Behavioral and neuronal investigations of hypervigilance in patients with fibromyalgia syndrome

Attentional deficits in fibromyalgia: an ERP study with the oddball dual task and emotional stroop task

The present study investigated the neural correlates of attentional deficits in fibromyalgia through an Oddball Dual Task and an Emotional Stroop Task, both performed during EEG recordings. Thirty female participants were recruited, being divided into two groups: a group of patients with fibromyalgia (FM, n = 15, Mage = 51.87, SDage = 7.12) and a healthy control group (HC, n = 15, Mage = 46.13, SDage = 8.41). In the Emotional Stroop Task, the behavioural results showed that patients with FM had less hits and longer times reactions than healthy controls. These results were consistent with those obtained with our Event-related Potential (ERP) methodology, which evidenced that patients with FM had higher frontal latencies in the P200 time-window compared to healthy controls. Regarding the Oddball Dual Task, we found that patients with FM had lower P300 amplitudes than healthy participants. Moreover, we found that rare stimuli elicited higher P300 amplitudes than frequent stimuli for healthy controls, but this comparison was non-significant for patients with FM. Taken together, our results suggest that fibromyalgia may be associated to a reduced processing speed, along to reduced neural resources to process stimuli, mainly in distinguishing relevant (rare) and irrelevant (frequent) stimuli according to the goals of the task. Altogether, our results seem to support the hypothesis of generalized attentional deficits in FM.

Neurophysiological and Psychosocial Mechanisms of Fibromyalgia: A Comprehensive Review and Call for An Integrative Model

Research into the neurobiological and psychosocial mechanisms involved in fibromyalgia has progressed remarkably in recent years. Despite this, current accounts of fibromyalgia fail to capture the complex, dynamic, and mutual crosstalk between neurophysiological and psychosocial domains. We conducted a comprehensive review of the existing literature in order to: a) synthesize current knowledge on fibromyalgia; b) explore and highlight multi-level links and pathways between different systems; and c) build bridges connecting disparate perspectives. An extensive panel of international experts in neurophysiological and psychosocial aspects of fibromyalgia discussed the collected evidence and progressively refined and conceptualized its interpretation. This work constitutes an essential step towards the development of a model capable of integrating the main factors implicated in fibromyalgia into a single, unified construct which appears indispensable to foster the understanding, assessment, and intervention for fibromyalgia.

Gamma-band oscillations of pain and nociception: A systematic review and meta-analysis of human and rodent studies

Pain-induced gamma-band oscillations (GBOs) are one of the most promising biomarkers of the pain experience. Although GBOs reliably encode pain perception across different individuals and species, considerable heterogeneity could be observed in the characteristics and functions of GBOs. However, such heterogeneity of GBOs and its underlying sources have rarely been detailed previously. Here, we conducted a systematic review and meta-analysis to characterize the temporal, frequential, and spatial characteristics of GBOs and summarize the functional significance of distinct GBOs. We found that GBO heterogeneity was mainly related to pain types, with a higher frequency (∼66 Hz) GBOs at the sensorimotor cortex elicited by phasic pain and a lower frequency (∼55 Hz) GBOs at the prefrontal cortex associated with tonic and chronic pains. Positive correlations between GBO magnitudes and pain intensity were observed in healthy participants. Notably, the characteristics and functions of GBOs seemed to be phylogenetically conserved across humans and rodents. Altogether, we provided a comprehensive description of heterogeneous GBOs in pain and nociception, laying the foundation for clinical applications of GBOs.

Neural correlates of the attentional bias towards pain-related faces in fibromyalgia patients: An ERP study using a dot-probe task

BACKGROUND

One of the major cognitive deficits in fibromyalgia has been linked to the hypervigilance phenomenon. It is mainly reflected as a negative bias for allocating attentional resources towards both threatening and pain-related information. Although the interest in its study has recently grown, the neural temporal dynamics of the attentional bias in fibromyalgia still remains an open question.

