both subjective pain ratings and pain-evoked potentials are attenuated under conditioned pain modulation (CPM; formerly termed diffuse noxious inhibitory controls, or DNIC). Although essentially spinal-bulbar, this inhibition is under cortical control. This is the first study to observe temporal as well as spatial changes in cortical activations under CPM. Specifically, we aimed to investigate the interplay of areas involved in the perception and processing of pain and those involved in controlling descending inhibition. We examined brief consecutive poststimulus time windows of 50 ms using a method of source-localization from pain evoked potentials, sLORETA. This enabled determination of dynamic changes in localized cortical generators evoked by phasic noxious heat stimuli to the left volar forearm in healthy young males, with and without conditioning hot-water pain to the right hand. We found a CPM effect characterized by an initial increased activation in the orbitofrontal cortex (OFC) and amygdala at 250-300 ms poststimulus, which was correlated with the extent of psychophysical pain reduction. This was followed by reduced activations in the primary and secondary somatosensory cortices, supplementary motor area, posterior insula, and anterior cingulate cortex from 400 ms poststimulus. Our findings show that the prefrontal pain-controlling areas of OFC and amygdala increase their activity in parallel with subjective pain reduction under CPM, and that this increased activity occurs prior to reductions in activations of the pain sensory areas. In conclusion, achieving pain inhibition by the CPM process seems to be under control of the OFC and the amygdala. Copyright © 2011 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

An oral TRPV1 antagonist attenuates laser radiant-heat-evoked potentials and pain ratings from UV(B)-inflamed and normal skin.

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Schaffler, Klaus; Reeh, Peter; Duan, W Rachel; Best, Andrea E; Othman, Ahmed A; Faltynek, Connie R; Locke, Charles; Nothaft, Wolfram

2013-02-01

Laser (radiant-heat) evoked potentials (LEPs) from vertex-EEG peak-to-peak (PtP) amplitude were used to determine acute antinociceptive/antihyperalgesic efficacy of ABT-102, a novel TRPV1 antagonist efficacious in preclinical pain models, compared with active controls and placebo in normal and UV(B)-inflamed skin. This was a randomized, placebo- and active-controlled, double-blind, intra-individual, crossover trial. Twenty-four healthy subjects received six sequences of single doses of ABT-102 (0.5, 2, 6 mg), etoricoxib 90 mg, tramadol 100 mg and placebo. Painful stimuli were induced by CO(2) -laser on normal and UV(B) -inflamed skin. LEPs and visual analogue scale (VAS-pain) ratings were taken at baseline and hourly up to 8 h post-dose from both skin types. Compared with placebo, significant mean decreases in the primary variable of LEP PtP-amplitude from UV(B)-inflamed skin were observed with ABT-102 6 mg (P < 0.001), ABT-102 2 mg (P = 0.002), tramadol 100 mg (P < 0.001), and etoricoxib 90 mg (P = 0.001) over the 8 h period; ABT-102 0.5 mg was similar to placebo. ABT-102 6 mg was superior to active controls over the 8 h period (P < 0.05) whereas ABT-102 2 mg was comparable. Improvements in VAS scores compared with placebo were observed with ABT-102 6 mg (P < 0.001) and ABT-102 2 mg (P = 0.002). ABT-102 average plasma concentrations were 1.3, 4.4 and 9.4 ng ml(-1) for the 0.5, 2 and 6 mg doses, respectively. There were no clinically significant safety findings. TRPV-1 antagonism appears promising in the management of clinical pain, but requires further investigation. © 2012 Abbott. British Journal of Clinical Pharmacology © 2012 The British Pharmacological Society.

Steady-state VEP responses to uncomfortable stimuli.

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O'Hare, Louise

2017-02-01

Periodic stimuli, such as op-art, can evoke a range of aversive sensations included in the term visual discomfort. Illusory motion effects are elicited by fixational eye movements, but the cortex might also contribute to effects of discomfort. To investigate this possibility, steady-state visually evoked responses (SSVEPs) to contrast-matched op-art-based stimuli were measured at the same time as discomfort judgements. On average, discomfort reduced with increasing spatial frequency of the pattern. In contrast, the peak amplitude of the SSVEP response was around the midrange spatial frequencies. Like the discomfort judgements, SSVEP responses to the highest spatial frequencies were lowest amplitude, but the relationship breaks down between discomfort and SSVEP for the lower spatial frequency stimuli. This was not explicable by gross eye movements as measured using the facial electrodes. There was a weak relationship between the peak SSVEP responses and discomfort judgements for some stimuli, suggesting that discomfort can be explained in part by electrophysiological responses measured at the level of the cortex. However, there is a breakdown of this relationship in the case of lower spatial frequency stimuli, which remains unexplained. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

High frequency electrical stimulation concurrently induces central sensitization and ipsilateral inhibitory pain modulation.

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Vo, L; Drummond, P D

2013-03-01

In healthy humans, analgesia to blunt pressure develops in the ipsilateral forehead during various forms of limb pain. The aim of the current study was to determine whether this analgesic response is induced by ultraviolet B radiation (UVB), which evokes signs of peripheral sensitization, or by high-frequency electrical stimulation (HFS), which triggers signs of central sensitization. Before and after HFS and UVB conditioning, sensitivity to heat and to blunt and sharp stimuli was assessed at and adjacent to the treated site in the forearm. In addition, sensitivity to blunt pressure was measured bilaterally in the forehead. The effect of ipsilateral versus contralateral temple cooling on electrically evoked pain in the forearm was then examined, to determine whether HFS or UVB conditioning altered inhibitory pain modulation. UVB conditioning triggered signs of peripheral sensitization, whereas HFS conditioning triggered signs of central sensitization. Importantly, ipsilateral forehead analgesia developed after HFS but not UVB conditioning. In addition, decreases in electrically evoked pain at the HFS-treated site were greater during ipsilateral than contralateral temple cooling, whereas decreases at the UVB-treated site were similar during both procedures. HFS conditioning induced signs of central sensitization in the forearm and analgesia both in the ipsilateral forehead and the HFS-treated site. This ipsilateral analgesia was not due to peripheral sensitization or other non-specific effects, as it failed to develop after UVB conditioning. Thus, the supra-spinal mechanisms that evoke central sensitization might also trigger a hemilateral inhibitory pain modulation process. This inhibitory process could sharpen the boundaries of central sensitization or limit its spread. © 2012 European Federation of International Association for the Study of Pain Chapters.

Endogenous sequential cortical activity evoked by visual stimuli.

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Carrillo-Reid, Luis; Miller, Jae-Eun Kang; Hamm, Jordan P; Jackson, Jesse; Yuste, Rafael

2015-06-10

Although the functional properties of individual neurons in primary visual cortex have been studied intensely, little is known about how neuronal groups could encode changing visual stimuli using temporal activity patterns. To explore this, we used in vivo two-photon calcium imaging to record the activity of neuronal populations in primary visual cortex of awake mice in the presence and absence of visual stimulation. Multidimensional analysis of the network activity allowed us to identify neuronal ensembles defined as groups of cells firing in synchrony. These synchronous groups of neurons were themselves activated in sequential temporal patterns, which repeated at much higher proportions than chance and were triggered by specific visual stimuli such as natural visual scenes. Interestingly, sequential patterns were also present in recordings of spontaneous activity without any sensory stimulation and were accompanied by precise firing sequences at the single-cell level. Moreover, intrinsic dynamics could be used to predict the occurrence of future neuronal ensembles. Our data demonstrate that visual stimuli recruit similar sequential patterns to the ones observed spontaneously, consistent with the hypothesis that already existing Hebbian cell assemblies firing in predefined temporal sequences could be the microcircuit substrate that encodes visual percepts changing in time. Copyright © 2015 Carrillo-Reid et al.

Exploring relationships for visceral and somatic pain with autonomic control and personality.

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Paine, Peter; Kishor, Jessin; Worthen, Sian F; Gregory, Lloyd J; Aziz, Qasim

2009-08-01

The autonomic nervous system (ANS) integrates afferent and motor activity for homeostatic processes including pain. The aim of the study was to compare hitherto poorly characterised relations between brainstem autonomic control and personality in response to visceral and somatic pain. Eighteen healthy subjects (16 females, mean age 34) had recordings during rest and pain of heart rate (HR), cardiac vagal tone (CVT), cardiac sensitivity to baroreflex (CSB), skin conductance level (SC), cardiac sympathetic index (CSI) and mean blood pressure (MBP). Visceral pain was induced by balloon distension in proximal (PB) and distal (DB) oesophagus and somatic pain by nail-bed pressure (NBP). Eight painful stimuli were delivered at each site and unpleasantness and intensity measured. Personality was profiled with the Big Five inventory. (1) Oesophageal intubation evoked "fight-flight" responses: HR and sympathetic (CSI, SC, MBP) elevation with parasympathetic (CVT) withdrawal (pintrovert subjects had greater positive pain-related CVT slope change (neuroticism r 0.8, p<0.05; extroversion r -0.5, p<0.05). Pain-evoked heart rate increases were mediated by parasympathetic and sympathetic co-activation - a novel finding in humans but recently described in mammals too. Visceral pain-related parasympathetic change correlated with personality. ANS defence responses are nuanced and may relate to personality type for visceral pain. Clinical relevance of these findings warrants further exploration.

Cortical activities evoked by the signals ascending through unmyelinated C fibers in humans. A fMRI study

International Nuclear Information System (INIS)

Kakigi, Ryusuke; Qiu, Yunhai; Noguchi, Yasuki

2006-01-01

Acute pain is classified as first and second pain associated with rapidly conducting Aδ fibers and slowly conducting unmyelinated C fibers, respectively. First pain aims at achieving relative safety from the source of injury, whereas second pain, with its strong affective component, attracts longer-lasting attention and initiates behavioral responses in order to limit further injury and optimize recovery. Accordingly, the distinct brain representations for first and second pain should reflect distinct biological functions of both sensations. In this study, therefore, an event-related functional magnetic resonance imaging (fMRI) was used to investigate brain processing of the signals ascending from peripheral C and Aδ fibers evoked by phasic laser stimuli on the right hand in humans. The stimulation of both C and Aδ nociceptors activated the bilateral thalamus, bilateral secondary somatosensory cortex (SII), right (ipsilateral) middle insula, and bilateral Brodmann's area (BA) 24/32, with the majority of activity found in the posterior portion of the anterior cingulate cortex (pACC). However, magnitude of activity in the right (ipsilateral) BA32/8/6, including dorsal parts in the anterior portion of the ACC (aACC) and pre-supplementary motor area (pre-SMA), and the bilateral anterior insula was significantly stronger following the stimulation of C nociceptors than Aδ nociceptors. It was concluded that the activation of C nociceptors, related to second pain, evokes different brain processing from that of Aδ nociceptors, related to first pain, probably due to the differences in the emotional and motivational aspects of either pain, which are mainly related to the aACC, pre-SMA and anterior insula. (author)

Impact of visual learning on facial expressions of physical distress: a study on voluntary and evoked expressions of pain in congenitally blind and sighted individuals.

Science.gov (United States)

Kunz, Miriam; Faltermeier, Nicole; Lautenbacher, Stefan

2012-02-01

The ability to facially communicate physical distress (e.g. pain) can be essential to ensure help, support and clinical treatment for the individual experiencing physical distress. So far, it is not known to which degree this ability represents innate and biologically prepared programs or whether it requires visual learning. Here, we address this question by studying evoked and voluntary facial expressions of pain in congenitally blind (N=21) and sighted (N=42) individuals. The repertoire of evoked facial expressions was comparable in congenitally blind and sighted individuals; however, blind individuals were less capable of facially encoding different intensities of experimental pain. Moreover, blind individuals were less capable of voluntarily modulating their pain expression. We conclude that the repertoire of facial muscles being activated during pain is biologically prepared. However, visual learning is a prerequisite in order to encode different intensities of physical distress as well as for up- and down-regulation of one's facial expression. Copyright © 2011 Elsevier B.V. All rights reserved.

Scaling Up Cortical Control Inhibits Pain

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Jahrane Dale

2018-05-01

Full Text Available Summary: Acute pain evokes protective neural and behavioral responses. Chronic pain, however, disrupts normal nociceptive processing. The prefrontal cortex (PFC is known to exert top-down regulation of sensory inputs; unfortunately, how individual PFC neurons respond to an acute pain signal is not well characterized. We found that neurons in the prelimbic region of the PFC increased firing rates of the neurons after noxious stimulations in free-moving rats. Chronic pain, however, suppressed both basal spontaneous and pain-evoked firing rates. Furthermore, we identified a linear correlation between basal and evoked firing rates of PFC neurons, whereby a decrease in basal firing leads to a nearly 2-fold reduction in pain-evoked response in chronic pain states. In contrast, enhancing basal PFC activity with low-frequency optogenetic stimulation scaled up prefrontal outputs to inhibit pain. These results demonstrate a cortical gain control system for nociceptive regulation and establish scaling up prefrontal outputs as an effective neuromodulation strategy to inhibit pain. : Dale et al. find that acute pain increases activity levels in the prefrontal cortex. Chronic pain reduces both basal spontaneous and pain-evoked activity in this region, whereas neurostimulation to restore basal activities can in turn enhance nociception-evoked prefrontal activities to inhibit pain. Keywords: chronic pain, neuromodulation, prefrontal cortex, PFC, cortical gain control

Skin denervation does not alter cortical potentials to surface concentric electrode stimulation: A comparison with laser evoked potentials and contact heat evoked potentials.

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La Cesa, S; Di Stefano, G; Leone, C; Pepe, A; Galosi, E; Alu, F; Fasolino, A; Cruccu, G; Valeriani, M; Truini, A

2018-01-01

In the neurophysiological assessment of patients with neuropathic pain, laser evoked potentials (LEPs), contact heat evoked potentials (CHEPs) and the evoked potentials by the intraepidermal electrical stimulation via concentric needle electrode are widely agreed as nociceptive specific responses; conversely, the nociceptive specificity of evoked potentials by surface concentric electrode (SE-PREPs) is still debated. In this neurophysiological study we aimed at verifying the nociceptive specificity of SE-PREPs. We recorded LEPs, CHEPs and SE-PREPs in eleven healthy participants, before and after epidermal denervation produced by prolonged capsaicin application. We also used skin biopsy to verify the capsaicin-induced nociceptive nerve fibre loss in the epidermis. We found that whereas LEPs and CHEPs were suppressed after capsaicin-induced epidermal denervation, the surface concentric electrode stimulation of the same denervated skin area yielded unchanged SE-PREPs. The suppression of LEPs and CHEPs after nociceptive nerve fibre loss in the epidermis indicates that these techniques are selectively mediated by nociceptive system. Conversely, the lack of SE-PREP changes suggests that SE-PREPs do not provide selective information on nociceptive system function. Capsaicin-induced epidermal denervation abolishes laser evoked potentials (LEPs) and contact heat evoked potentials (CHEPs), but leaves unaffected pain-related evoked potentials by surface concentric electrode (SE-PREPs). These findings suggest that unlike LEPs and CHEPs, SE-PREPs are not selectively mediated by nociceptive system. © 2017 European Pain Federation - EFIC®.

Intradermal administration of magnesium sulphate and magnesium chloride produces hypesthesia to mechanical but hyperalgesia to heat stimuli in humans

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Ikemoto Tatsunori

2009-08-01

Full Text Available Abstract Background Although magnesium ions (Mg2+ are known to display many similar features to other 2+ charged cations, they seem to have quite an important and unique role in biological settings, such as NMDA blocking effect. However, the role of Mg2+ in the neural transmission system has not been studied as sufficiently as calcium ions (Ca2+. To clarify the sensory effects of Mg2+ in peripheral nervous systems, sensory changes after intradermal injection of Mg2+ were studied in humans. Methods Magnesium sulphate, magnesium chloride and saline were injected into the skin of the anterior region of forearms in healthy volunteers and injection-induced irritating pain ("irritating pain", for short, tactile sensation, tactile pressure thresholds, pinch-pain changes and intolerable heat pain thresholds of the lesion were monitored. Results Flare formation was observed immediately after magnesium sulphate or magnesium chloride injection. We found that intradermal injections of magnesium sulphate and magnesium chloride transiently caused irritating pain, hypesthesia to noxious and innocuous mechanical stimulations, whereas secondary hyperalgesia due to mechanical stimuli was not observed. In contrast to mechanical stimuli, intolerable heat pain-evoking temperature was significantly decreased at the injection site. In addition to these results, spontaneous pain was immediately attenuated by local cooling. Conclusion Membrane-stabilizing effect and peripheral NMDA-blocking effect possibly produced magnesium-induced mechanical hypesthesia, and extracellular cation-induced sensitization of TRPV1 channels was thought to be the primary mechanism of magnesium-induced heat hyperalgesia.

Altered Brain Activation in Early Drug-Naive Parkinson’s Disease during Heat Pain Stimuli: An fMRI Study

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Ying Tan

2015-01-01

Full Text Available Parkinson’s disease (PD is a progressive neurodegenerative disease characterized by motor and nonmotor signs and symptoms. To date, many studies of PD have focused on its cardinal motor symptoms. To study the nonmotor signs of early PD, we investigated the reactions solicited by heat pain stimuli in early untreated PD patients without pain using fMRI. The activation patterns of contact heat stimuli (51°C were assessed in 14 patients and 17 age- and sex-matched healthy controls. Patients with PD showed significant decreases in activation of the superior temporal gyrus (STG and insula compared with controls. In addition, a significant relationship between activation of the insula and STG and the pain scores was observed in healthy controls but not in PD. This study provided further support that the insula and STG are important parts of the somatosensory circuitry recruited during the period of pain. The hypoactivity of the STG and insula in PD implied that functions including affective, cognitive, and sensory-discriminative processes, which are associated with the insula and STG, were disturbed. This finding supports the view that leaving early PD untreated could be tied directly to central nervous system dysfunction.

Vibration and muscle contraction affect somatosensory evoked potentials

OpenAIRE

Cohen, LG; Starr, A

1985-01-01

We recorded potentials evoked by specific somatosensory stimuli over peripheral nerve, spinal cord, and cerebral cortex. Vibration attenuated spinal and cerebral potentials evoked by mixed nerve and muscle spindle stimulation; in one subject that was tested, there was no effect on cutaneous input. Presynaptic inhibition of Ia input in the spinal cord and muscle spindle receptor occupancy are probably the responsible mechanisms. In contrast, muscle contraction attenuated cerebral potentials to...

Hypersensitivity to mechanical and intra-articular electrical stimuli in persons with painful temporomandibular joints

DEFF Research Database (Denmark)

Ayesh, Emad; Jensen, Troels Staehelin; Svensson, P

2007-01-01

This study tested whether persons with TMJ arthralgia have a modality-specific and site-specific hypersensitivity to somatosensory stimuli assessed by quantitative sensory tests (QST). Forty-three healthy persons and 20 with TMJ arthralgia participated. The QST consisted of: sensory and pain dete...... of sensitization of the TMJs as well as central nociceptive pathways. QST may facilitate a mechanism-based classification of temporomandibular disorders. Udgivelsesdato: 2007-Dec...

Laser heat hyperalgesia is not a feature of non-specific chronic low back pain.

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Franz, M; Ritter, A; Puta, C; Nötzel, D; Miltner, W H R; Weiss, T

2014-11-01

Based upon studies using mechanical pin-prick, pressure, electrical or heat stimuli applied to painful and/or pain-free parts of the body, chronic low back pain (CLBP) has been shown to be associated with generalized and enhanced pain sensitivity and altered brain responses to noxious stimuli. To date, no study examined the processing of noxious laser heat pulses, which are known to selectively excite thermal nociceptors located in the superficial skin layers, in CLBP. We studied laser heat pain thresholds (LHPTs) and nociceptive laser-evoked brain electrical potentials (LEPs) following skin stimulation of the pain-affected back and the pain-free abdomen using noxious laser heat stimulation in 16 CLBP patients and 16 age- and gender-matched healthy controls (HCs). We observed no statistically significant differences in LHPTs between CLBP patients and HCs, neither on the back nor on the abdomen. Furthermore, we found no evidence for altered brain responses between CLBP patients and HCs in response to stimulation of the back and abdomen in single-trial latencies and amplitudes of LEP components (N2, P2). The results are in contrast to previous studies showing hypersensitivity to different experimental noxious stimuli (e.g., contact heat). We argue that these discrepancies may be due to low spatial and temporal summation within the central nervous system following laser heat stimulation. Our results indicate important methodological differences between laser heat and thermode stimulation that should be taken into account when interpreting results, such as from thermal quantitative sensory testing. © 2014 European Pain Federation - EFIC®

Separating discriminative and function-altering effects of verbal stimuli

OpenAIRE

Schlinger, Henry D.

1993-01-01

Ever since Skinner's first discussion of rule-governed behavior, behavior analysts have continued to define rules, either explicitly or implicitly, as verbal discriminative stimuli. Consequently, it is not difficult to find, in the literature on rule-governed behavior, references to stimulus control, antecedent control, or to rules occasioning behavior. However, some verbal stimuli have effects on behavior that are not easily described as discriminative. Such stimuli don't evoke behavior as d...

Do pain-associated contexts increase pain sensitivity? An investigation using virtual reality.

Science.gov (United States)

Harvie, Daniel S; Sterling, Michele; Smith, Ashley D

2018-04-30

Pain is not a linear result of nociception, but is dependent on multisensory inputs, psychological factors, and prior experience. Since nociceptive models appear insufficient to explain chronic pain, understanding non-nociceptive contributors is imperative. Several recent models propose that cues associatively linked to painful events might acquire the capacity to augment, or even cause, pain. This experiment aimed to determine whether contexts associated with pain, could modulate mechanical pain thresholds and pain intensity. Forty-eight healthy participants underwent a contextual conditioning procedure, where three neutral virtual reality contexts were paired with either unpredictable noxious stimulation, unpredictable vibrotactile stimulation, or no stimulation. Following the conditioning procedure, mechanical pain thresholds and pain evoked by a test stimulus were examined in each context. In the test phase, the effect of expectancy was equalised across conditions by informing participants when thresholds and painful stimuli would be presented. Contrary to our hypothesis, scenes that were associated with noxious stimulation did not increase mechanical sensitivity (p=0.08), or increase pain intensity (p=0.46). However, an interaction with sex highlighted the possibility that pain-associated contexts may alter pain sensitivity in females but not males (p=0.03). Overall, our data does not support the idea that pain-associated contexts can alter pain sensitivity in healthy asymptomatic individuals. That an effect was shown in females highlights the possibility that some subgroups may be susceptible to such an effect, although the magnitude of the effect may lack real-world significance. If pain-associated cues prove to have a relevant pain augmenting effect, in some subgroups, procedures aimed at extinguishing pain-related associations may have therapeutic potential.

Brain Network Response to Acupuncture Stimuli in Experimental Acute Low Back Pain: An fMRI Study

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Yu Shi

2015-01-01

Full Text Available Most neuroimaging studies have demonstrated that acupuncture can significantly modulate brain activation patterns in healthy subjects, while only a few studies have examined clinical pain. In the current study, we combined an experimental acute low back pain (ALBP model and functional magnetic resonance imaging (fMRI to explore the neural mechanisms of acupuncture analgesia. All ALBP subjects first underwent two resting state fMRI scans at baseline and during a painful episode and then underwent two additional fMRI scans, once during acupuncture stimulation (ACUP and once during tactile stimulation (SHAM pseudorandomly, at the BL40 acupoint. Our results showed that, compared with the baseline, the pain state had higher regional homogeneity (ReHo values in the pain matrix, limbic system, and default mode network (DMN and lower ReHo values in frontal gyrus and temporal gyrus; compared with the OFF status, ACUP yielded broad deactivation in subjects, including nearly all of the limbic system, pain status, and DMN, and also evoked numerous activations in the attentional and somatosensory systems; compared with SHAM, we found that ACUP induced more deactivations and fewer activations in the subjects. Multiple brain networks play crucial roles in acupuncture analgesia, suggesting that ACUP exceeds a somatosensory-guided mind-body therapy for ALBP.

Time course and hemispheric lateralization effects of complex pitch processing: evoked magnetic fields in response to rippled noise stimuli.

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Hertrich, Ingo; Mathiak, Klaus; Lutzenberger, Werner; Ackermann, Hermann

2004-01-01

To delineate the time course and processing stages of pitch encoding at the level of the supratemporal plane, the present study recorded evoked magnetic fields in response to rippled noise (RN) stimuli. RN largely masks simple tonotopic representations and addresses pitch processing within the temporal domain (periodicity encoding). Four dichotic stimulus types (111 or 133 Hz RN at one ear, white noise to the other one) were applied in randomized order during either visual distraction or selective auditory attention. Strictly periodic signals, noise-like events, and mixtures of both signals served as control conditions. (1) Attention-dependent ear x hemisphere interactions were observed within the time domain of the M50 field, indicating early streaming of auditory information. (2) M100 responses to strictly periodic stimuli were found lateralized to the right hemisphere. Furthermore, the higher-pitched stimuli yielded enhanced activation as compared to the lower-pitch signals (pitch scaling), conceivably reflecting sensory memory operations. (3) Besides right-hemisphere pitch scaling, the relatively late M100 component in association with the RN condition (latency = 136 ms) showed significantly stronger field strengths over the left hemisphere. Control experiments revealed this lateralization effect to be related to noise rather than pitch processing. Furthermore, subtle noise variations interacted with signal periodicity. Obviously, thus, complex task demands such as RN encoding give rise to functional segregation of auditory processing across the two hemispheres (left hemisphere: noise, right hemisphere: periodicity representation). The observed noise/periodicity interactions, furthermore, might reflect pitch-synchronous spectral evaluation at the level of the left supratemporal plane, triggered by right-hemisphere representation of signal periodicity. Copyright 2004 Elsevier Ltd.

Analgesic effect of the neuropeptide cortistatin in murine models of arthritic inflammatory pain.

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Morell, Maria; Souza-Moreira, Luciana; Caro, Marta; O'Valle, Francisco; Forte-Lago, Irene; de Lecea, Luis; Gonzalez-Rey, Elena; Delgado, Mario

2013-05-01

To investigate the role of the antiinflammatory neuropeptide cortistatin in chronic pain evoked by joint inflammation. Thermal and mechanical hyperalgesia was evoked in mouse knee joints by intraplantar injection of tumor necrosis factor α and intraarticular infusion of Freund's complete adjuvant, and the analgesic effects of cortistatin, administered centrally, peripherally, and systemically, were assessed. In addition, the effects of cortistatin on the production of nociceptive peptides and the activation of pain signaling were assayed in dorsal root ganglion cultures and in inflammatory pain models. The role of endogenous cortistatin in pain sensitization and perpetuation of chronic inflammatory states was evaluated in cortistatin-deficient mice. Finally, the effect of noxious/inflammatory stimuli in the production of cortistatin by the peripheral nociceptive system was assayed in vitro and in vivo. Expression of cortistatin was observed in peptidergic nociceptors of the peripheral nociceptive system, and endogenous cortistatin was found to participate in the tuning of pain sensitization, especially in pathologic inflammatory conditions. Results showed that cortistatin acted both peripherally and centrally to reduce the tactile allodynia and heat hyperalgesia evoked by arthritis and peripheral tissue inflammation in mice, via mechanisms that were independent of its antiinflammatory action. These mechanisms involved direct action on nociceptive neurons and regulation of central sensitization. The analgesic effects of cortistatin in murine arthritic pain were linked to binding of the neuropeptide to somatostatin and ghrelin receptors, activation of the G protein subunit Gαi , impairment of ERK signaling, and decreased production of calcitonin gene-related peptide in primary nociceptors. These findings indicate that cortistatin is an antiinflammatory factor with potent analgesic effects that may offer a new approach to pain therapy in pathologic inflammatory

Sympathetic skin response evoked by laser skin stimulation

OpenAIRE

Rossi, P.; Truini, A.; Serrao, M.; Iannetti, G. D.; Parisi, L.; Pozzessere, G.; Cruccu, G.

2002-01-01

The objective of this study was to evoke sympathetic skin responses (SSRs) in healthy subjects using laser stimulation and to compare these responses with those induced by conventional electrical stimuli. Twenty healthy subjects were investigated. SSRs were obtained using electrical and laser stimuli delivered to the wrist controlateral to the recording site. The sympathetic sudomotor conduction velocity (SSFCV) was measured in 8 subjects by simultaneously recording the SSR from the hand and ...

Abdominal acupuncture reduces laser-evoked potentials in healthy subjects

DEFF Research Database (Denmark)

Pazzaglia, C.; Liguori, S.; Minciotti, I.

2015-01-01

Objective: Acupuncture is known to reduce clinical pain, although the exact mechanism is unknown. The aim of the current study was to investigate the effect of acupuncture on laser-evoked potential amplitudes and laser pain perception. Methods: In order to evaluate whether abdominal acupuncture...... is able to modify pain perception, 10 healthy subjects underwent a protocol in which laser-evoked potentials (LEPs) and laser pain perception were collected before the test (baseline), during abdominal acupuncture, and 15. min after needle removal. The same subjects also underwent a similar protocol...... in which, however, sham acupuncture without any needle penetration was used. Results: During real acupuncture, both N1 and N2/P2 amplitudes were reduced, as compared to baseline (p . < 0.01). The reduction lasted up to 15. min after needle removal. Furthermore, laser pain perception was reduced during...

Advances in pain control in palliative care

African Journals Online (AJOL)

2011-07-02

Jul 2, 2011 ... pain evoked by light touch or pain evoked by change in temperature. This type of pain is .... the drugs; drug interactions; co-morbidities that can be alleviated by .... AIDS and cancer. • Because pain in palliative care is multi-.

Pain Processing and Vegetative Dysfunction in Fibromyalgia: A Study by Sympathetic Skin Response and Laser Evoked Potentials

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Marina de Tommaso

2017-01-01

Full Text Available Background. A dysfunction of pain processing at central and peripheral levels was reported in fibromyalgia (FM. We aimed to correlate laser evoked potentials (LEPs, Sympathetic Skin Response (SSR, and clinical features in FM patients. Methods. Fifty FM patients and 30 age-matched controls underwent LEPs and SSR by the right hand and foot. The clinical evaluation included FM disability (FIQ and severity scores (WPI, anxiety (SAS and depression (SDS scales, and questionnaires for neuropathic pain (DN4. Results. The LEP P2 latency and amplitude and the SSR latency were increased in FM group. This latter feature was more evident in anxious patients. The LEPs habituation was reduced in FM patients and correlated to pain severity scores. In a significant number of patients (32% with higher DN4 and FIQ scores, SSR or LEP responses were absent. Conclusions. LEPs and SSR might contribute to clarifying the peripheral and central nervous system involvement in FM patients.

Influência dos contrastes de fala nos potenciais evocados auditivos corticais The influence of speech stimuli contrast in cortical auditory evoked potentials

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Kátia de Freitas Alvarenga

2013-06-01

Full Text Available Estudos voltados aos potenciais evocados auditivos com estímulos de fala em indivíduos ouvintes são importantes para compreender como a complexidade do estímulo influencia nas características do potencial cognitivo auditivo gerado. OBJETIVO: Caracterizar o potencial evocado auditivo cortical e o potencial cognitivo auditivo P3 com estímulos de contrastes vocálico e consonantal em indivíduos com audição normal. MÉTODO: Participaram deste estudo 31 indivíduos sem alterações auditivas, neurológicas e de linguagem na faixa etária de 7 a 30 anos. Os potenciais evocados auditivos corticais e cognitivo auditivo P3 foram registrados nos canais ativos Fz e Cz utilizando-se os contrastes de fala consonantal (/ba/-/da/ e vocálico (/i/-/a/. Desenho: Estudo de coorte, transversal e prospectivo. RESULTADOS: Houve diferença entre o contraste de fala utilizado e as latências dos componentes N2 (p = 0,00 e P3 (p = 0,00, assim como entre o canal ativo considerado (Fz/Cz e os valores de latência e amplitude de P3. Estas diferenças não ocorreram para os componentes exógenos N1 e P2. CONCLUSÃO: O contraste do estímulo de fala, vocálico ou consonantal, deve ser considerado na análise do potencial evocado cortical, componente N2, e do potencial cognitivo auditivo P3.Studies about cortical auditory evoked potentials using the speech stimuli in normal hearing individuals are important for understanding how the complexity of the stimulus influences the characteristics of the cortical potential generated. OBJECTIVE: To characterize the cortical auditory evoked potential and the P3 auditory cognitive potential with the vocalic and consonantal contrast stimuli in normally hearing individuals. METHOD: 31 individuals with no risk for hearing, neurologic and language alterations, in the age range between 7 and 30 years, participated in this study. The cortical auditory evoked potentials and the P3 auditory cognitive one were recorded in the Fz and Cz

Attentional load modulates responses of human primary visual cortex to invisible stimuli.

Science.gov (United States)

Bahrami, Bahador; Lavie, Nilli; Rees, Geraint

2007-03-20

Visual neuroscience has long sought to determine the extent to which stimulus-evoked activity in visual cortex depends on attention and awareness. Some influential theories of consciousness maintain that the allocation of attention is restricted to conscious representations [1, 2]. However, in the load theory of attention [3], competition between task-relevant and task-irrelevant stimuli for limited-capacity attention does not depend on conscious perception of the irrelevant stimuli. The critical test is whether the level of attentional load in a relevant task would determine unconscious neural processing of invisible stimuli. Human participants were scanned with high-field fMRI while they performed a foveal task of low or high attentional load. Irrelevant, invisible monocular stimuli were simultaneously presented peripherally and were continuously suppressed by a flashing mask in the other eye [4]. Attentional load in the foveal task strongly modulated retinotopic activity evoked in primary visual cortex (V1) by the invisible stimuli. Contrary to traditional views [1, 2, 5, 6], we found that availability of attentional capacity determines neural representations related to unconscious processing of continuously suppressed stimuli in human primary visual cortex. Spillover of attention to cortical representations of invisible stimuli (under low load) cannot be a sufficient condition for their awareness.

Mast cell deficiency attenuates acupuncture analgesia for mechanical pain using c-kit gene mutant rats

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Cui X

2018-03-01

effects for mechanical pain (46°C, 3 mA EA, MA (P<0.01, P<0.001. Additionally, the net increases in MWL and MWT induced by most stimuli were greater in WT than in mutant rats (P<0.05. For thermal nociception, either high- or low-intensity stimuli could significantly augment TWL in two rats (P<0.001, and the net increases of TWL evoked by most stimuli were to the same extent in two genetic variants. Conclusion: MCs influence the basic mechanical but not thermal pain threshold. MCs participate in acupuncture analgesia in mechanical but not in thermal nociception, in that MC deficiency may attenuate the mechanical analgesia evoked by high-intensity stimuli and eliminate analgesia provoked by low-intensity stimuli. Keywords: WsRC-Ws/Ws rats, tryptase, stimulus intensity, mechanical withdrawal threshold, thermal withdrawal latency

Brain Activity Associated with Slow Temporal Summation of C-fiber Evoked Pain in Fibromyalgia Patients and Healthy Controls

OpenAIRE

Staud, Roland; Craggs, Jason G.; Perlstein, William M.; Robinson, Michael E.; Price, Donald D.

2008-01-01

Temporal summation of “second pain” (TSSP) is the result of C-fiber-evoked responses of dorsal-horn neurons, termed ‘windup’. This phenomenon is dependent on stimulus frequency (≥0.33 Hz) and relevant for central sensitization as well as chronic pain. Whereas our previous functional magnetic resonance imaging (fMRI) study characterized neural correlates of TSSP in eleven healthy volunteers, the present study was designed to compare brain responses associated with TSSP across these healthy par...

A Potential Role of Chronic Exposure to Extremely Low-Frequency Electromagnetic Fields in Triggering Persistent Pain Post Breast Cancer Surgery: A Review

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Azadeh Stark

2017-10-01

Full Text Available Persistent Pain after Breast Cancer Surgery (PPBCS ranks second to amputation of extremities for neuropathic chronic pain. PPBCS is associated with the formation of intercostobrachial neuroma bulbs along the lateral chest. These neuroma bulbs are either un-/thinly myelinated and express hypersensitivity to environmental stimuli. Hypersensitivity is manifested as spontaneous pain in response to innocuous stimuli and exaggerating pain in response to noxious stimuli. Excision of neuromas, a common intervention to alleviate pain, has been reported as ineffective. Experience of individuals with amputation of extremities and experimental models of human nerve injuries confirm anthropogenic EMF evoke excruciating pain. Findings from invitro and animal studies clearly support that EMF exposure depolarizes cell membranes, interrupts voltage gated calcium channels which then activates peripheral sensory neurons and initiates propagation of a train of action potentials along the axons of primary afferent nerve fibers. The World Health Organization guidelines, established based on approximation of the human anatomy are limited and assumes no potential compounding effects of nerve injuries or alterations of physiological milieu of tissues. The objective of this review is to direct the attention of the medical community to the potential role of anthropogenic EMF as a risk factor for persistent pain after breast surgery. Patients rely heavily on the recommendations of their providers to manage their pain. The current epidemic of opioid abuse in the US has been partially attributed to the high prescription rate of opioid-based pain killers. Understanding the potential triggers of chronic pain can reduce dependency on pharmaceutical agents.

Perceptual and cerebro-spinal responses to graded innocuous and noxious stimuli following aerobic exercise.

Science.gov (United States)

Micalos, P S; Harris, J; Drinkwater, E J; Cannon, J; Marino, F E

2015-11-01

The aim of this study was to evaluate the effect of aerobic exercise on perceptual and cerebro-spinal responses to graded electrocutaneous stimuli. The design comprised 2 x 30 min of cycling exercise at 30% and 70% of peak oxygen consumption (VO2 peak) on separate occasions in a counter-balanced order in 10 healthy participants. Assessment of nociceptive withdrawal reflex threshold (NWR-T), pain threshold (PT), and somatosensory evoked potentials (SEPs) to graded electrocutaneous stimuli were performed before and after exercise. Perceptual magnitude ratings and SEPs were compared at 30%PT, 60%PT, 100%PT before (Pre), 5 min after (Post1), and 15 min after (Post2) aerobic exercise. There was no difference in the NWR-T and the PT following exercise at 30% and 70% of VO2 peak. ANOVA for the perceptual response within pooled electrocutaneous stimuli show a significant main effect for time (F2,18=5.41, P=0.01) but no difference for exercise intensity (F1,9=0.02, P=0.88). Within-subject contrasts reveal trend differences between 30%PT and 100%PT for Pre-Post1 (P=0.09) and Pre-Post2 (P=0.02). ANOVA for the SEPs peak-to-peak signal amplitude (N1-P1) show significant main effect for time (F2,18=4.04, P=0.04) but no difference for exercise intensity (F1,9=1.83, P=0.21). Pairwise comparisons for time reveal differences between Pre-Post1 (P=0.06) and Pre-Post2 (P=0.01). There was a significant interaction for SEPs N1-P1 between exercise intensity and stimulus intensity (F2,18=3.56, P=0.05). These results indicate that aerobic exercise did not increase the electrocutaneous threshold for pain and the NWR-T. Aerobic exercise attenuated perceptual responses to innocuous stimuli and SEPs N1-P1 response to noxious stimuli.

Evaluation of an automated analysis for pain-related evoked potentials

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Wulf Michael

2017-09-01

Full Text Available This paper presents initial steps towards an auto-mated analysis for pain-related evoked potentials (PREP to achieve a higher objectivity and non-biased examination as well as a reduction in the time expended during clinical daily routines. While manually examining, each epoch of an en-semble of stimulus-locked EEG signals, elicited by electrical stimulation of predominantly intra-epidermal small nerve fibers and recorded over the central electrode (Cz, is in-spected for artifacts before calculating the PREP by averag-ing the artifact-free epochs. Afterwards, specific peak-latencies (like the P0-, N1 and P1-latency are identified as certain extrema in the PREP’s waveform. The proposed automated analysis uses Pearson’s correlation and low-pass differentiation to perform these tasks. To evaluate the auto-mated analysis’ accuracy its results of 232 datasets were compared to the results of the manually performed examina-tion. Results of the automated artifact rejection were compa-rable to the manual examination. Detection of peak-latencies was more heterogeneous, indicating some sensitivity of the detected events upon the criteria used during data examina-tion.

Pain Report and Pain-Related Evoked Potentials Operantly Conditioned

NARCIS (Netherlands)

Lousberg, Richel; Vuurman, Eric; Lamers, Theo; van Breukelen, Gerard; Jongen, Ellen; Rijnen, Heidi; Maessen, Christa; Hermens, Hermanus J.

Objective: The purpose of the present study was to answer the ques- tion whether pain report can be increased and decreased by operant conditioning. We predicted that the conditioned pain effects would remain significant after correction for social desirability and fantasy proneness. Furthermore, we

Alteration of basal ganglia and right frontoparietal network in early drug-naïve Parkinson’s disease during heat pain stimuli and resting state

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Ying eTan

2015-08-01

Full Text Available Background: The symptoms and pathogenesis of Parkinson’s disease (PD are complicated and accurate diagnosis is difficult, particularly in early-stage. Functional magnetic resonance imaging is noninvasive and characterized by the integration of different brain areas at functional connectivity (FC. Considering pain process in PD, we hypothesized that pain is one of the earliest symptoms and investigated whether FC of the pain network was disrupted in PD without pain.Methods: Fourteen early drug-naïve PD without pain and 17 age- and sex-matched healthy controls (HC participated in our test. We investigate abnormalities in FC and in functional network connectivity in PD compared with HC during the task (51 °C heat pain stimuli and at rest.Results: Compared with HC, PD showed decreased FC in basal ganglia network (BGN, salience network (SN and sensorimotor network in two states respectively. FNC between the BGN and the SN are reduced during both states in PD compared with HC. In addition, the FNC associated with right frontoparietal network (RFPN was also significantly disturbed during the task.Conclusion: These findings suggest that BGN plays a role in the pathological mechanisms of pain underlying PD, and RFPN likely contributes greatly to harmonization between intrinsic brain activity and external stimuli.

Pain and other symptoms of CRPS can be increased by ambiguous visual stimuli--an exploratory study.

Science.gov (United States)

Hall, Jane; Harrison, Simon; Cohen, Helen; McCabe, Candida S; Harris, N; Blake, David R

2011-01-01

Visual disturbance, visuo-spatial difficulties, and exacerbations of pain associated with these, have been reported by some patients with Complex Regional Pain Syndrome (CRPS). We investigated the hypothesis that some visual stimuli (i.e. those which produce ambiguous perceptions) can induce pain and other somatic sensations in people with CRPS. Thirty patients with CRPS, 33 with rheumatology conditions and 45 healthy controls viewed two images: a bistable spatial image and a control image. For each image participants recorded the frequency of percept change in 1 min and reported any changes in somatosensation. 73% of patients with CRPS reported increases in pain and/or sensory disturbances including changes in perception of the affected limb, temperature and weight changes and feelings of disorientation after viewing the bistable image. Additionally, 13% of the CRPS group responded with striking worsening of their symptoms which necessitated task cessation. Subjects in the control groups did not report pain increases or somatic sensations. It is possible to worsen the pain suffered in CRPS, and to produce other somatic sensations, by means of a visual stimulus alone. This is a newly described finding. As a clinical and research tool, the experimental method provides a means to generate and exacerbate somaesthetic disturbances, including pain, without moving the affected limb and causing nociceptive interference. This may be particularly useful for brain imaging studies. Copyright © 2010 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved.