METHOD

Fifty participants (25 fibromyalgia patients and 25 healthy control subjects) performed a dot-probe task. Two types of facial expressions (pain-related and neutral) were employed as signal stimuli. Then, as a target stimulus, a single dot replaced the location of one of these two faces. Event-related potentials (ERP) in response to facial expressions and target stimulation (i.e., dot) were recorded. Reaction time (RT) and accuracy measures in the experimental task were collected as behavioural outcomes.

RESULTS

Temporal dynamics of brain electrical activity were analysed on two ERP components (P2 and N2a) sensitive to the facial expressions meaning. Pain-related faces elicited higher frontal P2 amplitudes than neutral faces for the whole sample. Interestingly, an interaction effect between group and facial expressions was also found showing that pain-related faces elicited enhanced P2 amplitudes (at fronto-central regions, in this case) compared to neutral faces only when the group of patients was considered. Furthermore, higher P2 amplitudes were observed in response to pain-related faces in patients with fibromyalgia compared to healthy control participants. Additionally, a shorter latency of P2 (at centro-parietal regions) was also detected for pain-related facial expressions compared to neutral faces. Regarding the amplitude of N2a, it was lower for patients as compared to the control group. Non-relevant effects of the target stimulation on the ERPs were found. However, patients with fibromyalgia exhibited slower RT to locate the single dot for incongruent trials as compared to congruent and neutral trials.

CONCLUSIONS

Data suggest the presence of an attentional bias in fibromyalgia that it would be followed by a deficit in the allocation of attentional resources to further process pain-related information. Altogether the current results suggest that attentional biases in fibromyalgia might be explained by automatic attentional mechanisms, which seem to be accompanied by an alteration of more strategic or controlled attentional components.

Are You Listening? Facilitation of the Auditory Blink Response in People with Fibromyalgia

The purpose of the current study was to determine whether auditory prepulse inhibition (PPI) and/or prepulse facilitation (PPF) were altered in people with fibromyalgia (FM) when compared with controls. Eyeblink responses were recorded from 29 females with FM and 27 controls, while they listened to 3 blocks of auditory stimuli that delivered pulses with either PPI or PPF. Using a linear mixed model, our main findings were that there was a GROUP*CONDITION interaction (F4, 1084 = 4.01, P= .0031) indicating that the difference in amplitude between FM group and control group changed depending on the condition (PPI or PPF). Post hoc tests revealed no differences between the groups in response to PPI. The FM group showed a greater reactivity of response to the PPF conditioned stimulus than the control group did (t(39.7) = 2.03, P= .0494). Augmentation of PPF, as demonstrated by the FM group is thought to be linked to alterations in information processing mediated by an autonomically driven general orienting process. Activities that decrease autonomic drive or rebalance autonomic and parasympathetic tone such as vagal stimulation might be pursued as effective interventions for people with FM. PERSPECTIVE: This article presents evidence of preservation of neural circuitry that underpins response suppression and evidence of neural circuit disturbance mediated by autonomic drive-in people with FM. These results are important because intact circuitry underpins the effectiveness of therapies and may be harnessed, and rebalancing autonomic drive may be indicated.

Virtual Reality-Guided Meditation for Chronic Pain in Patients With Cancer: Exploratory Analysis of Electroencephalograph Activity

BACKGROUND

Mindfulness-based stress reduction has demonstrated some efficacy for chronic pain management. More recently, virtual reality (VR)-guided meditation has been used to assist mindfulness-based stress reduction. Although studies have also found electroencephalograph (EEG) changes in the brain during mindfulness meditation practices, such changes have not been demonstrated during VR-guided meditation.

OBJECTIVE

This exploratory study is designed to explore the potential for recording and analyzing EEG during VR experiences in terms of the power of EEG waveforms, topographic mapping, and coherence. We examine how these measures changed during a VR-guided meditation experience in participants with cancer-related chronic pain.