UVB radiation generates sunburn pain and affects skin by activating epidermal TRPV4 ion channels and triggering endothelin-1 signaling.

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Moore, Carlene; Cevikbas, Ferda; Pasolli, H Amalia; Chen, Yong; Kong, Wei; Kempkes, Cordula; Parekh, Puja; Lee, Suk Hee; Kontchou, Nelly-Ange; Yeh, Iwei; Ye, Iwei; Jokerst, Nan Marie; Fuchs, Elaine; Steinhoff, Martin; Liedtke, Wolfgang B

2013-08-20

At our body surface, the epidermis absorbs UV radiation. UV overexposure leads to sunburn with tissue injury and pain. To understand how, we focus on TRPV4, a nonselective cation channel highly expressed in epithelial skin cells and known to function in sensory transduction, a property shared with other transient receptor potential channels. We show that following UVB exposure mice with induced Trpv4 deletions, specifically in keratinocytes, are less sensitive to noxious thermal and mechanical stimuli than control animals. Exploring the mechanism, we find that epidermal TRPV4 orchestrates UVB-evoked skin tissue damage and increased expression of the proalgesic/algogenic mediator endothelin-1. In culture, UVB causes a direct, TRPV4-dependent Ca(2+) response in keratinocytes. In mice, topical treatment with a TRPV4-selective inhibitor decreases UVB-evoked pain behavior, epidermal tissue damage, and endothelin-1 expression. In humans, sunburn enhances epidermal expression of TRPV4 and endothelin-1, underscoring the potential of keratinocyte-derived TRPV4 as a therapeutic target for UVB-induced sunburn, in particular pain.

Symptom-Based Treatment of Neuropathic Pain in Spinal Cord-Injured Patients: A Randomized Crossover Clinical Trial.

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Min, Kyunghoon; Oh, Yoongul; Lee, Sang-Hyuk; Ryu, Ju Seok

2016-05-01

The objective of this study was to identify the differences in medication effect according to pain characteristics in spinal cord-injured patients. This study is a prospective, randomized, crossover study. Fifty-five patients and 66 locations of neuropathic pain were included. Pain was classified into four spontaneous characteristics and three evoked pain characteristics. Oxcarbazepine (Na channel blocker) and pregabalin (calcium channel α2-δ ligand medication) were tried. Patients were divided into two groups: evoked pain present and evoked pain absent. Overall average visual analog scale was obtained. Oxcarbazepine was significantly more effective for patients without evoked pain than in those with it for electrical, burning, and pricking pain. The effect of pregabalin was not different regarding the presence or absence of evoked pain for all pain categories, except burning pain. In patients with evoked pain, pregabalin was shown to be significantly more effective for electrical pain, allodynia, and heat hyperalgesia than oxcarbazepine. In the evoked pain absent group, oxcarbazepine showed greater improvement than pregabalin but was not significant. In summary, the phenotype of neuropathic pain was associated with the efficacy of different pharmacologic treatments. Symptom-based treatment, therefore, can lead to more efficient analgesia.

Quantitative sensory testing and pain-evoked cytokine reactivity: comparison of patients with sickle cell disease to healthy matched controls.

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Campbell, Claudia M; Carroll, C Patrick; Kiley, Kasey; Han, Dingfen; Haywood, Carlton; Lanzkron, Sophie; Swedberg, Lauren; Edwards, Robert R; Page, Gayle G; Haythornthwaite, Jennifer A

2016-04-01

Sickle cell disease (SCD) is an inherited blood disorder associated with significant morbidity, which includes severe episodic pain, and, often, chronic pain. Compared to healthy individuals, patients with SCD report enhanced sensitivity to thermal detection and pain thresholds and have altered inflammatory profiles, yet no studies to date have examined biomarker reactivity after laboratory-induced pain. We sought to examine this relationship in patients with SCD compared to healthy control participants. We completed quantitative sensory testing in 83 patients with SCD and sequential blood sampling in 27 of them, whom we matched (sex, age, race, body mass index, and education) to 27 healthy controls. Surprisingly, few quantitative sensory testing differences emerged between groups. Heat pain tolerance, pressure pain threshold at the trapezius, thumb, and quadriceps, and thermal temporal summation at 45°C differed between groups in the expected direction, whereas conditioned pain modulation and pain ratings to hot water hand immersion were counterintuitive, possibly because of tailoring the water temperature to a perceptual level; patients with SCD received milder temperatures. In the matched subsample, group differences and group-by-time interactions were observed in biomarkers including tumor necrosis factor alpha, interleukin-1ß, interleukin-4, and neuropeptide Y. These findings highlight the utility of laboratory pain testing methods for understanding individual differences in inflammatory cytokines. Our findings suggest amplified pain-evoked proinflammatory cytokine reactivity among patients with SCD relative to carefully matched controls. Future research is warranted to evaluate the impact of enhanced pain-related cytokine response and whether it is predictive of clinical characteristics and the frequency/severity of pain crises in patients with SCD.

A comparison of myogenic motor evoked responses to electrical and magnetic transcranial stimulation during nitrous oxide/opioid anesthesia

NARCIS (Netherlands)

Ubags, L. H.; Kalkman, C. J.; Been, H. D.; Koelman, J. H.; Ongerboer de Visser, B. W.

1999-01-01

Transcranial motor evoked potentials (tc-MEPs) are used to monitor spinal cord integrity intraoperatively. We compared myogenic motor evoked responses with electrical and magnetic transcranial stimuli during nitrous oxide/opioid anesthesia. In 11 patients undergoing spinal surgery, anesthesia was

Impact of the number of painful stimuli on life satisfaction among Korean industrial accident workers completing convalescence: dual mediating effects of self-esteem and sleeping time

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CHOI, Wan-Suk; KIM, Bo-Kyung; KIM, Ki-Do; MOON, Ok-Kon; YEUM, Dong-Moon

2016-01-01

This study examined the impact of the number of painful stimuli on life satisfaction among workers who experienced an industrial accident and investigated how self-esteem and sleeping time affected life satisfaction. The Korea Workers’ Compensation & Welfare Service conducted the first nationwide panel survey on occupational health and safety insurance in 2013–2014 through a stratified systematic sampling on 2,000 industrial accident workers who completed convalescence. Based on the dataset, our study analyzed 1,832 workers experiencing an industrial accident after excluding 168 disease patients. For the research model analysis, a four-stage hierarchical regression analysis technique was applied using the SPSS regression analysis Macro program of PROCESS Procedure. To test mediated indirect effects of the self-esteem and sleeping time, the bootstrapping technique was applied. Life satisfaction, self-esteem and sleeping time decreased as the number of painful stimuli increased. Life satisfaction decreased as self-esteem and sleeping time decreased. On balance, the partial mediation model confirmed that self-esteem and sleeping time both mediate the impact of the number of painful stimuli on life satisfaction. PMID:27021061

Impact of the number of painful stimuli on life satisfaction among Korean industrial accident workers completing convalescence: dual mediating effects of self-esteem and sleeping time.

Science.gov (United States)

Choi, Wan-Suk; Kim, Bo-Kyung; Kim, Ki-Do; Moon, Ok-Kon; Yeum, Dong-Moon

2016-10-08

This study examined the impact of the number of painful stimuli on life satisfaction among workers who experienced an industrial accident and investigated how self-esteem and sleeping time affected life satisfaction. The Korea Workers' Compensation & Welfare Service conducted the first nationwide panel survey on occupational health and safety insurance in 2013-2014 through a stratified systematic sampling on 2,000 industrial accident workers who completed convalescence. Based on the dataset, our study analyzed 1,832 workers experiencing an industrial accident after excluding 168 disease patients. For the research model analysis, a four-stage hierarchical regression analysis technique was applied using the SPSS regression analysis Macro program of PROCESS Procedure. To test mediated indirect effects of the self-esteem and sleeping time, the bootstrapping technique was applied. Life satisfaction, self-esteem and sleeping time decreased as the number of painful stimuli increased. Life satisfaction decreased as self-esteem and sleeping time decreased. On balance, the partial mediation model confirmed that self-esteem and sleeping time both mediate the impact of the number of painful stimuli on life satisfaction.

Disorders of Consciousness: Painless or Painful Conditions?—Evidence from Neuroimaging Studies

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Francesca Pistoia

2016-10-01

Full Text Available The experience of pain in disorders of consciousness is still debated. Neuroimaging studies, using functional Magnetic Resonance Imaging (fMRI, Positron Emission Tomography (PET, multichannel electroencephalography (EEG and laser-evoked potentials, suggest that the perception of pain increases with the level of consciousness. Brain activation in response to noxious stimuli has been observed in patients with unresponsive wakefulness syndrome (UWS, which is also referred to as a vegetative state (VS, as well as those in a minimally conscious state (MCS. However, all of these techniques suggest that pain-related brain activation patterns of patients in MCS more closely resemble those of healthy subjects. This is further supported by fMRI findings showing a much greater functional connectivity within the structures of the so-called pain matrix in MCS as compared to UWS/VS patients. Nonetheless, when interpreting the results, a distinction is necessary between autonomic responses to potentially harmful stimuli and conscious experience of the unpleasantness of pain. Even more so if we consider that the degree of residual functioning and cortical connectivity necessary for the somatosensory, affective and cognitive-evaluative components of pain processing are not yet clear. Although procedurally challenging, the particular value of the aforementioned techniques in the assessment of pain in disorders of consciousness has been clearly demonstrated. The study of pain-related brain activation and functioning can contribute to a better understanding of the networks underlying pain perception while addressing clinical and ethical questions concerning patient care. Further development of technology and methods should aim to increase the availability of neuroimaging, objective assessment of functional connectivity and analysis at the level of individual cases as well as group comparisons. This will enable neuroimaging to truly become a clinical tool to

Descending serotonergic facilitation and the antinociceptive effects of pregabalin in a rat model of osteoarthritic pain

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Dolphin Annette C

2009-08-01

Full Text Available Abstract Background Descending facilitation, from the brainstem, promotes spinal neuronal hyperexcitability and behavioural hypersensitivity in many chronic pain states. We have previously demonstrated enhanced descending facilitation onto dorsal horn neurones in a neuropathic pain model, and shown this to enable the analgesic effectiveness of gabapentin. Here we have tested if this hypothesis applies to other pain states by using a combination of approaches in a rat model of osteoarthritis (OA to ascertain if 1 a role for descending 5HT mediated facilitation exists, and 2 if pregabalin (a newer analogue of gabapentin is an effective antinociceptive agent in this model. Further, quantitative-PCR experiments were undertaken to analyse the α2δ-1 and 5-HT3A subunit mRNA levels in L3–6 DRG in order to assess whether changes in these molecular substrates have a bearing on the pharmacological effects of ondansetron and pregabalin in OA. Results Osteoarthritis was induced via intra-articular injection of monosodium iodoacetate (MIA into the knee joint. Control animals were injected with 0.9% saline. Two weeks later in vivo electrophysiology was performed, comparing the effects of spinal ondansetron (10–100 μg/50 μl or systemic pregabalin (0.3 – 10 mg/kg on evoked responses of dorsal horn neurones to electrical, mechanical and thermal stimuli in MIA or control rats. In MIA rats, ondansetron significantly inhibited the evoked responses to both innocuous and noxious natural evoked neuronal responses, whereas only inhibition of noxious evoked responses was seen in controls. Pregabalin significantly inhibited neuronal responses in the MIA rats only; this effect was blocked by a pre-administration of spinal ondansetron. Analysis of α2δ-1 and 5-HT3A subunit mRNA levels in L3–6 DRG revealed a significant increase in α2δ-1 levels in ipsilateral L3&4 DRG in MIA rats. 5-HT3A subunit mRNA levels were unchanged. Conclusion These data suggest

Speech Evoked Auditory Brainstem Response in Stuttering

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Ali Akbar Tahaei

2014-01-01

Full Text Available Auditory processing deficits have been hypothesized as an underlying mechanism for stuttering. Previous studies have demonstrated abnormal responses in subjects with persistent developmental stuttering (PDS at the higher level of the central auditory system using speech stimuli. Recently, the potential usefulness of speech evoked auditory brainstem responses in central auditory processing disorders has been emphasized. The current study used the speech evoked ABR to investigate the hypothesis that subjects with PDS have specific auditory perceptual dysfunction. Objectives. To determine whether brainstem responses to speech stimuli differ between PDS subjects and normal fluent speakers. Methods. Twenty-five subjects with PDS participated in this study. The speech-ABRs were elicited by the 5-formant synthesized syllable/da/, with duration of 40 ms. Results. There were significant group differences for the onset and offset transient peaks. Subjects with PDS had longer latencies for the onset and offset peaks relative to the control group. Conclusions. Subjects with PDS showed a deficient neural timing in the early stages of the auditory pathway consistent with temporal processing deficits and their abnormal timing may underlie to their disfluency.

Experimental knee pain evoke spreading hyperalgesia and facilitated temporal summation of pain

DEFF Research Database (Denmark)

Jørgensen, Tanja Schjødt; Henriksen, Marius; Danneskiold-Samsøe, Bente

2013-01-01

OBJECTIVES: This study evaluated the deep-tissue pressure pain sensitivity and temporal summation of pain within and around healthy knees exposed to experimental pain. DESIGN: The study was designed as a randomized crossover trial, with each subject tested on 1 day. SETTING: All tests were carried...... occasions: baseline, immediately after the injection, and when pain had vanished. Assessments sites were located in the peripatellar region, vastus lateralis, and tibialis anterior muscles. RESULTS: The experimental knee pain model demonstrated 1) hyperalgesia to pressure stimulation on the infrapatellar...... fat pad during experimental pain, and 2) facilitated temporal summation of pressure pain at the infrapatellar fat pad and knee-related muscles. CONCLUSION: The increased sensitivity and temporal summation found in this study were exclusive to deep -tissue with no contralateral decreased pain...

Differential effects of systemically administered ketamine and lidocaine on dynamic and static hyperalgesia induced by intradermal capsaicin in humans

DEFF Research Database (Denmark)

Gottrup, Hanne; Hansen, Peter Orm; Arendt-Nielsen, Lars

2000-01-01

We have examined the effect of systemic administration of ketamine and lidocaine on brush-evoked (dynamic) pain and punctate-evoked (static) hyperalgesia induced by capsaicin. In a randomized, double-blind, placebo-controlled, crossover study, we studied 12 volunteers in three experiments....... Capsaicin 100 micrograms was injected intradermally on the volar forearm followed by an i.v. infusion of ketamine (bolus 0.1 mg kg-1 over 10 min followed by infusion of 7 micrograms kg-1 min-1), lidocaine 5 mg kg-1 or saline for 50 min. Infusion started 15 min after injection of capsaicin. The following...... were measured: spontaneous pain, pain evoked by punctate and brush stimuli (VAS), and areas of brush-evoked and punctate-evoked hyperalgesia. Ketamine reduced both the area of brush-evoked and punctate-evoked hyperalgesia significantly and it tended to reduce brush-evoked pain. Lidocaine reduced...

Abnormal pain processing in chronic tension-type headache: a high-density EEG brain mapping study

DEFF Research Database (Denmark)

Buchgreitz, L.; Egsgaard, L.L.; Jensen, R.

2008-01-01

Central sensitization caused by prolonged nociceptive input from muscles is considered to play an important role for chronification of tension-type headache. In the present study we used a new high-density EEG brain mapping technique to investigate spatiotemporal aspects of brain activity...... in response to muscle pain in 19 patients with chronic tension-type headache (CTTH) and 19 healthy, age- and sex-matched controls. Intramuscular electrical stimuli (single and train of five pulses delivered at 2 Hz) were applied to the trapezius muscle and somatosensory evoked potentials were recorded...... with 128-channel EEG both in- and outside a condition with induced tonic neck/shoulder muscle pain (glutamate injection into the trapezius muscle). Significant reduction in magnitude during and after induced tonic muscle pain was found in controls at the P200 dipole in response to both the first (baseline...

DESCRIPTION OF BRAINSTEM AUDITORY EVOKED RESPONSES (AIR AND BONE CONDUCTION IN CHILDREN WITH NORMAL HEARING

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A. V. Pashkov

2014-01-01

Full Text Available Diagnosis of hearing level in small children with conductive hearing loss associated with congenital craniofacial abnormalities, particularly with agenesis of external ear and external auditory meatus is a pressing issue. Conventional methods of assessing hearing in the first years of life, i. e. registration of brainstem auditory evoked responses to acoustic stimuli in the event of air conduction, does not give an indication of the auditory analyzer’s condition due to potential conductive hearing loss in these patients. This study was aimed at assessing potential of diagnosing the auditory analyzer’s function with registering brainstem auditory evoked responses (BAERs to acoustic stimuli transmitted by means of a bone vibrator. The study involved 17 children aged 3–10 years with normal hearing. We compared parameters of registering brainstem auditory evoked responses (peak V depending on the type of stimulus transmission (air/bone in children with normal hearing. The data on thresholds of the BAERs registered to acoustic stimuli in the event of air and bone conduction obtained in this study are comparable; hearing thresholds in the event of acoustic stimulation by means of a bone vibrator correlates with the results of the BAERs registered to the stimuli transmitted by means of air conduction earphones (r = 0.9. High correlation of thresholds of BAERs to the stimuli transmitted by means of a bone vibrator with thresholds of BAERs registered when air conduction earphones were used helps to assess auditory analyzer’s condition in patients with any form of conductive hearing loss.  

Conditioned pain modulation and situational pain catastrophizing as preoperative predictors of pain following chest wall surgery: a prospective observational cohort study.

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Kasper Grosen

Full Text Available Variability in patients' postoperative pain experience and response to treatment challenges effective pain management. Variability in pain reflects individual differences in inhibitory pain modulation and psychological sensitivity, which in turn may be clinically relevant for the disposition to acquire pain. The aim of this study was to investigate the effects of conditioned pain modulation and situational pain catastrophizing on postoperative pain and pain persistency.Preoperatively, 42 healthy males undergoing funnel chest surgery completed the Spielberger's State-Trait Anxiety Inventory and Beck's Depression Inventory before undergoing a sequential conditioned pain modulation paradigm. Subsequently, the Pain Catastrophizing Scale was introduced and patients were instructed to reference the conditioning pain while answering. Ratings of movement-evoked pain and consumption of morphine equivalents were obtained during postoperative days 2-5. Pain was reevaluated at six months postoperatively.Patients reporting persistent pain at six months follow-up (n = 15 were not significantly different from pain-free patients (n = 16 concerning preoperative conditioned pain modulation response (Z = 1.0, P = 0.3 or level of catastrophizing (Z = 0.4, P = 1.0. In the acute postoperative phase, situational pain catastrophizing predicted movement-evoked pain, independently of anxiety and depression (β = 1.0, P = 0.007 whereas conditioned pain modulation predicted morphine consumption (β = -0.005, P = 0.001.Preoperative conditioned pain modulation and situational pain catastrophizing were not associated with the development of persistent postoperative pain following funnel chest repair. Secondary outcome analyses indicated that conditioned pain modulation predicted morphine consumption and situational pain catastrophizing predicted movement-evoked pain intensity in the acute postoperative phase. These findings may have

Orbitofrontal disinhibition of pain in migraine with aura: an interictal EEG-mapping study.

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Lev, Rina; Granovsky, Yelena; Yarnitsky, David

2010-08-01

This study aimed to identify the cortical mechanisms underlying the processes of interictal dishabituation to experimental pain in subjects suffering from migraine with aura (MWA). In 21 subjects with MWA and 22 healthy controls, cortical responses to two successive trials of noxious contact-heat stimuli were analyzed using EEG-tomography software. When compared with controls, MWA patients showed significantly increased pain-evoked potential amplitudes accompanied by reduced activity in the orbitofrontal cortex (OFC) and increased activity in the pain matrix regions, including the primary somatosensory cortex (SI) (p < .05). Similarly to controls, MWA subjects displayed an inverse correlation between the OFC and SI activities, and positive interrelations between other pain-specific regions. The activity changes in the OFC negatively correlated with lifetime headache duration and longevity (p < .05). Reduced inhibitory functioning of the prefrontal cortex is a possible cause for disinhibition of the pain-related sensory cortices in migraine. The finding of OFC hypofunction over the disease course is in keeping with current concepts of migraine as a progressive brain disorder.

Spatial summation and spatial discrimination of cold pain: effect of spatial configuration and skin type.

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Defrin, Ruth; Sheraizin, Anat; Malichi, Liron; Shachen, Orit

2011-12-01

Spatial summation (SS) and spatial discrimination (SD) are essential for pain perception. In the cold-pain sensation, these processes have hardly been studied. Our aim was to study the SS and SD of cold pain, as well as the SS of cold-pain threshold (CPT) in hairy and glabrous skin. Two discrete stimuli (9 cm(2) each) were applied to the forearm with separation distances of 0-40 cm and in addition, a single stimulus on each forearm. For each configuration, the CPT, suprathreshold cold-pain ratings, and the reported number of activated stimuli (SD) were obtained. In another experiment, SS of CPT was tested in the hairy and glabrous skin of the hand using small (2.25 cm(2)) and large (9 cm(2)) probe sizes. The SS of CPT and of cold pain existed over separation distances of up to 30-40 cm, at which point SD became better than chance. When the 2 forearms were stimulated, SS was abolished and cold pain was inhibited. CPT was significantly higher in hairy than glabrous skin, but the amount of SS of CPT was similar in the 2 skin types. Noxious cold-evoked thermal qualities were more common in the glabrous than the hairy skin. (1) SS and SD of cold pain are reciprocal; (2) whereas cold pain can summate over large distances, the SD of cold pain is poor; (3) SS of cold pain does not exist between contralateral body sides, however, inhibition occurs; (4) SS is independent of skin type and sensitivity to cold pain; (5) differences in pain quality between hairy and glabrous skin may reflect innervation differences. Copyright © 2011 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Stimulator with arbitrary waveform for auditory evoked potentials

International Nuclear Information System (INIS)

Martins, H R; Romao, M; Placido, D; Provenzano, F; Tierra-Criollo, C J

2007-01-01

The technological improvement helps many medical areas. The audiometric exams involving the auditory evoked potentials can make better diagnoses of auditory disorders. This paper proposes the development of a stimulator based on Digital Signal Processor. This stimulator is the first step of an auditory evoked potential system based on the ADSP-BF533 EZ KIT LITE (Analog Devices Company - USA). The stimulator can generate arbitrary waveform like Sine Waves, Modulated Amplitude, Pulses, Bursts and Pips. The waveforms are generated through a graphical interface programmed in C++ in which the user can define the parameters of the waveform. Furthermore, the user can set the exam parameters as number of stimuli, time with stimulation (Time ON) and time without stimulus (Time OFF). In future works will be implemented another parts of the system that includes the acquirement of electroencephalogram and signal processing to estimate and analyze the evoked potential

Stimulator with arbitrary waveform for auditory evoked potentials

Energy Technology Data Exchange (ETDEWEB)

Martins, H R; Romao, M; Placido, D; Provenzano, F; Tierra-Criollo, C J [Universidade Federal de Minas Gerais (UFMG), Departamento de Engenharia Eletrica (DEE), Nucleo de Estudos e Pesquisa em Engenharia Biomedica NEPEB, Av. Ant. Carlos, 6627, sala 2206, Pampulha, Belo Horizonte, MG, 31.270-901 (Brazil)

2007-11-15

The technological improvement helps many medical areas. The audiometric exams involving the auditory evoked potentials can make better diagnoses of auditory disorders. This paper proposes the development of a stimulator based on Digital Signal Processor. This stimulator is the first step of an auditory evoked potential system based on the ADSP-BF533 EZ KIT LITE (Analog Devices Company - USA). The stimulator can generate arbitrary waveform like Sine Waves, Modulated Amplitude, Pulses, Bursts and Pips. The waveforms are generated through a graphical interface programmed in C++ in which the user can define the parameters of the waveform. Furthermore, the user can set the exam parameters as number of stimuli, time with stimulation (Time ON) and time without stimulus (Time OFF). In future works will be implemented another parts of the system that includes the acquirement of electroencephalogram and signal processing to estimate and analyze the evoked potential.

Central pain processing in chronic chemotherapy-induced peripheral neuropathy: a functional magnetic resonance imaging study.

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Elaine G Boland

Full Text Available Life expectancy in multiple myeloma has significantly increased. However, a high incidence of chemotherapy induced peripheral neuropathy (CIPN can negatively influence quality of life during this period. This study applied functional magnetic resonance imaging (fMRI to compare areas associated with central pain processing in patients with multiple myeloma who had chemotherapy induced peripheral neuropathy (MM-CIPN with those from healthy volunteers (HV. Twenty-four participants (n = 12 MM-CIPN, n = 12 HV underwent Blood Oxygen Level-Dependent (BOLD fMRI at 3T whilst noxious heat-pain stimuli were applied to the foot and then thigh. Patients with MM-CIPN demonstrated greater activation during painful stimulation in the precuneus compared to HV (p = 0.014, FWE-corrected. Patients with MM-CIPN exhibited hypo-activation of the right superior frontal gyrus compared to HV (p = 0.031, FWE-corrected. Significant positive correlation existed between the total neuropathy score (reduced version and activation in the frontal operculum (close to insular cortex during foot stimulation in patients with MM-CIPN (p = 0.03, FWE-corrected; adjusted R2 = 0.87. Painful stimuli delivered to MM-CIPN patients evoke differential activation of distinct cortical regions, reflecting a unique pattern of central pain processing compared with healthy volunteers. This characteristic activation pattern associated with pain furthers the understanding of the pathophysiology of painful chemotherapy induced peripheral neuropathy. Functional MRI provides a tool for monitoring cerebral changes during anti-cancer and analgesic treatment.

Aspects of dentinal and pulpal pain. Pain of dentinal and pulpal origin--a review for the clinician.

Science.gov (United States)

Figdor, D

1994-04-01

Recent advances in understanding the mechanisms of pain arising from the dental pulp serve to benefit patients by improving the clinician's ability to diagnose and treat pain. There are two types of pain arising from the pulp which are mediated by entirely different nerve fibres, each with their own individual characteristics. One is a short, sharp fast pain which is induced by stimuli which cause a rapid fluid flow within the dentinal tubules. Such stimuli include cold, heat, air, drilling, and osmotic stimuli. Once the affected teeth are identified, they can often be treated by sealing the open, exposed dentine. The second type of pain is experienced as a slow, dull, aching, poorly localized pain which is mediated by pain fibres activated by stimuli which are noxious to the pulp, such as prolonged damaging heat and inflammatory mediators. Pain of this character can be difficult to diagnose and often indicates serious pulp damage necessitating removal of the offending pulp by endodontic therapy.

No Pain Relief with the Rubber Hand Illusion

Science.gov (United States)

Petkova, Valeria I.; Dey, Abishikta; Barnsley, Nadia; Ingvar, Martin; McAuley, James H.; Moseley, G. Lorimer; Ehrsson, Henrik H.

2012-01-01

The sense of body ownership can be easily disrupted during illusions and the most common illusion is the rubber hand illusion. An idea that is rapidly gaining popularity in clinical pain medicine is that body ownership illusions can be used to modify pathological pain sensations and induce analgesia. However, this idea has not been empirically evaluated. Two separate research laboratories undertook independent randomized repeated measures experiments, both designed to detect an effect of the rubber hand illusion on experimentally induced hand pain. In Experiment 1, 16 healthy volunteers rated the pain evoked by noxious heat stimuli (5 s duration; interstimulus interval 25 s) of set temperatures (47°, 48° and 49°C) during the rubber hand illusion or during a control condition. There was a main effect of stimulus temperature on pain ratings, but no main effect of condition (p = 0.32), nor a condition x temperature interaction (p = 0.31). In Experiment 2, 20 healthy volunteers underwent quantitative sensory testing to determine heat and cold pain thresholds during the rubber hand illusion or during a control condition. Secondary analyses involved heat and cold detection thresholds and paradoxical heat sensations. Again, there was no main effect of condition on heat pain threshold (p = 0.17), nor on cold pain threshold (p = 0.65), nor on any of the secondary measures (pillusion does not induce analgesia. PMID:23285026

No pain relief with the rubber hand illusion.

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Rahul Mohan

Full Text Available The sense of body ownership can be easily disrupted during illusions and the most common illusion is the rubber hand illusion. An idea that is rapidly gaining popularity in clinical pain medicine is that body ownership illusions can be used to modify pathological pain sensations and induce analgesia. However, this idea has not been empirically evaluated. Two separate research laboratories undertook independent randomized repeated measures experiments, both designed to detect an effect of the rubber hand illusion on experimentally induced hand pain. In Experiment 1, 16 healthy volunteers rated the pain evoked by noxious heat stimuli (5 s duration; interstimulus interval 25 s of set temperatures (47°, 48° and 49°C during the rubber hand illusion or during a control condition. There was a main effect of stimulus temperature on pain ratings, but no main effect of condition (p = 0.32, nor a condition x temperature interaction (p = 0.31. In Experiment 2, 20 healthy volunteers underwent quantitative sensory testing to determine heat and cold pain thresholds during the rubber hand illusion or during a control condition. Secondary analyses involved heat and cold detection thresholds and paradoxical heat sensations. Again, there was no main effect of condition on heat pain threshold (p = 0.17, nor on cold pain threshold (p = 0.65, nor on any of the secondary measures (p<0.56 for all. We conclude that the rubber hand illusion does not induce analgesia.

Enhanced early visual processing in response to snake and trypophobic stimuli

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J.W. van Strien (Jan); Van der Peijl, M.K. (Manja K.)

2018-01-01

textabstractBackground: Trypophobia refers to aversion to clusters of holes. We investigated whether trypophobic stimuli evoke augmented early posterior negativity (EPN). Methods: Twenty-four participants filled out a trypophobia questionnaire and watched the random rapid serial presentation of 450

Optical study of interactions among propagation waves of neural excitation in the rat somatosensory cortex evoked by forelimb and hindlimb stimuli.

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Hama, Noriyuki; Kawai, Minako; Ito, Shin-Ichi; Hirota, Akihiko

2018-02-14

Multisite optical recording has revealed that the neural excitation wave induced by a sensory stimulation begins at a focus and propagates on the cortex. This wave is considered to be important for computation in the sensory cortex, particularly the integration of sensory information; however, the nature of this wave remains largely unknown. In the present study, we examined the interaction between two waves in the rat sensory cortex induced by hindlimb and forelimb stimuli with different inter-stimulus intervals. We classified the resultant patterns as follows: 1) the collision of two waves; 2) the hindlimb response being evoked while the forelimb-induced wave is passing the hindlimb focus; and 3) the hindlimb response being evoked after the forelimb-induced wave has passed the hindlimb focus. In pattern 1, the two waves fused into a single wave, but the propagation pattern differed from that predicted by the superimposition of two solely induced propagation courses. In pattern 2, the state of the interaction between the two waves varied depending on the phase of optical signals constituting the forelimb-induced wave around the hindlimb focus. Although no hindlimb-induced wave was observed in the rising phase, the propagating velocity of the forelimb-induced wave increased. At the peak, neither the hindlimb-induced response nor a modulatory effect on the forelimb-induced wave was detected. In pattern 3, the hindlimb-induced wave showed a reduced amplitude and spatial extent. These results indicate that the state of the interaction between waves was strongly influenced by the relative timing of sensory inputs.

INVESTIGATING CONSCIOUS PAIN WITH LASER-EVOKED POTENTIALS IN HEALTHY VOLUNTEERS%健康志愿者主观疼痛感觉相关的激光诱发电位研究

Institute of Scientific and Technical Information of China (English)

韩舒颜; 陈日新; 万有; 伊鸣

2017-01-01

目的:通过激光诱发电位比较眶额皮质和初级体感皮层两个脑区与主观疼痛感觉的相关程度.方法:利用激光刺激诱发疼痛,令25名受试者用视觉模拟评分评价疼痛,同时用脑电记录激光诱发电位.用安慰剂干预受试者的主观疼痛感知.利用叠加平均、精准低分辨率层析成像(exact low resolution brain electromagnetic tomography,eLORETA)分析事件相关电位数据,结合统计方法评价眶额皮层和初级体感皮层内部的源信号变化与视觉模拟评分(visual analogue scale,VAS)变化之间的相关性,比较两个脑区与主观疼痛的相关度.结果:疼痛刺激对侧眶额皮质与主观疼痛的关系更加密切,初级体感皮层与主观疼痛的相关度不及眶额皮质.结论:疼痛刺激部位对侧眶额皮质更可能为编码主观疼痛感觉的大脑区域,而初级体感皮层可能只反映外周伤害性信息的传入.%Objective:To compare the correlation with conscious pain between orbitofrontal cortex (OFC) and primary somatosensory cortex (SI) with laser-evoked potentials (LEPs).Methods:Twenty-fivehealthy volun-teer participants had their left hands stimulated by a series of nociceptive laser pulses. Their pain evoked by laser stimuli was evaluated using the visual analogue scale (VAS), and LEPs were recorded with EEG simulta-neously. A placebo manipulation was used to modulate conscious pain. Source localization analysis of LEP was carried out using exact low resolution brain electromagnetic tomography (eLORETA).Results:Based on the changes induced by placebo effects and the linear correlation between VAS scores and LEP sources, we found that contralateral OFC showed higher correlation with conscious pain than SI did.Conclusion:Compared with SI, contralateral OFC is more probably brain area that encodes conscious pain.

Recording visual evoked potentials and auditory evoked P300 at 9.4T static magnetic field.

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Arrubla, Jorge; Neuner, Irene; Hahn, David; Boers, Frank; Shah, N Jon

2013-01-01

Simultaneous recording of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) has shown a number of advantages that make this multimodal technique superior to fMRI alone. The feasibility of recording EEG at ultra-high static magnetic field up to 9.4 T was recently demonstrated and promises to be implemented soon in fMRI studies at ultra high magnetic fields. Recording visual evoked potentials are expected to be amongst the most simple for simultaneous EEG/fMRI at ultra-high magnetic field due to the easy assessment of the visual cortex. Auditory evoked P300 measurements are of interest since it is believed that they represent the earliest stage of cognitive processing. In this study, we investigate the feasibility of recording visual evoked potentials and auditory evoked P300 in a 9.4 T static magnetic field. For this purpose, EEG data were recorded from 26 healthy volunteers inside a 9.4 T MR scanner using a 32-channel MR compatible EEG system. Visual stimulation and auditory oddball paradigm were presented in order to elicit evoked related potentials (ERP). Recordings made outside the scanner were performed using the same stimuli and EEG system for comparison purposes. We were able to retrieve visual P100 and auditory P300 evoked potentials at 9.4 T static magnetic field after correction of the ballistocardiogram artefact using independent component analysis. The latencies of the ERPs recorded at 9.4 T were not different from those recorded at 0 T. The amplitudes of ERPs were higher at 9.4 T when compared to recordings at 0 T. Nevertheless, it seems that the increased amplitudes of the ERPs are due to the effect of the ultra-high field on the EEG recording system rather than alteration in the intrinsic processes that generate the electrophysiological responses.

Pain when walking: individual sensory profiles in the foot soles of torture victims - a controlled study using quantitative sensory testing

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Prip Karen

2012-12-01

Full Text Available Abstract Background With quantitative sensory testing (QST we recently found no differences in sensory function of the foot soles between groups of torture victims with or without exposure to falanga (beatings under the feet. Compared to matched controls the torture victims had hyperalgesia to deep mechano-nociceptive stimuli and hypoesthesia to non-noxious cutaneous stimuli. The purpose of the present paper was to extend the group analysis into individual sensory profiles of victims’ feet to explore possible relations between external violence (torture, reported pain, sensory symptoms and QST data to help clarify the underlying mechanisms. Methods We employed interviews and assessments of the pain and sensory symptoms and QST by investigators blinded to whether the patients, 32 male torture victims from the Middle East, had (n=15, or had not (n=17 been exposed to falanga. Pain intensity, area and stimulus dependence were used to characterize the pain. QST included thresholds for touch, cold, warmth, cold-pain, heat-pain, deep pressure pain and wind-up to cutaneous noxious stimuli. An ethnically matched control group was available.The normality criterion, from our control group data, was set as the mean +/− 1.28SD, thus including 80% of all values.QST data were transformed into three categories in relation to our normality range; hypoesthesia, normoesthesia or hyperesthesia/hyperalgesia. Results Most patients, irrespective of having been exposed to falanga or not, reported severe pain when walking. This was often associated with hyperalgesia to deep mechanical pressure. Hypoesthesia to mechanical stimuli co-occurred with numbness, burning and with deep mechanical hyperalgesia more often than not, but otherwise, a hypoesthesia to cutaneous sensory modalities did not co-occur systematically to falanga, pain or sensory symptoms. Conclusion In torture victims, there seem to be overriding mechanisms, manifested by hyperalgesia to pressure pain

Prediction of postoperative pain by preoperative pain response to heat stimulation in total knee arthroplasty

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Lunn, Troels H; Gaarn-Larsen, Lissi; Kehlet, Henrik

2013-01-01

It has been estimated that up to 54% of the variance in postoperative pain experience may be predicted with preoperative pain responses to experimental stimuli, with suprathreshold heat pain as the most consistent test modality. We aimed to explore if 2 heat test paradigms could predict postopera......It has been estimated that up to 54% of the variance in postoperative pain experience may be predicted with preoperative pain responses to experimental stimuli, with suprathreshold heat pain as the most consistent test modality. We aimed to explore if 2 heat test paradigms could predict...... and logistic regressions analyses were carried out including 8 potential preoperative explanatory variables (among these anxiety, depression, preoperative pain and pain catastrophizing) to assess pain response to preoperative heat pain stimulation as independent predictor for postoperative pain. 100 patients...... by the linear and logistic regression analyses, where only anxiety, preoperative pain and pain catastrophizing were significant explanatory variables (but with low R-Squares;0.05-0.08). Pain responses to 2 types of preoperative heat stimuli were not independent clinical relevant predictors for postoperative...

Dopaminergic tone does not influence pain levels during placebo interventions in patients with chronic neuropathic pain.

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Skyt, Ina; Moslemi, Kurosh; Baastrup, Cathrine; Grosen, Kasper; Benedetti, Fabrizio; Petersen, Gitte L; Price, Donald D; Hall, Kathryn T; Kaptchuk, Ted J; Svensson, Peter; Jensen, Troels S; Vase, Lene

2017-10-23

Placebo effects have been reported in patients with chronic neuropathic pain. Expected pain levels and positive emotions are involved in the observed pain relief, but the underlying neurobiology is largely unknown. Patients with neuropathic pain are highly motivated for pain relief, and as motivational factors such as expectations of reward, as well as pain processing in itself, are related to the dopaminergic system, it can be speculated that dopamine release contributes to placebo effects in neuropathic pain. Nineteen patients with neuropathic pain after thoracic surgery were tested during a placebo intervention consisting of open and hidden applications of the pain-relieving agent lidocaine (2 mL) and no treatment. The dopamine antagonist haloperidol (2 mg) and the agonist levodopa/carbidopa (100/25 mg) were administered to test the involvement of dopamine. Expected pain levels, desire for pain relief, and ongoing and evoked pain were assessed on mechanical visual analog scales (0-10). Significant placebo effects on ongoing (P ≤ 0.003) and evoked (P ≤ 0.002) pain were observed. Expectancy and desire accounted for up to 41.2% and 71.5% of the variance in ongoing and evoked pain, respectively, after the open application of lidocaine. We found no evidence for an effect of haloperidol and levodopa/carbidopa on neuropathic pain levels (P = 0.071-0.963). Dopamine seemed to influence the levels of expectancy and desire, yet there was no evidence for indirect or interaction effects on the placebo effect. This is the first study to suggest that dopamine does not contribute to placebo effects in chronic neuropathic pain.

Hypersensitivity to pain in congenital blindness

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Slimani, Hocine; Danti, Sabrina; Ricciardi, Emiliano

2013-01-01

Vision is important for avoiding encounters with objects in the environment that may imperil physical integrity. We tested whether, in the absence of vision, a lower pain threshold would arise from an adaptive shift to other sensory channels. We therefore measured heat and cold pain thresholds an...... that blind subjects are more attentive to signals of external threats. These findings indicate that the absence of vision from birth induces a hypersensitivity to painful stimuli, lending new support to a model of sensory integration of vision and pain processing......., congenitally blind subjects have lower heat pain thresholds, rate suprathreshold heat pain stimuli as more painful, and have increased sensitivity for cold pain stimuli. Thresholds for nonpainful thermal stimulation did not differ between groups. The results of the pain questionnaires further indicated...

Effects of external trigeminal nerve stimulation (eTNS) on laser evoked cortical potentials (LEP): A pilot study in migraine patients and controls.

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Vecchio, Eleonora; Gentile, Eleonora; Franco, Giovanni; Ricci, Katia; de Tommaso, Marina

2017-01-01

Background Transcutaneous external supraorbital nerve stimulation has emerged as a treatment option for primary headache disorders, though its action mechanism is still unclear. Study aim In this randomized, sham-controlled pilot study we aimed to test the effects of a single external transcutaneous nerve stimulation session on pain perception and cortical responses induced by painful laser stimuli delivered to the right forehead and the right hand in a cohort of migraine without aura patients and healthy controls. Methods Seventeen migraine without aura patients and 21 age- and sex-matched controls were selected and randomly assigned to a real or sham external transcutaneous nerve stimulation single stimulation session. The external transcutaneous nerve stimulation was delivered with a self-adhesive electrode placed on the forehead and generating a 60 Hz pulse at 16 mA intensity for 20 minutes. For sham stimulation, we used 2 mA intensity. Laser evoked responses were recorded from 21 scalp electrodes in basal condition (T0), during external transcutaneous nerve stimulation and sham stimulation (T1), and immediately after these (T2). The laser evoked responses were analyzed by LORETA software. Results The real external transcutaneous nerve stimulation reduced the trigeminal N2P2 amplitude in migraine and control groups significantly in respect to placebo. The real stimulation was associated with lower activity in the anterior cingulate cortex under trigeminal laser stimuli. The pattern of LEP-reduced habituation was reverted by real and sham transcutaneous stimulation in migraine patients. Conclusions The present results could suggest that the external transcutaneous nerve stimulation may interfere with the threshold and the extent of trigeminal system activation, with a mechanism of potential utility in the resolution and prevention of migraine attacks.

Brain-immune interaction accompanying odor-evoked autobiographic memory.

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Matsunaga, Masahiro; Bai, Yu; Yamakawa, Kaori; Toyama, Asako; Kashiwagi, Mitsuyoshi; Fukuda, Kazuyuki; Oshida, Akiko; Sanada, Kazue; Fukuyama, Seisuke; Shinoda, Jun; Yamada, Jitsuhiro; Sadato, Norihiro; Ohira, Hideki

2013-01-01

The phenomenon in which a certain smell evokes a specific memory is known as the Proust phenomenon. Odor-evoked autobiographic memories are more emotional than those elicited by other sensory stimuli. The results of our previous study indicated that odor-evoked autobiographic memory accompanied by positive emotions has remarkable effects on various psychological and physiological activities, including the secretion of cytokines, which are immune-signaling molecules that modulate systemic inflammation. In this study, we aimed to clarify the neural substrates associated with the interaction between odor-evoked autobiographic memory and peripheral circulating cytokines. We recruited healthy male and female volunteers and investigated the association between brain responses and the concentration of several cytokines in the plasma by using positron emission tomography (PET) recordings when an autographic memory was evoked in participants by asking them to smell an odor that was nostalgic to them. Participants experienced positive emotions and autobiographic memories when nostalgic odors were presented to them. The levels of peripheral proinflammatory cytokines, such as the tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ), were significantly reduced after experiencing odor-evoked autobiographic memory. Subtraction analysis of PET images indicated that the medial orbitofrontal cortex (mOFC) and precuneus/posterior cingulate cortex (PCC) were significantly activated during experiences of odor-evoked autobiographic memory. Furthermore, a correlation analysis indicated that activities of the mOFC and precuneus/PCC were negatively correlated with IFN-γ concentration. These results indicate that the neural networks including the precuneus/PCC and mOFC might regulate the secretion of peripheral proinflammatory cytokines during the experience of odor-evoked autobiographic memories accompanied with positive emotions.

Brain–Immune Interaction Accompanying Odor-Evoked Autobiographic Memory

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Matsunaga, Masahiro; Bai, Yu; Yamakawa, Kaori; Toyama, Asako; Kashiwagi, Mitsuyoshi; Fukuda, Kazuyuki; Oshida, Akiko; Sanada, Kazue; Fukuyama, Seisuke; Shinoda, Jun; Yamada, Jitsuhiro; Sadato, Norihiro; Ohira, Hideki

2013-01-01

The phenomenon in which a certain smell evokes a specific memory is known as the Proust phenomenon. Odor-evoked autobiographic memories are more emotional than those elicited by other sensory stimuli. The results of our previous study indicated that odor-evoked autobiographic memory accompanied by positive emotions has remarkable effects on various psychological and physiological activities, including the secretion of cytokines, which are immune-signaling molecules that modulate systemic inflammation. In this study, we aimed to clarify the neural substrates associated with the interaction between odor-evoked autobiographic memory and peripheral circulating cytokines. We recruited healthy male and female volunteers and investigated the association between brain responses and the concentration of several cytokines in the plasma by using positron emission tomography (PET) recordings when an autographic memory was evoked in participants by asking them to smell an odor that was nostalgic to them. Participants experienced positive emotions and autobiographic memories when nostalgic odors were presented to them. The levels of peripheral proinflammatory cytokines, such as the tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ), were significantly reduced after experiencing odor-evoked autobiographic memory. Subtraction analysis of PET images indicated that the medial orbitofrontal cortex (mOFC) and precuneus/posterior cingulate cortex (PCC) were significantly activated during experiences of odor-evoked autobiographic memory. Furthermore, a correlation analysis indicated that activities of the mOFC and precuneus/PCC were negatively correlated with IFN-γ concentration. These results indicate that the neural networks including the precuneus/PCC and mOFC might regulate the secretion of peripheral proinflammatory cytokines during the experience of odor-evoked autobiographic memories accompanied with positive emotions. PMID:23977312

Brain-immune interaction accompanying odor-evoked autobiographic memory.

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Masahiro Matsunaga

Full Text Available The phenomenon in which a certain smell evokes a specific memory is known as the Proust phenomenon. Odor-evoked autobiographic memories are more emotional than those elicited by other sensory stimuli. The results of our previous study indicated that odor-evoked autobiographic memory accompanied by positive emotions has remarkable effects on various psychological and physiological activities, including the secretion of cytokines, which are immune-signaling molecules that modulate systemic inflammation. In this study, we aimed to clarify the neural substrates associated with the interaction between odor-evoked autobiographic memory and peripheral circulating cytokines. We recruited healthy male and female volunteers and investigated the association between brain responses and the concentration of several cytokines in the plasma by using positron emission tomography (PET recordings when an autographic memory was evoked in participants by asking them to smell an odor that was nostalgic to them. Participants experienced positive emotions and autobiographic memories when nostalgic odors were presented to them. The levels of peripheral proinflammatory cytokines, such as the tumor necrosis factor-α (TNF-α and interferon-γ (IFN-γ, were significantly reduced after experiencing odor-evoked autobiographic memory. Subtraction analysis of PET images indicated that the medial orbitofrontal cortex (mOFC and precuneus/posterior cingulate cortex (PCC were significantly activated during experiences of odor-evoked autobiographic memory. Furthermore, a correlation analysis indicated that activities of the mOFC and precuneus/PCC were negatively correlated with IFN-γ concentration. These results indicate that the neural networks including the precuneus/PCC and mOFC might regulate the secretion of peripheral proinflammatory cytokines during the experience of odor-evoked autobiographic memories accompanied with positive emotions.

Optokinetic stimulation increases limb pain and forehead hyperalgesia in complex regional pain syndrome

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Knudsen, Lone F.; Drummond, Peter D.

2015-01-01

BACKGROUND: Ambiguous visual stimuli increase limb pain in patients with complex regional pain syndrome (CRPS), possibly due to afferent sensory feedback conflicts. Conflicting sensory stimuli can also generate unpleasant sensations in healthy people such as during motion sickness. We wanted to i...

Psychological and physiological responses to odor-evoked autobiographic memory.

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Matsunaga, Masahiro; Isowa, Tokiko; Yamakawa, Kaori; Kawanishi, Yoko; Tsuboi, Hirohito; Kaneko, Hiroshi; Sadato, Norihiro; Oshida, Akiko; Katayama, Atsushi; Kashiwagi, Mitsuyoshi; Ohira, Hideki

2011-01-01

The "Proust phenomenon" occurs when a certain smell evokes a specific memory. Recent studies have demonstrated that odor-evoked autobiographic memories are more emotional than those elicited by other sensory stimuli because of the direct neural communication between the olfactory system and the amygdala. The amygdala is known to regulate various physiological activities including the endocrine and immune systems; therefore, odor-evoked autobiographic memory may trigger various psychological and physiological responses; however, the responses elicited by this memory remains obscure. In this study, we aimed to investigate the psychological and physiological responses accompanying odor-evoked autobiographic memory. We recruited healthy male and female volunteers and investigated changes in their mood states and autonomic nervous, endocrine, and immune activities when autobiographic memory was evoked in the participants by asking them to smell an odor(s) that was nostalgic to them. The autobiographic memories associated with positive emotion resulted in increased positive mood states, such as comfort and happiness, and decreased negative mood states, such as anxiety. Furthermore, heart rate was decreased, skin-conductance level was increased, and peripheral interleukin-2 level was decreased after smelling the nostalgic odor. These psychological and physiological responses were significantly correlated. The present study suggests that odor-evoked autobiographic memory along with a positive feeling induce various physiological responses, including the autonomic nervous and immune activities. To the best of our knowledge, the present study is the first to observe an interaction between odor-evoked autobiographic memories and immune function.

Experimental orofacial pain and sensory deprivation lead to perceptual distortion of the face in healthy volunteers.

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Dagsdóttir, Lilja Kristín; Skyt, Ina; Vase, Lene; Baad-Hansen, Lene; Castrillon, Eduardo; Svensson, Peter

2015-09-01

Patients suffering from persistent orofacial pain may sporadically report that the painful area feels "swollen" or "differently," a phenomenon that may be conceptualized as a perceptual distortion because there are no clinical signs of swelling present. Our aim was to investigate whether standardized experimental pain and sensory deprivation of specific orofacial test sites would lead to changes in the size perception of these face areas. Twenty-four healthy participants received either 0.2 mL hypertonic saline (HS) or local anesthetics (LA) into six regions (buccal, mental, lingual, masseter muscle, infraorbital and auriculotemporal nerve regions). Participants estimated the perceived size changes in percentage (0 % = no change, -100 % = half the size or +100 % = double the size), and somatosensory function was checked with tactile stimuli. The pain intensity was rated on a 0-10 Verbal Numerical Rating Scale (VNRS), and sets of psychological questionnaires were completed. HS and LA were associated with significant self-reported perceptual distortions as indicated by consistent increases in perceived size of the adjacent face areas (P ≤ 0.050). Perceptual distortion was most pronounced in the buccal region, and the smallest increase was observed in the auriculotemporal region. HS was associated with moderate levels of pain VNRS = 7.3 ± 0.6. Weak correlations were found between HS-evoked perceptual distortion and level of dissociation in two regions (P pain and transient sensory deprivation evoked perceptual distortions in all face regions and overall demonstrated the importance of afferent inputs for the perception of the face. We propose that perceptual distortion may be an important phenomenon to consider in persistent orofacial pain conditions.

Pain Modulation after Oromucosal Cannabinoid Spray (SATIVEX® in Patients with Multiple Sclerosis: A Study with Quantitative Sensory Testing and Laser-Evoked Potentials

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Mara Turri

2018-06-01

Full Text Available Background. Delta-9-tetrahydrocannabinol (THC/cannabidiol (CBD (nabiximols or Sativex® is an oromucosal spray formulation containing THC and CBD at an approximately 1:1 fixed ratio. Its administration for the treatment of pain in patients with multiple sclerosis (MS has been established. MS patients generally complain of different kinds of pain, including spasticity-related and neuropathic pain. In this study, we compared and evaluated pain modulation and thermal/pain threshold of MS patients before and after THC/CBD administration. Methods. 19 MS patients underwent clinical examination, numerical rating scale (NRS, quantitative sensory testing (QST, and laser-evoked potentials (LEPs before and after 1 month of therapy. Psychophysiological and neurophysiological data were compared to sex- and age-matched controls. Results. Patients reported a significant reduction in pain. We found statistically significant differences in LEP parameters between patients and controls but no significant change in LEP measures after THC/CBD therapy. Cold and heat detection thresholds were altered in patients but did not change after THC/CBD therapy. There was a significant increase in cold pain threshold by hand stimulation and a significant reduction in abnormal cold perception thresholds. Conclusions. Our results indicate that Sativex® therapy provides pain relief in MS patients and suggest that it might modulate peripheral cold-sensitive TRP channels.

Phosphatidylinositol 3-kinase is a key mediator of central sensitization in painful inflammatory conditions

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Pezet, Sophie; Marchand, Fabien; D'Mello, Richard; Grist, John; Clark, Anna K.; Malcangio, Marzia; Dickenson, Anthony H.; Williams, Robert J.; McMahon, Stephen B.

2010-01-01

Here we show that phosphatidylinositol 3-kinase (PI3K) is a key player in the establishment of central sensitization, the spinal cord phenomenon associated with persistent afferent inputs and contributing to chronic pain states. We demonstrated electrophysiologically that PI3K is required for the full expression of spinal neuronal wind-up. In an inflammatory pain model, intrathecal administration of LY294002, a potent PI3K inhibitor, dose-dependently inhibited pain related behavior. This effect was correlated with a reduction of the phosphorylation of extracellular signal-regulated kinase (ERK) and CaMKinase II. In addition, we observed a significant decrease in the phosphorylation of the NMDA receptor subunit NR2B, decreased translocation to the plasma membrane of the GluR1 AMPA receptor subunit in the spinal cord and a reduction of evoked neuronal activity as measured using c-Fos immunohistochemistry. Our study suggests that PI3K is a major factor in the expression of central sensitization after noxious inflammatory stimuli. PMID:18417706

Empathy, Pain and Attention: Cues that Predict Pain Stimulation to the Partner and the Self Capture Visual Attention

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Lingdan Wu

2017-09-01

Full Text Available Empathy motivates helping and cooperative behaviors and plays an important role in social interactions and personal communication. The present research examined the hypothesis that a state of empathy guides attention towards stimuli significant to others in a similar way as to stimuli relevant to the self. Sixteen couples in romantic partnerships were examined in a pain-related empathy paradigm including an anticipation phase and a stimulation phase. Abstract visual symbols (i.e., arrows and flashes signaled the delivery of a Pain or Nopain stimulus to the partner or the self while dense sensor event-related potentials (ERPs were simultaneously recorded from both persons. During the anticipation phase, stimuli predicting Pain compared to Nopain stimuli to the partner elicited a larger early posterior negativity (EPN and late positive potential (LPP, which were similar in topography and latency to the EPN and LPP modulations elicited by stimuli signaling pain for the self. Noteworthy, using abstract cue symbols to cue Pain and Nopain stimuli suggests that these effects are not driven by perceptual features. The findings demonstrate that symbolic stimuli relevant for the partner capture attention, which implies a state of empathy to the pain of the partner. From a broader perspective, states of empathy appear to regulate attention processing according to the perceived needs and goals of the partner.

Color vision in attention-deficit/hyperactivity disorder: a pilot visual evoked potential study.

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Kim, Soyeon; Banaschewski, Tobias; Tannock, Rosemary

2015-01-01

Individuals with attention-deficit/hyperactivity disorder (ADHD) are reported to manifest visual problems (including ophthalmological and color perception, particularly for blue-yellow stimuli), but findings are inconsistent. Accordingly, this study investigated visual function and color perception in adolescents with ADHD using color Visual Evoked Potentials (cVEP), which provides an objective measure of color perception. Thirty-one adolescents (aged 13-18), 16 with a confirmed diagnosis of ADHD, and 15 healthy peers, matched for age, gender, and IQ participated in the study. All underwent an ophthalmological exam, as well as electrophysiological testing color Visual Evoked Potentials (cVEP), which measured the latency and amplitude of the neural P1 response to chromatic (blue-yellow, red-green) and achromatic stimuli. No intergroup differences were found in the ophthalmological exam. However, significantly larger P1 amplitude was found for blue and yellow stimuli, but not red/green or achromatic stimuli, in the ADHD group (particularly in the medicated group) compared to controls. Larger amplitude in the P1 component for blue-yellow in the ADHD group compared to controls may account for the lack of difference in color perception tasks. We speculate that the larger amplitude for blue-yellow stimuli in early sensory processing (P1) might reflect a compensatory strategy for underlying problems including compromised retinal input of s-cones due to hypo-dopaminergic tone. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

Unmasking of an early laser evoked potential by a point localization task

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Valeriani, M.; Restuccia, D.; Le Pera, D.

2000-01-01

Objectives: The investigation of the CO2 laser evoked potential (LEP) modifications following a point localization task. Methods: LEPs were recorded from 10 healthy subjects in two different conditions. (1) Task condition: laser stimuli were shifted among 3 different locations on the right hand d...

Uncertainty about the intensity of impending pain increases ensuing pain responses in congenital blindness

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Holten-Rossing, S.; Slimani, H.; Ptito, M.

2018-01-01

about the intensity of a pending painful stimulus affects pain differently in congenitally blind and sighted control subjects. We measured pain and anxiety in a group of 11 congenitally blind and 11 age- and sex-matched normal sighted control participants. Painful stimuli were delivered under two...... psychological conditions, whereby participants were either certain or uncertain about the intensity of a pending noxious stimuli. Although both blind and sighted participants had increased anxiety ratings in the uncertain condition, pain ratings increased only in the congenitally blind participants. Our data...

Intensity modulation of cutaneous electrical stimulation: : EPs and subjective ratings

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van der Heide, E.M.; Buitenweg, Jan R.; Marani, Enrico; Rutten, Wim

2006-01-01

Chronic pain research is increasingly focused on the neuroplastic mechanisms underlying subjective pain experience. The latter is often measured using reported pain intensity, e.g. using a numeric rating scale (NRS). Evoked Potentials (EPs) reflect the cortical representation of applied stimuli and

Race effects on temporal summation to heat pain in youth.

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Morris, Matthew C; Walker, Lynn; Bruehl, Stephen; Hellman, Natalie; Sherman, Amanda L; Rao, Uma

2015-05-01

Racial differences in pain responsiveness have been demonstrated in adults. However, it is unclear whether racial differences are also present in youth and whether they extend to experimental pain indices assessing temporal summation of second pain (TSSP). Temporal summation of second pain provides an index of pain sensitivity and may be especially relevant in determining risk for chronic pain. This study assessed pain tolerance and TSSP to evoked thermal pain in 78 healthy youth (age range, 10-17), 51% of whom were African American and 49% were non-Hispanic white. Multilevel models revealed within-individual increases in pain ratings during the temporal summation task in non-Hispanic white youth that were consistent with TSSP. Pain ratings did not change significantly during the temporal summation task in African-American youth. Baseline evoked pain ratings were significantly higher in African-American compared with non-Hispanic white youth. These findings suggest that enhanced responsiveness to evoked thermal pain in African Americans is present in adolescence but is unlikely to be related to elevated TSSP. These results may have implications for understanding racial differences in chronic pain experience in adulthood.

Peripheral vascular response to mild indirect cooling in patients with homozygous sickle cell (SS) disease and the frequency of painful crisis.

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Mohan, J; Marshall, J M; Reid, H L; Thomas, P W; Hambleton, I; Serjeant, G R

1998-02-01

1. In homozygous sickle cell (SS) disease, skin cooling is a common precipitating factor of the painful crisis which is associated with avascular necrosis of active bone marrow. Since skin cooling does not directly induce sickling, we have investigated the nature of the reflex vascular responses to mild cooling in SS patients in a steady state of the disease and compared them with their history of painful crises. 2. Experiments were performed in Jamaica on 60 male SS patients and 30 matched control subjects with normal haemoglobin (AA) genotype. Forearm blood flow (FBF) was measured by venous occlusion plethysmography and mean arterial pressure (MAP) by a Finapres device: forearm vascular resistance (FVR) was calculated as MAP/FBF. Cutaneous erythrocyte flux in forearm and hand was monitored by a laser Doppler meter. The contralateral hand was immersed in cool water at 16 degrees C for 2 min, 6 times, at random intervals of 0.5-3 min. 3. The first cool immersion evoked an increase in MAP, cutaneous vasoconstriction and a net increase in FVR in both AA and SS subjects. However, the direction of change in FVR varied between individuals such that 18 AA subjects showed an increase in FVR (constrictor group) while 12 showed a decrease in FVR, indicating vasodilatation in forearm muscle (dilator group). In contrast, 50 SS subjects showed an increase in FVR and only 10 showed a decrease in FVR. The proportion of subjects who showed net vasoconstriction was significantly greater in the SS than in the AA group (83% versus 60%, P = 0.03, chi 2 test). 4. By the sixth cool stimulus, the 'dilator' group of AA subjects showed no change in FVR while the 'dilator' group of SS patients showed an increase in FVR. We suggest that forearm muscle vasodilatation was the characteristic component of the alerting/defence response to novel or noxious stimuli which habituates on repetition. 5. In the whole group of SS patients, baseline values of cutaneous vascular resistance and FVR

Click-evoked otoacoustic emissions in children and adolescents with gender identity disorder

NARCIS (Netherlands)

Burke, Sarah M; Menks, Willeke M; Cohen-Kettenis, Peggy T; Klink, Daniel T; Bakker, J.

2014-01-01

Click-evoked otoacoustic emissions (CEOAEs) are echo-like sounds that are produced by the inner ear in response to click-stimuli. CEOAEs generally have a higher amplitude in women compared to men and neonates already show a similar sex difference in CEOAEs. Weaker responses in males are proposed to

Click-Evoked Otoacoustic Emissions in Children and Adolescents with Gender Identity Disorder

NARCIS (Netherlands)

Burke, S.M.; Menks, W.M.; Cohen-Kettenis, P.T.; Klink, D.T.; Bakker, J.

2014-01-01

Click-evoked otoacoustic emissions (CEOAEs) are echo-like sounds that are produced by the inner ear in response to click-stimuli. CEOAEs generally have a higher amplitude in women compared to men and neonates already show a similar sex difference in CEOAEs. Weaker responses in males are proposed to

Exploring combinations of different color and facial expression stimuli for gaze-independent BCIs

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Long eChen

2016-01-01

Full Text Available AbstractBackground: Some studies have proven that a conventional visual brain computer interface (BCI based on overt attention cannot be used effectively when eye movement control is not possible. To solve this problem, a novel visual-based BCI system based on covert attention and feature attention had been proposed and was called the gaze-independent BCI. Color and shape difference between stimuli and backgrounds have generally been used in examples of gaze-independent BCIs. Recently, a new paradigm based on facial expression change had been presented, and obtained high performance. However, some facial expressions were so similar that users couldn’t tell them apart. Especially they were presented at the same position in a rapid serial visual presentation (RSVP paradigm. Consequently, the performance of BCIs is reduced.New Method: In this paper, we combined facial expressions and colors to optimize the stimuli presentation in the gaze-independent BCI. This optimized paradigm was called the colored dummy face pattern. It is suggested that different colors and facial expressions could help subjects to locate the target and evoke larger event-related potentials (ERPs. In order to evaluate the performance of this new paradigm, two other paradigms were presented, called the grey dummy face pattern and the colored ball pattern. Comparison with Existing Method(s: The key point that determined the value of the colored dummy faces stimuli in BCI systems were whether dummy face stimuli could obtain higher performance than grey faces or colored balls stimuli. Ten healthy subjects (7 male, aged 21-26 years, mean 24.5±1.25 participated in our experiment. Online and offline results of four different paradigms were obtained and comparatively analyzed.Results: The results showed that the colored dummy face pattern could evoke higher P300 and N400 ERP amplitudes, compared with the grey dummy face pattern and the colored ball pattern. Online results showed

Effects of single cycle binaural beat duration on auditory evoked potentials.

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Mihajloski, Todor; Bohorquez, Jorge; Özdamar, Özcan

2014-01-01

Binaural beat (BB) illusions are experienced as continuous central pulsations when two sounds with slightly different frequencies are delivered to each ear. It has been shown that steady-state auditory evoked potentials (AEPs) to BBs can be captured and investigated. The authors recently developed a new method of evoking transient AEPs to binaural beats using frequency modulated stimuli. This methodology was able to create single BBs in predetermined intervals with varying carrier frequencies. This study examines the effects of the BB duration and the frequency modulating component of the stimulus on the binaural beats and their evoked potentials. Normal hearing subjects were tested with a set of four durations (25, 50, 100, and 200 ms) with two stimulation configurations, binaural dichotic (binaural beats) and diotic (frequency modulation). The results obtained from the study showed that out of the given durations, the 100 ms beat, was capable of evoking the largest amplitude responses. The frequency modulation effect showed a decrease in peak amplitudes with increasing beat duration until their complete disappearance at 200 ms. Even though, at 200 ms, the frequency modulation effects were not present, the binaural beats were still perceived and captured as evoked potentials.

The Effect of the Type and Colour of Placebo Stimuli on Placebo Effects Induced by Observational Learning

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Świder, Karolina; Bąbel, Przemysław

2016-01-01

Research shows that placebo analgesia and nocebo hyperalgesia can be induced through observational learning. Our aim was to replicate and extend these results by studying the influence of the type and colour of stimuli used as placebos on the placebo effects induced by observational learning. Three experimental and two control groups were tested. All participants received pain stimuli of the same intensity preceded by colour lights (green and red) or geometric shapes (circles and squares). Before receiving pain stimuli, participants in the experimental groups, but not in the control groups, observed a model who rated pain stimuli that were preceded by either green lights (green placebo group), red lights (red placebo group), or circles (circle placebo group) as being less painful than those preceded by either red lights (green placebo group), green lights (red placebo group), or squares (circle placebo group). As a result participants in the experimental groups rated pain stimuli preceded by either green lights (green placebo group), red lights (red placebo group), or circles (circle placebo group) as being less painful than the participants in the control groups did, indicating that placebo effect was induced. No statistically significant differences were found in the magnitudes of the placebo effects between the three experimental groups (green placebo, red placebo, and circle placebo groups), indicating that neither the type nor the colour of placebo stimuli affected the placebo effects induced by observational learning. The placebo effects induced by observational learning were found to be unrelated to the individual differences in pain anxiety, fear of pain, and empathy. PMID:27362552

Time-Course Analysis of the Neuroanatomical Correlates of Sexual Arousal Evoked by Erotic Video Stimuli in Healthy Males

International Nuclear Information System (INIS)

Sundaram, Thirunavukkarasu; Jeong, Gwang Woo; Kim, Tae Hoon; Kim, Gwang Won; Baek, Han Su; Kang, Heoung Keun

2010-01-01

To assess the dynamic activations of the key brain areas associated with the time-course of the sexual arousal evoked by visual sexual stimuli in healthy male subjects. Fourteen right-handed heterosexual male volunteers participated in this study. Alternatively combined rest period and erotic video visual stimulation were used according to the standard block design. In order to illustrate and quantify the spatiotemporal activation patterns of the key brain regions, the activation period was divided into three different stages as the EARLY, MID and LATE stages. For the group result (p < 0.05), when comparing the MID stage with the EARLY stage, a significant increase of the brain activation was observed in the areas that included the inferior frontal gyrus, the supplementary motor area, the hippocampus, the head of the caudate nucleus, the midbrain, the superior occipital gyrus and the fusiform gyrus. At the same time, when comparing the EARLY stage with the MID stage, the putamen, the globus pallidus, the pons, the thalamus, the hypothalamus, the lingual gyrus and the cuneus yielded significantly increased activations. When comparing the LATE stage with the MID stage, all the above mentioned brain regions showed elevated activations except the hippocampus. Our results illustrate the spatiotemporal activation patterns of the key brain regions across the three stages of visual sexual arousal

Time-Course Analysis of the Neuroanatomical Correlates of Sexual Arousal Evoked by Erotic Video Stimuli in Healthy Males

Energy Technology Data Exchange (ETDEWEB)

Sundaram, Thirunavukkarasu; Jeong, Gwang Woo; Kim, Tae Hoon; Kim, Gwang Won; Baek, Han Su; Kang, Heoung Keun [Chonnam National University Hospital, Chonnam National University Medical School, Gwangju (Korea, Republic of)

2010-06-15

To assess the dynamic activations of the key brain areas associated with the time-course of the sexual arousal evoked by visual sexual stimuli in healthy male subjects. Fourteen right-handed heterosexual male volunteers participated in this study. Alternatively combined rest period and erotic video visual stimulation were used according to the standard block design. In order to illustrate and quantify the spatiotemporal activation patterns of the key brain regions, the activation period was divided into three different stages as the EARLY, MID and LATE stages. For the group result (p < 0.05), when comparing the MID stage with the EARLY stage, a significant increase of the brain activation was observed in the areas that included the inferior frontal gyrus, the supplementary motor area, the hippocampus, the head of the caudate nucleus, the midbrain, the superior occipital gyrus and the fusiform gyrus. At the same time, when comparing the EARLY stage with the MID stage, the putamen, the globus pallidus, the pons, the thalamus, the hypothalamus, the lingual gyrus and the cuneus yielded significantly increased activations. When comparing the LATE stage with the MID stage, all the above mentioned brain regions showed elevated activations except the hippocampus. Our results illustrate the spatiotemporal activation patterns of the key brain regions across the three stages of visual sexual arousal.

Time-course analysis of the neuroanatomical correlates of sexual arousal evoked by erotic video stimuli in healthy males.

Science.gov (United States)

Sundaram, Thirunavukkarasu; Jeong, Gwang-Woo; Kim, Tae-Hoon; Kim, Gwang-Won; Baek, Han-Su; Kang, Heoung-Keun

2010-01-01

To assess the dynamic activations of the key brain areas associated with the time-course of the sexual arousal evoked by visual sexual stimuli in healthy male subjects. Fourteen right-handed heterosexual male volunteers participated in this study. Alternatively combined rest period and erotic video visual stimulation were used according to the standard block design. In order to illustrate and quantify the spatiotemporal activation patterns of the key brain regions, the activation period was divided into three different stages as the EARLY, MID and LATE stages. For the group result (p < 0.05), when comparing the MID stage with the EARLY stage, a significant increase of the brain activation was observed in the areas that included the inferior frontal gyrus, the supplementary motor area, the hippocampus, the head of the caudate nucleus, the midbrain, the superior occipital gyrus and the fusiform gyrus. At the same time, when comparing the EARLY stage with the MID stage, the putamen, the globus pallidus, the pons, the thalamus, the hypothalamus, the lingual gyrus and the cuneus yielded significantly increased activations. When comparing the LATE stage with the MID stage, all the above mentioned brain regions showed elevated activations except the hippocampus. Our results illustrate the spatiotemporal activation patterns of the key brain regions across the three stages of visual sexual arousal.

Towards a physiology-based measure of pain: patterns of human brain activity distinguish painful from non-painful thermal stimulation.

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Justin E Brown

Full Text Available Pain often exists in the absence of observable injury; therefore, the gold standard for pain assessment has long been self-report. Because the inability to verbally communicate can prevent effective pain management, research efforts have focused on the development of a tool that accurately assesses pain without depending on self-report. Those previous efforts have not proven successful at substituting self-report with a clinically valid, physiology-based measure of pain. Recent neuroimaging data suggest that functional magnetic resonance imaging (fMRI and support vector machine (SVM learning can be jointly used to accurately assess cognitive states. Therefore, we hypothesized that an SVM trained on fMRI data can assess pain in the absence of self-report. In fMRI experiments, 24 individuals were presented painful and nonpainful thermal stimuli. Using eight individuals, we trained a linear SVM to distinguish these stimuli using whole-brain patterns of activity. We assessed the performance of this trained SVM model by testing it on 16 individuals whose data were not used for training. The whole-brain SVM was 81% accurate at distinguishing painful from non-painful stimuli (p<0.0000001. Using distance from the SVM hyperplane as a confidence measure, accuracy was further increased to 84%, albeit at the expense of excluding 15% of the stimuli that were the most difficult to classify. Overall performance of the SVM was primarily affected by activity in pain-processing regions of the brain including the primary somatosensory cortex, secondary somatosensory cortex, insular cortex, primary motor cortex, and cingulate cortex. Region of interest (ROI analyses revealed that whole-brain patterns of activity led to more accurate classification than localized activity from individual brain regions. Our findings demonstrate that fMRI with SVM learning can assess pain without requiring any communication from the person being tested. We outline tasks that should be

Vicarious pain experiences while observing another in pain: an experimental approach

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Sophie eVandenbroucke

2013-06-01

Full Text Available Objective: This study aimed at developing an experimental paradigm to assess vicarious pain experiences. We further explored the putative moderating role of observer’s characteristics such as hypervigilance for pain and dispositional empathy. Methods: Two experiments are reported using a similar procedure. Undergraduate students were selected based upon whether they reported vicarious pain in daily life, and categorized into a pain responder group or a comparison group. Participants were presented a series of videos showing hands being pricked whilst receiving occasionally pricking (electrocutaneous stimuli themselves. In congruent trials, pricking and visual stimuli were applied to the same spatial location. In incongruent trials, pricking and visual stimuli were in the opposite spatial location. Participants were required to report on which location they felt a pricking sensation. Of primary interest was the effect of viewing another in pain upon vicarious pain errors, i.e., the number of trials in which an illusionary sensation was reported. Furthermore, we explored the effect of individual differences in hypervigilance to pain, dispositional empathy and the rubber hand illusion (RHI upon vicarious pain errors. Results: Results of both experiments indicated that the number of vicarious pain errors was overall low. In line with expectations, the number of vicarious pain errors was higher in the pain responder group than in the comparison group. Self-reported hypervigilance for pain lowered the probability of reporting vicarious pain errors in the pain responder group, but dispositional empathy and the RHI did not. Conclusion: Our paradigm allows measuring vicarious pain experiences in students. However, the prevalence of vicarious experiences of pain is low, and only a small percentage of participants display the phenomenon. It remains however unknown which variables affect its occurrence.

Brain potentials evoked by intraepidermal electrical stimuli reflect the central sensitization of nociceptive pathways.

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Liang, M; Lee, M C; O'Neill, J; Dickenson, A H; Iannetti, G D

2016-08-01

Central sensitization (CS), the increased sensitivity of the central nervous system to somatosensory inputs, accounts for secondary hyperalgesia, a typical sign of several painful clinical conditions. Brain potentials elicited by mechanical punctate stimulation using flat-tip probes can provide neural correlates of CS, but their signal-to-noise ratio is limited by poor synchronization of the afferent nociceptive input. Additionally, mechanical punctate stimulation does not activate nociceptors exclusively. In contrast, low-intensity intraepidermal electrical stimulation (IES) allows selective activation of type II Aδ-mechano-heat nociceptors (II-AMHs) and elicits reproducible brain potentials. However, it is unclear whether hyperalgesia from IES occurs and coexists with secondary mechanical punctate hyperalgesia, and whether the magnitude of the electroencephalographic (EEG) responses evoked by IES within the hyperalgesic area is increased. To address these questions, we explored the modulation of the psychophysical and EEG responses to IES by intraepidermal injection of capsaicin in healthy human subjects. We obtained three main results. First, the intensity of the sensation elicited by IES was significantly increased in participants who developed robust mechanical punctate hyperalgesia after capsaicin injection (i.e., responders), indicating that hyperalgesia from IES coexists with punctate mechanical hyperalgesia. Second, the N2 peak magnitude of the EEG responses elicited by IES was significantly increased after the intraepidermal injection of capsaicin in responders only. Third, a receiver-operator characteristics analysis showed that the N2 peak amplitude is clearly predictive of the presence of CS. These findings suggest that the EEG responses elicited by IES reflect secondary hyperalgesia and therefore represent an objective correlate of CS. Copyright © 2016 the American Physiological Society.

Sex differences in the neural representation of pain unpleasantness.

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Girard-Tremblay, Lydia; Auclair, Vincent; Daigle, Kathya; Léonard, Guillaume; Whittingstall, Kevin; Goffaux, Philippe

2014-08-01

Sex differences in pain perception are still poorly understood, but they may be related to the way the brains of men and women respond to the affective dimensions of pain. Using a matched pain intensity paradigm, where pain intensity was kept constant across participants but pain unpleasantness was left free to vary among participants, we studied the relationship between pain unpleasantness and pain-evoked brain activity in healthy men and women separately. Experimental pain was provoked using transcutaneous electrical stimulation of the sural nerve while pain-related brain activity was measured using somatosensory-evoked brain potentials with source localization. Cardiac responses to pain were also measured using electrocardiac recordings. Results revealed that subjective pain unpleasantness was strongly associated with increased perigenual anterior cingulate cortex activity in women, whereas it was strongly associated with decreased ventromedial prefrontal cortex activity in men. Only ventromedial prefrontal cortex deactivations in men were additionally associated with increased autonomic cardiac arousal. These results suggest that in order to deal with pain's objectionable properties, men preferentially deactivate prefrontal suppression regions, leading to the mobilization of threat-control circuits, whereas women recruit well-known emotion-processing areas of the brain. This article presents neuroimaging findings demonstrating that subjective pain unpleasantness ratings are associated with different pain-evoked brain responses in men and women, which has potentially important implications regarding sex differences in the risk of developing chronic pain. Copyright © 2014 American Pain Society. Published by Elsevier Inc. All rights reserved.

Do patients with chronic unilateral orofacial pain due to a temporomandibular disorder show increased attending to somatosensory input at the painful side of the jaw?

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Van Damme, Stefaan; Vanden Bulcke, Charlotte; Van Den Berghe, Linda; Poppe, Louise; Crombez, Geert

2018-01-01

Patients with chronic orofacial pain due to temporomandibular disorders (TMD) display alterations in somatosensory processing at the jaw, such as amplified perception of tactile stimuli, but the underlying mechanisms remain unclear. This study investigated one possible explanation, namely hypervigilance, and tested if TMD patients with unilateral pain showed increased attending to somatosensory input at the painful side of the jaw. TMD patients with chronic unilateral orofacial pain ( n  = 20) and matched healthy volunteers ( n  = 20) performed a temporal order judgment (TOJ) task indicated which one of two tactile stimuli, presented on each side of the jaw, they had perceived first. TOJ methodology allows examining spatial bias in somatosensory processing speed. Furthermore, after each block of trials, the participants rated the perceived intensity of tactile stimuli separately for both sides of the jaw. Finally, questionnaires assessing pain catastrophizing, fear-avoidance beliefs, and pain vigilance, were completed. TMD patients tended to perceive tactile stimuli at the painful jaw side as occurring earlier in time than stimuli at the non-painful side but this effect did not reach conventional levels of significance ( p  = .07). In the control group, tactile stimuli were perceived as occurring simultaneously. Secondary analyses indicated that the magnitude of spatial bias in the TMD group is positively associated with the extent of fear-avoidance beliefs. Overall, intensity ratings of tactile stimuli were significantly higher in the TMD group than in the control group, but there was no significant difference between the painful and non-painful jaw side in the TMD patients. The hypothesis that TMD patients with chronic unilateral orofacial pain preferentially attend to somatosensory information at the painful side of the jaw was not statistically supported, although lack of power could not be ruled out as a reason for this. The findings are discussed within

Muscle synergies evoked by microstimulation are preferentially encoded during behavior

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Simon Alexander Overduin

2014-03-01

Full Text Available Electrical microstimulation studies provide some of the most direct evidence for the neural representation of muscle synergies. These synergies, i.e. coordinated activations of groups of muscles, have been proposed as building blocks for the construction of motor behaviors by the nervous system. Intraspinal or intracortical microstimulation has been shown to evoke muscle patterns that can be resolved into a small set of synergies similar to those seen in natural behavior. However, questions remain about the validity of microstimulation as a probe of neural function, particularly given the relatively long trains of supratheshold stimuli used in these studies. Here, we examined whether muscle synergies evoked during intracortical microstimulation in two rhesus macaques were similarly encoded by nearby motor cortical units during a purely voluntary behavior involving object reach, grasp, and carry movements. At each microstimulation site we identified the synergy most strongly evoked among those extracted from muscle patterns evoked over all microstimulation sites. For each cortical unit recorded at the same microstimulation site, we then identified the synergy most strongly encoded among those extracted from muscle patterns recorded during the voluntary behavior. We found that the synergy most strongly evoked at an intracortical microstimulation site matched the synergy most strongly encoded by proximal units more often than expected by chance. These results suggest a common neural substrate for microstimulation-evoked motor responses and for the generation of muscle patterns during natural behaviors.

A human experimental model of episodic pain

DEFF Research Database (Denmark)

Petrini, Laura; Hennings, Kristian; Li, Xi

2014-01-01

(VRS). Physiological (blood flow and axon flare reflex), psychophysical (perception threshold and verbal pain ratings) and electrophysiological (128 channels recorded somatosensory evoked potential (SEP)) measurements were recorded. The stimulation evoked a visible axon flare reflex and caused...

Stimulus specificity of a steady-state visual-evoked potential-based brain-computer interface

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Ng, Kian B.; Bradley, Andrew P.; Cunnington, Ross

2012-06-01

The mechanisms of neural excitation and inhibition when given a visual stimulus are well studied. It has been established that changing stimulus specificity such as luminance contrast or spatial frequency can alter the neuronal activity and thus modulate the visual-evoked response. In this paper, we study the effect that stimulus specificity has on the classification performance of a steady-state visual-evoked potential-based brain-computer interface (SSVEP-BCI). For example, we investigate how closely two visual stimuli can be placed before they compete for neural representation in the cortex and thus influence BCI classification accuracy. We characterize stimulus specificity using the four stimulus parameters commonly encountered in SSVEP-BCI design: temporal frequency, spatial size, number of simultaneously displayed stimuli and their spatial proximity. By varying these quantities and measuring the SSVEP-BCI classification accuracy, we are able to determine the parameters that provide optimal performance. Our results show that superior SSVEP-BCI accuracy is attained when stimuli are placed spatially more than 5° apart, with size that subtends at least 2° of visual angle, when using a tagging frequency of between high alpha and beta band. These findings may assist in deciding the stimulus parameters for optimal SSVEP-BCI design.

Usefulness of laser-evoked potentials and quantitative sensory testing in the diagnosis of neuropathic spinal cord injury pain: a multiple case study.

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Landmann, G; Berger, M F; Stockinger, L; Opsommer, E

2017-06-01

A retrospective study. The aim of this study was to investigate the contribution of laser-evoked potentials (LEPs) and quantitative sensory testing (QST) to the diagnosis of neuropathic pain in patients with spinal cord injury (SCI) and inconclusive magnetic resonance imaging (MRI) findings. A multidisciplinary pain center. QST (DFNS protocol) and Tm-YAG-laser stimulation of the skin were applied within the pain site corresponding with dermatomes of altered sensation. Available MRI scans were reviewed. Thirteen individuals (50±16 years) with SCI were examined. In four cases with no detectable neural lesion on MRI, all QST but three LEP were abnormal. In four patients with poorly defined spinal lesion on MRI, all QST but three LEP only were abnormal. In four cases where pain was not matching adequately with MRI lesions, all patients had abnormal LEP and QST. In one patient showing a spinal cord atrophy, LEP was normal but QST was abnormal. Findings supported the diagnoses at-level (n=5) and below-level (n=8) SCI pain. Spinothalamic tract function assessed by LEP was normal in three cases, but QST was abnormal in all cases. As QST is a psychophysical examination depending on patient cooperation, we suggest that the combination of QST and LEP might be a valuable diagnostic tool to detect lesions of the somatosensory system in a subgroup of patients with neuropathic spinal cord injury pain and inconclusive MRI findings.

Increased wind-up to heat pain in women with a childhood history of functional abdominal pain.

Science.gov (United States)

Dengler-Crish, Christine M; Bruehl, Stephen; Walker, Lynn S

2011-04-01

Idiopathic or functional abdominal pain (FAP) is common in school-age children and typically reflects a functional gastrointestinal disorder (FGID). FGIDs in adults have been distinguished by enhanced responses of the central nervous system to pain stimuli, known as central sensitization. This study investigated whether adolescents and young adults with a history of pediatric FAP (n=144), compared with well control subjects (n=78), showed enhanced central sensitization demonstrated by greater temporal summation (wind-up) to brief, repetitive heat pulses. We also assessed the role of gender and trait anxiety in wind-up to heat pain. Women with a history of FAP showed greater wind-up to heat pain than men with a history of FAP (Ppain was ongoing at follow-up and those whose pain had resolved. Although anxiety was significantly higher in the FAP group compared with control subjects (Ppain associated with enhanced central nervous system responses to pain stimuli. Young women with a childhood history of functional abdominal pain may have a long-term vulnerability to pain that is associated with enhanced responses of the central nervous system to pain stimuli. Copyright © 2010 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Inhibition of Inactive States of Tetrodotoxin-Sensitive Sodium Channels Reduces Spontaneous Firing of C-Fiber Nociceptors and Produces Analgesia in Formalin and Complete Freund's Adjuvant Models of Pain.

Directory of Open Access Journals (Sweden)

David J Matson

Full Text Available While genetic evidence shows that the Nav1.7 voltage-gated sodium ion channel is a key regulator of pain, it is unclear exactly how Nav1.7 governs neuronal firing and what biophysical, physiological, and distribution properties of a pharmacological Nav1.7 inhibitor are required to produce analgesia. Here we characterize a series of aminotriazine inhibitors of Nav1.7 in vitro and in rodent models of pain and test the effects of the previously reported "compound 52" aminotriazine inhibitor on the spiking properties of nociceptors in vivo. Multiple aminotriazines, including some with low terminal brain to plasma concentration ratios, showed analgesic efficacy in the formalin model of pain. Effective concentrations were consistent with the in vitro potency as measured on partially-inactivated Nav1.7 but were far below concentrations required to inhibit non-inactivated Nav1.7. Compound 52 also reversed thermal hyperalgesia in the complete Freund's adjuvant (CFA model of pain. To study neuronal mechanisms, electrophysiological recordings were made in vivo from single nociceptive fibers from the rat tibial nerve one day after CFA injection. Compound 52 reduced the spontaneous firing of C-fiber nociceptors from approximately 0.7 Hz to 0.2 Hz and decreased the number of action potentials evoked by suprathreshold tactile and heat stimuli. It did not, however, appreciably alter the C-fiber thresholds for response to tactile or thermal stimuli. Surprisingly, compound 52 did not affect spontaneous activity or evoked responses of Aδ-fiber nociceptors. Results suggest that inhibition of inactivated states of TTX-S channels, mostly likely Nav1.7, in the peripheral nervous system produces analgesia by regulating the spontaneous discharge of C-fiber nociceptors.