METHODS

A total of 10 adult patients with chronic cancer pain underwent a VR-guided meditation experience while EEG signals were recorded during the session using a BioSemi ActiveTwo system (64 channels, standard 10-20 configuration). The EEG recording session consisted of an 8-minute resting condition (pre), a 30-minute sequence of 3 VR-guided meditation conditions (med), and a final rest condition (post). Power spectral density (PSD) was compared between each condition using a cluster-based permutation test and across conditions using multivariate analysis of variance. A topographic analysis, including coherence exploration, was performed. In addition, an exploratory repeated measures correlation was used to examine possible associations between pain scores and EEG signal power.

RESULTS

The predominant pattern was for increased β and γ bandwidth power in the meditation condition (P<.025), compared with both the baseline and postexperience conditions. Increased power in the δ bandwidth was evident, although not statistically significant. The pre versus post comparison also showed changes in the θ and α bands (P=.02) located around the frontal, central, and parietal cortices. Across conditions, multivariate analysis of variance tests identified 4 clusters with significant (P<.05) PSD differences in the δ, θ, β, and γ bands located around the frontal, central, and parietal cortices. Topographically, 5 peak channels were identified: AF7, FP2, FC1, CP5, and P5, and verified the changes in power in the different brain regions. Coherence changes were observed primarily between the frontal, parietal, and occipital regions in the θ, α, and γ bands (P<.0025). No significant associations were observed between pain scores and EEG PSD.

CONCLUSIONS

This study demonstrates the feasibility of EEG recording in exploring neurophysiological changes in brain activity during VR-guided meditation and its effect on pain reduction. These findings suggest that distinct altered neurophysiological brain signals are detectable during VR-guided meditation. However, these changes were not necessarily associated with pain. These exploratory findings may guide further studies to investigate the highlighted regions and EEG bands with respect to VR-guided meditation.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00102401; http://clinicaltrials.gov/ct2/show/NCT00102401.

Sleep spindles as a diagnostic and therapeutic target for chronic pain

Pain is known to disrupt sleep patterns, and disturbances in sleep can further worsen pain symptoms. Sleep spindles occur during slow wave sleep and have established effects on sensory and affective processing in mammals. A number of chronic neuropsychiatric conditions, meanwhile, are known to alter sleep spindle density. The effect of persistent pain on sleep spindle waves, however, remains unknown, and studies of sleep spindles are challenging due to long period of monitoring and data analysis. Utilizing automated sleep spindle detection algorithms built on deep learning, we can monitor the effect of pain states on sleep spindle activity. In this study, we show that in a chronic pain model in rodents, there is a significant decrease in sleep spindle activity compared to controls. Meanwhile, methods to restore sleep spindles are associated with decreased pain symptoms. These results suggest that sleep spindle density correlates with chronic pain and may be both a potential biomarker for chronic pain and a target for neuromodulation therapy.

Attentional bias to somatosensory stimuli in chronic pain patients: a systematic review and meta-analysis

ABSTRACT

This systematic review and meta-analysis aimed to evaluate the evidence pertaining to attentional bias for painful and nonpainful somatosensory stimuli in individuals with chronic pain. Eligible studies were identified through searches of Medline, PsycINFO, CINAHL, Web of Science, Scopus, and Cochrane Library databases. Search terms were words and phrases organised into 3 concept blocks: pain condition, cognitive process, and stimuli/paradigm. The search identified 29 eligible studies (reporting 32 eligible experiments), of which quantitative meta-analysis was possible for 16 studies (19 experiments). The meta-analysis found that chronic pain patients, excluding somatoform pain patients, showed significantly greater attentional bias to stimuli in the somatosensory modality than healthy controls (k = 9, g = 0.34). In addition, meta-analysis of studies that used a temporal order judgement task found that patients with unilateral chronic pain showed a spatial attentional bias away from somatosensory stimuli (k = 7, effect estimate = 22.43 ms) and visual stimuli (k = 2, effect estimate = 13.75 ms) on or near the painful body side. Most studies of attentional bias to the somatosensory modality recruited samples of patients with fibromyalgia, whereas most studies of spatial attentional bias assessed patients with complex regional pain syndrome. The extent to which these results generalise to other pain conditions is therefore unclear. We recommend future research test spatial and modality attentional biases across chronic pain conditions and examine the psychometric properties of attentional bias measurement paradigms for use with chronic pain populations. PROSPERO registration number CRD42019124510.