Alleged Approach-Avoidance Conflict for Food Stimuli in Binge Eating Disorder.

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Elisabeth J Leehr

Full Text Available Food stimuli are omnipresent and naturally primary reinforcing stimuli. One explanation for the intake of high amounts of food in binge eating disorder (BED is a deviant valuation process. Valuation of food stimuli is supposed to influence approach or avoidance behaviour towards food. Focusing on self-reported and indirect (facial electromyography valuation process, motivational aspects in the processing of food stimuli were investigated.We compared an overweight sample with BED (BED+ with an overweight sample without BED (BED- and with normal weight controls (NWC regarding their self-reported and indirect (via facial electromyography valuation of food versus non-food stimuli.Regarding the self-reported valuation, the BED+ sample showed a significantly stronger food-bias compared to the BED- sample, as food stimuli were rated as significantly more positive than the non-food stimuli in the BED+ sample. This self-reported valuation pattern could not be displayed in the indirect valuation. Food stimuli evoked negative indirect valuation in all groups. The BED+ sample showed the plainest approach-avoidance conflict marked by a diverging self-reported (positive and indirect (negative valuation of food stimuli.BED+ showed a deviant self-reported valuation of food as compared to BED-. The valuation process of the BED+ sample seems to be characterized by a motivational ambivalence. This ambivalence should be subject of further studies and may be of potential use for therapeutic interventions.

Enhancement of subjective pain experience and changes of brain function on sadness

International Nuclear Information System (INIS)

Yoshino, Atsuo; Takahashi, Terumichi; Okamoto, Yasumasa; Yoshimura, Shinpei; Kunisato, Yoshihiko; Okada, Go; Yamawaki, Shigeto; Onoda, Keiichi

2012-01-01

Pain is a multidimensional experience. Previous psychological studies have shown that a person's subjective pain threshold can change when certain emotions are recognized. We examined this association by using functional magnetic resonance imaging (fMRI) (15 healthy subjects) and magnetoencephalography (MEG) (19 healthy subjects). Subjects experienced pain stimuli in different emotional contexts induced by the presentation of sad, happy or neutral facial stimuli. They also rated their subjective pain intensity. We found: The intensity of subjective pain ratings increased in the sad emotional context, pain-related activation in the anterior cingulate cortex (ACC) was more pronounced in the sad context, and we demonstrated amygdala to ACC connections during the experience of pain in the sad context, and event-related desynchronization (ERD) of lower beta bands in the right hemisphere after pain stimuli was larger in the sad emotional condition. These results show that emotional stimuli can modulate neural responses to pain stimuli, and that it may be relevant to understanding the broader relationship between somatic complaints and negative emotion. (author)

Influence of glutamate-evoked pain and sustained elevated muscle activity on blood oxygenation in the human masseter muscle.

Science.gov (United States)

Suzuki, Shunichi; Arima, Taro; Kitagawa, Yoshimasa; Svensson, Peter; Castrillon, Eduardo

2017-12-01

This study aimed to investigate the effect of glutamate-evoked masseter muscle pain on intramuscular oxygenation during rest and sustained elevated muscle activity (SEMA). Seventeen healthy individuals participated in two sessions in which they were injected with glutamate and saline in random order. Each session was divided into three, 10-min periods. During the first (period 1) and the last (period 3) 10-min periods, participants performed five intercalated 1-min bouts of masseter SEMA with 1-min periods of 'rest'. At onset of the second 10-min period, glutamate (0.5 ml, 1 M; Ajinomoto, Tokyo, Japan) or isotonic saline (0.5 ml; 0.9%) was injected into the masseter muscle and the participants kept the muscle relaxed in a resting position for 10 min (period 2). The hemodynamic characteristics of the masseter muscle were recorded simultaneously during the experiment by a laser blood-oxygenation monitor. The results demonstrated that glutamate injections caused significant levels of self-reported pain in the masseter muscle; however, this nociceptive input did not have robust effects on intramuscular oxygenation during rest or SEMA tasks. Interestingly, these findings suggest an uncoupling between acute nociceptive activity and hemodynamic parameters in both resting and low-level active jaw muscles. Further studies are needed to explore the pathophysiological significance of blood-flow changes for persistent jaw-muscle pain conditions. © 2017 Eur J Oral Sci.

Effects of propofol anesthesia on the processing of noxious stimuli in the spinal cord and the brain.

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Lichtner, Gregor; Auksztulewicz, Ryszard; Kirilina, Evgeniya; Velten, Helena; Mavrodis, Dionysios; Scheel, Michael; Blankenburg, Felix; von Dincklage, Falk

2018-05-15

Drug-induced unconsciousness is an essential component of general anesthesia, commonly attributed to attenuation of higher-order processing of external stimuli and a resulting loss of information integration capabilities of the brain. In this study, we investigated how the hypnotic drug propofol at doses comparable to those in clinical practice influences the processing of somatosensory stimuli in the spinal cord and in primary and higher-order cortices. Using nociceptive reflexes, somatosensory evoked potentials and functional magnet resonance imaging (fMRI), we found that propofol abolishes the processing of innocuous and moderate noxious stimuli at low to medium concentration levels, but that intense noxious stimuli evoked spinal and cerebral responses even during deep propofol anesthesia that caused profound electroencephalogram (EEG) burst suppression. While nociceptive reflexes and somatosensory potentials were affected only in a minor way by further increasing doses of propofol after the loss of consciousness, fMRI showed that increasing propofol concentration abolished processing of intense noxious stimuli in the insula and secondary somatosensory cortex and vastly increased processing in the frontal cortex. As the fMRI functional connectivity showed congruent changes with increasing doses of propofol - namely the temporal brain areas decreasing their connectivity with the bilateral pre-/postcentral gyri and the supplementary motor area, while connectivity of the latter with frontal areas is increased - we conclude that the changes in processing of noxious stimuli during propofol anesthesia might be related to changes in functional connectivity. Copyright © 2018 Elsevier Inc. All rights reserved.

Do patients with chronic unilateral orofacial pain due to a temporomandibular disorder show increased attending to somatosensory input at the painful side of the jaw?

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Stefaan Van Damme

2018-01-01

Full Text Available Background Patients with chronic orofacial pain due to temporomandibular disorders (TMD display alterations in somatosensory processing at the jaw, such as amplified perception of tactile stimuli, but the underlying mechanisms remain unclear. This study investigated one possible explanation, namely hypervigilance, and tested if TMD patients with unilateral pain showed increased attending to somatosensory input at the painful side of the jaw. Methods TMD patients with chronic unilateral orofacial pain (n = 20 and matched healthy volunteers (n = 20 performed a temporal order judgment (TOJ task indicated which one of two tactile stimuli, presented on each side of the jaw, they had perceived first. TOJ methodology allows examining spatial bias in somatosensory processing speed. Furthermore, after each block of trials, the participants rated the perceived intensity of tactile stimuli separately for both sides of the jaw. Finally, questionnaires assessing pain catastrophizing, fear-avoidance beliefs, and pain vigilance, were completed. Results TMD patients tended to perceive tactile stimuli at the painful jaw side as occurring earlier in time than stimuli at the non-painful side but this effect did not reach conventional levels of significance (p = .07. In the control group, tactile stimuli were perceived as occurring simultaneously. Secondary analyses indicated that the magnitude of spatial bias in the TMD group is positively associated with the extent of fear-avoidance beliefs. Overall, intensity ratings of tactile stimuli were significantly higher in the TMD group than in the control group, but there was no significant difference between the painful and non-painful jaw side in the TMD patients. Discussion The hypothesis that TMD patients with chronic unilateral orofacial pain preferentially attend to somatosensory information at the painful side of the jaw was not statistically supported, although lack of power could not be ruled out as a

Tlx3 Function in the Dorsal Root Ganglion is Pivotal to Itch and Pain Sensations

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Chengcheng Huang

2017-06-01

Full Text Available Itch, a sensation eliciting a desire to scratch, is distinct from but not completely independent of pain. Inspiring achievements have been made in the characterization of itch-related receptors and neurotransmitters, but the molecular mechanisms controlling the development of pruriceptors remain poorly understood. Here, our RNAseq and in situ hybridization data show that the transcription factor Tlx3 is required for the expression of a majority of itch-related molecules in the dorsal root ganglion (DRG. As a result, Tlx3F/F;Nav1.8-cre mice exhibit significantly attenuated acute and dry skin-induced chronic itch. Furthermore, our study indicates that TRPV1 plays a pivotal role in the chronic itch evoked by dry skin and allergic contact dermatitis (ACD. The mutants also display impaired response to cold and inflammatory pain and elevated response to capsaicin, whereas the responses to acute mechanical, thermal stimuli and neuropathic pain remain normal. In Tlx3F/F;Nav1.8-cre mice, TRPV1 is derepressed and expands predominantly into IB4+ non-peptidergic (NP neurons. Collectively, our data reveal a molecular mechanism in regulating the development of pruriceptors and controlling itch and pain sensations.

Behavioral and molecular processing of visceral pain in the brain of mice: impact of colitis and psychological stress

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Piyush eJain

2015-07-01

Full Text Available Gastrointestinal disorders with abdominal pain are associated with central sensitization and psychopathologies that are often exacerbated by stress. Here we investigated the impact of colitis induced by dextran sulfate sodium (DSS and repeated water avoidance stress (WAS on spontaneous and nociception-related behavior and molecular signaling in the mouse brain. DSS increased the mechanical pain sensitivity of the abdominal skin while both WAS and DSS enhanced the mechanical and thermal pain sensitivity of the plantar skin. These manifestations of central sensitization were associated with augmented c-Fos expression in spinal cord, thalamus, hypothalamus, amygdala and prefrontal cortex. While WAS stimulated phosphorylation of mitogen-activated protein kinase (MAPK p42/44, DSS activated another signaling pathway, both of which converged on c-Fos. The DSS- and WAS-induced hyperalgesia in the abdominal and plantar skin and c-Fos expression in the brain disappeared when the mice were subjected to WAS+DSS treatment. Intrarectal allyl isothiocyanate (AITC evoked aversive behavior (freezing, reduction of locomotion and exploration in association with p42/44 MAPK and c-Fos activation in spinal cord and brain. These effects were inhibited by morphine, which attests to their relationship with nociception. DSS and WAS exerted opposite effects on AITC-evoked p42/44 MAPK and c-Fos activation, which indicates that these transduction pathways subserve different aspects of visceral pain processing in the brain. In summary, behavioral perturbations caused by colitis and psychological stress are associated with distinct alterations in cerebral signaling. These findings provide novel perspectives on central sensitization and the sensory and emotional processing of visceral pain stimuli in the brain.

Psychophysics, flare, and neurosecretory function in human pain models: capsaicin versus electrically evoked pain.

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Geber, Christian; Fondel, Ricarda; Krämer, Heidrun H; Rolke, Roman; Treede, Rolfe-Detlef; Sommer, Claudia; Birklein, Frank

2007-06-01

Intradermal capsaicin injection (CAP) and electrical current stimulation (ES) are analyzed in respect to patterns and test-retest reliability of pain as well as sensory and neurosecretory changes. In 10 healthy subjects, 2x CAP (50 microg) and 2x ES (5 to 30 mA) were applied to the volar forearm. The time period between 2 identical stimulations was about 4 months. Pain ratings, areas of mechanical hyperalgesia, and allodynia were assessed. The intensity of sensory changes was quantified by using quantitative sensory testing. Neurogenic flare was assessed by using laser Doppler imaging. Calcitonin gene-related peptide (CGRP) release was quantified by dermal microdialysis in combination with an enzyme immunoassay. Time course and peak pain ratings were different between CAP and ES. Test-retest correlation was high (r > or = 0.73). Both models induced primary heat hyperalgesia and primary plus secondary pin-prick hyperalgesia. Allodynia occurred in about half of the subjects. Maximum flare sizes did not differ between CAP and ES, but flare intensities were higher for ES. Test-retest correlation was higher for flare sizes than for flare intensity. A significant CGRP release could only be measured after CAP. The different time courses of pain stimulation (CAP: rapidly decaying pain versus ES: pain plateau) led to different peripheral neurosecretory effects but induced similar central plasticity and hyperalgesia. The present study gives a detailed overview of psychophysical and neurosecretory characteristics induced by noxious stimulation with capsaicin and electrical current. We describe differences, similarities, and reproducibility of these human pain models. These data might help to interpret past and future results of human pain studies using experimental pain.

Measuring empathy for human and robot hand pain using electroencephalography.

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Suzuki, Yutaka; Galli, Lisa; Ikeda, Ayaka; Itakura, Shoji; Kitazaki, Michiteru

2015-11-03

This study provides the first physiological evidence of humans' ability to empathize with robot pain and highlights the difference in empathy for humans and robots. We performed electroencephalography in 15 healthy adults who observed either human- or robot-hand pictures in painful or non-painful situations such as a finger cut by a knife. We found that the descending phase of the P3 component was larger for the painful stimuli than the non-painful stimuli, regardless of whether the hand belonged to a human or robot. In contrast, the ascending phase of the P3 component at the frontal-central electrodes was increased by painful human stimuli but not painful robot stimuli, though the interaction of ANOVA was not significant, but marginal. These results suggest that we empathize with humanoid robots in late top-down processing similarly to human others. However, the beginning of the top-down process of empathy is weaker for robots than for humans.

Filtering the reality: functional dissociation of lateral and medial pain systems during sleep in humans.

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Bastuji, Hélène; Mazza, Stéphanie; Perchet, Caroline; Frot, Maud; Mauguière, François; Magnin, Michel; Garcia-Larrea, Luis

2012-11-01

Behavioral reactions to sensory stimuli during sleep are scarce despite preservation of sizeable cortical responses. To further understand such dissociation, we recorded intracortical field potentials to painful laser pulses in humans during waking and all-night sleep. Recordings were obtained from the three cortical structures receiving 95% of the spinothalamic cortical input in primates, namely the parietal operculum, posterior insula, and mid-anterior cingulate cortex. The dynamics of responses during sleep differed among cortical sites. In sleep Stage 2, evoked potential amplitudes were similarly attenuated relative to waking in all three cortical regions. During paradoxical, or rapid eye movements (REM), sleep, opercular and insular potentials remained stable in comparison with Stage 2, whereas the responses from mid-anterior cingulate abated drastically, and decreasing below background noise in half of the subjects. Thus, while the lateral operculo-insular system subserving sensory analysis of somatic stimuli remained active during paradoxical-REM sleep, mid-anterior cingulate processes related to orienting and avoidance behavior were suppressed. Dissociation between sensory and orienting-motor networks might explain why nociceptive stimuli can be either neglected or incorporated into dreams without awakening the subject. Copyright © 2011 Wiley Periodicals, Inc.

Music-Evoked Emotions—Current Studies

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Schaefer, Hans-Eckhardt

2017-01-01

The present study is focused on a review of the current state of investigating music-evoked emotions experimentally, theoretically and with respect to their therapeutic potentials. After a concise historical overview and a schematic of the hearing mechanisms, experimental studies on music listeners and on music performers are discussed, starting with the presentation of characteristic musical stimuli and the basic features of tomographic imaging of emotional activation in the brain, such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), which offer high spatial resolution in the millimeter range. The progress in correlating activation imaging in the brain to the psychological understanding of music-evoked emotion is demonstrated and some prospects for future research are outlined. Research in psychoneuroendocrinology and molecular markers is reviewed in the context of music-evoked emotions and the results indicate that the research in this area should be intensified. An assessment of studies involving measuring techniques with high temporal resolution down to the 10 ms range, as, e.g., electroencephalography (EEG), event-related brain potentials (ERP), magnetoencephalography (MEG), skin conductance response (SCR), finger temperature, and goose bump development (piloerection) can yield information on the dynamics and kinetics of emotion. Genetic investigations reviewed suggest the heredity transmission of a predilection for music. Theoretical approaches to musical emotion are directed to a unified model for experimental neurological evidence and aesthetic judgment. Finally, the reports on musical therapy are briefly outlined. The study concludes with an outlook on emerging technologies and future research fields. PMID:29225563

The effect of opioid receptor blockade on the neural processing of thermal stimuli.

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Eszter D Schoell

Full Text Available The endogenous opioid system represents one of the principal systems in the modulation of pain. This has been demonstrated in studies of placebo analgesia and stress-induced analgesia, where anti-nociceptive activity triggered by pain itself or by cognitive states is blocked by opioid antagonists. The aim of this study was to characterize the effect of opioid receptor blockade on the physiological processing of painful thermal stimulation in the absence of cognitive manipulation. We therefore measured BOLD (blood oxygen level dependent signal responses and intensity ratings to non-painful and painful thermal stimuli in a double-blind, cross-over design using the opioid receptor antagonist naloxone. On the behavioral level, we observed an increase in intensity ratings under naloxone due mainly to a difference in the non-painful stimuli. On the neural level, painful thermal stimulation was associated with a negative BOLD signal within the pregenual anterior cingulate cortex, and this deactivation was abolished by naloxone.

Secondary hyperalgesia to heat stimuli after burn injury in man

DEFF Research Database (Denmark)

Pedersen, J L; Kehlet, H

1998-01-01

The aim of the study was to examine the presence of hyperalgesia to heat stimuli within the zone of secondary hyperalgesia to punctate mechanical stimuli. A burn was produced on the medial part of the non-dominant crus in 15 healthy volunteers with a 50 x 25 mm thermode (47 degrees C, 7 min......), and assessments were made 70 min and 40 min before, and 0, 1, and 2 h after the burn injury. Hyperalgesia to mechanical and heat stimuli were examined by von Frey hairs and contact thermodes (3.75 and 12.5 cm2), and pain responses were rated with a visual analog scale (0-100). The area of secondary hyperalgesia...... to punctate stimuli was assessed with a rigid von Frey hair (462 mN). The heat pain responses to 45 degrees C in 5 s (3.75 cm2) were tested in the area just outside the burn, where the subjects developed secondary hyperalgesia, and on the lateral crus where no subject developed secondary hyperalgesia (control...

Neural Activation during Anticipation of Near Pain-Threshold Stimulation among the Pain-Fearful.

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Yang, Zhou; Jackson, Todd; Huang, Chengzhi

2016-01-01

Fear of pain (FOP) can increase risk for chronic pain and disability but little is known about corresponding neural responses in anticipation of potential pain. In this study, more (10 women, 6 men) and less (7 women, 6 men) pain-fearful groups underwent whole-brain functional magnetic resonance imaging (fMRI) during anticipation of near pain-threshold stimulation. Groups did not differ in the proportion of stimuli judged to be painful but pain-fearful participants reported significantly more state fear prior to stimulus exposure. Within the entire sample, stronger activation was found in several pain perception regions (e.g., bilateral insula, midcingulate cortex (MCC), thalamus, superior frontal gyrus) and visual areas linked to decoding stimulus valences (inferior orbital cortex) during anticipation of "painful" stimuli. Between groups and correlation analyses indicated pain-fearful participants experienced comparatively more activity in regions implicated in evaluating potential threats and processing negative emotions during anticipation (i.e., MCC, mid occipital cortex, superior temporal pole), though group differences were not apparent in most so-called "pain matrix" regions. In sum, trait- and task-based FOP is associated with enhanced responsiveness in regions involved in threat processing and negative affect during anticipation of potentially painful stimulation.

Direct electrical stimulation of human cortex evokes high gamma activity that predicts conscious somatosensory perception

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Muller, Leah; Rolston, John D.; Fox, Neal P.; Knowlton, Robert; Rao, Vikram R.; Chang, Edward F.

2018-04-01

Objective. Direct electrical stimulation (DES) is a clinical gold standard for human brain mapping and readily evokes conscious percepts, yet the neurophysiological changes underlying these percepts are not well understood. Approach. To determine the neural correlates of DES, we stimulated the somatosensory cortex of ten human participants at frequency-amplitude combinations that both elicited and failed to elicit conscious percepts, meanwhile recording neural activity directly surrounding the stimulation site. We then compared the neural activity of perceived trials to that of non-perceived trials. Main results. We found that stimulation evokes distributed high gamma activity, which correlates with conscious perception better than stimulation parameters themselves. Significance. Our findings suggest that high gamma activity is a reliable biomarker for perception evoked by both natural and electrical stimuli.

Inhibition of somatosensory-evoked cortical responses by a weak leading stimulus.

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Nakagawa, Kei; Inui, Koji; Yuge, Louis; Kakigi, Ryusuke

2014-11-01

We previously demonstrated that auditory-evoked cortical responses were suppressed by a weak leading stimulus in a manner similar to the prepulse inhibition (PPI) of startle reflexes. The purpose of the present study was to investigate whether a similar phenomenon was present in the somatosensory system, and also whether this suppression reflected an inhibitory process. We recorded somatosensory-evoked magnetic fields following stimulation of the median nerve and evaluated the extent by which they were suppressed by inserting leading stimuli at an intensity of 2.5-, 1.5-, 1.1-, or 0.9-fold the sensory threshold (ST) in healthy participants (Experiment 1). The results obtained demonstrated that activity in the secondary somatosensory cortex in the hemisphere contralateral to the stimulated side (cSII) was significantly suppressed by a weak leading stimulus with the intensity larger than 1.1-fold ST. This result implied that the somatosensory system had an inhibitory process similar to that of PPI. We then presented two successive leading stimuli before the test stimulus, and compared the extent of suppression between the test stimulus-evoked responses and those obtained with the second prepulse alone and with two prepulses (first and second) (Experiment 2). When two prepulses were preceded, cSII responses to the second prepulse were suppressed by the first prepulse, whereas the ability of the second prepulse to suppress the test stimulus remained unchanged. These results suggested the presence of at least two individual pathways; response-generating and inhibitory pathways. Copyright © 2014 Elsevier Inc. All rights reserved.

The influence of pain-related expectations on intensity perception of non-painful somatosensory stimuli

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Zaman, Jonas; Wiech, Katja; Claes, Nathalie; Van Oudenhove, Lukas; Van Diest, Ilse; Vlaeyen, Johan W. S.

2018-01-01

OBJECTIVE: The extent to which pain-related expectations, known to affect pain perception, also affect perception of non-painful sensations remains unclear, as well as the potential role of unpredictability in this context. METHODS: In a proprioceptive fear conditioning paradigm, various arm

High frequency migraine is associated with lower acute pain sensitivity and abnormal insula activity related to migraine pain intensity, attack frequency, and pain catastrophizing

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Vani A Mathur

2016-09-01

Full Text Available Migraine is a pain disorder associated with abnormal brain structure and function, yet the effect of migraine on acute pain processing remains unclear. It also remains unclear whether altered pain-related brain responses and related structural changes are associated with clinical migraine characteristics. Using fMRI and three levels of thermal stimuli (non-painful, mildly painful, and moderately painful, we compared whole-brain activity between 14 migraine patients and 14 matched controls. Although, there were no significant differences in pain thresholds and pre-scan pain ratings to mildly painful thermal stimuli, patients had aberrant suprathreshold nociceptive processing. Compared to controls, patients had reduced activity in pain modulatory regions including left dorsolateral prefrontal, posterior parietal, and middle temporal cortices and, at a lower-threshold, greater activation in the right mid-insula to moderate pain versus mild pain. We also found that pain-related activity in the insula was associated with clinical variables in patients, including associations between: bilateral anterior insula and pain catastrophizing (PCS; bilateral anterior insula and contralateral posterior insula and migraine pain intensity; and bilateral posterior insula and migraine frequency at a lower-threshold. PCS and migraine pain intensity were also negatively associated with activity in midline regions including posterior cingulate and medial prefrontal cortices. Diffusion tensor imaging revealed a negative correlation between fractional anisotropy (a measure of white matter integrity; FA and migraine duration in the right mid-insula and a positive correlation between left mid-insula FA and PCS. In sum, while patients showed lower sensitivity to acute noxious stimuli, the neuroimaging findings suggest enhanced nociceptive processing and significantly disrupted modulatory networks, particularly involving the insula cortex, associated with indices of

The effect of repeated laser stimuli to ink-marked skin on skin temperature—recommendations for a safe experimental protocol in humans

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Victoria J. Madden

2016-01-01

Full Text Available Background. Nd:YAP laser is widely used to investigate the nociceptive and pain systems, generating perpetual and laser-evoked neurophysiological responses. A major procedural concern for the use of Nd:YAP laser stimuli in experimental research is the risk of skin damage. The absorption of Nd:YAP laser stimuli is greater in darker skin, or in pale skin that has been darkened with ink, prompting some ethics boards to refuse approval to experimenters wishing to track stimulus location by marking the skin with ink. Some research questions, however, require laser stimuli to be delivered at particular locations or within particular zones, a requirement that is very difficult to achieve if marking the skin is not possible. We thoroughly searched the literature for experimental evidence and protocol recommendations for safe delivery of Nd:YAP laser stimuli over marked skin, but found nothing.Methods. We designed an experimental protocol to define safe parameters for the use of Nd:YAP laser stimuli over skin that has been marked with black dots, and used thermal imaging to assess the safety of the procedure at the forearm and the back.Results. Using thermal imaging and repeated laser stimulation to ink-marked skin, we demonstrated that skin temperature did not increase progressively across the course of the experiment, and that the small change in temperature seen at the forearm was reversed during the rest periods between blocks. Furthermore, no participant experienced skin damage due to the procedure.Conclusion. This protocol offers parameters for safe, confident and effective experimentation using repeated Nd:YAP laser on skin marked with ink, thus paving the way for investigations that depend on it.

Speech-evoked auditory brainstem responses in children with hearing loss.

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Koravand, Amineh; Al Osman, Rida; Rivest, Véronique; Poulin, Catherine

2017-08-01

The main objective of the present study was to investigate subcortical auditory processing in children with sensorineural hearing loss. Auditory Brainstem Responses (ABRs) were recorded using click and speech/da/stimuli. Twenty-five children, aged 6-14 years old, participated in the study: 13 with normal hearing acuity and 12 with sensorineural hearing loss. No significant differences were observed for the click-evoked ABRs between normal hearing and hearing-impaired groups. For the speech-evoked ABRs, no significant differences were found for the latencies of the following responses between the two groups: onset (V and A), transition (C), one of the steady-state wave (F), and offset (O). However, the latency of the steady-state waves (D and E) was significantly longer for the hearing-impaired compared to the normal hearing group. Furthermore, the amplitude of the offset wave O and of the envelope frequency response (EFR) of the speech-evoked ABRs was significantly larger for the hearing-impaired compared to the normal hearing group. Results obtained from the speech-evoked ABRs suggest that children with a mild to moderately-severe sensorineural hearing loss have a specific pattern of subcortical auditory processing. Our results show differences for the speech-evoked ABRs in normal hearing children compared to hearing-impaired children. These results add to the body of the literature on how children with hearing loss process speech at the brainstem level. Copyright © 2017 Elsevier B.V. All rights reserved.

Selective attention towards painful faces among chronic pain patients: evidence from a modified version of the dot-probe.

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Khatibi, Ali; Dehghani, Mohsen; Sharpe, Louise; Asmundson, Gordon J G; Pouretemad, Hamidreza

2009-03-01

Evidence that patients with chronic pain selectively attend to pain-related stimuli presented in modified Stroop and dot-probe paradigms is mixed. The pain-related stimuli used in these studies have been primarily verbal in nature (i.e., words depicting themes of pain). The purpose of the present study was to determine whether patients with chronic pain, relative to healthy controls, show selective attention for pictures depicting painful faces. To do so, 170 patients with chronic pain and 40 age- and education-matched healthy control participants were tested using a dot-probe task in which painful, happy, and neutral facial expressions were presented. Selective attention was denoted using the mean reaction time and the bias index. Results indicated that, while both groups shifted attention away from happy faces (and towards neutral faces), only the control group shifted attention away from painful faces. Additional analyses were conducted on chronic pain participants after dividing them into groups on the basis of fear of pain/(re)injury. The results of these analyses revealed that while chronic pain patients with high and low levels of fear both shifted attention away from happy faces, those with low fear shifted attention away from painful faces, whereas those with high fear shifted attention towards painful faces. These results suggest that patients with chronic pain selectively attend to facial expressions of pain and, importantly, that the tendency to shift attention towards such stimuli is positively influenced by high fear of pain/(re)injury. Implications of the findings and future research directions are discussed.

Human psychophysics and rodent spinal neurones exhibit peripheral and central mechanisms of inflammatory pain in the UVB and UVB heat rekindling models.

Science.gov (United States)

O'Neill, Jessica; Sikandar, Shafaq; McMahon, Stephen B; Dickenson, Anthony H

2015-09-01

Translational research is key to bridging the gaps between preclinical findings and the patients, and a translational model of inflammatory pain will ideally induce both peripheral and central sensitisation, more effectively mimicking clinical pathophysiology in some chronic inflammatory conditions. We conducted a parallel investigation of two models of inflammatory pain, using ultraviolet B (UVB) irradiation alone and UVB irradiation with heat rekindling. We used rodent electrophysiology and human quantitative sensory testing to characterise nociceptive processing in the peripheral and central nervous systems in both models. In both species, UVB irradiation produces peripheral sensitisation measured as augmented evoked activity of rat dorsal horn neurones and increased perceptual responses of human subjects to mechanical and thermal stimuli. In both species, UVB with heat rekindling produces central sensitisation. UVB irradiation alone and UVB with heat rekindling are translational models of inflammation that produce peripheral and central sensitisation, respectively. The predictive value of laboratory models for human pain processing is crucial for improving translational research. The discrepancy between peripheral and central mechanisms of pain is an important consideration for drug targets, and here we describe two models of inflammatory pain that involve ultraviolet B (UVB) irradiation, which can employ peripheral and central sensitisation to produce mechanical and thermal hyperalgesia in rats and humans. We use electrophysiology in rats to measure the mechanically- and thermally-evoked activity of rat spinal neurones and quantitative sensory testing to assess human psychophysical responses to mechanical and thermal stimulation in a model of UVB irradiation and in a model of UVB irradiation with heat rekindling. Our results demonstrate peripheral sensitisation in both species driven by UVB irradiation, with a clear mechanical and thermal hypersensitivity of

Attention bias towards personally relevant stimuli: the individual emotional Stroop task.

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Wingenfeld, Katja; Bullig, Renate; Mensebach, Christoph; Hartje, Wolfgang; Driessen, Martin; Beblo, Thomas

2006-12-01

The emotional Stroop task is a widely used method for investigating attentional bias towards stimuli due to mood or affect. In general, standardized stimuli are used, which might not be appropriate when investigating individual contextual frameworks. It was investigated whether words chosen to be related to individuals' personal life events would produce more pronounced Stroop interference (as an indicator of attentional bias) than stimuli without any personal relevance. Twenty-six nonclinical subjects, 20 female and 6 male, participated in the study. Mean age was 36.1 yr. (SD = 18.1). All were recruited by means of local advertising. Stimulus material consisted of four word types: personal words related to negative life events with and without current personal relevance, and negative and neutral words without any personal relevance. Words were presented in three blocks. Analysis of variance showed main effects for word type and blocks, with slower reactions in the personally relevant conditions than in the negative, or neutral conditions, and in response to the first blocks as opposed to the last. These findings indicate that regardless of the word valence, personally relevant stimuli evoke more pronounced Stroop interference than do stimuli without personal relevance.

Hypotonic stimuli enhance proton-gated currents of acid-sensing ion channel-1b

International Nuclear Information System (INIS)

Ugawa, Shinya; Ishida, Yusuke; Ueda, Takashi; Yu, Yong; Shimada, Shoichi

2008-01-01

Acid-sensing ion channels (ASICs) are strong candidates for mammalian mechanoreceptors. We investigated whether mouse acid-sensing ion channel-1b (ASIC1b) is sensitive to mechanical stimuli using oocyte electrophysiology, because ASIC1b is located in the mechanosensory stereocilia of cochlear hair cells. Hypotonic stimuli that induced membrane stretch of oocytes evoked no significant current in ASIC1b-expressing oocytes at pH 7.5. However, acid (pH 4.0 or 5.0)-evoked currents in the oocytes were substantially enhanced by the hypotonicity, showing mechanosensitivity of ASIC1b and possible mechanogating of the channel in the presence of other components. Interestingly, the ASIC1b channel was permeable to K + (a principal charge carrier for cochlear sensory transduction) and the affinity of the channel for amiloride (IC 50 (inhibition constant) = approximately 48.3 μM) was quite similar to that described for the mouse hair cell mechanotransducer current. Taken together, these data raise the possibility that ASIC1b participates in cochlear mechanoelectrical transduction

A comparison of auditory evoked potentials to acoustic beats and to binaural beats.

Science.gov (United States)

Pratt, Hillel; Starr, Arnold; Michalewski, Henry J; Dimitrijevic, Andrew; Bleich, Naomi; Mittelman, Nomi

2010-04-01

The purpose of this study was to compare cortical brain responses evoked by amplitude modulated acoustic beats of 3 and 6 Hz in tones of 250 and 1000 Hz with those evoked by their binaural beats counterparts in unmodulated tones to indicate whether the cortical processes involved differ. Event-related potentials (ERPs) were recorded to 3- and 6-Hz acoustic and binaural beats in 2000 ms duration 250 and 1000 Hz tones presented with approximately 1 s intervals. Latency, amplitude and source current density estimates of ERP components to beats-evoked oscillations were determined and compared across beat types, beat frequencies and base (carrier) frequencies. All stimuli evoked tone-onset components followed by oscillations corresponding to the beat frequency, and a subsequent tone-offset complex. Beats-evoked oscillations were higher in amplitude in response to acoustic than to binaural beats, to 250 than to 1000 Hz base frequency and to 3 Hz than to 6 Hz beat frequency. Sources of the beats-evoked oscillations across all stimulus conditions located mostly to left temporal lobe areas. Differences between estimated sources of potentials to acoustic and binaural beats were not significant. The perceptions of binaural beats involve cortical activity that is not different than acoustic beats in distribution and in the effects of beat- and base frequency, indicating similar cortical processing. Copyright 2010 Elsevier B.V. All rights reserved.

Cortical evoked potentials to an auditory illusion: binaural beats.

Science.gov (United States)

Pratt, Hillel; Starr, Arnold; Michalewski, Henry J; Dimitrijevic, Andrew; Bleich, Naomi; Mittelman, Nomi

2009-08-01

To define brain activity corresponding to an auditory illusion of 3 and 6Hz binaural beats in 250Hz or 1000Hz base frequencies, and compare it to the sound onset response. Event-Related Potentials (ERPs) were recorded in response to unmodulated tones of 250 or 1000Hz to one ear and 3 or 6Hz higher to the other, creating an illusion of amplitude modulations (beats) of 3Hz and 6Hz, in base frequencies of 250Hz and 1000Hz. Tones were 2000ms in duration and presented with approximately 1s intervals. Latency, amplitude and source current density estimates of ERP components to tone onset and subsequent beats-evoked oscillations were determined and compared across beat frequencies with both base frequencies. All stimuli evoked tone-onset P(50), N(100) and P(200) components followed by oscillations corresponding to the beat frequency, and a subsequent tone-offset complex. Beats-evoked oscillations were higher in amplitude with the low base frequency and to the low beat frequency. Sources of the beats-evoked oscillations across all stimulus conditions located mostly to left lateral and inferior temporal lobe areas in all stimulus conditions. Onset-evoked components were not different across stimulus conditions; P(50) had significantly different sources than the beats-evoked oscillations; and N(100) and P(200) sources located to the same temporal lobe regions as beats-evoked oscillations, but were bilateral and also included frontal and parietal contributions. Neural activity with slightly different volley frequencies from left and right ear converges and interacts in the central auditory brainstem pathways to generate beats of neural activity to modulate activities in the left temporal lobe, giving rise to the illusion of binaural beats. Cortical potentials recorded to binaural beats are distinct from onset responses. Brain activity corresponding to an auditory illusion of low frequency beats can be recorded from the scalp.

Inattentional Deafness: Visual Load Leads to Time-Specific Suppression of Auditory Evoked Responses.

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Molloy, Katharine; Griffiths, Timothy D; Chait, Maria; Lavie, Nilli

2015-12-09

Due to capacity limits on perception, conditions of high perceptual load lead to reduced processing of unattended stimuli (Lavie et al., 2014). Accumulating work demonstrates the effects of visual perceptual load on visual cortex responses, but the effects on auditory processing remain poorly understood. Here we establish the neural mechanisms underlying "inattentional deafness"--the failure to perceive auditory stimuli under high visual perceptual load. Participants performed a visual search task of low (target dissimilar to nontarget items) or high (target similar to nontarget items) load. On a random subset (50%) of trials, irrelevant tones were presented concurrently with the visual stimuli. Brain activity was recorded with magnetoencephalography, and time-locked responses to the visual search array and to the incidental presence of unattended tones were assessed. High, compared to low, perceptual load led to increased early visual evoked responses (within 100 ms from onset). This was accompanied by reduced early (∼ 100 ms from tone onset) auditory evoked activity in superior temporal sulcus and posterior middle temporal gyrus. A later suppression of the P3 "awareness" response to the tones was also observed under high load. A behavioral experiment revealed reduced tone detection sensitivity under high visual load, indicating that the reduction in neural responses was indeed associated with reduced awareness of the sounds. These findings support a neural account of shared audiovisual resources, which, when depleted under load, leads to failures of sensory perception and awareness. The present work clarifies the neural underpinning of inattentional deafness under high visual load. The findings of near-simultaneous load effects on both visual and auditory evoked responses suggest shared audiovisual processing capacity. Temporary depletion of shared capacity in perceptually demanding visual tasks leads to a momentary reduction in sensory processing of auditory

Neural Activation during Anticipation of Near Pain-Threshold Stimulation Among the Pain-Fearful

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Zhou Yang

2016-07-01

Full Text Available Fear of pain (FOP can increase risk for chronic pain and disability but little is known about corresponding neural responses in anticipation of potential pain. In this study, more (10 women, 6 men and less (7 women, 6 men pain-fearful groups underwent whole-brain functional magnetic resonance imaging (fMRI during anticipation of near pain-threshold stimulation. Groups did not differ in the proportion of stimuli judged to be painful but pain-fearful participants reported significantly more state fear prior to stimulus exposure. Within the entire sample, stronger activation was found in several pain regions (e.g., bilateral insula, midcingulate cortex (MCC, thalamus, superior frontal gyrus and visual areas linked to decoding stimulus valences (inferior orbital cortex during anticipation of painful stimuli. Between groups and correlation analyses indicated pain-fearful participants experienced comparatively more activity in regions implicated in evaluating potential threats and processing negative emotions during anticipation (i.e., MCC, mid occipital cortex, superior temporal pole, though group differences were not apparent in most so-called pain matrix regions. In sum, trait- and task-based FOP is associated with enhanced responsiveness in regions involved in threat processing and negative affect during anticipation of potentially painful stimulation.

Fast detection of unexpected sound intensity decrements as revealed by human evoked potentials.

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Heike Althen

Full Text Available The detection of deviant sounds is a crucial function of the auditory system and is reflected by the automatically elicited mismatch negativity (MMN, an auditory evoked potential at 100 to 250 ms from stimulus onset. It has recently been shown that rarely occurring frequency and location deviants in an oddball paradigm trigger a more negative response than standard sounds at very early latencies in the middle latency response of the human auditory evoked potential. This fast and early ability of the auditory system is corroborated by the finding of neurons in the animal auditory cortex and subcortical structures, which restore their adapted responsiveness to standard sounds, when a rare change in a sound feature occurs. In this study, we investigated whether the detection of intensity deviants is also reflected at shorter latencies than those of the MMN. Auditory evoked potentials in response to click sounds were analyzed regarding the auditory brain stem response, the middle latency response (MLR and the MMN. Rare stimuli with a lower intensity level than standard stimuli elicited (in addition to an MMN a more negative potential in the MLR at the transition from the Na to the Pa component at circa 24 ms from stimulus onset. This finding, together with the studies about frequency and location changes, suggests that the early automatic detection of deviant sounds in an oddball paradigm is a general property of the auditory system.

Do episodic migraineurs selectively attend to headache-related visual stimuli?

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McDermott, Michael J; Peck, Kelly R; Walters, A Brooke; Smitherman, Todd A

2013-02-01

To assess pain-related attentional biases among individuals with episodic migraine. Prior studies have examined whether chronic pain patients selectively attend to pain-related stimuli in the environment, but these studies have produced largely mixed findings and focused primarily on patients with chronic musculoskeletal pain. Limited research has implicated attentional biases among chronic headache patients, but no studies have been conducted among episodic migraineurs, who comprise the overwhelming majority of the migraine population. This was a case-control, experimental study. Three hundred and eight participants (mean age = 19.2 years [standard deviation = 3.3]; 69.5% female; 36.4% minority), consisting of 84 episodic migraineurs, diagnosed in accordance with International Classification of Headache Disorders (2(nd) edition) criteria using a structured diagnostic interview, and 224 non-migraine controls completed a computerized dot probe task to assess attentional bias toward headache-related pictorial stimuli. The task consisted of 192 trials and utilized 2 emotional-neutral stimulus pairing conditions (headache-neutral and happy-neutral). No within-group differences for reaction time latencies to headache vs happy conditions were found among those with episodic migraine or among the non-migraine controls. Migraine status was unrelated to attentional bias indices for both headache (F [1,306] = 0.56, P = .45) and happy facial stimuli (F [1,306] = 0.37, P = .54), indicating a lack of between-group differences. Lack of within- and between-group differences was confirmed with repeated measures analysis of variance. In light of the large sample size and prior pilot testing of presented images, results suggest that episodic migraineurs do not differentially attend to headache-related facial stimuli. Given modest evidence of attentional biases among chronic headache samples, these findings suggest potential differences in attentional

Prediction of postoperative pain by preoperative pain response to heat stimulation in total knee arthroplasty.

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Lunn, Troels H; Gaarn-Larsen, Lissi; Kehlet, Henrik

2013-09-01

It has been estimated that up to 54% of the variance in postoperative pain experience may be predicted with preoperative pain responses to experimental stimuli, with suprathreshold heat pain as the most consistent test modality. This study aimed to explore whether 2 heat test paradigms could predict postoperative pain after total knee arthroplasty (TKA). Patients scheduled for elective, unilateral, primary TKA under spinal anesthesia were consecutively included in this prospective, observational study. Perioperative analgesia was standardized for all patients. Outcomes were postoperative pain during walk: from 6 to 24 hours (primary), from postoperative day (POD) 1 to 7 (secondary), and from POD 14 to 30 (tertiary). Two preoperative tonic heat stimuli with 47°C were used; short (5 seconds) and long (7 minutes) stimulation upon which patients rated their pain response on an electronic visual analog scale. Multivariate stepwise linear and logistic regressions analyses were carried out, including 8 potential preoperative explanatory variables (among these anxiety, depression, preoperative pain, and pain catastrophizing) to assess pain response to preoperative heat pain stimulation as an independent predictor for postoperative pain. A total of 100 patients were included, and 3 were later excluded. A weak correlation [rho (95% confidence interval); P value] was observed between pain from POD 1 to 7 and pain response to short [rho=0.25(0.04 to 0.44); P=.02] and to long [rho=0.27 (0.07 to 0.46); P=.01] heat pain stimulation. However, these positive correlations were not supported by the linear and logistic regression analyses, in which only anxiety, preoperative pain, and pain catastrophizing were significant explanatory variables (but with low R-squares; 0.05 to 0.08). Pain responses to 2 types of preoperative heat stimuli were not independent clinically relevant predictors for postoperative pain after TKA. Copyright © 2013 International Association for the Study of

Experiencing Physical Pain Leads to More Sympathetic Moral Judgments

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Xiao, Qianguo; Zhu, Yi; Luo, Wen-bo

2015-01-01

Previous studies have shown that observing another’s pain can evoke other-oriented emotions, which instigate empathic concern for another’s needs. It is not clear whether experiencing first-hand physical pain may also evoke other-oriented emotion and thus influence people’s moral judgment. Based on the embodied simulation literature and neuroimaging evidence, the present research tested the idea that participants who experienced physical pain would be more sympathetic in their moral judgments. Study 1 showed that ice-induced physical pain facilitated higher self-assessments of empathy, which motivated participants to be more sympathetic in their moral judgments. Study 2 confirmed findings in study 1 and also showed that State Perspective Taking subscale of the State Empathy Scale mediated the effects of physical pain on moral judgment. These results provide support for embodied view of morality and for the view that pain can serve a positive psychosocial function. PMID:26465603

Relationship of Corneal Pain Sensitivity With Dry Eye Symptoms in Dry Eye With Short Tear Break-Up Time.

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Kaido, Minako; Kawashima, Motoko; Ishida, Reiko; Tsubota, Kazuo

2016-03-01

The purpose of this prospective comparative study was to investigate corneal sensitivity in subjects with unstable tear film, with and without dry eye (DE) symptoms. Forty-one eyes of 41 volunteers (mean age: 45.1 ± 9.4 years; age range, 23-57 years), with normal tear function and ocular surface except for tear stability, were studied. The eyes were divided into two groups depending on the presence or absence of DE symptoms: 21 eyes with DE symptoms (symptomatic group); and 20 eyes without DE symptoms (asymptomatic group). Three types of corneal sensitivity values were measured using a Cochet-Bonnet esthesiometer: the sensitivity for perception of touch (S-touch), the sensitivity for blinking (S-blink), and the sensitivity for pain (S-pain). Mean S-blink and S-pain were significantly higher in the symptomatic group than in the asymptomatic group (P 0.05). Corneal sensitivity for blinking and pain evoked by increased stimuli was higher in the symptomatic group (subjects with short break-up time DE) compared with subjects who have no DE symptoms despite decreased tear stability. The presence of both tear instability and hyperesthesia, rather than tear instability alone, may contribute to DE pathogenesis.

A Brain Computer Interface for Robust Wheelchair Control Application Based on Pseudorandom Code Modulated Visual Evoked Potential

DEFF Research Database (Denmark)

Mohebbi, Ali; Engelsholm, Signe K.D.; Puthusserypady, Sadasivan

2015-01-01

In this pilot study, a novel and minimalistic Brain Computer Interface (BCI) based wheelchair control application was developed. The system was based on pseudorandom code modulated Visual Evoked Potentials (c-VEPs). The visual stimuli in the scheme were generated based on the Gold code...

Visual attention to erotic images in women reporting pain with intercourse.

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Lykins, Amy D; Meana, Marta; Minimi, Jillian

2011-01-01

The coupling of sex and pain creates an interesting theoretical conundrum of clinical significance: Are women with dyspareunia distracted from sexual stimuli, or are they hypervigilant to sexual stimuli because these stimuli elicit thoughts and expectations of pain? This study measured attention to sexual stimuli in women reporting persistent pain with intercourse, women reporting low sexual desire, and women reporting no sexual problems. Participants viewed a series of erotic images, each containing an object intended to distract from the erotic scene regions, while an eye tracker recorded their eye movements. Women with pain looked for shorter periods of time and fewer times at the sexual scene region than did both women with low sexual desire (p = .024 and p = .018, respectively) and the no-dysfunction control group (p < .001 and p = .003, respectively). Women with pain also looked at the context (nonsexual) scene region significantly more times and for longer periods than did the no-dysfunction control women (p = .013 and p = .042, respectively). Results are interpreted to be potentially supportive of the cognitive distraction hypothesis associated with sexual dysfunction, with an additional component of cognitive avoidance of sexual stimuli for the women reporting sexual pain.

Heightened eating drive and visual food stimuli attenuate central nociceptive processing

OpenAIRE

Wright, Hazel; Li, Xiaoyun; Fallon, Nicholas B.; Giesbrecht, Timo; Thomas, Anna; Harrold, Joanne A.; Halford, Jason C. G.; Stancak, Andrej

2014-01-01

Hunger and pain are basic drives that compete for a behavioral response when experienced together. To investigate the cortical processes underlying hunger-pain interactions, we manipulated participants' hunger and presented photographs of appetizing food or inedible objects in combination with painful laser stimuli. Fourteen healthy participants completed two EEG sessions: one after an overnight fast, the other following a large breakfast. Spatio-temporal patterns of cortical activation under...

Prediction of postoperative pain after percutaneous nephrolithotomy

DEFF Research Database (Denmark)

Pedersen, Katja Venborg; Olesen, Anne Estrup; Osther, Palle Jørn Sloth

2013-01-01

Postoperative pain remains a significant problem and the individual variance in postoperative pain is not fully understood. In recent years, there has been focus on identifying risk factors predicting patients with high postoperative pain intensity or consumption of analgesics, which may facilitate...... thresholds were measured using electrical (single and 5 repeated) and pressure pain stimulation over the flank bilaterally (stone-side = operation side and control-side = non-operation side). Postoperative pain scores were recorded on a numerical rating scale and analgesic consumption was registered....... The responses to repeated electrical stimuli (temporal summation) were preoperatively increased on the stone-side compared to the control-side (P = 0.016). Preoperative electrical pain thresholds from the control-side correlated inversely with postoperative opioid consumption (single stimuli: ρ = -0.43, P

Evaluating the Influence of Chromatic and Luminance Stimuli on SSVEPs from Behind-the-Ears and Occipital Areas

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Alan Floriano

2018-02-01

Full Text Available This work presents a study of chromatic and luminance stimuli in low-, medium-, and high-frequency stimulation to evoke steady-state visual evoked potential (SSVEP in the behind-the-ears area. Twelve healthy subjects participated in this study. The electroencephalogram (EEG was measured on occipital (Oz and left and right temporal (TP9 and TP10 areas. The SSVEP was evaluated in terms of amplitude, signal-to-noise ratio (SNR, and detection accuracy using power spectral density analysis (PSDA, canonical correlation analysis (CCA, and temporally local multivariate synchronization index (TMSI methods. It was found that stimuli based on suitable color and luminance elicited stronger SSVEP in the behind-the-ears area, and that the response of the SSVEP was related to the flickering frequency and the color of the stimuli. Thus, green-red stimulus elicited the highest SSVEP in medium-frequency range, and green-blue stimulus elicited the highest SSVEP in high-frequency range, reaching detection accuracy rates higher than 80%. These findings will aid in the development of more comfortable, accurate and stable BCIs with electrodes positioned on the behind-the-ears (hairless areas.

Skinfold thickness affects the isometric knee extension torque evoked by Neuromuscular Electrical Stimulation.

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Medeiros, Flávia V A; Vieira, Amilton; Carregaro, Rodrigo L; Bottaro, Martim; Maffiuletti, Nicola A; Durigan, João L Q

2015-01-01

Subcutaneous adipose tissue may influence the transmission of electrical stimuli through to the skin, thus affecting both evoked torque and comfort perception associated with neuromuscular electrical stimulation (NMES). This could seriously affect the effectiveness of NMES for either rehabilitation or sports purposes. To investigate the effects of skinfold thickness (SFT) on maximal NMES current intensity, NMES-evoked torque, and NMES-induced discomfort. First, we compared NMES current intensity, NMES-induced discomfort, and NMES-evoked torque between two subgroups of subjects with thicker (n=10; 20.7 mm) vs. thinner (n=10; 29.4 mm) SFT. Second, we correlated SFT to NMES current intensity, NMES-induced discomfort, and NMES-evoked knee extension torque in 20 healthy women. The NMES-evoked torque was normalized to the maximal voluntary contraction (MVC) torque. The discomfort induced by NMES was assessed with a visual analog scale (VAS). NMES-evoked torque was 27.5% lower in subjects with thicker SFT (p=0.01) while maximal current intensity was 24.2% lower in subjects with thinner SFT (p=0.01). A positive correlation was found between current intensity and SFT (r=0.540, p=0.017). A negative correlation was found between NMES-evoked torque and SFT (r=-0.563, p=0.012). No significant correlation was observed between discomfort scores and SFT (rs=0.15, p=0.53). These results suggest that the amount of subcutaneous adipose tissue (as reflected by skinfold thickness) affected NMES current intensity and NMES-evoked torque, but had no effect on discomfort perception. Our findings may help physical therapists to better understand the impact of SFT on NMES and to design more rational stimulation strategies.

Slow brushing reduces heat pain in humans.

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Liljencrantz, J; Strigo, I; Ellingsen, D M; Krämer, H H; Lundblad, L C; Nagi, S S; Leknes, S; Olausson, H

2017-08-01

C-tactile (CT) afferents are unmyelinated low-threshold mechanoreceptors optimized for signalling affective, gentle touch. In three separate psychophysical experiments, we examined the contribution of CT afferents to pain modulation. In total, 44 healthy volunteers experienced heat pain and CT optimal (slow brushing) and CT sub-optimal (fast brushing or vibration) stimuli. Three different experimental paradigms were used: Concurrent application of heat pain and tactile (slow brushing or vibration) stimulation; Slow brushing, applied for variable duration and intervals, preceding heat pain; Slow versus fast brushing preceding heat pain. Slow brushing was effective in reducing pain, whereas fast brushing or vibration was not. The reduction in pain was significant not only when the CT optimal touch was applied simultaneously with the painful stimulus but also when the two stimuli were separated in time. For subsequent stimulation, the pain reduction was more pronounced for a shorter time interval between brushing and pain. Likewise, the effect was more robust when pain was preceded by a longer duration of brush stimulation. Strong CT-related pain reduction was associated with low anxiety and high calmness scores obtained by a state anxiety questionnaire. Slow brushing - optimal for CT activation - is effective in reducing pain from cutaneous heating. The precise mechanisms for the pain relief are as yet unknown but possible mechanisms include inhibition of nociceptive projection neurons at the level of the dorsal horn as well as analgesia through cortical mechanisms. Slow brushing stimuli - optimal for activation of C-tactile fibres - can reduce pain from cutaneous heating. No such effect was seen with fast brushing or vibration. These observations indicate the role of C-tactile fibres in pain modulation. © 2017 European Pain Federation - EFIC®.

Suppression of bulboreticular unit responses to noxious stimuli by analgesic mesencephalic stimulation.

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Morrow, T J; Casey, K L

1983-01-01

The responses of 302 neurons in the medial medullary reticular formation (MRF) to a variety of noxious and innocuous somatic stimuli were studied in anesthetized and awake rats. In addition, the effects of analgesic electrical stimulation in the mesencephalon (MES) on unit responses were examined. Tail shock was the most effective stimulus, exciting more than 80% of all units recorded. This stimulus was considered separately during data analysis, since it could not be classified as noxious or innocuous. Noxious somatic stimuli (including pinch, firm pressure, pin prick, and radiant heating of the tail above 45 degrees C were especially effective in eliciting discharge in a significant fraction of all cells in both awake (123/205) and anesthetized (45/97) animals. Nociceptive neurons could be classified as nociceptive specific (NS) or wide dynamic range (WDR) depending on their responses to all somatic stimuli tested. Nociceptive neurons showed no preferential anatomical distribution. Most neurons, including those responsive to noxious inputs, exhibited large, often bilateral receptive fields which frequently covered the tail, one or more limbs, and extensive areas of the body or head. Electrical stimulation within or adjacent to the mesencephalic periaqueductal gray matter depressed the spontaneous and evoked discharge of MRF neurons in both acute and chronic preparations. This inhibition showed a significant preference (p less than 0.001, chi-square statistic) for units that were excited by somatic and especially noxious stimuli. No units were facilitated by MES stimulation. In the awake rat, unit suppression closely followed the time course and level of MES-induced analgesia. Excitability data from the acute experiments suggest that this response inhibition may be the result of a direct action on MRF neurons. Anesthesia severely depressed the spontaneous discharge of MRF neurons as well as the activity evoked by innocuous somatic stimulation. Our data suggest

Neurochemical responses to chromatic and achromatic stimuli in the human visual cortex.

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Bednařík, Petr; Tkáč, Ivan; Giove, Federico; Eberly, Lynn E; Deelchand, Dinesh K; Barreto, Felipe R; Mangia, Silvia

2018-02-01

In the present study, we aimed at determining the metabolic responses of the human visual cortex during the presentation of chromatic and achromatic stimuli, known to preferentially activate two separate clusters of neuronal populations (called "blobs" and "interblobs") with distinct sensitivity to color or luminance features. Since blobs and interblobs have different cytochrome-oxidase (COX) content and micro-vascularization level (i.e., different capacities for glucose oxidation), different functional metabolic responses during chromatic vs. achromatic stimuli may be expected. The stimuli were optimized to evoke a similar load of neuronal activation as measured by the bold oxygenation level dependent (BOLD) contrast. Metabolic responses were assessed using functional 1 H MRS at 7 T in 12 subjects. During both chromatic and achromatic stimuli, we observed the typical increases in glutamate and lactate concentration, and decreases in aspartate and glucose concentration, that are indicative of increased glucose oxidation. However, within the detection sensitivity limits, we did not observe any difference between metabolic responses elicited by chromatic and achromatic stimuli. We conclude that the higher energy demands of activated blobs and interblobs are supported by similar increases in oxidative metabolism despite the different capacities of these neuronal populations.

Differentiation of pain ratings in combat-related posttraumatic stress disorder.

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Kraus, Anja; Geuze, Elbert; Schmahl, Christian; Greffrath, Wolfgang; Treede, Rolf-Detlef; Bohus, Martin; Vermetten, Eric

2009-06-01

Although posttraumatic stress disorder (PTSD) is associated with chronic pain, preliminary evidence suggests reduced experimental pain sensitivity in this disorder. The questions addressed in the present study were whether pain perception would also be reduced in PTSD patients who are not suffering from chronic pain symptoms, and whether a reduction in pain sensitivity would also be present in combat veterans who did not develop PTSD. For this, we determined thermal detection and pain thresholds in 10 male combat-related PTSD patients, 10 combat control subjects (no PTSD) and 10 healthy controls without combat experience. All subjects were pain free. First, we measured thermal sensory thresholds with ramped heat and cold stimuli using the method of limits. Ramped thermal sensory stimulation revealed no deficits for the detection of (non-noxious) f2.1thermal stimuli between groups. In contrast, heat and cold pain thresholds in both combat groups (PTSD and combat controls) were significantly increased compared to healthy controls. However, these stimuli could not distinguish between the two groups due to ceiling effects. When using longer-lasting heat stimulation at different temperatures (30s duration; method of fixed stimuli), we found significantly lower frequency of pain reports in PTSD patients compared with both combat and healthy controls, as well as significantly lower pain ratings. Our results suggest an association of PTSD with reduced pain sensitivity, which could be related to PTSD-related (neuro-)psychological alterations or to a pre-existing risk factor for the disorder.

Pain adaptability in individuals with chronic musculoskeletal pain is not associated with conditioned pain modulation

DEFF Research Database (Denmark)

Wan, Dawn Wong Lit; Arendt-Nielsen, Lars; Wang, Kelun

2018-01-01

(MSK). CPTs at 2°C and 7°C were used to assess the status of pain adaptability in participants with either chronic non-specific low back pain or knee osteoarthritis. The participants' potency of conditioned pain modulation (CPM) and local inhibition were measured. The strengths of pain adaptability...... at both CPTs were highly correlated. PA and PNA did not differ in their demographics, pain thresholds from thermal and pressure stimuli, or potency of local inhibition or CPM. PA reached their maximum pain faster than PNA (t41=-2.76, p... days whereas PNA did not (F (6,246) = 3.01, p = 0.01). The dichotomy of pain adaptability exists in MSK patients. Consistent with the healthy human study, the strength of pain adaptability and potency of CPM are not related. Pain adaptability could be another form of endogenous pain inhibition which...

Do Event-Related Evoked Potentials Reflect Apathy Tendency and Motivation?

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Takayoshi, Hiroyuki; Onoda, Keiichi; Yamaguchi, Shuhei

2018-01-01

Apathy is a mental state of diminished motivation. Although the reward system as the foundation of the motivation in the human brain has been studied extensively with neuroimaging techniques, the electrophysiological correlates of motivation and apathy have not been fully explored. Thus, in 14 healthy volunteers, we examined whether event-related evoked potentials (ERP) obtained during a simple number discrimination task with/without rewards reflected apathy tendency and a reward-dependent tendency, which were assessed separately using the apathy scale and the temperament and character inventory (TCI). Participants were asked to judge the size of a number, and received feedback based on their performance in each trial. The P3 amplitudes related to the feedback stimuli increased only in the reward condition. Furthermore, the P2 amplitudes related to the negative feedback stimuli in the reward condition had a positive correlation with the reward-dependent tendency in TCI, whereas the P3 amplitudes related to the positive feedback stimuli had a negative correlation with the apathy score. Our result suggests that the P2 and P3 ERPs to reward-related feedback stimuli are modulated in a distinctive manner by the motivational reward dependence and apathy tendency, and thus the current paradigm may be useful for investigating the brain activity associated with motivation. PMID:29445331

Influence of body position on cortical pain-related somatosensory processing: an ERP study.

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Chiara Spironelli

Full Text Available BACKGROUND: Despite the consistent information available on the physiological changes induced by head down bed rest, a condition which simulates space microgravity, our knowledge on the possible perceptual-cortical alterations is still poor. The present study investigated the effects of 2-h head-down bed rest on subjective and cortical responses elicited by electrical, pain-related somatosensory stimulation. METHODOLOGY/PRINCIPAL FINDINGS: Twenty male subjects were randomly assigned to two groups, head-down bed rest (BR or sitting control condition. Starting from individual electrical thresholds, Somatosensory Evoked Potentials were elicited by electrical stimuli administered randomly to the left wrist and divided into four conditions: control painless condition, electrical pain threshold, 30% above pain threshold, 30% below pain threshold. Subjective pain ratings collected during the EEG session showed significantly reduced pain perception in BR compared to Control group. Statistical analysis on four electrode clusters and sLORETA source analysis revealed, in sitting controls, a P1 component (40-50 ms in the right somatosensory cortex, whereas it was bilateral and differently located in BR group. Controls' N1 (80-90 ms had widespread right hemisphere activation, involving also anterior cingulate, whereas BR group showed primary somatosensory cortex activation. The P2 (190-220 ms was larger in left-central locations of Controls compared with BR group. CONCLUSIONS/SIGNIFICANCE: Head-down bed rest was associated to an overall decrease of pain sensitivity and an altered pain network also outside the primary somatosensory cortex. Results have implications not only for astronauts' health and spaceflight risks, but also for the clinical aspects of pain detection in bedridden patients at risk of fatal undetected complications.

Auditory-visual aversive stimuli modulate the conscious experience of fear.

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Taffou, Marine; Guerchouche, Rachid; Drettakis, George; Viaud-Delmon, Isabelle

2013-01-01

In a natural environment, affective information is perceived via multiple senses, mostly audition and vision. However, the impact of multisensory information on affect remains relatively undiscovered. In this study, we investigated whether the auditory-visual presentation of aversive stimuli influences the experience of fear. We used the advantages of virtual reality to manipulate multisensory presentation and to display potentially fearful dog stimuli embedded in a natural context. We manipulated the affective reactions evoked by the dog stimuli by recruiting two groups of participants: dog-fearful and non-fearful participants. The sensitivity to dog fear was assessed psychometrically by a questionnaire and also at behavioral and subjective levels using a Behavioral Avoidance Test (BAT). Participants navigated in virtual environments, in which they encountered virtual dog stimuli presented through the auditory channel, the visual channel or both. They were asked to report their fear using Subjective Units of Distress. We compared the fear for unimodal (visual or auditory) and bimodal (auditory-visual) dog stimuli. Dog-fearful participants as well as non-fearful participants reported more fear in response to bimodal audiovisual compared to unimodal presentation of dog stimuli. These results suggest that fear is more intense when the affective information is processed via multiple sensory pathways, which might be due to a cross-modal potentiation. Our findings have implications for the field of virtual reality-based therapy of phobias. Therapies could be refined and improved by implicating and manipulating the multisensory presentation of the feared situations.

Diagnostic uncertainty and recall bias in chronic low back pain.

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Serbic, Danijela; Pincus, Tamar

2014-08-01

Patients' beliefs about the origin of their pain and their cognitive processing of pain-related information have both been shown to be associated with poorer prognosis in low back pain (LBP), but the relationship between specific beliefs and specific cognitive processes is not known. The aim of this study was to examine the relationship between diagnostic uncertainty and recall bias in 2 groups of chronic LBP patients, those who were certain about their diagnosis and those who believed that their pain was due to an undiagnosed problem. Patients (N=68) endorsed and subsequently recalled pain, illness, depression, and neutral stimuli. They also provided measures of pain, diagnostic status, mood, and disability. Both groups exhibited a recall bias for pain stimuli, but only the group with diagnostic uncertainty also displayed a recall bias for illness-related stimuli. This bias remained after controlling for depression and disability. Sensitivity analyses using grouping by diagnosis/explanation received supported these findings. Higher levels of depression and disability were found in the group with diagnostic uncertainty, but levels of pain intensity did not differ between the groups. Although the methodology does not provide information on causality, the results provide evidence for a relationship between diagnostic uncertainty and recall bias for negative health-related stimuli in chronic LBP patients. Copyright © 2014 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

An improved behavioural assay demonstrates that ultrasound vocalizations constitute a reliable indicator of chronic cancer pain and neuropathic pain

Directory of Open Access Journals (Sweden)

Selvaraj Deepitha

2010-03-01

Full Text Available Abstract Background On-going pain is one of the most debilitating symptoms associated with a variety of chronic pain disorders. An understanding of mechanisms underlying on-going pain, i.e. stimulus-independent pain has been hampered so far by a lack of behavioural parameters which enable studying it in experimental animals. Ultrasound vocalizations (USVs have been proposed to correlate with pain evoked by an acute activation of nociceptors. However, literature on the utility of USVs as an indicator of chronic pain is very controversial. A majority of these inconsistencies arise from parameters confounding behavioural experiments, which include novelty, fear and stress due to restrain, amongst others. Results We have developed an improved assay which overcomes these confounding factors and enables studying USVs in freely moving mice repetitively over several weeks. Using this improved assay, we report here that USVs increase significantly in mice with bone metastases-induced cancer pain or neuropathic pain for several weeks, in comparison to sham-treated mice. Importantly, analgesic drugs which are known to alleviate tumour pain or neuropathic pain in human patients significantly reduce USVs as well as mechanical allodynia in corresponding mouse models. Conclusions We show that studying USVs and mechanical allodynia in the same cohort of mice enables comparing the temporal progression of on-going pain (i.e. stimulus-independent pain and stimulus-evoked pain in these clinically highly-relevant forms of chronic pain.

Are females more responsive to emotional stimuli? A neurophysiological study across arousal and valence dimensions.

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Lithari, C; Frantzidis, C A; Papadelis, C; Vivas, Ana B; Klados, M A; Kourtidou-Papadeli, C; Pappas, C; Ioannides, A A; Bamidis, P D

2010-03-01

Men and women seem to process emotions and react to them differently. Yet, few neurophysiological studies have systematically investigated gender differences in emotional processing. Here, we studied gender differences using Event Related Potentials (ERPs) and Skin Conductance Responses (SCR) recorded from participants who passively viewed emotional pictures selected from the International Affective Picture System (IAPS). The arousal and valence dimension of the stimuli were manipulated orthogonally. The peak amplitude and peak latency of ERP components and SCR were analyzed separately, and the scalp topographies of significant ERP differences were documented. Females responded with enhanced negative components (N100 and N200), in comparison to males, especially to the unpleasant visual stimuli, whereas both genders responded faster to high arousing or unpleasant stimuli. Scalp topographies revealed more pronounced gender differences on central and left hemisphere areas. Our results suggest a difference in the way emotional stimuli are processed by genders: unpleasant and high arousing stimuli evoke greater ERP amplitudes in women relatively to men. It also seems that unpleasant or high arousing stimuli are temporally prioritized during visual processing by both genders.

Neurotransmitters behind pain relief with transcranial magnetic stimulation - positron emission tomography evidence for release of endogenous opioids.

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Lamusuo, S; Hirvonen, J; Lindholm, P; Martikainen, I K; Hagelberg, N; Parkkola, R; Taiminen, T; Hietala, J; Helin, S; Virtanen, A; Pertovaara, A; Jääskeläinen, S K

2017-10-01

Repetitive transcranial magnetic stimulation (rTMS) at M1/S1 cortex has been shown to alleviate neuropathic pain. To investigate the possible neurobiological correlates of cortical neurostimulation for the pain relief. We studied the effects of M1/S1 rTMS on nociception, brain dopamine D2 and μ-opioid receptors using a randomized, sham-controlled, double-blinded crossover study design and 3D-positron emission tomography (PET). Ten healthy subjects underwent active and sham rTMS treatments to the right M1/S1 cortex with E-field navigated device. Dopamine D2 and μ-receptor availabilities were assessed with PET radiotracers [ 11 C]raclopride and [ 11 C]carfentanil after each rTMS treatment. Thermal quantitative sensory testing (QST), contact heat evoked potential (CHEP) and blink reflex (BR) recordings were performed between the PET scans. μ-Opioid receptor availability was lower after active than sham rTMS (P ≤ 0.0001) suggested release of endogenous opioids in the right ventral striatum, medial orbitofrontal, prefrontal and anterior cingulate cortices, and left insula, superior temporal gyrus, dorsolateral prefrontal cortex and precentral gyrus. There were no differences in striatal dopamine D2 receptor availability between active and sham rTMS, consistent with lack of long-lasting measurable dopamine release. Active rTMS potentiated the dopamine-regulated habituation of the BR compared to sham (P = 0.02). Thermal QST and CHEP remained unchanged after active rTMS. rTMS given to M1/S1 activates the endogenous opioid system in a wide brain network associated with processing of pain and other salient stimuli. Direct enhancement of top-down opioid-mediated inhibition may partly explain the clinical analgesic effects of rTMS. Neurobiological correlates of rTMS for the pain relief are unclear. rTMS on M1/S1 with 11 C-carfentanyl-PET activates endogenous opioids. Thermal and heat pain thresholds remain unchanged. rTMS induces top-down opioid-mediated inhibition

Mental Simulation of Painful Situations Has an Impact on Posture and Psychophysiological Parameters

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Thierry Lelard

2017-11-01

Full Text Available Embodiment is made possible by the ability to imagine ourselves in a particular situation (mental simulation. Postural changes have been demonstrated in response to painful situations, but the effect of an implicit instruction has not been studied. The present study was designed to record differential responses according to whether or not subjects were instructed to imagine themselves in a painful or non-painful situation. Painful stimuli and instructions to mentally simulate the displayed situation were hypothesized to induce postural changes that could be demonstrated by changes in the center of pressure (COP trajectory compared to viewing the same stimuli with no instructions. We hypothesized that mental simulation of a painful situation would induce embodiment of the emotional situation as reflected by posterior displacement of the COP and physiological responses as compared to passive observation of the same visual scene. Thirty-one subjects participated in this study while standing quietly on a posturographic platform with presentation of visual stimuli depicting scenes defining three experimental conditions (painful, non-painful and neutral situations for 12 s. Physiological measurements [heart rate (HR and electrodermal activity] and postural responses (COP displacements were recorded in response to the stimuli with or without instructions to imagine themselves in the situation. Time-course analyses (1 s sliding window were conducted for several postural parameters, HR and electrodermal response. An interaction effect (instruction × stimuli × time demonstrated that mental simulation induced posterior displacement of the mean position of the COP at different times during presentation of visual stimuli (4 s; 9–12 s. An effect of instruction was reported for HR (HR was higher in the mental simulation condition, while a stimulation effect was reported only for HR (lower for painful stimuli than for non-painful stimuli. The results of

Prediction of postoperative pain: a systematic review of predictive experimental pain studies

DEFF Research Database (Denmark)

Werner, Mads Utke; Mjöbo, Helena N; Nielsen, Per R

2010-01-01

Quantitative testing of a patient's basal pain perception before surgery has the potential to be of clinical value if it can accurately predict the magnitude of pain and requirement of analgesics after surgery. This review includes 14 studies that have investigated the correlation between...... preoperative responses to experimental pain stimuli and clinical postoperative pain and demonstrates that the preoperative pain tests may predict 4-54% of the variance in postoperative pain experience depending on the stimulation methods and the test paradigm used. The predictive strength is much higher than...

Enhanced early visual processing in response to snake and trypophobic stimuli

OpenAIRE

Strien, Jan; Van der Peijl, M.K. (Manja K.)

2018-01-01

textabstractBackground: Trypophobia refers to aversion to clusters of holes. We investigated whether trypophobic stimuli evoke augmented early posterior negativity (EPN). Methods: Twenty-four participants filled out a trypophobia questionnaire and watched the random rapid serial presentation of 450 trypophobic pictures, 450 pictures of poisonous animals, 450 pictures of snakes, and 450 pictures of small birds (1800 pictures in total, at a rate of 3 pictures/s). The EPN was scored as the mean ...

Music-evoked emotions in schizophrenia.

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Abe, Daijyu; Arai, Makoto; Itokawa, Masanari

2017-07-01

Previous studies have reported that people with schizophrenia have impaired musical abilities. Here we developed a simple music-based assay to assess patient's ability to associate a minor chord with sadness. We further characterize correlations between impaired musical responses and psychiatric symptoms. We exposed participants sequentially to two sets of sound stimuli, first a C-major progression and chord, and second a C-minor progression and chord. Participants were asked which stimulus they associated with sadness, the first set, the second set, or neither. The severity of psychiatric symptoms was assessed using the Positive and Negative Syndrome Scale (PANSS). Study participants were 29 patients diagnosed with schizophrenia and 29 healthy volunteers matched in age, gender and musical background. 37.9% (95% confidence interval [CI]:19.1-56.7) of patients with schizophrenia associated the minor chord set as sad, compared with 97.9% (95%CI: 89.5-103.6) of controls. Four patients were diagnosed with treatment-resistant schizophrenia, and all four failed to associate the minor chord with sadness. Patients who did not recognize minor chords as sad had significantly higher scores on all PANSS subscales. A simple test allows music-evoked emotions to be assessed in schizophrenia patient, and may show potential relationships between music-evoked emotions and psychiatric symptoms. Copyright © 2016. Published by Elsevier B.V.

Light scattering changes follow evoked potentials from hippocampal Schaeffer collateral stimulation

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Rector, D M; Poe, G R; Kristensen, Morten Pilgaard

1997-01-01

, concurrently with larger population postsynaptic potentials. Optical signals occurred over a time course similar to that for electrical signals and increased with larger stimulation amplitude to a maximum, then decreased with further increases in stimulation current. Camera images revealed a topographic......We assessed relationships of evoked electrical and light scattering changes from cat dorsal hippocampus following Schaeffer collateral stimulation. Under anesthesia, eight stimulating electrodes were placed in the left hippocampal CA field and an optic probe, coupled to a photodiode or a charge....... Electrode recordings and photodiode output were simultaneously acquired at 2.4 kHz during single biphasic pulse stimuli 0.5 ms in duration with 0.1-Hz intervals. Camera images were digitized at 100 Hz. An average of 150 responses was calculated for each of six stimulating current levels. Stimuli elicited...

Objective measures of binaural masking level differences and comodulation masking release based on late auditory evoked potentials.

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Epp, Bastian; Yasin, Ifat; Verhey, Jesko L

2013-12-01

The audibility of important sounds is often hampered due to the presence of other masking sounds. The present study investigates if a correlate of the audibility of a tone masked by noise is found in late auditory evoked potentials measured from human listeners. The audibility of the target sound at a fixed physical intensity is varied by introducing auditory cues of (i) interaural target signal phase disparity and (ii) coherent masker level fluctuations in different frequency regions. In agreement with previous studies, psychoacoustical experiments showed that both stimulus manipulations result in a masking release (i: binaural masking level difference; ii: comodulation masking release) compared to a condition where those cues are not present. Late auditory evoked potentials (N1, P2) were recorded for the stimuli at a constant masker level, but different signal levels within the same set of listeners who participated in the psychoacoustical experiment. The data indicate differences in N1 and P2 between stimuli with and without interaural phase disparities. However, differences for stimuli with and without coherent masker modulation were only found for P2, i.e., only P2 is sensitive to the increase in audibility, irrespective of the cue that caused the masking release. The amplitude of P2 is consistent with the psychoacoustical finding of an addition of the masking releases when both cues are present. Even though it cannot be concluded where along the auditory pathway the audibility is represented, the P2 component of auditory evoked potentials is a candidate for an objective measure of audibility in the human auditory system. Copyright © 2013 Elsevier B.V. All rights reserved.

Napping reverses increased pain sensitivity due to sleep restriction.

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Faraut, Brice; Léger, Damien; Medkour, Terkia; Dubois, Alexandre; Bayon, Virginie; Chennaoui, Mounir; Perrot, Serge

2015-01-01

To investigate pain sensitivity after sleep restriction and the restorative effect of napping. A strictly controlled randomized crossover study with continuous polysomnography monitoring was performed. Laboratory-based study. 11 healthy male volunteers. Volunteers attended two three-day sessions: "sleep restriction" alone and "sleep restriction and nap". Each session involved a baseline night of normal sleep, a night of sleep deprivation and a night of free recovery sleep. Participants were allowed to sleep only from 02:00 to 04:00 during the sleep deprivation night. During the "sleep restriction and nap" session, volunteers took two 30-minute naps, one in the morning and one in the afternoon. Quantitative sensory testing was performed with heat, cold and pressure, at 10:00 and 16:00, on three areas: the supraspinatus, lower back and thigh. After sleep restriction, quantitative sensory testing revealed differential changes in pain stimuli thresholds, but not in thermal threshold detection: lower back heat pain threshold decreased, pressure pain threshold increased in the supraspinatus area and no change was observed for the thigh. Napping restored responses to heat pain stimuli in the lower back and to pressure stimuli in the supraspinatus area. Sleep restriction induces different types of hypersensitivity to pain stimuli in different body areas, consistent with multilevel mechanisms, these changes being reversed by napping. The napping restorative effect on pain thresholds result principally from effects on pain mechanisms, since it was independent of vigilance status.

Napping reverses increased pain sensitivity due to sleep restriction.

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Brice Faraut

Full Text Available To investigate pain sensitivity after sleep restriction and the restorative effect of napping.A strictly controlled randomized crossover study with continuous polysomnography monitoring was performed.Laboratory-based study.11 healthy male volunteers.Volunteers attended two three-day sessions: "sleep restriction" alone and "sleep restriction and nap". Each session involved a baseline night of normal sleep, a night of sleep deprivation and a night of free recovery sleep. Participants were allowed to sleep only from 02:00 to 04:00 during the sleep deprivation night. During the "sleep restriction and nap" session, volunteers took two 30-minute naps, one in the morning and one in the afternoon.Quantitative sensory testing was performed with heat, cold and pressure, at 10:00 and 16:00, on three areas: the supraspinatus, lower back and thigh. After sleep restriction, quantitative sensory testing revealed differential changes in pain stimuli thresholds, but not in thermal threshold detection: lower back heat pain threshold decreased, pressure pain threshold increased in the supraspinatus area and no change was observed for the thigh. Napping restored responses to heat pain stimuli in the lower back and to pressure stimuli in the supraspinatus area.Sleep restriction induces different types of hypersensitivity to pain stimuli in different body areas, consistent with multilevel mechanisms, these changes being reversed by napping. The napping restorative effect on pain thresholds result principally from effects on pain mechanisms, since it was independent of vigilance status.

The Influence of Social Threat on Pain, Aggression, and Empathy in Women.

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Karos, Kai; Meulders, Ann; Goubert, Liesbet; Vlaeyen, Johan W S

2018-03-01

Only one published study has investigated the effect of a threatening social context on the perception and expression of pain, showing that social threat leads to increased pain reports but reduced nonverbal pain expression. The current study aimed to replicate and extend these findings to further explore the effects of a threatening social context. Healthy, female participants (N = 71) received 10 electrocutaneous stimuli delivered by a confederate. They were led to believe that the confederate was requested to administer 10 painful stimuli (control group) or that the confederate deliberately chose to deliver 10 painful stimuli when given the choice to deliver between 1 to 10 painful stimuli (social threat group). Self-reported pain intensity, unpleasantness, threat value of pain, and painful facial expression were assessed. Additionally, empathy and aggression toward the confederate were investigated. Social threat did not affect painful facial expression or self-reported pain intensity, but led to increased aggression toward the confederate. Moreover, perceived social threat predicted the threat value of pain and reduced empathy toward the confederate. We were not able to replicate the previously reported dissociation between pain reports and pain expression as a result of social threat. However, social threat was associated with an increased threat value of pain, increased aggression, and reduced empathy. A threatening social context affects how threatening pain is perceived and has interpersonal consequences such as increased aggression and reduced empathy, thereby creating a double burden on the individual suffering from pain. Copyright © 2017 The American Pain Society. Published by Elsevier Inc. All rights reserved.

Differential pain modulation in patients with peripheral neuropathic pain and fibromyalgia.

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Gormsen, Lise; Bach, Flemming W; Rosenberg, Raben; Jensen, Troels S

2017-12-29

Background The definition of neuropathic pain has recently been changed by the International Association for the Study of Pain. This means that conditions such as fibromyalgia cannot, as sometimes discussed, be included in the neuropathic pain conditions. However, fibromyalgia and peripheral neuropathic pain share common clinical features such as spontaneous pain and hypersensitivity to external stimuli. Therefore, it is of interest to directly compare the conditions. Material and methods In this study we directly compared the pain modulation in neuropathic pain versus fibromyalgia by recording responses to a cold pressor test in 30 patients with peripheral neuropathic pain, 28 patients with fibromyalgia, and 26 pain-free age-and gender-matched healthy controls. Patients were asked to rate their spontaneous pain on a visual analog scale (VAS (0-100 mm) immediately before and immediately after the cold pressor test. Furthermore the duration (s) of extremity immersion in cold water was used as a measure of the pain tolerance threshold, and the perceived pain intensity at pain tolerance on the VAS was recorded on the extremity in the water after the cold pressor test. In addition, thermal (thermo tester) and mechanical stimuli (pressure algometer) were used to determine sensory detection, pain detection, and pain tolerance thresholds in different body parts. All sensory tests were done by the same examiner, in the same room, and with each subject in a supine position. The sequence of examinations was the following: (1) reaction time, (2) pressure thresholds, (3) thermal thresholds, and (4) cold pressor test. Reaction time was measured to ensure that psychomotoric inhibitions did not influence pain thresholds. Results Pain modulation induced by a cold pressor test reduced spontaneous pain by 40% on average in neuropathic pain patients, but increased spontaneous pain by 2.6% in fibromyalgia patients. This difference between fibromyalgia and neuropathic pain patients was

Jaw-motor effects of experimental jaw-muscle pain and stress in patients with deep bite and matched control subjects

DEFF Research Database (Denmark)

Sonnesen, Liselotte; Svensson, Peter

2013-01-01

clenching, during evoked pain and stress between deep bite patients and controls was investigated. DESIGN: In 30 deep bite patients and in 30 sex-/age-matched controls with neutral occlusion EMG activity was recorded bilaterally from masseter and anterior temporalis muscles before and during evoked pain......OBJECTIVE: The effect of experimental jaw-muscle pain and stress on masticatory muscle activity in TMD-patients has been discussed. Furthermore, associations between TMD and deep bite patients have been studied. Accordingly in the present study, comparison of EMG responses at rest, maximal...... and before and during a stress task. Evoked pain was induced by injections of glutamate into the masseter (local pain) and brachioradialis (remote pain) muscles and resting EMG activity was recorded before and after 1, 2, 3, 4, 5 and 10min. A precision task was used to simulate a stressful condition and EMG...

Short-term pre- and post-operative stress prolongs incision-induced pain hypersensitivity without changing basal pain perception.

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Cao, Jing; Wang, Po-Kai; Tiwari, Vinod; Liang, Lingli; Lutz, Brianna Marie; Shieh, Kun-Ruey; Zang, Wei-Dong; Kaufman, Andrew G; Bekker, Alex; Gao, Xiao-Qun; Tao, Yuan-Xiang

2015-12-02

Chronic stress has been reported to increase basal pain sensitivity and/or exacerbate existing persistent pain. However, most surgical patients have normal physiological and psychological health status such as normal pain perception before surgery although they do experience short-term stress during pre- and post-operative periods. Whether or not this short-term stress affects persistent postsurgical pain is unclear. In this study, we showed that pre- or post-surgical exposure to immobilization 6 h daily for three consecutive days did not change basal responses to mechanical, thermal, or cold stimuli or peak levels of incision-induced hypersensitivity to these stimuli; however, immobilization did prolong the duration of incision-induced hypersensitivity in both male and female rats. These phenomena were also observed in post-surgical exposure to forced swimming 25 min daily for 3 consecutive days. Short-term stress induced by immobilization was demonstrated by an elevation in the level of serum corticosterone, an increase in swim immobility, and a decrease in sucrose consumption. Blocking this short-term stress via intrathecal administration of a selective glucocorticoid receptor antagonist, RU38486, or bilateral adrenalectomy significantly attenuated the prolongation of incision-induced hypersensitivity to mechanical, thermal, and cold stimuli. Our results indicate that short-term stress during the pre- or post-operative period delays postoperative pain recovery although it does not affect basal pain perception. Prevention of short-term stress may facilitate patients' recovery from postoperative pain.

Equal pain – Unequal fear response: Enhanced susceptibility of tooth pain to fear conditioning

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Michael Lukas Meier

2014-07-01

Full Text Available Experimental fear conditioning in humans is widely used as a model to investigate the neural basis of fear learning and to unravel the pathogenesis of anxiety disorders. It has been observed that fear conditioning depends on stimulus salience and subject vulnerability to fear. It is further known that the prevalence of dental-related fear and phobia is exceedingly high in the population. Dental phobia is unique as no other body part is associated with a specific phobia. Therefore, we hypothesized that painful dental stimuli exhibit an enhanced susceptibility to fear conditioning when comparing to equal perceived stimuli applied to other body sites. Differential susceptibility to pain-related fear was investigated by analyzing responses to an unconditioned stimulus (UCS applied to the right maxillary canine (UCS-c versus the right tibia (UCS-t. For fear conditioning, UCS-c and USC-t consisted of painful electric stimuli, carefully matched at both application sites for equal intensity and quality perception. UCSs were paired to simple geometrical forms which served as conditioned stimuli (CS+. Unpaired CS+ were presented for eliciting and analyzing conditioned fear responses. Outcome parameter were 1 skin conductance changes and 2 time-dependent brain activity (BOLD responses in fear-related brain regions such as the amygdala, anterior cingulate cortex, insula, thalamus, orbitofrontal cortex and medial prefrontal cortex.A preferential susceptibility of dental pain to fear conditioning was observed, reflected by heightened skin conductance responses and enhanced time-dependent brain activity (BOLD responses in the fear network. For the first time, this study demonstrates fear-related neurobiological mechanisms that point towards a superior conditionability of tooth pain. Beside traumatic dental experiences our results offer novel evidence that might explain the high prevalence of dental-related fears in the population.

Personalized Pain Therapy : Is the answer in the genes?

NARCIS (Netherlands)

M. Matić (Maja)

2017-01-01

textabstractThe experience of pain is very subjective and multidimensional, displaying substantial variability between individuals even when exposed to an identical pain-evoking stimulus. Differences in gender, age, ethnicity and anxiety level are among the known factors that contribute to this

Effects of intravenous propranolol on heat pain sensitivity in healthy men.

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Schweinhardt, P; Abulhasan, Y B; Koeva, V; Balderi, T; Kim, D J; Alhujairi, M; Carli, F

2013-05-01

Clinical studies have shown opioid-sparing effects of β-adrenergic antagonists perioperatively and β-blockers are being investigated for chronic musculoskeletal pain. However, the direct analgesic effects of β-blockers have rarely been examined in healthy humans. In a randomized, counter-balanced, double-blind, within-subject crossover design, we tested the effect of the lipophilic β-blocker propranolol (0.035 mg/kg body weight i.v.) on heat pain sensitivity in 39 healthy males, compared with placebo. To test for peripheral versus central effects, the peripherally acting β-blocker sotalol was also examined. Experimental stimuli were brief superficial noxious heat stimuli applied to the volar forearm. Non-painful cold stimuli were included to test for specificity. Sedation, mood and anxiety were assessed to investigate potential mechanisms underlying any analgesic effect. β-blocker effects on blood pressure were incorporated into the analysis because of a known inverse relationship between pain sensitivity and systolic blood pressure. Propranolol significantly decreased perceived intensity of heat pain stimuli but only in participants with small propranolol-induced blood pressure decreases. Even in this group, the effect was small (4%). Propranolol did not influence perceived intensity of non-noxious stimuli and had no effect on sedation, anxiety or mood. Sotalol did not influence heat pain sensitivity. Propranolol decreased pain sensitivity but its analgesic effects were small and counteracted by blood pressure decreases. The analgesic effects were not mediated by peripheral β-receptor blockade, sedation, mood or anxiety. The small effect indicates that the utility of β-blockers for clinical pain must be related to factors that do not play a significant role for experimental pain. © 2012 European Federation of International Association for the Study of Pain Chapters.

Absence of both auditory evoked potentials and auditory percepts dependent on timing cues.

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Starr, A; McPherson, D; Patterson, J; Don, M; Luxford, W; Shannon, R; Sininger, Y; Tonakawa, L; Waring, M

1991-06-01

An 11-yr-old girl had an absence of sensory components of auditory evoked potentials (brainstem, middle and long-latency) to click and tone burst stimuli that she could clearly hear. Psychoacoustic tests revealed a marked impairment of those auditory perceptions dependent on temporal cues, that is, lateralization of binaural clicks, change of binaural masked threshold with changes in signal phase, binaural beats, detection of paired monaural clicks, monaural detection of a silent gap in a sound, and monaural threshold elevation for short duration tones. In contrast, auditory functions reflecting intensity or frequency discriminations (difference limens) were only minimally impaired. Pure tone audiometry showed a moderate (50 dB) bilateral hearing loss with a disproportionate severe loss of word intelligibility. Those auditory evoked potentials that were preserved included (1) cochlear microphonics reflecting hair cell activity; (2) cortical sustained potentials reflecting processing of slowly changing signals; and (3) long-latency cognitive components (P300, processing negativity) reflecting endogenous auditory cognitive processes. Both the evoked potential and perceptual deficits are attributed to changes in temporal encoding of acoustic signals perhaps occurring at the synapse between hair cell and eighth nerve dendrites. The results from this patient are discussed in relation to previously published cases with absent auditory evoked potentials and preserved hearing.

Do Event-Related Evoked Potentials Reflect Apathy Tendency and Motivation?

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Hiroyuki Takayoshi

2018-01-01

Full Text Available Apathy is a mental state of diminished motivation. Although the reward system as the foundation of the motivation in the human brain has been studied extensively with neuroimaging techniques, the electrophysiological correlates of motivation and apathy have not been fully explored. Thus, in 14 healthy volunteers, we examined whether event-related evoked potentials (ERP obtained during a simple number discrimination task with/without rewards reflected apathy tendency and a reward-dependent tendency, which were assessed separately using the apathy scale and the temperament and character inventory (TCI. Participants were asked to judge the size of a number, and received feedback based on their performance in each trial. The P3 amplitudes related to the feedback stimuli increased only in the reward condition. Furthermore, the P2 amplitudes related to the negative feedback stimuli in the reward condition had a positive correlation with the reward-dependent tendency in TCI, whereas the P3 amplitudes related to the positive feedback stimuli had a negative correlation with the apathy score. Our result suggests that the P2 and P3 ERPs to reward-related feedback stimuli are modulated in a distinctive manner by the motivational reward dependence and apathy tendency, and thus the current paradigm may be useful for investigating the brain activity associated with motivation.

Neuropathic pain and cytokines: current perspectives

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Clark AK

2013-11-01

Full Text Available Anna K Clark, Elizabeth A Old, Marzia Malcangio Wolfson Centre for Age Related Diseases, King's College London, London, UK Abstract: Neuropathic pain represents a major problem in clinical medicine because it causes debilitating suffering and is largely resistant to currently available analgesics. A characteristic of neuropathic pain is abnormal response to somatic sensory stimulation. Thus, patients suffering peripheral neuropathies may experience pain caused by stimuli which are normally nonpainful, such as simple touching of the skin or by changes in temperature, as well as exaggerated responses to noxious stimuli. Convincing evidence suggests that this hypersensitivity is the result of pain remaining centralized. In particular, at the first pain synapse in the dorsal horn of the spinal cord, the gain of neurons is increased and neurons begin to be activated by innocuous inputs. In recent years, it has become appreciated that a remote damage in the peripheral nervous system results in neuronal plasticity and changes in microglial and astrocyte activity, as well as infiltration of macrophages and T cells, which all contribute to central sensitization. Specifically, the release of pronociceptive factors such as cytokines and chemokines from neurons and non-neuronal cells can sensitize neurons of the first pain synapse. In this article we review the current evidence for the role of cytokines in mediating spinal neuron–non-neuronal cell communication in neuropathic pain mechanisms following peripheral nerve injury. Specific and selective control of cytokine-mediated neuronal–glia interactions results in attenuation of the hypersensitivity to both noxious and innocuous stimuli observed in neuropathic pain models, and may represent an avenue for future therapeutic intervention. Keywords: anti-inflammatory cytokines, proinflammatory cytokines, microglia, astrocytes, first pain synapse

The genetic influence on the cortical processing of experimental pain and the moderating effect of pain status.

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Helen Vossen

Full Text Available BACKGROUND: Research suggests that the COMT Val(158Met, BDNF Val(66Met and OPRM1 A(118G polymorphisms moderate the experience of pain. In order to obtain experimental confirmation and extension of findings, cortical processing of experimentally-induced pain was used. METHOD: A sample of 78 individuals with chronic low back pain complaints and 37 healthy controls underwent EEG registration. Event-Related Potentials were measured in response to electrical nociceptive stimuli and moderation by COMT Val(158Met, BDNF Val(66Met and OPRM1 A(118G polymorphisms was assessed. RESULTS: Genetic variation did not have a direct effect on cortical processing of experimental pain. However, genetic effects (COMT Val(158Met and BDNF Val(66Met on experimental pain were moderated by the presence of chronic pain. In the presence of chronic pain, the COMT Met allele and the BDNF Met allele augmented cortical pain processing, whilst reducing pain processing in pain-free controls. No significant effects were found concerning the OPRM1 A(118G polymorphism. CONCLUSIONS: The current study suggests that chronic experience of pain enhances genetic sensitivity to experimentally induced mildly painful stimuli, possibly through a process of epigenetic modification.

Home cage wheel running is an objective and clinically relevant method to assess inflammatory pain in male and female rats

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Kandasamy, Ram; Calsbeek, Jonas J.; Morgan, Michael M.

2016-01-01

Background The assessment of nociception in preclinical studies is undergoing a transformation from pain-evoked to pain-depressed tests to more closely mimic the effects of clinical pain. Many inflammatory pain-depressed behaviors (reward seeking, locomotion) have been examined, but these tests are limited because of confounds such as stress and difficulties in quantifying behavior. New Method The present study evaluates home cage wheel running as an objective method to assess the magnitude and duration of inflammatory pain in male and female rats. Results Injection of Complete Freund’s Adjuvant (CFA) into the right hindpaw to induce inflammatory pain almost completely inhibited wheel running for 2 days in males and females. Wheel running gradually returned to baseline levels within 12 days despite persistent mechanical hypersensitivity (von Frey test). Comparison with Existing Methods Continuously monitoring home cage wheel running improves on previous studies examining inflammatory pain-depressed wheel running because it is more sensitive to noxious stimuli, avoids the stress of removing the rat from its cage for testing, and provides a complete analysis of the time course for changes in nociception. Conclusions The present data indicate that home cage wheel running is a clinically relevant method to assess inflammatory pain in the rat. The decrease in activity caused by inflammatory pain and subsequent gradual recovery mimics the changes in activity caused by pain in humans. The tendency for pain-depressed wheel running to be greater in female than male rats is consistent with the tendency for women to be at greater risk of chronic pain than men. PMID:26891874

Experimental human pain models in gastro-esophageal reflux disease and unexplained chest pain

Institute of Scientific and Technical Information of China (English)

Asbj(φ)rn Mohr Drewes; Lars Arendt-Nielsen; Peter Funch-Jensen; Hans Gregersen

2006-01-01

Methods related to experimental human pain research aim at activating different nociceptors, evoke pain from different organs and activate specific pathways and mechanisms. The different possibilities for using mechanical, electrical, thermal and chemical methods in visceral pain research are discussed with emphasis of combinations (e.g., the multimodal approach). The methods have been used widely in assessment of pain mechanisms in the esophagus and have contributed to our understanding of the symptoms reported in these patients. Hence abnormal activation and plastic changes of central pain pathways seem to play a major role in the symptoms in some patients with gastro-esophageal reflux disease and in patients with functional chest pain of esophageal origin. These findings may lead to an alternative approach for treatment in patients that does not respond to conventional medical or surgical therapy.

Auditory Evoked Potentials and Hand Preference in 6-Month-Old Infants: Possible Gender-Related Differences in Cerebral Organization.

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Shucard, Janet L.; Shucard, David W.

1990-01-01

Verbal and musical stimuli were presented to infants in a study of the relations of evoked potential left-right amplitude asymmetries to gender and hand preference. There was a relation between asymmetry and hand preference, and for girls, between asymmetry and stimulus condition. Results suggest a gender difference in cerebral hemisphere…

Persistent idiopathic facial pain

DEFF Research Database (Denmark)

Maarbjerg, Stine; Wolfram, Frauke; Heinskou, Tone Bruvik

2017-01-01

Introduction: Persistent idiopathic facial pain (PIFP) is a poorly understood chronic orofacial pain disorder and a differential diagnosis to trigeminal neuralgia. To address the lack of systematic studies in PIFP we here report clinical characteristics and neuroimaging findings in PIFP. Methods...... pain 7 (13%), hypoesthesia 23 (48%), depression 16 (30%) and other chronic pain conditions 17 (32%) and a low prevalence of stabbing pain 21 (40%), touch-evoked pain 14 (26%) and remission periods 10 (19%). The odds ratio between neurovascular contact and the painful side was 1.4 (95% Cl 0.4–4.4, p = 0.......565) and the odds ratio between neurovascular contact with displacement of the trigeminal nerve and the painful side was 0.2 (95% Cl 0.0–2.1, p = 0.195). Conclusion: PIFP is separated from trigeminal neuralgia both with respect to the clinical characteristics and neuroimaging findings, as NVC was not associated...

Conditioned pain modulation in patients with nonspecific chronic back pain with chronic local pain, chronic widespread pain, and fibromyalgia.

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Gerhardt, Andreas; Eich, Wolfgang; Treede, Rolf-Detlef; Tesarz, Jonas

2017-03-01

Findings considering conditioned pain modulation (CPM) in chronic back pain (CBP) are contradictory. This might be because many patients with CBP report pain in further areas of the body, and altered CPM might influence spatial extent of pain rather than CBP per se. Therefore, we compared CPM in patients with CBP with different pain extent. Patients with fibromyalgia syndrome (FMS), for whom CPM impairment is reported most consistently, were measured for comparison. Based on clinical evaluation and pain drawings, patients were categorized into chronic local back pain (CLP; n = 53), chronic widespread back pain (CWP; n = 32), and FMS (n = 92). Conditioned pain modulation was measured by the difference in pressure pain threshold (test stimuli) at the lower back before and after tonic heat pain (conditioning stimulus). We also measured psychosocial variables. Pressure pain threshold was significantly increased in CLP patients after tonic heat pain (P pain modulation in CLP was significantly higher than that in CWP and FMS (P painful areas (0-10) were associated with lower CPM (r = 0.346, P = 0.001) in CBP but not in FMS (r = -0.013, P = 0.903). Anxiety and depression were more pronounced in FMS than in CLP or CWP (P values pain inhibition seem to be more indicated the higher the pain extent.

A comprehensive Fabry-related pain questionnaire for adult patients.

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Üçeyler, Nurcan; Magg, Barbara; Thomas, Phillip; Wiedmann, Silke; Heuschmann, Peter; Sommer, Claudia

2014-11-01

Pain may be the earliest symptom in Fabry disease and presents with a distinct phenotype including triggerable pain attacks, evoked pain, pain crises, and chronic pain. Current pain questionnaires do not reflect the special phenotype of Fabry disease-associated pain, which hampers its systematic evaluation as the basis of correct diagnosis and effective treatment. A questionnaire specifically designed to assess Fabry disease-associated pain is thus urgently needed. At the Würzburg Fabry Center for Interdisciplinary Therapy (FAZIT), Germany, we developed and validated the first face-to-face Fabry Pain Questionnaire (FPQ) for adult patients. The initial version of the FPQ was tested in a pilot study with 20 consecutive Fabry disease patients. The performance of the revised FPQ was assessed in a first (n=56) and second (n=20) validation phase in consecutive Fabry disease patients. For this, patients were interviewed at baseline and 2 weeks later. We determined the test-retest reliability and validity of the FPQ in comparison to data obtained with the Neuropathic Pain Symptom Inventory. The FPQ contains 15 questions on the 4 pain phenotypes of Fabry disease (pain attacks, pain crises, evoked pain, chronic pain) in childhood and adulthood, on pain development during life with and without enzyme replacement therapy, and on everyday life impairment due to pain. This first disease-specific questionnaire is a valuable tool for baseline and follow-up assessment of pain in Fabry disease patients and may guide treatment in this distinct pain phenotype. Copyright © 2014 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Differences in cortical response to acupressure and electroacupuncture stimuli

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Vangel Mark G

2011-07-01

Full Text Available Abstract Background FMRI studies focus on sub-cortical effects of acupuncture stimuli. The purpose of this study was to assess changes in primary somatosensory (S1 activity over the course of different types of acupuncture stimulation. We used whole head magnetoencephalography (MEG to map S1 brain response during 15 minutes of electroacupuncture (EA and acupressure (AP. We further assessed how brain response changed during the course of stimulation. Results Evoked brain response to EA differed from AP in its temporal dynamics by showing clear contralateral M20/M30 peaks while the latter demonstrated temporal dispersion. Both EA and AP demonstrated significantly decreased response amplitudes following five minutes of stimulation. However, the latency of these decreases were earlier in EA (~30 ms post-stimulus than AP (> 100 ms. Time-frequency responses demonstrated early onset, event related synchronization (ERS, within the gamma band at ~70-130 ms and the theta band at ~50-200 ms post-stimulus. A prolonged event related desynchronization (ERD of alpha and beta power occurred at ~100-300 ms post-stimulus. There was decreased beta ERD at ~100-300 ms over the course of EA, but not AP. Conclusion Both EA and AP demonstrated conditioning of SI response. In conjunction with their subcortical effects on endogenous pain regulation, these therapies show potential for affecting S1 processing and possibly altering maladaptive neuroplasticity. Thus, further investigation in neuropathic populations is needed.

Decreased pain perception by unconscious emotional pictures

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Irene Peláez

2016-10-01

Full Text Available Pain perception arises from a complex interaction between a nociceptive stimulus and different emotional and cognitive factors, which appear to be mediated by both automatic and controlled systems. Previous evidence has shown that whereas conscious processing of unpleasant stimuli enhances pain perception, emotional influences on pain under unaware conditions are much less known. The aim of the present study was to investigate the modulation of pain perception by unconscious emotional pictures through an emotional masking paradigm. Two kinds of both somatosensory (painful and non-painful and emotional stimulation (negative and neutral pictures were employed. Fifty pain-free participants were asked to rate the perception of pain they were feeling in response to laser-induced somatosensory stimuli as faster as they can. Data from pain intensity and reaction times were measured. Statistical analyses revealed a significant effect for the interaction between pain and emotional stimulation, but surprisingly this relationship was opposite to expected. In particular, lower pain intensity scores and longer reaction times were found in response to negative images being strengthened this effect for painful stimulation. Present findings suggest a clear pain perception modulation by unconscious emotional contexts. Attentional capture mechanisms triggered by unaware negative stimulation could explain this phenomenon leading to a withdrawal of processing resources from pain.

Pain and Coping in The Religious Mind

DEFF Research Database (Denmark)

Jegindø, Else-Marie Elmholdt; Geertz, Armin W.; Roepstorff, Andreas

institutions, i.e. the Religion, Cognition and Culture (RCC) research area at The Faculty of Theology, Centre of Functionally Integrative Neuroscience (CFIN) and The Danish Pain Research Centre (DPRC) at the University of Aarhus and Aarhus University Hospital. The team will design fMRI (functional magnetic...... hypothesize that the target group will have a higher pain threshold and pain tolerance during religious practice compared to a non-religious control group, and the fMRI experiments are expected to show reduced neural activity (BOLD) in areas of the brain correlating with pain experience during personal prayer...... and religious stimuli (target) and increased neural activity in reward systems during personal prayer and religious stimuli (target). To complement the clinical experiments, field work in Mauritius during the Hindu Thaipusam Festival 2010 will explore how pain in an online ritual setting is experienced...

Altered Pain Sensitivity in Elderly Women with Chronic Neck Pain

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Uthaikhup, Sureeporn; Prasert, Romchat; Paungmali, Aatit; Boontha, Kritsana

2015-01-01

Background Age-related changes occur in both the peripheral and central nervous system, yet little is known about the influence of chronic pain on pain sensitivity in older persons. The aim of this study was to investigate pain sensitivity in elders with chronic neck pain compared to healthy elders. Methods Thirty elderly women with chronic neck pain and 30 controls were recruited. Measures of pain sensitivity included pressure pain thresholds, heat/cold pain thresholds and suprathreshold heat pain responses. The pain measures were assessed over the cervical spine and at a remote site, the tibialis anterior muscle. Results Elders with chronic neck pain had lower pressure pain threshold over the articular pillar of C5-C6 and decreased cold pain thresholds over the cervical spine and tibialis anterior muscle when compared with controls (p pain thresholds and suprathreshold heat pain responses (p > 0.05). Conclusion The presence of pain hypersensitivity in elderly women with chronic neck pain appears to be dependent on types of painful stimuli. This may reflect changes in the peripheral and central nervous system with age. PMID:26039149

Do intensity ratings and skin conductance responses reliably discriminate between different stimulus intensities in experimentally induced pain?

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Breimhorst, Markus; Sandrock, Stephan; Fechir, Marcel; Hausenblas, Nadine; Geber, Christian; Birklein, Frank

2011-01-01

The present study addresses the question whether pain-intensity ratings and skin conductance responses (SCRs) are able to detect different intensities of phasic painful stimuli and to determine the reliability of this discrimination. For this purpose, 42 healthy participants of both genders were assigned to either electrical, mechanical, or laser heat-pain stimulation (each n = 14). A whole range of single brief painful stimuli were delivered on the right volar forearm of the dominant hand in a randomized order. Pain-intensity ratings and SCRs were analyzed. Using generalizability theory, individual and gender differences were the main contributors to the variability of both intensity ratings and SCRs. Most importantly, we showed that pain-intensity ratings are a reliable measure for the discrimination of different pain stimulus intensities in the applied modalities. The reliability of SCR was adequate when mechanical and heat stimuli were tested but failed for the discrimination of electrical stimuli. Further studies are needed to reveal the reason for this lack of accuracy for SCRs when applying electrical pain stimuli. Our study could help researchers to better understand the relationship between pain and activation of the sympathetic nervous system. Pain researchers are furthermore encouraged to consider individual and gender differences when measuring pain intensity and the concomitant SCRs in experimental settings. Copyright © 2011 American Pain Society. Published by Elsevier Inc. All rights reserved.

Objective assessment of spectral ripple discrimination in cochlear implant listeners using cortical evoked responses to an oddball paradigm.

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Lopez Valdes, Alejandro; Mc Laughlin, Myles; Viani, Laura; Walshe, Peter; Smith, Jaclyn; Zeng, Fan-Gang; Reilly, Richard B

2014-01-01

Cochlear implants (CIs) can partially restore functional hearing in deaf individuals. However, multiple factors affect CI listener's speech perception, resulting in large performance differences. Non-speech based tests, such as spectral ripple discrimination, measure acoustic processing capabilities that are highly correlated with speech perception. Currently spectral ripple discrimination is measured using standard psychoacoustic methods, which require attentive listening and active response that can be difficult or even impossible in special patient populations. Here, a completely objective cortical evoked potential based method is developed and validated to assess spectral ripple discrimination in CI listeners. In 19 CI listeners, using an oddball paradigm, cortical evoked potential responses to standard and inverted spectrally rippled stimuli were measured. In the same subjects, psychoacoustic spectral ripple discrimination thresholds were also measured. A neural discrimination threshold was determined by systematically increasing the number of ripples per octave and determining the point at which there was no longer a significant difference between the evoked potential response to the standard and inverted stimuli. A correlation was found between the neural and the psychoacoustic discrimination thresholds (R2=0.60, p<0.01). This method can objectively assess CI spectral resolution performance, providing a potential tool for the evaluation and follow-up of CI listeners who have difficulty performing psychoacoustic tests, such as pediatric or new users.

Visual evoked potentials and selective attention to points in space

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Van Voorhis, S.; Hillyard, S. A.

1977-01-01

Visual evoked potentials (VEPs) were recorded to sequences of flashes delivered to the right and left visual fields while subjects responded promptly to designated stimuli in one field at a time (focused attention), in both fields at once (divided attention), or to neither field (passive). Three stimulus schedules were used: the first was a replication of a previous study (Eason, Harter, and White, 1969) where left- and right-field flashes were delivered quasi-independently, while in the other two the flashes were delivered to the two fields in random order (Bernoulli sequence). VEPs to attended-field stimuli were enhanced at both occipital (O2) and central (Cz) recording sites under all stimulus sequences, but different components were affected at the two scalp sites. It was suggested that the VEP at O2 may reflect modality-specific processing events, while the response at Cz, like its auditory homologue, may index more general aspects of selective attention.

Personalized pain medicine: the clinical value of psychophysical assessment of pain modulation profile.

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Granovsky, Yelena; Yarnitsky, David

2013-01-01

Experimental pain stimuli can be used to simulate patients' pain experience. We review recent developments in psychophysical pain testing, focusing on the application of the dynamic tests-conditioned pain modulation (CPM) and temporal summation (TS). Typically, patients with clinical pain of various types express either less efficient CPM or enhanced TS, or both. These tests can be used in prediction of incidence of acquiring pain and of its intensity, as well as in assisting the correct choice of analgesic agents for individual patients. This can help to shorten the commonly occurring long and frustrating process of adjusting analgesic agents to the individual patients. We propose that evaluating pain modulation can serve as a step forward in individualizing pain medicine.

Scent-evoked nostalgia.

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Reid, Chelsea A; Green, Jeffrey D; Wildschut, Tim; Sedikides, Constantine

2015-01-01

Can scents evoke nostalgia; what might be the psychological implications of such an evocation? Participants sampled 12 scents and rated the extent to which each scent was familiar, arousing and autobiographically relevant, as well as the extent to which each scent elicited nostalgia. Participants who were high (compared to low) in nostalgia proneness reported more scent-evoked nostalgia, and scents elicited greater nostalgia to the extent that they were arousing, familiar and autobiographically relevant. Scent-evoked nostalgia predicted higher levels of positive affect, self-esteem, self-continuity, optimism, social connectedness and meaning in life. In addition, scent-evoked nostalgia was characterised by more positive emotions than either non-nostalgic autobiographical memories or non-nostalgic non-autobiographical memories. Finally, scent-evoked nostalgia predicted in-the-moment feelings of personal (general or object-specific) nostalgia. The findings represent a foray into understanding the triggers and affective signature of scent-evoked nostalgia.

Effect of hypnotic pain modulation on brain activity in patients with temporomandibular disorder pain

DEFF Research Database (Denmark)

Abrahamsen, Randi; Dietz, Martin; Lodahl, Sanne

2010-01-01

hyperalgesia. Direct contrasts between control and hypnotic hypoalgesia conditions demonstrated significant decreases in right posterior insula and BA21, as well as left BA40 during hypoalgesia. These findings are the first to describe hypnotic modulation of brain activity associated with nociceptive......Hypnosis modulates pain perception but the associated brain mechanisms in chronic pain conditions are poorly understood. Brain activity evoked by painful repetitive pin-prick stimulation of the left mental nerve region was investigated with use of fMRI in 19 patients with painful temporomandibular...... condition and significantly higher in the hypnotic hyperalgesia condition. In the control condition, painful stimulation caused significant activation of right posterior insula, primary somatosensory cortex (SI), BA21, and BA6, and left BA40 and BA4. Painful stimulation during hypnotic hyperalgesia...

Osteoarthritis-dependent changes in antinociceptive action of Nav1.7 and Nav1.8 sodium channel blockers: An in vivo electrophysiological study in the rat.

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Rahman, W; Dickenson, A H

2015-06-04

Voltage-gated sodium channel blockers are not traditionally recommended for osteoarthritis (OA) pain therapy, but given the large peripheral drive that follows OA development there is a rationale for their use. Using a rat model of monosodium iodoacetate (MIA)-induced OA we used in vivo electrophysiology to assess the effects of the Nav1.7- and Nav1.8-selective antagonists, ProTxII and A-803467 respectively, on the evoked activity of spinal dorsal horn neurons in response to electrical, mechanical and thermal stimuli applied to the peripheral receptive field. These studies allow examination of the roles of these channels in suprathreshold stimuli, not amenable to behavioral threshold measures. Spinal administration of ProTxII significantly reduced neuronal responses evoked by mechanical punctate (von Frey (vF) 8-60g) and noxious thermal (45 and 48°C) stimuli in MIA rats only. A-803467 significantly inhibited neuronal responses evoked by vF 8-60g and 48°C heat after spinal administration; significantly inhibited responses evoked by brush, vFs 26-60g and 40-48°C stimuli after systemic administration; significantly inhibited the electrically evoked Aδ-, C-fiber, post-discharge, Input and wind-up responses and the brush, vFs 8-60g and 45-48°C evoked neuronal responses after intra plantar injection in the MIA group. In comparison A-803467 effects in the sham group were minimal and included a reduction of the neuronal response evoked by vF 60g and 45°C heat stimulation after spinal administration, no effect after systemic administration and an inhibition of the evoked response to 45°C heat after intra plantar injection only. The observed selective inhibitory effect of ProTxII and A-803467 for the MIA-treated group suggests an increased role of Nav1.7 and 1.8 within nociceptive pathways in the arthritic condition, located at peripheral and central sites. These findings demonstrate the importance of, and add to, the mechanistic understanding of these channels in

Prediction of post-operative pain after a laparoscopic tubal ligation procedure

DEFF Research Database (Denmark)

Rudin, A.; Wolner-Hanssen, P.; Hellbom, M.

2008-01-01

ligation procedure. METHODS: Assessments of anxiety, mood, psychological vulnerability and pre-operative pain were made before surgery using the State-Trait Anxiety Inventory (STAI), the Hospital Anxiety Depression Scale (HADS), a psychological vulnerability test and the Short-Form McGill Pain......BACKGROUND: Pre-operative identification of reliable predictors of post-operative pain may lead to improved pain management strategies. We investigated the correlation between pre-operative pain, psychometric variables, response to heat stimuli and post-operative pain following a laparoscopic tubal...... Questionnaire (SF-MPQ), respectively. Pre-operative assessments of thermal thresholds and pain response to randomized series of heat stimuli (1 s, 44-48 degrees C) were made with quantitative sensory testing technique. Post-operative pain intensity was evaluated daily by a visual analogue scale during rest...

Profiles in fibromyalgia: algometry, auditory evoked potentials and clinical characterization of different subtypes.

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Triñanes, Yolanda; González-Villar, Alberto; Gómez-Perretta, Claudio; Carrillo-de-la-Peña, María T

2014-11-01

The heterogeneity found in fibromyalgia (FM) patients has led to the investigation of disease subgroups, mainly based on clinical features. The aim of this study was to test the hypothesis that clinical FM subgroups are associated with different underlying pathophysiological mechanisms. Sixty-three FM patients were classified in type I or type II, according to the Fibromyalgia Impact Questionnaire (FIQ), and in mild/moderate versus severe FM, according to the severity of three cardinal symptoms considered in the American College of Rheumatology (ACR) 2010 criteria (unrefreshed sleep, cognitive problems and fatigue). To validate the subgroups obtained by these two classifications, we calculated the area under the receiver operating characteristic curves for various clinical variables and for two potential biomarkers of FM: Response to experimental pressure pain (algometry) and the amplitude/intensity slopes of the auditory evoked potentials (AEPs) obtained to stimuli of increasing intensity. The variables that best discriminated type I versus type II were those related to depression, while the indices of clinical or experimental pain (threshold or tolerance) did not significantly differ between them. The variables that best discriminated the mild/moderate versus severe subgroups were those related to the algometry. The AEPs did not allow discrimination among the generated subsets. The FIQ-based classification allows the identification of subgroups that differ in psychological distress, while the index based on the ACR 2010 criteria seems to be useful to characterize the severity of FM mainly based on hyperalgesia. The incorporation of potential biomarkers to generate or validate classification criteria is crucial to advance in the knowledge of FM and in the understanding of pathophysiological pathways.

Experimental human pain models in gastro-esophageal reflux disease and unexplained chest pain

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Drewes, Asbjørn Mohr; Arendt-Nielsen, Lars; Funch-Jensen, Peter; Gregersen, Hans

2006-01-01

Methods related to experimental human pain research aim at activating different nociceptors, evoke pain from different organs and activate specific pathways and mechanisms. The different possibilities for using mechanical, electrical, thermal and chemical methods in visceral pain research are discussed with emphasis of combinations (e.g., the multimodal approach). The methods have been used widely in assessment of pain mechanisms in the esophagus and have contributed to our understanding of the symptoms reported in these patients. Hence abnormal activation and plastic changes of central pain pathways seem to play a major role in the symptoms in some patients with gastro-esophageal reflux disease and in patients with functional chest pain of esophageal origin. These findings may lead to an alternative approach for treatment in patients that does not respond to conventional medical or surgical therapy. PMID:16718803

The local and referred pain from myofascial trigger points in the temporalis muscle contributes to pain profile in chronic tension-type headache.

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Fernández-de-Las-Peñas, César; Ge, Hong-You; Arendt-Nielsen, Lars; Cuadrado, Maria Luz; Pareja, Juan A

2007-01-01

To assess the local and referred pain areas and pain characteristics evoked from temporalis muscle trigger points (TrPs) in chronic tension-type headache (CTTH). Thirty CTTH patients and 30 age and sex-matched controls were studied. A headache diary was kept for 4 weeks to substantiate the diagnosis and record the pain history. Both temporalis muscles were examined for the presence of myofascial TrPs in a blinded fashion. The local and referred pain intensities, referred pain pattern, and pressure pain threshold were recorded. Referred pain was evoked in 87% and 54% on the dominant and nondominant sides in CTTH patients, which was significantly higher (P<0.001) than in controls (10% vs. 17%, respectively). Referred pain spread to the temple ipsilateral to the stimulated muscle in both patients and controls, with additional referral behind the eyes in most patients, but none in controls. CTTH patients reported a higher local [visual analog scale (VAS): 5.6+/-1.2 right side, 5.3+/-1.4 left side] and referred pain (VAS: 4.7+/-2 right side, 3.5+/-2.8 left side) intensity than healthy controls (VAS: 0.8+/-0.7 right side, 0.7+/-0.7 left side for local pain; and 0.3+/-0.2 right side, 0.4+/-0.3 left side for referred pain) in both temporalis muscles (both, P<0.001). The local and referred pain areas were larger in patients than in controls (P<0.001). Twenty-three out of 30 CTTH patients (77%) had active TrPs in the temporalis muscle leading to their usual headache (17 patients on the right side; 12 on the left side, whereas 6 with bilateral active TrPs). CTTH patients with active TrPs in either right or left temporalis muscle showed longer headache duration than those with latent TrPs (P=0.004). CTTH patients showed significantly (P<0.001) lower pressure pain threshold (1.1+/-0.2 right side, 1.2+/-0.3 left side) as compared with controls (2.5+/-0.5 right side, 2.6+/-0.4 left side). In CTTH patients, the evoked local and referred pain from active TrPs in the temporalis

Tonic pain and continuous EEG: prediction of subjective pain perception by alpha-1 power during stimulation and at rest.

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Nir, Rony-Reuven; Sinai, Alon; Moont, Ruth; Harari, Eyal; Yarnitsky, David

2012-03-01

Pain neurophysiology has been chiefly characterized via event-related potentials (ERPs), which are exerted using brief, phase-locked noxious stimuli. Striving for objectively characterizing clinical pain states using more natural, prolonged stimuli, tonic pain has been recently associated with the individual peak frequency of alpha oscillations. This finding encouraged us to explore whether alpha power, reflecting the magnitude of the synchronized activity within this frequency range, will demonstrate a corresponding relationship with subjective perception of tonic pain. Five-minute-long continuous EEG was recorded in 18 healthy volunteers under: (i) resting-state; (ii) innocuous temperature; and (iii) psychophysically-anchored noxious temperature. Numerical pain scores (NPSs) collected during the application of tonic noxious stimuli were tested for correlation with alpha-1 and alpha-2 power. NPSs and alpha power remained stable throughout the recording conditions (Ps⩾0.381). In the noxious condition, alpha-1 power obtained at the bilateral temporal scalp was negatively correlated with NPSs (Ps⩽0.04). Additionally, resting-state alpha-1 power recorded at the bilateral temporal scalp was negatively correlated with NPSs reported during the noxious condition (Ps⩽0.038). Current findings suggest alpha-1 power may serve as a direct, objective and experimentally stable measure of subjective perception of tonic pain. Furthermore, resting-state alpha-1 power might reflect individuals' inherent tonic pain responsiveness. The relevance of alpha-1 power to tonic pain perception may deepen the understanding of the mechanisms underlying the processing of prolonged noxious stimulation. Copyright © 2011 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Neurosteroid 3α-androstanediol efficiently counteracts paclitaxel-induced peripheral neuropathy and painful symptoms.

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Laurence Meyer

Full Text Available Painful peripheral neuropathy belongs to major side-effects limiting cancer chemotherapy. Paclitaxel, widely used to treat several cancers, induces neurological symptoms including burning pain, allodynia, hyperalgesia and numbness. Therefore, identification of drugs that may effectively counteract paclitaxel-induced neuropathic symptoms is crucial. Here, we combined histopathological, neurochemical, behavioral and electrophysiological methods to investigate the natural neurosteroid 3α-androstanediol (3α-DIOL ability to counteract paclitaxel-evoked peripheral nerve tissue damages and neurological symptoms. Prophylactic or corrective 3α-DIOL treatment (4 mg/kg/2 days prevented or suppressed PAC-evoked heat-thermal hyperalgesia, cold-allodynia and mechanical allodynia/hyperalgesia, by reversing to normal, decreased thermal and mechanical pain thresholds of PAC-treated rats. Electrophysiological studies demonstrated that 3α-DIOL restored control values of nerve conduction velocity and action potential peak amplitude significantly altered by PAC-treatment. 3α-DIOL also repaired PAC-induced nerve damages by restoring normal neurofilament-200 level in peripheral axons and control amount of 2',3'-cyclic-nucleotide-3'-phosphodiesterase in myelin sheaths. Decreased density of intraepidermal nerve fibers evoked by PAC-therapy was also counteracted by 3α-DIOL treatment. More importantly, 3α-DIOL beneficial effects were not sedation-dependent but resulted from its neuroprotective ability, nerve tissue repairing capacity and long-term analgesic action. Altogether, our results showing that 3α-DIOL efficiently counteracted PAC-evoked painful symptoms, also offer interesting possibilities to develop neurosteroid-based strategies against chemotherapy-induced peripheral neuropathy. This article shows that the prophylactic or corrective treatment with 3α-androstanediol prevents or suppresses PAC-evoked painful symptoms and peripheral nerve dysfunctions in

Feasibility and performance evaluation of generating and recording visual evoked potentials using ambulatory Bluetooth based system.

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Ellingson, Roger M; Oken, Barry

2010-01-01

Report contains the design overview and key performance measurements demonstrating the feasibility of generating and recording ambulatory visual stimulus evoked potentials using the previously reported custom Complementary and Alternative Medicine physiologic data collection and monitoring system, CAMAS. The methods used to generate visual stimuli on a PDA device and the design of an optical coupling device to convert the display to an electrical waveform which is recorded by the CAMAS base unit are presented. The optical sensor signal, synchronized to the visual stimulus emulates the brain's synchronized EEG signal input to CAMAS normally reviewed for the evoked potential response. Most importantly, the PDA also sends a marker message over the wireless Bluetooth connection to the CAMAS base unit synchronized to the visual stimulus which is the critical averaging reference component to obtain VEP results. Results show the variance in the latency of the wireless marker messaging link is consistent enough to support the generation and recording of visual evoked potentials. The averaged sensor waveforms at multiple CPU speeds are presented and demonstrate suitability of the Bluetooth interface for portable ambulatory visual evoked potential implementation on our CAMAS platform.

Attention Strongly Modulates Reliability of Neural Responses to Naturalistic Narrative Stimuli.

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Ki, Jason J; Kelly, Simon P; Parra, Lucas C

2016-03-09

Attentional engagement is a major determinant of how effectively we gather information through our senses. Alongside the sheer growth in the amount and variety of information content that we are presented with through modern media, there is increased variability in the degree to which we "absorb" that information. Traditional research on attention has illuminated the basic principles of sensory selection to isolated features or locations, but it provides little insight into the neural underpinnings of our attentional engagement with modern naturalistic content. Here, we show in human subjects that the reliability of an individual's neural responses with respect to a larger group provides a highly robust index of the level of attentional engagement with a naturalistic narrative stimulus. Specifically, fast electroencephalographic evoked responses were more strongly correlated across subjects when naturally attending to auditory or audiovisual narratives than when attention was directed inward to a mental arithmetic task during stimulus presentation. This effect was strongest for audiovisual stimuli with a cohesive narrative and greatly reduced for speech stimuli lacking meaning. For compelling audiovisual narratives, the effect is remarkably strong, allowing perfect discrimination between attentional state across individuals. Control experiments rule out possible confounds related to altered eye movement trajectories or order of presentation. We conclude that reliability of evoked activity reproduced across subjects viewing the same movie is highly sensitive to the attentional state of the viewer and listener, which is aided by a cohesive narrative. Copyright © 2016 Ki et al.

Consequences of a human TRPA1 genetic variant on the perception of nociceptive and olfactory stimuli.

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Michael Schütz

Full Text Available BACKGROUND: TRPA1 ion channels are involved in nociception and are also excited by pungent odorous substances. Based on reported associations of TRPA1 genetics with increased sensitivity to thermal pain stimuli, we therefore hypothesized that this association also exists for increased olfactory sensitivity. METHODS: Olfactory function and nociception was compared between carriers (n = 38 and non-carriers (n = 43 of TRPA1 variant rs11988795 G>A, a variant known to enhance cold pain perception. Olfactory function was quantified by assessing the odor threshold, odor discrimination and odor identification, and by applying 200-ms pulses of H2S intranasal. Nociception was assessed by measuring pain thresholds to experimental nociceptive stimuli (blunt pressure, electrical stimuli, cold and heat stimuli, and 200-ms intranasal pulses of CO2. RESULTS: Among the 11 subjects with moderate hyposmia, carriers of the minor A allele (n = 2 were underrepresented (34 carriers among the 70 normosmic subjects; p = 0.049. Moreover, carriers of the A allele discriminated odors significantly better than non-carriers (13.1±1.5 versus 12.3±1.6 correct discriminations and indicated a higher intensity of the H2S stimuli (29.2±13.2 versus 21±12.8 mm VAS, p = 0.006, which, however, could not be excluded to have involved a trigeminal component during stimulation. Finally, the increased sensitivity to thermal pain could be reproduced. CONCLUSIONS: The findings are in line with a previous association of a human TRPA1 variant with nociceptive parameters and extend the association to the perception of odorants. However, this addresses mainly those stimulants that involve a trigeminal component whereas a pure olfactory effect may remain disputable. Nevertheless, findings suggest that future TRPA1 modulating drugs may modify the perception of odorants.

Personalized Pain Medicine: The Clinical Value of Psychophysical Assessment of Pain Modulation Profile

Directory of Open Access Journals (Sweden)

Yelena Granovsky

2013-10-01

Full Text Available Experimental pain stimuli can be used to simulate patients’ pain experience. We review recent developments in psychophysical pain testing, focusing on the application of the dynamic tests—conditioned pain modulation (CPM and temporal summation (TS. Typically, patients with clinical pain of various types express either less efficient CPM or enhanced TS, or both. These tests can be used in prediction of incidence of acquiring pain and of its intensity, as well as in assisting the correct choice of analgesic agents for individual patients. This can help to shorten the commonly occurring long and frustrating process of adjusting analgesic agents to the individual patients. We propose that evaluating pain modulation can serve as a step forward in individualizing pain medicine.

Efficacy of kilohertz-frequency and conventional spinal cord stimulation in rat models of different pain conditions.

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Song, Zhiyang; Viisanen, Hanna; Meyerson, Björn A; Pertovaara, Antti; Linderoth, Bengt

2014-04-01

The aim was to compare the effects of high-frequency spinal cord stimulation (HF-SCS) at subparesthetic intensity with conventional SCS in rat models of different types of pain. In addition, microrecordings of afferent activity in the dorsal columns during both types of SCS were performed to elucidate their mode of action. Miniature SCS electrodes were implanted in all rats. One group was submitted to the spared nerve injury procedure (SNI) and another to inflammatory pain after carrageenan injection into a hind paw. All animals were tested for hypersensitivity to normally innocuous tactile and thermal stimuli. One group of normal healthy rats was submitted to acute nociceptive (pinch, heat) pain. Microrecording of afferent activity in the gracile nucleus (GN) was performed in a group of nerve-lesioned rats responding to conventional SCS. HF-SCS at 500, 1,000, or 10,000 Hz at subparesthetic amplitudes produced similar reductions in hypersensitivity due to nerve lesion as did conventional SCS at 50 Hz. HF-SCS showed no effect on thermal pain. A trial to rescue non-responders to conventional SCS using HF-SCS was not successful. There were no effects either of conventional or of HF-SCS on acute or inflammatory pain. Conventional SCS produced massive activation in the GN but no activation during HF-SCS, though normal peripherally evoked afferent activity remained. Conventional SCS proved equally effective to HF-SCS in various pain models. As no activity is conveyed rostrally in subparesthetic HF-SCS, we hypothesize that its mechanisms of action are primarily segmental. © 2014 International Neuromodulation Society.

Frequency-dependent changes in sensorimotor and pain affective systems induced by empathy for pain

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Motoyama Y

2017-05-01

Full Text Available Yoshimasa Motoyama,1,2,* Katsuya Ogata,1,* Sumio Hoka,2 Shozo Tobimatsu1 1Department of Clinical Neurophysiology, Neurological Institute, 2Department of Anesthesiology and Critical Care Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan *These authors contributed equally to this work Background: Empathy for pain helps us to understand the pain of others indirectly. To better comprehend the processing of empathic pain, we report the frequency-dependent modulation of cortical oscillations induced by watching movies depicting pain using high-density electroencephalography (EEG, magnetoencephalography (MEG, and motor evoked potentials (MEP. Methods: Event-related desynchronization of EEG and MEG was assessed while participants viewed videos of painful (needle or neutral (cotton swab situations. The amplitudes of MEPs were also compared between the needle and cotton swab conditions.Results: The degree of suppression in α/β band power was significantly increased, whereas that of γ band power was significantly decreased, in the needle condition compared with the cotton swab condition. EEG revealed that significant differences in α/β band were distributed in the right frontocentral and left parietooccipital regions, whereas significant γ band differences were distributed predominantly over the right hemisphere, which were confirmed by source estimation using MEG. There was a significant positive correlation between the difference in γ power of the two conditions and the visual analog scale subjective rating of aversion, but not in the α/β band. The amplitude of MEPs decreased in the needle condition, which confirmed the inhibition of the primary motor cortex.Conclusion: MEP suppression supports that modulation of cortical oscillations by viewing movies depicting pain involves sensorimotor processing. Our results suggest that α/β oscillations underlie the sensory qualities of others’ pain, whereas the γ band

Gender differences in pain: do emotions play a role?

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Rhudy, Jamie L; Williams, Amy E

2005-12-01

Research suggests that the influence of gender on the processing and experience of pain is a result of several mechanisms. One mediating variable is emotion, which may modulate pain through an interaction of valence (pleasant-unpleasant) and arousal (calm-excited). This review examines whether gender differences in the experience and processing of emotion contribute to differences in the modulation and perception of pain. An English-language search of MEDLINE and PsycINFO was conducted from 1887 to May 2005. Additional literature was obtained from reference lists of articles retained in the initial search. Emotion appears to influence pain through a valence-by-arousal interaction. Specifically, negatively valenced emotions with low to moderate arousal (eg, anxiety) enhance pain, whereas negatively valenced emotions with high arousal (eg, fear) reduce pain. In contrast, positively valenced emotions always reduce pain, as long as minimal arousal is achieved. Some evidence suggests that women are more sensitive than men to threat-related stimuli and thus experience more negative affect than men. This would generally lead to enhanced pain perception in women. It is also possible that women are more likely than men to experience negative affect with high arousal (intense fear) and thus pain inhibition. However, the relatively lower base rate of intense negative emotions is not likely to contribute much to gender differences in pain. Evidence also suggests that men may be more sensitive to positive events, particularly sexual/erotic stimuli, which may lead to more positive emotion-induced pain reduction in men, relative to women. This review suggests that gender differences in the experience of pain may arise from differences in the experience and processing of emotion that, in turn, differentially alter pain processing. Specifically, the system associated with negative affect may be more attuned to threatening stimuli in women, and the system associated with positive

A Randomized, Placebo-Controlled, Crossover Trial of Cannabis Cigarettes in Neuropathic Pain

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Wilsey, Barth; Marcotte, Thomas; Tsodikov, Alexander; Millman, Jeanna; Bentley, Heather; Gouaux, Ben; Fishman, Scott

2016-01-01

The Food and Drug Administration (FDA), Substance Abuse and Mental Health Services Administration (SAMHSA), and the National Institute for Drug Abuse (NIDA) report that no sound scientific studies support the medicinal use of cannabis. Despite this lack of scientific validation, many patients routinely use “medical marijuana,” and in many cases this use is for pain related to nerve injury. We conducted a double-blinded, placebo-controlled, crossover study evaluating the analgesic efficacy of smoking cannabis for neuropathic pain. Thirty-eight patients with central and peripheral neuropathic pain underwent a standardized procedure for smoking either high-dose (7%), low-dose (3.5%), or placebo cannabis. In addition to the primary outcome of pain intensity, secondary outcome measures included evoked pain using heat-pain threshold, sensitivity to light touch, psychoactive side effects, and neuropsychological performance. A mixed linear model demonstrated an analgesic response to smoking cannabis. No effect on evoked pain was seen. Psychoactive effects were minimal and well-tolerated, with some acute cognitive effects, particularly with memory, at higher doses. PMID:18403272

Central Pain Processing in Early-Stage Parkinson's Disease: A Laser Pain fMRI Study.

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Christine Petschow

Full Text Available Pain is a common non-motor symptom in Parkinson's disease. As dopaminergic dysfunction is suggested to affect intrinsic nociceptive processing, this study was designed to characterize laser-induced pain processing in early-stage Parkinson's disease patients in the dopaminergic OFF state, using a multimodal experimental approach at behavioral, autonomic, imaging levels.13 right-handed early-stage Parkinson's disease patients without cognitive or sensory impairment were investigated OFF medication, along with 13 age-matched healthy control subjects. Measurements included warmth perception thresholds, heat pain thresholds, and central pain processing with event-related functional magnetic resonance imaging (erfMRI during laser-induced pain stimulation at lower (E = 440 mJ and higher (E = 640 mJ target energies. Additionally, electrodermal activity was characterized during delivery of 60 randomized pain stimuli ranging from 440 mJ to 640 mJ, along with evaluation of subjective pain ratings on a visual analogue scale.No significant differences in warmth perception thresholds, heat pain thresholds, electrodermal activity and subjective pain ratings were found between Parkinson's disease patients and controls, and erfMRI revealed a generally comparable activation pattern induced by laser-pain stimuli in brain areas belonging to the central pain matrix. However, relatively reduced deactivation was found in Parkinson's disease patients in posterior regions of the default mode network, notably the precuneus and the posterior cingulate cortex.Our data during pain processing extend previous findings suggesting default mode network dysfunction in Parkinson's disease. On the other hand, they argue against a genuine pain-specific processing abnormality in early-stage Parkinson's disease. Future studies are now required using similar multimodal experimental designs to examine pain processing in more advanced stages of Parkinson's disease.

Fish welfare: Fish capacity to experience pain

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Vučinić Marijana

2009-01-01

Full Text Available Teleost fish possess similar nociceptive processing systems to those found in terrestrial vertebrates. It means that they react to potential painful stimuli in a similar manner as mammals and birds. However, the welfare of fish has been the focus of less research than that of higher vertebrates. Humans may affect the welfare of fish through fisheries, aquaculture and a number of other activities. There is scientific evidence to support the assumption that fish have the capacity to experience pain because they possess functional nociceptors, endogenous opioids and opioid receptors, brain structures involved in pain processing and pathways leading from nociceptors to higher brain structures. Also, it is well documented that some anaesthetics and analgesics may reduce nociceptive responses in fish. Behavioural indicators in fish such as lip-rubbing and rocking behaviours are the best proof that fish react to potential painful stimuli. This paper is an overview of some scientific evidence on fish capacity to experience pain.

Neonatal pain management

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Tarun Bhalla

2014-01-01

Full Text Available The past 2-3 decades have seen dramatic changes in the approach to pain management in the neonate. These practices started with refuting previously held misconceptions regarding nociception in preterm infants. Although neonates were initially thought to have limited response to painful stimuli, it was demonstrated that the developmental immaturity of the central nervous system makes the neonate more likely to feel pain. It was further demonstrated that untreated pain can have long-lasting physiologic and neurodevelopmental consequences. These concerns have resulted in a significant emphasis on improving and optimizing the techniques of analgesia for neonates and infants. The following article will review techniques for pain assessment, prevention, and treatment in this population with a specific focus on acute pain related to medical and surgical conditions.

A translational study on looming-evoked defensive response and the underlying subcortical pathway in autism.

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Hu, Yu; Chen, Zhuoming; Huang, Lu; Xi, Yue; Li, Bingxiao; Wang, Hong; Yan, Jiajian; Lee, Tatia M C; Tao, Qian; So, Kwok-Fai; Ren, Chaoran

2017-11-07

Rapidly approaching objects indicating threats can induce defensive response through activating a subcortical pathway comprising superior colliculus (SC), lateral posterior nucleus (LP), and basolateral amygdala (BLA). Abnormal defensive response has been reported in autism, and impaired synaptic connections could be the underlying mechanism. Whether the SC-LP-BLA pathway processes looming stimuli abnormally in autism is not clear. Here, we found that looming-evoked defensive response is impaired in a subgroup of the valproic acid (VPA) mouse model of autism. By combining the conventional neurotracer and transneuronal rabies virus tracing techniques, we demonstrated that synaptic connections in the SC-LP-BLA pathway were abnormal in VPA mice whose looming-evoked defensive responses were absent. Importantly, we further translated the finding to children with autism and observed that they did not present looming-evoked defensive response. Furthermore, the findings of the DTI with the probabilistic tractography showed that the structural connections of SC-pulvinar-amygdala in autism children were weak. The pulvinar is parallel to the LP in a mouse. Because looming-evoked defensive response is innate in humans and emerges much earlier than do social and language functions, the absence of defensive response could be an earlier sign of autism in children.

knowledge, attitude and use of pain relief in labour among women

African Journals Online (AJOL)

2014-07-01

Jul 1, 2014 ... Objective: To find out the knowledge, attitude and practice of pain relief methods during labour among ... all of which could adversely affect uterine blood flow. Pain relief in ... knowledge was low among women who did not use any form of ... Niven et al found that memories of labour pains can evoke intense ...

3D graphics, virtual reality, and motion-onset visual evoked potentials in neurogaming.

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Beveridge, R; Wilson, S; Coyle, D

2016-01-01

A brain-computer interface (BCI) offers movement-free control of a computer application and is achieved by reading and translating the cortical activity of the brain into semantic control signals. Motion-onset visual evoked potentials (mVEP) are neural potentials employed in BCIs and occur when motion-related stimuli are attended visually. mVEP dynamics are correlated with the position and timing of the moving stimuli. To investigate the feasibility of utilizing the mVEP paradigm with video games of various graphical complexities including those of commercial quality, we conducted three studies over four separate sessions comparing the performance of classifying five mVEP responses with variations in graphical complexity and style, in-game distractions, and display parameters surrounding mVEP stimuli. To investigate the feasibility of utilizing contemporary presentation modalities in neurogaming, one of the studies compared mVEP classification performance when stimuli were presented using the oculus rift virtual reality headset. Results from 31 independent subjects were analyzed offline. The results show classification performances ranging up to 90% with variations in conditions in graphical complexity having limited effect on mVEP performance; thus, demonstrating the feasibility of using the mVEP paradigm within BCI-based neurogaming. © 2016 Elsevier B.V. All rights reserved.

Different activation of opercular and posterior cingulate cortex (PCC) in patients with complex regional pain syndrome (CRPS I) compared with healthy controls during perception of electrically induced pain: a functional MRI study.

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Freund, Wolfgang; Wunderlich, Arthur P; Stuber, Gregor; Mayer, Florian; Steffen, Peter; Mentzel, Martin; Weber, Frank; Schmitz, Bernd

2010-05-01

Although the etiology of complex regional pain syndrome type 1 (CRPS 1) is still debated, many arguments favor central maladaptive changes in pain processing as an important causative factor. To look for the suspected alterations, 10 patients with CRPS affecting the left hand were explored with functional magnetic resonance imaging during graded electrical painful stimulation of both hands subsequently and compared with healthy participants. Activation of the anterior insula, posterior cingulate cortex (PCC), and caudate nucleus was seen in patients during painful stimulation. Compared with controls, CRPS patients had stronger activation of the PCC during painful stimulation of the symptomatic hand. The comparison of insular/opercular activation between controls and patients with CRPS I during painful stimulation showed stronger (posterior) opercular activation in controls than in patients. Stronger PCC activation during painful stimulation may be interpreted as a correlate of motor inhibition during painful stimuli different from controls. Also, the decreased opercular activation in CRPS patients shows less sensory-discriminative processing of painful stimuli.These results show that changed cerebral pain processing in CRPS patients is less sensory-discriminative but more motor inhibition during painful stimuli. These changes are not limited to the diseased side but show generalized alterations of cerebral pain processing in chronic pain patients.

Inhibitory effects of aspirin-triggered resolvin D1 on spinal nociceptive processing in rat pain models.

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Meesawatsom, Pongsatorn; Burston, James; Hathway, Gareth; Bennett, Andrew; Chapman, Victoria

2016-09-02

Harnessing the actions of the resolvin pathways has the potential for the treatment of a wide range of conditions associated with overt inflammatory signalling. Aspirin-triggered resolvin D1 (AT-RvD1) has robust analgesic effects in behavioural models of pain; however, the potential underlying spinal neurophysiological mechanisms contributing to these inhibitory effects in vivo are yet to be determined. This study investigated the acute effects of spinal AT-RvD1 on evoked responses of spinal neurones in vivo in a model of acute inflammatory pain and chronic osteoarthritic (OA) pain and the relevance of alterations in spinal gene expression to these neurophysiological effects. Pain behaviour was assessed in rats with established carrageenan-induced inflammatory or monosodium iodoacetate (MIA)-induced OA pain, and changes in spinal gene expression of resolvin receptors and relevant enzymatic pathways were examined. At timepoints of established pain behaviour, responses of deep dorsal horn wide dynamic range (WDR) neurones to transcutaneous electrical stimulation of the hind paw were recorded pre- and post direct spinal administration of AT-RvD1 (15 and 150 ng/50 μl). AT-RvD1 (15 ng/50 μl) significantly inhibited WDR neurone responses to electrical stimuli at C- (29 % inhibition) and Aδ-fibre (27 % inhibition) intensities. Both wind-up (53 %) and post-discharge (46 %) responses of WDR neurones in carrageenan-treated animals were significantly inhibited by AT-RvD1, compared to pre-drug response (p < 0.05). These effects were abolished by spinal pre-administration of a formyl peptide receptor 2 (FPR2/ALX) antagonist, butoxy carbonyl-Phe-Leu-Phe-Leu-Phe (BOC-2) (50 μg/50 μl). AT-RvD1 did not alter evoked WDR neurone responses in non-inflamed or MIA-treated rats. Electrophysiological effects in carrageenan-inflamed rats were accompanied by a significant increase in messenger RNA (mRNA) for chemerin (ChemR23) receptor and 5-lipoxygenase

Thermal and pressure pain sensitivity in patients with unilateral shoulder pain: comparison of involved and uninvolved sides.

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Coronado, Rogelio A; Kindler, Lindsay L; Valencia, Carolina; George, Steven Z

2011-03-01

Cross-sectional. In the examination of patients with unilateral shoulder pain, pain provocation testing to compare the involved and uninvolved sides has been considered useful. However, side-to-side comparisons of experimental pain sensitivity in patients with unilateral shoulder pain are not widely reported in the literature. To compare experimental pain sensitivity between the involved and uninvolved sides in patients with unilateral shoulder pain. In consecutive patients seeking operative treatment for shoulder pain, sensitivity measures of bilateral pressure pain threshold at the shoulder and forearm, and thermal pain threshold, tolerance, and temporal summation at the forearm, were examined. Pressure sensitivity was tested with a Fischer pressure algometer, and thermal sensitivity with a computer-controlled Medoc neurosensory analyzer. The involved and uninvolved sides were compared with an analysis of variance. Influence of sex and location of testing were considered as covariates in the analysis. Fifty-nine consecutively recruited participants completed experimental pain sensitivity testing. Participants reported significantly lower pressure pain thresholds in the involved side compared to the uninvolved side (F1,56 = 4.96, P = .030). In addition, female compared to male participants demonstrated lower pressure pain thresholds in the bilateral shoulder regions (F1,56 = 10.84, P = .002). There was no difference in thermal pain sensitivity between sides. Average clinical pain intensity was negatively correlated with pressure pain threshold at the involved local site (r = -0.284, P = .029), indicating an influence of clinical pain intensity on local pressure pain. The results of this study provide evidence for higher experimental pressure pain sensitivity in the involved side of patients with unilateral shoulder pain and no difference between sides for thermal pain sensitivity. Females demonstrated higher pain sensitivity than males to pressure stimuli at the

Sensory and sympathetic correlates of heat pain sensitization and habituation in men and women.

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Breimhorst, M; Hondrich, M; Rebhorn, C; May, A; Birklein, F

2012-10-01

Habituation and sensitization are important behavioural responses to repeated exposure to painful stimuli, but little is known about the factors determining sensory, affective and sympathetic habituation to repeated pain stimulation in men and women. Thirty volunteers (15 women) underwent a standardized heat pain paradigm spread over 8 consecutive days. At the beginning of the experiment, personality dimensions, coping strategies and pain catastrophizing thoughts were determined. Receiving a series of 10 blocks of six painful heat stimuli a day, participants rated pain intensity and unpleasantness. Skin conductance was recorded throughout the sessions. The results show similar habituation of both the sensory and affective dimensions of pain in men and women, although skin conductance did not undergo a significant decrease across the eight days. When focusing on single daily sessions, women showed pain sensitization but sympathetic habituation, while men showed pain sensitization but stable sympathetic activation. Our findings therefore indicate that the process of long-term habituation to painful heat stimuli is a common feature in both genders, whereas men and women might differently recruit their sympathetic nervous system for short-term pain processing. This study could potentially help to better evaluate gender-specific mechanisms in pain perception. © 2012 European Federation of International Association for the Study of Pain Chapters.

Intermediate Latency-Evoked Potentials of Multimodal Cortical Vestibular Areas: Galvanic Stimulation

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Stefan Kammermeier

2017-11-01

Full Text Available IntroductionHuman multimodal vestibular cortical regions are bilaterally anterior insulae and posterior opercula, where characteristic vestibular-related cortical potentials were previously reported under acoustic otolith stimulation. Galvanic vestibular stimulation likely influences semicircular canals preferentially. Galvanic stimulation was compared to previously established data under acoustic stimulation.Methods14 healthy right-handed subjects, who were also included in the previous acoustic potential study, showed normal acoustic and galvanic vestibular-evoked myogenic potentials. They received 2,000 galvanic binaural bipolar stimuli for each side during EEG recording.ResultsVestibular cortical potentials were found in all 14 subjects and in the pooled data of all subjects (“grand average” bilaterally. Anterior insula and posterior operculum were activated exclusively under galvanic stimulation at 25, 35, 50, and 80 ms; frontal regions at 30 and 45 ms. Potentials at 70 ms in frontal regions and at 110 ms at all of the involved regions could also be recorded; these events were also found using acoustic stimulation in our previous study.ConclusionGalvanic semicircular canal stimulation evokes specific potentials in addition to those also found with acoustic otolith stimulation in identically located regions of the vestibular cortex. Vestibular cortical regions activate differently by galvanic and acoustic input at the peripheral sensory level.SignificanceDifferential effects in vestibular cortical-evoked potentials may see clinical use in specific vertigo disorders.

Discrepancy between stimulus response and tolerance of pain in Alzheimer disease

DEFF Research Database (Denmark)

Jensen-Dahm, Christina; Werner, Mads U; Jensen, Troels Staehelin

2015-01-01

BACKGROUND: Affective-motivational and sensory-discriminative aspects of pain were investigated in patients with mild to moderate Alzheimer disease (AD) and healthy elderly controls using the cold pressor test tolerance and repetitive stimuli of warmth and heat stimuli, evaluating the stimulus....... The results further suggest that the attenuated cold pressor pain tolerance may relate to impairment of coping abilities. Paradoxically, we found an attenuated stimulus-response function, compared to controls, suggesting that AD dementia interferes with pain ratings over time, most likely due to memory...

A Diffusion Model Analysis of Decision Biases Affecting Delayed Recognition of Emotional Stimuli

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Bowen, Holly J.; Spaniol, Julia; Patel, Ronak; Voss, Andreas

2016-01-01

Previous empirical work suggests that emotion can influence accuracy and cognitive biases underlying recognition memory, depending on the experimental conditions. The current study examines the effects of arousal and valence on delayed recognition memory using the diffusion model, which allows the separation of two decision biases thought to underlie memory: response bias and memory bias. Memory bias has not been given much attention in the literature but can provide insight into the retrieval dynamics of emotion modulated memory. Participants viewed emotional pictorial stimuli; half were given a recognition test 1-day later and the other half 7-days later. Analyses revealed that emotional valence generally evokes liberal responding, whereas high arousal evokes liberal responding only at a short retention interval. The memory bias analyses indicated that participants experienced greater familiarity with high-arousal compared to low-arousal items and this pattern became more pronounced as study-test lag increased; positive items evoke greater familiarity compared to negative and this pattern remained stable across retention interval. The findings provide insight into the separate contributions of valence and arousal to the cognitive mechanisms underlying delayed emotion modulated memory. PMID:26784108

Different SEP recovery cycle in adolescent migraineurs with exploding or imploding pain.

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Iacovelli, Elisa; Tarantino, Samuela; Capuano, Alessandro; De Luca, Massimiliano; De Ranieri, Cristiana; Vigevano, Federico; Arendt-Nielsen, Lars; Valeriani, Massimiliano

2013-01-01

Our aim was to investigate whether migraine adolescents with pain directed inside (imploding pain--IP) and outside (exploding pain--EP) the head may have different levels of cortical excitability underlying their migraineous syndrome. Ten migraine children referring prevalent EP (mean age 14.5 ± 1.4 years, 3 girls, 7 boys), 10 patients with IP (mean age 14.1 ± 2.2 years, 4 girls, 6 boys), and 13 control subjects (mean age 13 ± 1.8 years, 6 males, 7 females) participated to the study. The recovery cycle of the somatosensory evoked potentials to electrical median nerve stimuli at interstimulus intervals of 5, 20, and 40 ms was measured. Anger expression, anxiety, and somatic concerns were investigated in migraine patients. Overall, SEP recovery cycle was shorter in migraineurs than in healthy controls. The recovery cycle of the frontal N30 SEP component was significantly shorter in IP than in EP patients. While among the EP patients those with faster N30 recovery cycle had higher Trait-Anger score, the opposite was found among the IP patients. Our results suggest that the inhibitory mechanisms within the somatosensory cortex are more impaired in IP than in EP migraine adolescents. The pathophysiological difference between IP and EP migraineurs was strengthened also by the opposite correlations between the brain excitability and the anger expression. Copyright © 2013 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.

The Effect of Perceived Injustice on Appraisals of Physical Activity: An Examination of the Mediating Role of Attention Bias to Pain in a Chronic Low Back Pain Sample.

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Trost, Zina; Van Ryckeghem, Dimitri; Scott, Whitney; Guck, Adam; Vervoort, Tine

2016-11-01

The current study examined the relationship between perceived injustice and attentional bias (AB) toward pain among individuals with chronic low back pain asked to perform and appraise the pain and difficulty of a standardized set of common physical activities. A pictorial dot-probe task assessed AB toward pain stimuli (ie, pain faces cueing pain), after which participants performed the physical tasks. Participants also rated face stimuli in terms of pain, sadness, and anger expression. As hypothesized, perceived injustice was positively associated with AB toward pain stimuli; additionally, perceived injustice and AB were positively associated with appraisals of pain and difficulty. Counter to expectations, AB did not mediate the relationship between perceived injustice and task appraisals, suggesting that AB is insufficient to explain this relationship. Exploratory analyses indicated that participants with higher levels of perceived injustice rated stimulus faces as sadder and angrier; no such differences emerged for pain ratings. To our knowledge, this is the first study to examine the association between perceived injustice and AB toward pain, as well as perceived injustice and in vivo appraisals of common physical activity. Results extend existing literature and suggest that attentional and potential interpretive bias should be considered in future research. This article identifies significant associations between perceived injustice, biased attention to pain, and appraisals of common physical activities among individuals with chronic low back pain. These findings suggest targets for intervention as well as directions for future research regarding individuals with high perceptions of injustice related to pain. Copyright © 2016 American Pain Society. Published by Elsevier Inc. All rights reserved.

Neural Conflict–Control Mechanisms Improve Memory for Target Stimuli

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Krebs, Ruth M.; Boehler, Carsten N.; De Belder, Maya; Egner, Tobias

2015-01-01

According to conflict-monitoring models, conflict serves as an internal signal for reinforcing top-down attention to task-relevant information. While evidence based on measures of ongoing task performance supports this idea, implications for long-term consequences, that is, memory, have not been tested yet. Here, we evaluated the prediction that conflict-triggered attentional enhancement of target-stimulus processing should be associated with superior subsequent memory for those stimuli. By combining functional magnetic resonance imaging (fMRI) with a novel variant of a face-word Stroop task that employed trial-unique face stimuli as targets, we were able to assess subsequent (incidental) memory for target faces as a function of whether a given face had previously been accompanied by congruent, neutral, or incongruent (conflicting) distracters. In line with our predictions, incongruent distracters not only induced behavioral conflict, but also gave rise to enhanced memory for target faces. Moreover, conflict-triggered neural activity in prefrontal and parietal regions was predictive of subsequent retrieval success, and displayed conflict-enhanced functional coupling with medial-temporal lobe regions. These data provide support for the proposal that conflict evokes enhanced top-down attention to task-relevant stimuli, thereby promoting their encoding into long-term memory. Our findings thus delineate the neural mechanisms of a novel link between cognitive control and memory. PMID:24108799

Perceptual learning of acoustic noise generates memory-evoked potentials.

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Andrillon, Thomas; Kouider, Sid; Agus, Trevor; Pressnitzer, Daniel

2015-11-02

Experience continuously imprints on the brain at all stages of life. The traces it leaves behind can produce perceptual learning [1], which drives adaptive behavior to previously encountered stimuli. Recently, it has been shown that even random noise, a type of sound devoid of acoustic structure, can trigger fast and robust perceptual learning after repeated exposure [2]. Here, by combining psychophysics, electroencephalography (EEG), and modeling, we show that the perceptual learning of noise is associated with evoked potentials, without any salient physical discontinuity or obvious acoustic landmark in the sound. Rather, the potentials appeared whenever a memory trace was observed behaviorally. Such memory-evoked potentials were characterized by early latencies and auditory topographies, consistent with a sensory origin. Furthermore, they were generated even on conditions of diverted attention. The EEG waveforms could be modeled as standard evoked responses to auditory events (N1-P2) [3], triggered by idiosyncratic perceptual features acquired through learning. Thus, we argue that the learning of noise is accompanied by the rapid formation of sharp neural selectivity to arbitrary and complex acoustic patterns, within sensory regions. Such a mechanism bridges the gap between the short-term and longer-term plasticity observed in the learning of noise [2, 4-6]. It could also be key to the processing of natural sounds within auditory cortices [7], suggesting that the neural code for sound source identification will be shaped by experience as well as by acoustics. Copyright © 2015 Elsevier Ltd. All rights reserved.

Functional resonance magnetic imaging (fMRI) in adolescents with idiopathic musculoskeletal pain: a paradigm of experimental pain.

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Molina, Juliana; Amaro, Edson; da Rocha, Liana Guerra Sanches; Jorge, Liliana; Santos, Flavia Heloisa; Len, Claudio A

2017-11-14

Studies on functional magnetic resonance imaging (fMRI) have shown that adults with musculoskeletal pain syndromes tolerate smaller amount of pressure (pain) as well as differences in brain activation patterns in areas related to pain.The objective of this study was to evaluate, through fMRI, the brain activation in adolescents with idiopathic musculoskeletal pain (IMP) while performing an experimental paradigm of pain. The study included 10 consecutive adolescents with idiopathic musculoskeletal pain (average age 16.3±1.0) and 10 healthy adolescents age-matched. fMRI exams were performed in a 3 T scanner (Magnetom Trio, Siemens) using an event-related design paradigm. Pressure stimuli were performed in the nondominant hand thumb, divided into two stages, fixed pain and variable pain. The two local Research Ethics Committees (Ethics Committee from Universidade Federal de São Paulo- Brazil, process number 0688/11, on July 1st, 2011 and Ethics Committee from Hospital Israelita Albert Einsten - Brazil, process number 1673, on October 19th, 2011) approved the study. The idiopathic musculoskeletal pain (IMP) group showed a reduced threshold for pain (3.7 kg/cm 2 versus 4.45 kg/cm 2 , p = 0.005). Control group presented increased bain activation when compared to IMP group in the following areas: thalamus (p = 0.00001), precentral gyrus (p = 0.0004) and middle frontal gyrus (p = 0.03). In intragroup analysis, IMP group showed greater brain activation during the unpredictable stimuli of the variable pain stage, especially in the lingual gyrus (p = 0.0001), frontal lobe (p = 0.0001), temporal gyrus (p = 0.0001) and precentral gyrus (p = 0.03), when compared to predictable stimulus of fixed pain. The same intragroup analysis with the control group showed greater activation during the unpredictable stimuli in regions of the precentral gyrus (p = 0.0001), subcallosal area (p = 0.0001), right and left occipital fusiform gyrus (p�

The role of fear of movement and injury in selective attentional processing in patients with chronic low back pain: a dot-probe evaluation.

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Roelofs, Jeffrey; Peters, Madelon L; Fassaert, Thijs; Vlaeyen, Johan W S

2005-05-01

The present study sought to investigate to what extent patients with chronic low back pain and pain-free control subjects selectively attend to pain-related stimuli as measured with 2 dot-probe tasks with word stimuli and pictorial stimuli. Selective attentional processing was measured by means of 3 indices: the bias index, a congruency effect, and an incongruency effect. Pain-related fear as a trait measure (Tampa Scale for Kinesiophobia [TSK]) was expected to be positively associated with all indices of selective attentional processing of pain stimuli. Results were analyzed with repeated-measures analysis of variance. An incongruency effect was found for patients and to a significantly less degree for pain-free control subjects on the dot-probe task with pictorial stimuli, indicating that pain patients have difficulty disengaging from threat pictures. Pain-related fear as a trait measure (TSK) was not associated with selective attentional processing of word and pictorial stimuli in either pain patients or control subjects. Results from the present study are discussed, and directions for future research are provided. Demonstrating difficulty to disengage from threat might be clinically relevant because patients might pay less attention to fear-disconfirming information and remain engaged in avoidance, which might eventually lead to prolonged anxiety states.

A psychophysical study of endogenous analgesia: the role of the conditioning pain in the induction and magnitude of conditioned pain modulation.

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Nir, Rony-Reuven; Granovsky, Yelena; Yarnitsky, David; Sprecher, Elliot; Granot, Michal

2011-05-01

Endogenous analgesia (EA) can be examined experimentally using a conditioned pain modulation (CPM) paradigm. While noxious conditioning stimulation intensities (CSIs) are mainly used, it has not been fully investigated in the same experimental design whether the experienced conditioning pain level affects CPM responses. The principal goal of the present study was to characterize CPM induction and magnitudes evoked by various conditioning pain levels. Furthermore, we explored associations between conditioning pain reports and CPM responses across various CSIs. Thirty healthy, young, right-handed males were tested with a parallel CPM paradigm. Three different CSIs (hand water-immersion) induced mild, moderate and intense pain levels, rated 12.41 ± 7.85, 31.57 ± 9.56 and 58.1 ± 11.43, respectively (0-100 numerical pain scale) (P < 0.0001). Contact-heat 'test-stimulus' levels were compared before and during conditioning. Within the group, (i) CPM was induced only by the moderate and intense CSIs (Ps ≤ 0.001); (ii) no difference was demonstrated between the magnitudes of these CPM responses. Regression analysis revealed that CPM induction was independent of the perceived conditioning pain level, but associated with the absolute CSI (P < 0.0001). Conditioning pain levels were correlated across all CSIs, as were CPM magnitudes (Ps ≤ 0.01). We conclude that among males, (i) once a CPM response is evoked by a required conditioning pain experience, its magnitude is not further affected by increasing conditioning pain and (ii) CPM magnitudes are inter-correlated, but unrelated to conditioning pain reports. These observations may suggest that CPM responses represent an intrinsic element of an individual's EA processes, which are not significantly affected by the experienced conditioning pain. Copyright © 2010 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved.

Beyond arousal and valence: the importance of the biological versus social relevance of emotional stimuli.

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Sakaki, Michiko; Niki, Kazuhisa; Mather, Mara

2012-03-01

The present study addressed the hypothesis that emotional stimuli relevant to survival or reproduction (biologically emotional stimuli) automatically affect cognitive processing (e.g., attention, memory), while those relevant to social life (socially emotional stimuli) require elaborative processing to modulate attention and memory. Results of our behavioral studies showed that (1) biologically emotional images hold attention more strongly than do socially emotional images, (2) memory for biologically emotional images was enhanced even with limited cognitive resources, but (3) memory for socially emotional images was enhanced only when people had sufficient cognitive resources at encoding. Neither images' subjective arousal nor their valence modulated these patterns. A subsequent functional magnetic resonance imaging study revealed that biologically emotional images induced stronger activity in the visual cortex and greater functional connectivity between the amygdala and visual cortex than did socially emotional images. These results suggest that the interconnection between the amygdala and visual cortex supports enhanced attention allocation to biological stimuli. In contrast, socially emotional images evoked greater activity in the medial prefrontal cortex (MPFC) and yielded stronger functional connectivity between the amygdala and MPFC than did biological images. Thus, it appears that emotional processing of social stimuli involves elaborative processing requiring frontal lobe activity.

Converging prefrontal pathways support associative and perceptual features of conditioned stimuli.

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Howard, James D; Kahnt, Thorsten; Gottfried, Jay A

2016-05-04

Perceptually similar stimuli often predict vastly different outcomes, requiring the brain to maintain specific associations in the face of potential ambiguity. This could be achieved either through local changes in stimulus representations, or through modulation of functional connections between stimulus-coding and outcome-coding regions. Here we test these competing hypotheses using classical conditioning of perceptually similar odours in the context of human fMRI. Pattern-based analyses of odour-evoked fMRI activity reveal that odour category, identity and value are coded in piriform (PC), orbitofrontal (OFC) and ventromedial prefrontal (vmPFC) cortices, respectively. However, we observe no learning-related reorganization of category or identity representations. Instead, changes in connectivity between vmPFC and OFC are correlated with learning-related changes in value, whereas connectivity changes between vmPFC and PC predict changes in perceived odour similarity. These results demonstrate that dissociable neural pathways support associative and perceptual representations of sensory stimuli.

Spontaneous behavioral responses in the orofacial region: A model of trigeminal pain in mouse

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Romero-Reyes, Marcela; Akerman, Simon; Nguyen, Elaine; Vijjeswarapu, Alice; Hom, Betty; Dong, Hong-Wei; Charles, Andrew C.

2012-01-01

OBJECTIVES To develop a translational mouse model for the study and measurement of non-evoked pain in the orofacial region by establishing markers of nociceptive-specific grooming behaviors in the mouse. BACKGROUND Some of the most prevalent and debilitating conditions involve pain in the trigeminal distribution. Although there are current therapies for these pain conditions, for many patients they are far from optimal. Understanding the pathophysiology of pain disorders arising from structures innervated by the trigeminal nerve is still limited and most animal behavioral models focus on the measurement of evoked pain. In patients, spontaneous (non-evoked) pain responses provide a more accurate representation of the pain experience than do responses that are evoked by an artificial stimulus. Therefore, the development of animal models that measure spontaneous nociceptive behaviors may provide a significant translational tool for a better understanding of pain neurobiology. METHODS C57BL/6 mice received either an injection of 0.9% Saline solution or complete Freund’s adjuvant (CFA) into the right masseter muscle. Animals were video recorded and then analyzed by an observer blind to the experiment group. The duration of different facial grooming patterns performed in the area of injection were measured. After 2 hrs, mice were euthanized, perfused and the brainstem was removed. Fos protein expression in the trigeminal nucleus caudalis was quantified using immunohistochemistry to investigate nociceptive-specific neuronal activation. A separate group of animals was treated with morphine sulfate, to determine the nociceptive-specific nature of their behaviors. RESULTS We characterized and quantified 3 distinct patterns of acute grooming behaviors: fore-paw rubbing, lower lip skin/cheek rubbing against enclosure floor and hind paw scratching. These behaviors occurred with a reproducible frequency and time course, and were inhibited by the analgesic morphine. CFA

When sex hurts, anxiety and fear orient attention towards pain.

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Payne, Kimberley A; Binik, Yitzchak M; Amsel, Rhonda; Khalifé, Samir

2005-08-01

Hypervigilance for pain-relevant stimuli has been associated with anxiety, fear of pain and anxiety sensitivity. This attentional bias has been primarily investigated in heterogeneous pain groups or pain-free controls, but has not been examined in pain conditions where anxiety and fear are likely to play a central role. Due to the intimate and interpersonal nature of genital pain experienced during sexual intercourse, Vulvar Vestibulitis Syndrome (VVS) constitutes an ideal sample in which to investigate the role of cognitive and affective factors in pain perception and maintenance. Seventeen women suffering from VVS and an equal number of age and education matched control women completed an emotional Stroop and memory recall task in addition to a series of questionnaires assessing pain-hypervigilance, state and trait anxiety, fear of pain, and anxiety sensitivity. VVS sufferers reported hypervigilance for coital pain and also exhibited a selective attentional bias towards pain stimuli on the emotional Stroop task as compared with controls. This effect was predicted by state and trait anxiety and fear of pain. According to these data, treament strategies for VVS should target anxiety and fear in addition to sensory systems.

Short-Term Sleep Disturbance-Induced Stress Does not Affect Basal Pain Perception, but Does Delay Postsurgical Pain Recovery.

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Wang, Po-Kai; Cao, Jing; Wang, Hongzhen; Liang, Lingli; Zhang, Jun; Lutz, Brianna Marie; Shieh, Kun-Ruey; Bekker, Alex; Tao, Yuan-Xiang

2015-11-01

Chronic sleep disturbance-induced stress is known to increase basal pain sensitivity. However, most surgical patients frequently report short-term sleep disturbance/deprivation during the pre- and postoperation periods and have normal pain perception presurgery. Whether this short-term sleep disturbance affects postsurgical pain is elusive. Here, we report that pre- or postexposure to rapid eye movement sleep disturbance (REMSD) for 6 hours daily for 3 consecutive days did not alter basal responses to mechanical, heat, and cold stimuli, but did delay recovery in incision-induced reductions in paw withdrawal threshold to mechanical stimulation and paw withdrawal latencies to heat and cold stimuli on the ipsilateral side of male or female rats. This short-term REMSD led to stress shown by an increase in swim immobility time, a decrease in sucrose consumption, and an increase in the level of corticosterone in serum. Blocking this stress via intrathecal RU38486 or bilateral adrenalectomy abolished REMSD-caused delay in recovery of incision-induced reductions in behavioral responses to mechanical, heat, and cold stimuli. Moreover, this short-term REMSD produced significant reductions in the levels of mu opioid receptor and kappa opioid receptor, but not Kv1.2, in the ipsilateral L4/5 spinal cord and dorsal root ganglia on day 9 after incision (but not after sham surgery). Our findings show that short-term sleep disturbance either pre- or postsurgery does not alter basal pain perception, but does exacerbate postsurgical pain hypersensitivity. The latter may be related to the reductions of mu and kappa opioid receptors in the spinal cord and dorsal root ganglia caused by REMSD plus incision. Prevention of short-term sleep disturbance may help recovery from postsurgical pain in patients. Copyright © 2015 American Pain Society. Published by Elsevier Inc. All rights reserved.

Chromatic spatial contrast sensitivity estimated by visual evoked cortical potential and psychophysics

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Barboni, M.T.S.; Gomes, B.D.; Souza, G.S.; Rodrigues, A.R.; Ventura, D.F.; Silveira, L.C.L.

2013-01-01

The purpose of the present study was to measure contrast sensitivity to equiluminant gratings using steady-state visual evoked cortical potential (ssVECP) and psychophysics. Six healthy volunteers were evaluated with ssVECPs and psychophysics. The visual stimuli were red-green or blue-yellow horizontal sinusoidal gratings, 5° × 5°, 34.3 cd/m2 mean luminance, presented at 6 Hz. Eight spatial frequencies from 0.2 to 8 cpd were used, each presented at 8 contrast levels. Contrast threshold was obtained by extrapolating second harmonic amplitude values to zero. Psychophysical contrast thresholds were measured using stimuli at 6 Hz and static presentation. Contrast sensitivity was calculated as the inverse function of the pooled cone contrast threshold. ssVECP and both psychophysical contrast sensitivity functions (CSFs) were low-pass functions for red-green gratings. For electrophysiology, the highest contrast sensitivity values were found at 0.4 cpd (1.95 ± 0.15). ssVECP CSF was similar to dynamic psychophysical CSF, while static CSF had higher values ranging from 0.4 to 6 cpd (P chromatic functions showed no specific tuning shape; however, at high spatial frequencies the evoked potentials showed higher contrast sensitivity than the psychophysical methods (P chromatic red-green CSFs in agreement with psychophysical thresholds, mainly if the same temporal properties are applied to the stimulus. For blue-yellow CSF, correlation between electrophysiology and psychophysics was poor at high spatial frequency, possibly due to a greater effect of chromatic aberration on this kind of stimulus. PMID:23369980

Linear Discriminant Analysis achieves high classification accuracy for the BOLD fMRI response to naturalistic movie stimuli.

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Hendrik eMandelkow

2016-03-01

Full Text Available Naturalistic stimuli like movies evoke complex perceptual processes, which are of great interest in the study of human cognition by functional MRI (fMRI. However, conventional fMRI analysis based on statistical parametric mapping (SPM and the general linear model (GLM is hampered by a lack of accurate parametric models of the BOLD response to complex stimuli. In this situation, statistical machine-learning methods, a.k.a. multivariate pattern analysis (MVPA, have received growing attention for their ability to generate stimulus response models in a data-driven fashion. However, machine-learning methods typically require large amounts of training data as well as computational resources. In the past this has largely limited their application to fMRI experiments involving small sets of stimulus categories and small regions of interest in the brain. By contrast, the present study compares several classification algorithms known as Nearest Neighbour (NN, Gaussian Naïve Bayes (GNB, and (regularised Linear Discriminant Analysis (LDA in terms of their classification accuracy in discriminating the global fMRI response patterns evoked by a large number of naturalistic visual stimuli presented as a movie.Results show that LDA regularised by principal component analysis (PCA achieved high classification accuracies, above 90% on average for single fMRI volumes acquired 2s apart during a 300s movie (chance level 0.7% = 2s/300s. The largest source of classification errors were autocorrelations in the BOLD signal compounded by the similarity of consecutive stimuli. All classifiers performed best when given input features from a large region of interest comprising around 25% of the voxels that responded significantly to the visual stimulus. Consistent with this, the most informative principal components represented widespread distributions of co-activated brain regions that were similar between subjects and may represent functional networks. In light of these

Modification of electrical pain threshold by voluntary breathing-controlled electrical stimulation (BreEStim in healthy subjects.

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Shengai Li

Full Text Available BACKGROUND: Pain has a distinct sensory and affective (i.e., unpleasantness component. BreEStim, during which electrical stimulation is delivered during voluntary breathing, has been shown to selectively reduce the affective component of post-amputation phantom pain. The objective was to examine whether BreEStim increases pain threshold such that subjects could have improved tolerance of sensation of painful stimuli. METHODS: Eleven pain-free healthy subjects (7 males, 4 females participated in the study. All subjects received BreEStim (100 stimuli and conventional electrical stimulation (EStim, 100 stimuli to two acupuncture points (Neiguan and Weiguan of the dominant hand in a random order. The two different treatments were provided at least three days apart. Painful, but tolerable electrical stimuli were delivered randomly during EStim, but were triggered by effortful inhalation during BreEStim. Measurements of tactile sensation threshold, electrical sensation and electrical pain thresholds, thermal (cold sensation, warm sensation, cold pain and heat pain thresholds were recorded from the thenar eminence of both hands. These measurements were taken pre-intervention and 10-min post-intervention. RESULTS: There was no difference in the pre-intervention baseline measurement of all thresholds between BreEStim and EStim. The electrical pain threshold significantly increased after BreEStim (27.5±6.7% for the dominant hand and 28.5±10.8% for the non-dominant hand, respectively. The electrical pain threshold significantly decreased after EStim (9.1±2.8% for the dominant hand and 10.2±4.6% for the non-dominant hand, respectively (F[1, 10] = 30.992, p = .00024. There was no statistically significant change in other thresholds after BreEStim and EStim. The intensity of electrical stimuli was progressively increased, but no difference was found between BreEStim and EStim. CONCLUSION: Voluntary breathing controlled electrical stimulation

Orofacial pain conditions

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Pedersen, Anne Marie Lynge; Forssell, Heli; Grinde, Bjørn

2016-01-01

Pain of the oral mucosa is a common accompanying symptom of various oral mucosal lesions caused by local and systemic diseases. Pain of the oral mucosa is usually associated with a known cause of tissue damage, e.g. mucosal ulcer or erosion, and it generally responds to adequate treatment...... and dissolves after healing. Chronic pain, on the other hand, persists months and years after apparent tissue healing, and attempts to alleviate pain are challenging. Neuropathic pain occurs due to damage neurogenic structures in the peripheral and/or the central nervous system. It may occur in the absence...... of any obvious noxious stimuli, and in the oral mucosal, the pain is often described as tingling and burning. In the oral cavity, burning mouth syndrome (BMS) is presently considered to have neuropathic background. It is important for dental practitioners to have a clear understanding of the various...

Pain hypersensitivity in congenital blindness is associated with faster central processing of C-fibre input

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Slimani, H.; Plaghki, L.; Ptito, M.

2016-01-01

Background We have recently shown that visual deprivation from birth exacerbates responses to painful thermal stimuli. However, the mechanisms underlying pain hypersensitivity in congenital blindness are unclear. Methods To study the contribution of Aδ- and C-fibres in pain perception, we measure...... The increased sensitivity to painful thermal stimulation in congenital blindness may be due to more efficient central processing of C-fibre–mediated input, which may help to avoid impending dangerous encounters with stimuli that threaten the bodily integrity....

Ensemble encoding of nociceptive stimulus intensity in the rat medial and lateral pain systems

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Woodward Donald J

2011-08-01

Full Text Available Abstract Background The ability to encode noxious stimulus intensity is essential for the neural processing of pain perception. It is well accepted that the intensity information is transmitted within both sensory and affective pathways. However, it remains unclear what the encoding patterns are in the thalamocortical brain regions, and whether the dual pain systems share similar responsibility in intensity coding. Results Multichannel single-unit recordings were used to investigate the activity of individual neurons and neuronal ensembles in the rat brain following the application of noxious laser stimuli of increasing intensity to the hindpaw. Four brain regions were monitored, including two within the lateral sensory pain pathway, namely, the ventral posterior lateral thalamic nuclei and the primary somatosensory cortex, and two in the medial pathway, namely, the medial dorsal thalamic nuclei and the anterior cingulate cortex. Neuron number, firing rate, and ensemble spike count codings were examined in this study. Our results showed that the noxious laser stimulation evoked double-peak responses in all recorded brain regions. Significant correlations were found between the laser intensity and the number of responsive neurons, the firing rates, as well as the mass spike counts (MSCs. MSC coding was generally more efficient than the other two methods. Moreover, the coding capacities of neurons in the two pathways were comparable. Conclusion This study demonstrated the collective contribution of medial and lateral pathway neurons to the noxious intensity coding. Additionally, we provide evidence that ensemble spike count may be the most reliable method for coding pain intensity in the brain.

[The Influence of Threatening Stimuli on the Component P200 in Patients with Paranoid Schizophrenia].

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Strelets, V B; Arkhipov, A Yu

2015-01-01

We studied schizophrenic patients with the dominance of pseudohallucinations. As is well known, pseudohallucinations are the main syndrome of schizophrenia, the so-called first rank syndrome. Pseudohallucinations are defined as a disorder of sense (affective) perception. This disorder is mainly diagnosed from the clinical picture or by pathopsychologichal observations. We investigated the evoked potentials (EP) of brain after neutral and emotionally meaningful (threatening) visual stimuli in order to specify the neurophysiological disorders of affective perception in schizophrenic patients with severe paranoid-hallucinatory syndrome who did not receive neuroleptic therapy. The analysis of P200 component in healthy subjects showed an increase in the amplitude and shortening of the latency of this wave in response to thretaning stimuli, as compared to neutral stimuli. In the group of patients with schizophrenia, the analysis showed the same increase in the level of excitation in response to emotionally threatening stimuli. However, in schizophrenic patients there were also found certain areas where the amplitude and latency decreased or increased at the same time. The results show that patients with schizophrenia have the pathological effect of having parameters typical of the processes of both excitation and inhibition.

The empathy impulse: A multinomial model of intentional and unintentional empathy for pain.

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Cameron, C Daryl; Spring, Victoria L; Todd, Andrew R

2017-04-01

Empathy for pain is often described as automatic. Here, we used implicit measurement and multinomial modeling to formally quantify unintentional empathy for pain: empathy that occurs despite intentions to the contrary. We developed the pain identification task (PIT), a sequential priming task wherein participants judge the painfulness of target experiences while trying to avoid the influence of prime experiences. Using multinomial modeling, we distinguished 3 component processes underlying PIT performance: empathy toward target stimuli (Intentional Empathy), empathy toward prime stimuli (Unintentional Empathy), and bias to judge target stimuli as painful (Response Bias). In Experiment 1, imposing a fast (vs. slow) response deadline uniquely reduced Intentional Empathy. In Experiment 2, inducing imagine-self (vs. imagine-other) perspective-taking uniquely increased Unintentional Empathy. In Experiment 3, Intentional and Unintentional Empathy were stronger toward targets with typical (vs. atypical) pain outcomes, suggesting that outcome information matters and that effects on the PIT are not reducible to affective priming. Typicality of pain outcomes more weakly affected task performance when target stimuli were merely categorized rather than judged for painfulness, suggesting that effects on the latter are not reducible to semantic priming. In Experiment 4, Unintentional Empathy was stronger for participants who engaged in costly donation to cancer charities, but this parameter was also high for those who donated to an objectively worse but socially more popular charity, suggesting that overly high empathy may facilitate maladaptive altruism. Theoretical and practical applications of our modeling approach for understanding variation in empathy are discussed. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Pain Adaptability in Individuals With Chronic Musculoskeletal Pain Is Not Associated With Conditioned Pain Modulation.

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Wan, Dawn Wong Lit; Arendt-Nielsen, Lars; Wang, Kelun; Xue, Charlie Changli; Wang, Yanyi; Zheng, Zhen

2018-03-27

Healthy humans can be divided into the pain adaptive (PA) and the pain nonadaptive (PNA) groups; PA showed a greater decrease in pain rating to a cold pressor test (CPT) than PNA. This study examined if the dichotomy of pain adaptability existed in individuals with chronic musculoskeletal pain. CPTs at 2°C and 7°C were used to assess the status of pain adaptability in participants with either chronic nonspecific low back pain or knee osteoarthritis. The participants' potency of conditioned pain modulation (CPM) and local inhibition were measured. The strengths of pain adaptability at both CPTs were highly correlated. PA and PNA did not differ in their demographic characteristics, pain thresholds from thermal and pressure stimuli, or potency of local inhibition or CPM. PA reached their maximum pain faster than PNA (t 41 = -2.76, P adaptability exists in musculoskeletal pain patients. Consistent with the healthy human study, the strength of pain adaptability and potency of CPM are not related. Pain adaptability could be another form of endogenous pain inhibition of which clinical implication is yet to be understood. The dichotomy of pain adaptability was identified in healthy humans. The current study confirms that this dichotomy also exists in individuals with chronic musculoskeletal pain, and could be reliably assessed with CPTs at 2°C and 7°C. Similar to the healthy human study, pain adaptability is not associated with CPM, and may reflect the temporal aspect of pain inhibition. Copyright © 2018 The American Pain Society. Published by Elsevier Inc. All rights reserved.

A novel method for delivering ramped cooling reveals rat behaviours at innocuous and noxious temperatures: A comparative study of human psychophysics and rat behaviour.

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Dunham, James P; Hulse, Richard P; Donaldson, Lucy F

2015-07-15

Thermal sensory testing in rodents informs human pain research. There are important differences in the methodology for delivering thermal stimuli to humans and rodents. This is particularly true in cold pain research. These differences confound extrapolation and de-value nociceptive tests in rodents. We investigated cooling-induced behaviours in rats and psychophysical thresholds in humans using ramped cooling stimulation protocols. A Peltier device mounted upon force transducers simultaneously applied a ramped cooling stimulus whilst measuring contact with rat hind paw or human finger pad. Rat withdrawals and human detection, discomfort and pain thresholds were measured. Ramped cooling of a rat hind paw revealed two distinct responses: Brief paw removal followed by paw replacement, usually with more weight borne than prior to the removal (temperature inter-quartile range: 19.1 °C to 2.8 °C). Full withdrawal was evoked at colder temperatures (inter quartile range: -11.3 °C to -11.8 °C). The profile of human cool detection threshold and cold pain threshold were remarkably similar to that of the rat withdrawals behaviours. Previous rat cold evoked behaviours utilise static temperature stimuli. By utilising ramped cold stimuli this novel methodology better reflects thermal testing in patients. Brief paw removal in the rat is driven by non-nociceptive afferents, as is the perception of cooling in humans. This is in contrast to the nociceptor-driven withdrawal from colder temperatures. These findings have important implications for the interpretation of data generated in older cold pain models and consequently our understanding of cold perception and pain. Copyright © 2015. Published by Elsevier B.V.

Analgesia induced by self-initiated electrotactile sensation is mediated by top-down modulations.

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Zhao, Ke; Tang, Zhengyu; Wang, Huiquan; Guo, Yifei; Peng, Weiwei; Hu, Li

2017-06-01

It is well known that sensory perception can be attenuated when sensory stimuli are controlled by self-initiated actions. This phenomenon is explained by the consistency between forward models of anticipated action effects and actual sensory feedback. Specifically, the brain state related to the binding between motor processing and sensory perception would have inhibitory function by gating sensory information via top-down control. Since the brain state could casually influence the perception of subsequent stimuli of different sensory modalities, we hypothesize that pain evoked by nociceptive stimuli following the self-initiated tactile stimulation would be attenuated as compared to that following externally determined tactile stimulation. Here, we compared psychophysical and neurophysiological responses to identical nociceptive-specific laser stimuli in two different conditions: self-initiated tactile sensation condition (STS) and nonself-initiated tactile sensation condition (N-STS). We observed that pain intensity and unpleasantness, as well as laser-evoked brain responses, were significantly reduced in the STS condition compared to the N-STS condition. In addition, magnitudes of alpha and beta oscillations prior to laser onset were significantly larger in the STS condition than in the N-STS condition. These results confirmed that pain perception and pain-related brain responses were attenuated when the tactile stimulation was initiated by subjects' voluntary actions, and exploited neural oscillations reflecting the binding between motor processing and sensory feedback. Thus, our study elaborated the understanding of underlying neural mechanisms related to top-down modulations of the analgesic effect induced by self-initiated tactile sensation, which provided theoretical basis to improve the analgesic effect in various clinical applications. © 2017 Society for Psychophysiological Research.

Electrophysiology as a tool to unravel the origin of pancreatic pain

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Lelic, Dina; Olesen, Søren Schou; Graversen, Carina

2014-01-01

Intense abdominal pain is the most common symptom in chronic pancreatitis, but the underlying mechanisms are not completely understood and pain management remains a significant clinical challenge. The focus of pain origin in chronic pancreatitis traditionally has been on the pancreatic gland...... for generation of evoked potentials and hence to study brain reorganization due to pain in chronic pancreatitis. The aim of this review is to give an overview of the current methods and findings in electroencephalography as a tool to unravel the origin of pancreatic pain....

Effect of ambient temperature on human pain and temperature perception.

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Strigo, I A; Carli, F; Bushnell, M C

2000-03-01

Animal studies show reduced nociceptive responses to noxious heat stimuli and increases in endogenous beta-endorphin levels in cold environments, suggesting that human pain perception may be dependent on ambient temperature. However, studies of changes in local skin temperature on human pain perception have yielded variable results. This study examines the effect of both warm and cool ambient temperature on the perception of noxious and innocuous mechanical and thermal stimuli. Ten subjects (7 men and 3 women, aged 20-23 yr) used visual analog scales to rate the stimulus intensity, pain intensity, and unpleasantness of thermal (0-50 degrees C) and mechanical (1.2-28.9 g) stimuli applied on the volar forearm with a 1-cm2 contact thermode and von Frey filaments, respectively. Mean skin temperatures were measured throughout the experiment by infrared pyrometer. Each subject was tested in ambient temperatures of 15 degrees C (cool), 25 degrees C (neutral), and 35 degrees C (warm) on separate days, after a 30-min acclimation to the environment. Studies began in the morning after an 8-h fast. Mean skin temperature was altered by ambient temperature (cool room: 30.1 degrees C; neutral room: 33.4 degrees C; warm room: 34.5 degrees C; P cool than in the neutral environment (P cool room and that noxious heat stimuli were more unpleasant in a warm environment. Environmental temperature did not alter ratings of warm (37 and 40 degrees C) or mechanical stimuli. These results indicate that, in humans, a decrease in skin temperature following exposure to cool environments reduces thermal pain. Suppression of Adelta primary afferent cold fiber activity has been shown to increase cold pain produced by skin cooling. Our current findings may represent the reverse phenomenon, i.e., a reduction in thermal nociceptive transmission by the activation of Adelta cutaneous cold fibers.

Chronic Pain and Selective Attention to Pain Arousing Daily Activity Pictures: Evidence From an Eye Tracking Study

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Masoumeh Mahmoodi-Aghdam

2017-11-01

Conclusion: Although these results did not provide unequivocal support for the vigilance-avoidance hypothesis, they are generally consistent with the results of studies using eye tracking technology. Furthermore, our findings put a question over characterization of attentional biases in patients with chronic pain by simply relating that to difficulty in disengaging from pain-related stimuli.

Cortical modulation of short-latency TMS-evoked potentials

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Domenica eVeniero

2013-01-01

Full Text Available Transcranial magnetic stimulation - electroencephalogram (TMS-EEG co-registration offers the opportunity to test reactivity of brain areas across distinct conditions through TMS-evoked potentials (TEPs. Several TEPs have been described, their functional meaning being largely unknown. In particular, short-latency potentials peaking at 5 (P5 and 8 (N8 ms after the TMS pulse have been recently described, but because of their huge amplitude, the problem of whether their origin is cortical or not has been opened. To gain information about these components, we employed a protocol that modulates primary motor cortex excitability (MI through an exclusively cortical phenomena: low frequency stimulation of premotor area (PMC. TMS was applied simultaneously with EEG recording from 70 electrodes. Amplitude of TEPs evoked by 200 single-pulses TMS delivered over MI at 110% of resting motor threshold was measured before and after applying 900 TMS conditioning stimuli to left premotor cortex with 1 Hz repetition rate. Single subject analyses showed reduction in TEPs amplitude after PMC conditioning in a sample of participants and increase in TEPs amplitude in two subjects. No effects were found on corticospinal excitability as recorded by motor evoked potentials (MEPs. Furthermore, correlation analysis showed an inverse relation between the effects of the conditioning protocol on P5-N8 complex amplitude and MEPs amplitude. Because the effects of the used protocol have been ascribed to a cortical interaction between premotor area and MI, we suggest that despite the sign of P5-N8 amplitude modulation is not consistent across participant, this modulation could indicate, at least in part, their cortical origin. We conclude that with an accurate experimental procedure early-latency components can be used to evaluate the reactivity of the stimulated cortex.

Statistical modeling of the response characteristics of mechanosensitive stimuli in the human esophagus

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Drewes, A.M.; Reddy, H.; Staahl, C.

2005-01-01

by using a statistical model based on correlation analysis. The esophagus was distended with a bag in 32 healthy subjects by using an inflation rate of 25 mL/min. The luminal cross-sectional areas and sensory ratings were determined during the distentions. The stimuli were repeated after relaxation...... of mechanical gut stimuli in human beings. This might increase our understanding of visceral pain in health and disease and guide the statistical analysis of experimental data obtained in the gastrointestinal tract....

Effect of caffeine on vestibular evoked myogenic potential: a systematic review with meta-analysis.

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Souza, Maria Eduarda Di Cavalcanti Alves de; Costa, Klinger Vagner Teixeira da; Menezes, Pedro de Lemos

2017-12-24

Caffeine can be considered the most consumed drug by adults worldwide, and can be found in several foods, such as chocolate, coffee, tea, soda and others. Overall, caffeine in moderate doses, results in increased physical and intellectual productivity, increases the capacity of concentration and reduces the time of reaction to sensory stimuli. On the other hand, high doses can cause noticeable signs of mental confusion and error induction in intellectual tasks, anxiety, restlessness, muscle tremors, tachycardia, labyrinthine changes, and tinnitus. Considering that the vestibular evoked myogenic potential is a clinical test that evaluates the muscular response of high intensity auditory stimulation, the present systematic review aimed to analyze the effects of caffeine on vestibular evoked myogenic potential. This study consisted of the search of the following databases: MEDLINE, CENTRAL, ScienceDirect, Scopus, Web of Science, LILACS, SciELO and ClinicalTrials.gov. Additionally, the gray literature was also searched. The search strategy included terms related to intervention (caffeine or coffee consumption) and the primary outcome (vestibular evoked myogenic potential). Based on the 253 potentially relevant articles identified through the database search, only two full-text publications were retrieved for further evaluation, which were maintained for qualitative analysis. Analyzing the articles found, caffeine has no effect on vestibular evoked myogenic potential in normal individuals. Copyright © 2017 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Published by Elsevier Editora Ltda. All rights reserved.

Transcutaneous electrical nerve stimulation: nonparallel antinociceptive effects on chronic clinical pain and acute experimental pain.

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Cheing, G L; Hui-Chan, C W

1999-03-01

To investigate to what extent a single 60-minute session of transcutaneous electrical nerve stimulation (TENS) would modify chronic clinical pain, acute experimental pain, and the flexion reflex evoked in chronic low back pain patients. Thirty young subjects with chronic low back pain were randomly allocated to two groups, receiving either TENS or placebo stimulation to the lumbosacral region for 60 minutes. The flexion reflex was elicited by an electrical stimulation applied to the subject's right sole and recorded electromyographically from the biceps femoris and the tibialis anterior muscles. Subjective sensation of low back pain and the electrically induced pain were measured by two separate visual analog scales, termed VAS(LBP) and VAS(FR), respectively. Data obtained before, during, and 60 minutes after TENS and placebo stimulations were analyzed using repeated measures ANOVA. The VAS(LBP) score was significantly reduced to 63.1% of the prestimulation value after TENS (pTENS protocol had different degrees of antinociceptive influence on chronic and acute pain in chronic low back pain patients.

Pain following hysterectomy: epidemiological and clinical aspects.

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Brandsborg, Birgitte

2012-01-01

It is well known that different surgical procedures like amputation, thoracotomy, inguinal herniotomy, and mastectomy are associated with a risk of developing chronic postsurgical pain. Hysterectomy is the most frequent gynecological procedure with an annual frequency of 5000 hysterectomies for a benign indication in Denmark, but is has not previously been documented in detail to what extent this procedure leads to chronic pain. The aim of this PhD thesis was therefore to describe the epidemiology, type of pain, risk factors, and predictive factors associated with chronic pain after hysterectomy for a benign indication. The thesis includes four papers, of which one is based on a questionnaire study, two are based on a prospective clinical study, and one is a review of chronic pain after hysterectomy. The questionnaire paper included 1135 women one year after hysterectomy. A postal questionnaire about pain before and after hysterectomy was combined with data from the Danish Hysterectomy Database. Chronic postoperative pain was described by 32%, and the identified risk factors were preoperative pelvic pain, previous cesarean section, other pain problems and pain as an indication for hysterectomy. Spinal anesthesia was associated with a decreased risk of having pain after one year. The type of surgery (i.e. abdominal or vaginal hysterectomy) did not influence chronic pain. The prospective paper included 90 women referred for a hysterectomy on benign indication. The tests were performed before, on day 1, and 4 months after surgery and included questionnaires about pain, coping, and quality of life together with quantitative sensory testing of pain thresholds. Seventeen percent had pain after 4 months, and the risk factors were preoperative pain problems elsewhere and a high intensity of acute postoperative pain. Type of surgery was not a risk factor. Preoperative brush-evoked allodynia, pinprick hyperalgesia, and vaginal pain threshold were associated with a high

Reaction to topical capsaicin in spinal cord injury patients with and without central pain

DEFF Research Database (Denmark)

Finnerup, Nanna Brix; Pedersen, Louise H.; Terkelsen, Astrid J.

2007-01-01

of a spinal cord injury which already is hyperexcitable, would cause enhanced responses in patients with central pain at the level of injury compared to patients without neuropathic pain and healthy controls. Touch, punctuate stimuli, cold stimuli and topical capsaicin was applied above, at, and below injury......Central neuropathic pain is a debilitating and frequent complication to spinal cord injury (SCI). Excitatory input from hyperexcitable cells around the injured grey matter zone is suggested to play a role for central neuropathic pain felt below the level of a spinal cord injury. Direct evidence...... at the level of injury. Keywords: Spinal cord injury; Neuropathic pain; Capsaicin; Neuronal hyperexcitability; Hyperalgesia; Blood flow...

Psychogenic Low-Back Pain and Hysterical Paralysis in Adolescence.

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Kanchiku, Tsukasa; Suzuki, Hidenori; Imajo, Yasuaki; Yoshida, Yuichiro; Nishida, Norihiro; Taguchi, Toshihiko

2017-10-01

A retrospective review. The purpose of this study was to investigate the clinical outcomes in adolescents diagnosed with psychogenic low-back pain and hysterical paralysis and to evaluate the efficacy of differential diagnosis methods. The incidence of low-back pain in adolescence is similar to that in adults, but the causes of low-back pain are difficult to determine in most cases. For these patients, a definitive diagnosis of psychogenic low-back pain and hysterical paralysis as well as adequate treatment are clinically important to avoid unnecessary surgical treatment. Eleven patients (3 males and 8 females; mean age, 16.5 years; range, 13-19 y) diagnosed with psychogenic low-back pain and hysterical paralysis were followed up for 2-10.25 years (mean, 4.67 y). Nonorganic signs were observed in almost all patients. For the purpose of excluding organic disorders, the thiopentone pain study was used in patients who complained mainly of pain, and motor evoked potentials using transcranial magnetic stimulation were measured in patients experiencing primarily muscle weakness. The psychiatric diagnosis was neurosis in 9 patients, whereas it was psychosomatic disorder in 2 patients. Conservative treatment, such as physiotherapy, was performed, and at the final follow-up evaluation, outcomes were regarded as excellent in 7 patients and good in 4 patients. The prognosis of psychogenic low-back pain and hysterical paralysis in adolescence is relatively good. However, it is important to understand the characteristics of psychogenic low-back pain and hysterical paralysis in childhood and young adulthood and to perform accurate diagnosis by screening for nonorganic signs and excluding organic disorders by using the thiopentone pain study and motor evoked potentials obtained using transcranial magnetic stimulation.

Neural conflict-control mechanisms improve memory for target stimuli.

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Krebs, Ruth M; Boehler, Carsten N; De Belder, Maya; Egner, Tobias

2015-03-01

According to conflict-monitoring models, conflict serves as an internal signal for reinforcing top-down attention to task-relevant information. While evidence based on measures of ongoing task performance supports this idea, implications for long-term consequences, that is, memory, have not been tested yet. Here, we evaluated the prediction that conflict-triggered attentional enhancement of target-stimulus processing should be associated with superior subsequent memory for those stimuli. By combining functional magnetic resonance imaging (fMRI) with a novel variant of a face-word Stroop task that employed trial-unique face stimuli as targets, we were able to assess subsequent (incidental) memory for target faces as a function of whether a given face had previously been accompanied by congruent, neutral, or incongruent (conflicting) distracters. In line with our predictions, incongruent distracters not only induced behavioral conflict, but also gave rise to enhanced memory for target faces. Moreover, conflict-triggered neural activity in prefrontal and parietal regions was predictive of subsequent retrieval success, and displayed conflict-enhanced functional coupling with medial-temporal lobe regions. These data provide support for the proposal that conflict evokes enhanced top-down attention to task-relevant stimuli, thereby promoting their encoding into long-term memory. Our findings thus delineate the neural mechanisms of a novel link between cognitive control and memory. © The Author 2013. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Reaction to topical capsaicin in spinal cord injury patients with and without central pain

DEFF Research Database (Denmark)

Finnerup, Nanna Brix; Pedersen, Louise H.; Terkelsen, Astrid J.

2007-01-01

of a spinal cord injury which already is hyperexcitable, would cause enhanced responses in patients with central pain at the level of injury compared to patients without neuropathic pain and healthy controls. Touch, punctuate stimuli, cold stimuli and topical capsaicin was applied above, at, and below injury......Central neuropathic pain is a debilitating and frequent complication to spinal cord injury (SCI). Excitatory input from hyperexcitable cells around the injured grey matter zone is suggested to play a role for central neuropathic pain felt below the level of a spinal cord injury. Direct evidence...... for this hypothesis is difficult to obtain. Capsaicin, activating TRPV1 receptors on small sensory afferents, induces enhanced cellular activity in dorsal horn neurons and produces a central mediated area of secondary hyperalgesia. We hypothesized that sensory stimuli and capsaicin applied at and just above the level...

The Relationship Between Ocular Itch, Ocular Pain, and Dry Eye Symptoms (An American Ophthalmological Society Thesis).

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Galor, Anat; Small, Leslie; Feuer, William; Levitt, Roy C; Sarantopoulos, Konstantinos D; Yosipovitch, Gil

2017-08-01

To evaluate associations between sensations of ocular itch and dry eye (DE) symptoms, including ocular pain, and DE signs. A cross-sectional study of 324 patients seen in the Miami Veterans Affairs eye clinic was performed. The evaluation consisted of questionnaires regarding ocular itch, DE symptoms, descriptors of neuropathic-like ocular pain (NOP), and evoked pain sensitivity testing on the forehead and forearm, followed by a comprehensive ocular surface examination including corneal mechanical sensitivity testing. Analyses were performed to examine for differences between those with and without subjective complaints of ocular itch. The mean age was 62 years with 92% being male. Symptoms of DE and NOP were more frequent in patients with moderate-severe ocular itch compared to those with no or mild ocular itch symptoms. With the exception of ocular surface inflammation (abnormal matrix metalloproteinase 9 testing) which was less common in those with moderate-severe ocular itch symptoms, DE signs were not related to ocular itch. Individuals with moderate-severe ocular itch also demonstrated greater sensitivity to evoked pain on the forearm and had higher non-ocular pain, depression, and post-traumatic stress disorders scores, compared to those with no or mild itch symptoms. Subjects with moderate-severe ocular itch symptoms have more severe symptoms of DE, NOP, non-ocular pain and demonstrate abnormal somatosensory testing in the form of increased sensitivity to evoked pain at a site remote from the eye, consistent with generalized hypersensitivity.

The Pain System in Oesophageal Disorders: Mechanisms, Clinical Characteristics, and Treatment

Directory of Open Access Journals (Sweden)

Christian Lottrup

2011-01-01

Full Text Available Pain is common in gastroenterology. This review aims at giving an overview of pain mechanisms, clinical features, and treatment options in oesophageal disorders. The oesophagus has sensory receptors specific for different stimuli. Painful stimuli are encoded by nociceptors and communicated via afferent nerves to the central nervous system. The pain stimulus is further processed and modulated in specific pain centres in the brain, which may undergo plastic alterations. Hence, tissue inflammation and long-term exposure to pain can cause sensitisation and hypersensitivity. Oesophageal sensitivity can be evaluated ,for example, with the oesophageal multimodal probe. Treatment should target the cause of the patient's symptoms. In gastro-oesophageal reflux diseases, proton pump inhibitors are the primary treatment option, surgery being reserved for patients with severe disease resistant to drug therapy. Functional oesophageal disorders are treated with analgesics, antidepressants, and psychological therapy. Lifestyle changes are another option with less documentation.

The effect of age and gender on pressure pain thresholds and suprathreshold stimuli

DEFF Research Database (Denmark)

Petrini, Laura; Tomczak Matthiesen, Susan; Arendt-Nielsen, Lars

2015-01-01

The study investigates the impact of age and gender on (1) experimental pressure pain detection thresholds (PPDT) and pressure pain tolerance thresholds (PPTolT) and (2) participants’self-reports of pain intensity and unpleasantness at suprathreshold and subthreshold levels. Methods: twenty young...... (20–34, mean age = 24.6 ± 3.5 years, ten female) and twenty elderly (65–88, mean age = 73.7 ± 6.6 years, ten female) healthy volunteers were compared. Mini-Mental State Examination (MMSE 28–30) assessed intact cognitive functioning. Pain thresholds were assessed together with the sensory intensity...... ratings to 1.3 × PPDT (pain) and 0.2 × PPDT (no pain). Results: PPDT and PPTolT significantly decreased with age and were lower in young females as compared with young males. No gender differences were observed in the elderly group. PPDT decreased significantly with age in males but not in females...

Hyperosmolar tears enhance cooling sensitivity of the corneal nerves in rats: possible neural basis for cold-induced dry eye pain.

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Hirata, Harumitsu; Rosenblatt, Mark I

2014-08-19

Tear hyperosmolarity is a ubiquitous feature of dry-eye disease. Although dry-eye patients' sensitivity to cooling is well known, the effects of tear hyperosmolarity on a small amount of cooling in the corneal nerves have not been quantitatively examined. Recently reported corneal afferents, high-threshold cold sensitive plus dry-sensitive (HT-CS + DS) neurons, in rats is normally excited by strong (>4°C) cooling of the cornea, which, when applied to healthy humans, evokes the sensation of discomfort. However, corneal cooling measured between blinks does not exceed 2°C normally. Thus, we sought to determine if these nociceptors could be sensitized by hyperosmolar tears such that they are now activated by small cooling of the ocular surface. Trigeminal ganglion neurons innervating the cornea were extracellularly recorded in isoflurane-anesthetized rats. The responses of single corneal neurons to cooling stimuli presented in the presence of hyperosmolar (350-800 mOsm NaCl) tears were examined. The HT-CS + DS neurons with thresholds averaging 4°C cooling responded to cooling stimuli presented after 15 minutes of hyperosmolar tears with thresholds of less than 1°C. The response magnitudes also were enhanced so that the responses to small (2°C) cooling emerged, where none was observed before. These results demonstrate that after exposure to hyperosmolar tears, these nociceptive corneal neurons now begin to respond to the slight cooling normally encountered between blinks, enabling the painful information to be carried to the brain, which could explain the cooling-evoked discomfort in dry eye patients. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

Opposite patterns of change in perception of imagined and physically induced pain over the course of repeated thermal stimulations.

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Gács, B; Szolcsányi, T; Csathó, Á

2017-08-01

Individuals frequently show habituation to repeated noxious heat. However, given the defensive function of human pain processing, it is reasonable to assume that individuals anticipate that they would become increasingly sensitive to repeated thermal pain stimuli. No previous studies have, however, been addressed to this assumption. Therefore, in the current study, we investigated how healthy human individuals imagine the intensity of repeated thermal pain stimulations, and compared this with the intensity ratings given after physically induced thermal pain trials. Healthy participants (N = 20) gave pain intensity ratings in two conditions: imagined and real thermal pain. In the real pain condition, thermal pain stimuli of two intensities (minimal and moderate pain) were delivered in four consecutive trials. The duration of the peak temperature was 20 s, and stimulation was always delivered to the same location. In each trial, participants rated the pain intensity twice, 5 and 15 s after the onset of the peak temperature. In the imagined pain condition, participants were subjected to a reference pain stimulus and then asked to imagine and rate the same sequence of stimulations as in the induced pain condition. Ratings of imagined pain and physically induced pain followed opposite courses over repeated stimulations: Ratings of imagined pain indicated sensitization, whereas ratings for physically induced pain indicated habituation. The findings were similar for minimal and moderate pain intensities. The findings suggest that, rather than habituating to pain, healthy individuals imagine that they would become increasingly sensitive to repeated thermal pain stimuli. This study identified opposite patterns of change in perception of imagined pain (sensitization) and physically induced pain (habituation). The findings show that individuals anticipate that they would become increasingly sensitive to repeated pain stimuli, which might also have clinical implications. �

How diagnostic tests help to disentangle the mechanisms underlying neuropathic pain symptoms in painful neuropathies.

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Truini, Andrea; Cruccu, Giorgio

2016-02-01

Neuropathic pain, ie, pain arising directly from a lesion or disease affecting the somatosensory afferent pathway, manifests with various symptoms, the commonest being ongoing burning pain, electrical shock-like sensations, and dynamic mechanical allodynia. Reliable insights into the mechanisms underlying neuropathic pain symptoms come from diagnostic tests documenting and quantifying somatosensory afferent pathway damage in patients with painful neuropathies. Neurophysiological investigation and skin biopsy studies suggest that ongoing burning pain primarily reflects spontaneous activity in nociceptive-fiber pathways. Electrical shock-like sensations presumably arise from high-frequency ectopic bursts generated in demyelinated, nonnociceptive, Aβ fibers. Although the mechanisms underlying dynamic mechanical allodynia remain debatable, normally innocuous stimuli might cause pain by activating spared and sensitized nociceptive afferents. Extending the mechanistic approach to neuropathic pain symptoms might advance targeted therapy for the individual patient and improve testing for new drugs.

Pain and neuroplasticity

Directory of Open Access Journals (Sweden)

Sabine Sator-Katzenschlager, MD.

2014-07-01

However, the cerebral processing of hyperalgesia and allodynia is still controversially discussed. In recent years, neuroimaging methods (functional magnetic resonance imaging, fMRI; magnetoencephalography, MEG; positron emission tomography, PET have provided new insightsinto the aberrant cerebral processing of neuropathic pain. Thepresent paper reviews different cerebral mechanisms contributing to chronicity processes in neuropathic pain syndromes. These mechanisms include reorganisation of cortical somatotopic maps in sensory or motor areas (highly relevant for phantom limb pain and CRPS, increased activity in primary nociceptive areas, recruitment of new cortical areas usually not activated by nociceptive stimuli and aberrant activity in brain areas normally involved in descending inhibitory pain networks. Moreover, there is evidence from PET studies for changes of excitatory and inhibitory transmitter systems. Finally, advanced methods of structural brain imaging (voxel-based morphometry, VBM show significant structural changes suggesting that chronic pain syndromes may be associated with neurodegeneration.

Pain thresholds, supra-threshold pain and lidocaine sensitivity in patients with erythromelalgia, including the I848Tmutation in NaV 1.7.

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Helås, T; Sagafos, D; Kleggetveit, I P; Quiding, H; Jönsson, B; Segerdahl, M; Zhang, Z; Salter, H; Schmelz, M; Jørum, E

2017-09-01

Nociceptive thresholds and supra-threshold pain ratings as well as their reduction upon local injection with lidocaine were compared between healthy subjects and patients with erythromelalgia (EM). Lidocaine (0.25, 0.50, 1.0 or 10 mg/mL) or placebo (saline) was injected intradermally in non-painful areas of the lower arm, in a randomized, double-blind manner, to test the effect on dynamic and static mechanical sensitivity, mechanical pain sensitivity, thermal thresholds and supra-threshold heat pain sensitivity. Heat pain thresholds and pain ratings to supra-threshold heat stimulation did not differ between EM-patients (n = 27) and controls (n = 25), neither did the dose-response curves for lidocaine. Only the subgroup of EM-patients with mutations in sodium channel subunits Na V 1.7, 1.8 or 1.9 (n = 8) had increased lidocaine sensitivity for supra-threshold heat stimuli, contrasting lower sensitivity to strong mechanical stimuli. This pattern was particularly clear in the two patients carrying the Na V 1.7 I848T mutations in whom lidocaine's hyperalgesic effect on mechanical pain sensitivity contrasted more effective heat analgesia. Heat pain thresholds are not sensitized in EM patients, even in those with gain-of-function mutations in Na V 1.7. Differential lidocaine sensitivity was overt only for noxious stimuli in the supra-threshold range suggesting that sensitized supra-threshold encoding is important for the clinical pain phenotype in EM in addition to lower activation threshold. Intracutaneous lidocaine dose-dependently blocked nociceptive sensations, but we did not identify EM patients with particular high lidocaine sensitivity that could have provided valuable therapeutic guidance. Acute pain thresholds and supra-threshold heat pain in controls and patients with erythromelalgia do not differ and have the same lidocaine sensitivity. Acute heat pain thresholds even in EM patients with the Na V 1.7 I848T mutation are normal and only nociceptor

Fish do not feel pain and its implications for understanding phenomenal consciousness.

Science.gov (United States)

Key, Brian

Phenomenal consciousness or the subjective experience of feeling sensory stimuli is fundamental to human existence. Because of the ubiquity of their subjective experiences, humans seem to readily accept the anthropomorphic extension of these mental states to other animals. Humans will typically extrapolate feelings of pain to animals if they respond physiologically and behaviourally to noxious stimuli. The alternative view that fish instead respond to noxious stimuli reflexly and with a limited behavioural repertoire is defended within the context of our current understanding of the neuroanatomy and neurophysiology of mental states. Consequently, a set of fundamental properties of neural tissue necessary for feeling pain or experiencing affective states in vertebrates is proposed. While mammals and birds possess the prerequisite neural architecture for phenomenal consciousness, it is concluded that fish lack these essential characteristics and hence do not feel pain.

Adverse Weather Evokes Nostalgia.

Science.gov (United States)

van Tilburg, Wijnand A P; Sedikides, Constantine; Wildschut, Tim

2018-03-01

Four studies examined the link between adverse weather and the palliative role of nostalgia. We proposed and tested that (a) adverse weather evokes nostalgia (Hypothesis 1); (b) adverse weather causes distress, which predicts elevated nostalgia (Hypothesis 2); (c) preventing nostalgia exacerbates weather-induced distress (Hypothesis 3); and (d) weather-evoked nostalgia confers psychological benefits (Hypothesis 4). In Study 1, participants listened to recordings of wind, thunder, rain, and neutral sounds. Adverse weather evoked nostalgia. In Study 2, participants kept a 10-day diary recording weather conditions, distress, and nostalgia. We also obtained meteorological data. Adverse weather perceptions were positively correlated with distress, which predicted higher nostalgia. Also, adverse natural weather was associated with corresponding weather perceptions, which predicted elevated nostalgia. (Results were mixed for rain.) In Study 3, preventing nostalgia (via cognitive load) increased weather-evoked distress. In Study 4, weather-evoked nostalgia was positively associated with psychological benefits. The findings pioneer the relevance of nostalgia as source of comfort in adverse weather.

The signaling lipid sphingosine 1-phosphate regulates mechanical pain

Science.gov (United States)

Hill, Rose Z; Hoffman, Benjamin U; Morita, Takeshi; Campos, Stephanie M; Lumpkin, Ellen A; Brem, Rachel B

2018-01-01

Somatosensory neurons mediate responses to diverse mechanical stimuli, from innocuous touch to noxious pain. While recent studies have identified distinct populations of A mechanonociceptors (AMs) that are required for mechanical pain, the molecular underpinnings of mechanonociception remain unknown. Here, we show that the bioactive lipid sphingosine 1-phosphate (S1P) and S1P Receptor 3 (S1PR3) are critical regulators of acute mechanonociception. Genetic or pharmacological ablation of S1PR3, or blockade of S1P production, significantly impaired the behavioral response to noxious mechanical stimuli, with no effect on responses to innocuous touch or thermal stimuli. These effects are mediated by fast-conducting A mechanonociceptors, which displayed a significant decrease in mechanosensitivity in S1PR3 mutant mice. We show that S1PR3 signaling tunes mechanonociceptor excitability via modulation of KCNQ2/3 channels. Our findings define a new role for S1PR3 in regulating neuronal excitability and establish the importance of S1P/S1PR3 signaling in the setting of mechanical pain thresholds. PMID:29561262

Sex dimorphism in a mediatory role of the posterior midcingulate cortex in the association between anxiety and pain sensitivity.

Science.gov (United States)

Kisler, Lee-Bareket; Granovsky, Yelena; Sinai, Alon; Sprecher, Elliot; Shamay-Tsoory, Simone; Weissman-Fogel, Irit

2016-11-01

Behavioral studies found greater pain sensitivity in females that vanishes fully or partially when controlling for the emotional state. Furthermore, pain-related brain activation hints at the role of limbic structures in sex differences in pain processing. We aimed to investigate the role of pain-related limbic structures in mediating the relation between subjects' affective state (i.e., anxiety) and pain. Contact heat-evoked potentials (CHEPs) were recorded in 26 healthy subjects (13 males) simultaneously with innocuous (42 °C) baseline and target noxious (52 °C) series of stimuli administered to the left non-dominant volar forearm. The N2 and P2 components were analyzed, and their generators' activity was estimated using standardized low-resolution brain electromagnetic tomography. Thereafter, structural equation modeling (SEM) was applied separately for females and males, examining the mediatory role of the CHEPs' limbic structures generators [posterior midcingulate cortex (pMCC), insula, amygdala, and hippocampus] in the anxiety-pain sensitivity association. Females exhibited greater P2 amplitudes that were highly associated with larger pMCC activity (r = 0.910, p < 0.001). This correlation was also evident in males, though with less strength (r = 0.578, p = 0.039). Moreover, the P2 amplitudes were associated both in females (r = 0.645, p = 0.017) and males (r = 0.608, p = 0.028) with the activity of the amygdala\\hippocampus\\insula. SEM revealed that the relationship between state anxiety and pain ratings was only in females fully mediated via the effect of the pMCC on the P2 amplitude. These findings suggest that sexual dimorphism in anxiety-related brain activity may explain the differences found in CHEPs and the sex-related association between anxiety and pain.