Comparison of two tDCS protocols on pain and EEG alpha-2 oscillations in women with fibromyalgia

Transcranial Direct Current Stimulation (tDCS) has been used as an alternative treatment for pain reduction in fibromyalgia. In this study, in addition to behavioral measures, we analyzed oscillations in alpha 2 frequency band in the frontal, occipital, and parietal regions, in response to the application of two neuromodulation protocols in fibromyalgia. The study was a randomized, double-blind, placebo-controlled clinical trial with 31 women diagnosed with fibromyalgia. The participants were allocated to three groups with the anodic stimulation applied on the left motor cortex: Group 1, for five consecutive days; Group 2, for 10 consecutive days; and Group 3, sham stimulation for five consecutive days. Statistical analysis showed a reduction in pain intensity after treatment for groups in general [F (1.28) = 8.02; p = 0.008; η2 = 0.223], in addition to a reduction in alpha 2 in the frontal (p = 0.039; d = 0.384) and parietal (p = 0.021; d = 0.520) regions after the treatment on five consecutive days. We conclude that neuromodulation protocols produced similar effects on pain reduction, but differed with respect to the changes in the alpha 2 frequency band in the frontal and parietal regions.

Bildgebende Untersuchungen des neuronalen Schmerznetzwerks

Der vorliegende Artikel soll eine Übersicht über bildgebende Untersuchungen im Bereich chronischer Schmerzsyndrome bieten. Auf die einleitenden Worte zur allgemeinen Phänomenologie des Schmerzes folgt ein umfassender Einblick in die gegenwärtige Anwendung funktioneller und struktureller Bildgebungstechniken am Beispiel ausgewählter Schmerzsyndrome (Chronischer Rückenschmerz, Fibromyalgiesyndrom (FMS), Phantomschmerz und Komplexes regionales Schmerzsyndrom (CRPS)). In diesem Zusammenhang werden Gemeinsamkeiten und Besonderheiten der spezifischen neurologischen Korrelate verschiedener chronischer Schmerzerkrankungen diskutiert.

Hypervigilance for Bodily Sensations in the Back During a Movement Task in People With Chronic and Recurrent Low Back Pain

OBJECTIVES

The current study assessed the role of hypervigilance for bodily sensations in the back in long-term low back pain problems.

METHODS

People with chronic low back pain, recurrent low back pain, and no low back pain were compared on the extent to which they attended to somatosensory stimuli on the back during a movement task. To measure hypervigilance, somatosensory event-related potentials (SEPs) to task-irrelevant tactile stimuli on the back were measured when preparing movements in either a threatening or a neutral condition, indicated by a cue signaling possible pain on the back during movement or not.

RESULTS

Results showed stronger attending to stimuli on the back in the threat condition than in the neutral condition, as reflected by increased amplitude of the N96 SEP. However, this effect did not differ between groups. Similarly, for all 3 groups the amplitude of the P172 was larger for the threatening condition, suggesting a more general state of arousal resulting in increased somatosensory responsiveness. No significant associations were found between somatosensory attending to the back and theorized antecedents such as pain catastrophizing, pain-related fear, and pain vigilance.

DISCUSSION

The current study confirmed that individuals preparing a movement attended more toward somatosensory stimuli at the lower back when anticipating back pain during the movement, as measured by the N96 SEP. However, no differences were found between participants with chronic low back pain or recurrent low back pain, or the pain-free controls.

Neuroimaging the pain network - Implications for treatment

In this chapter, we provide an overview of neuroimaging studies in chronic pain. We start with an introduction about the phenomenology of pain. In the following section, the application of functional and structural imaging techniques is shown in selected chronic pain syndromes (chronic back pain, fibromyalgia syndrome (FMS), phantom limb pain, and complex regional pain syndrome (CRPS)), and commonalities and peculiarities of imaging correlates across different types of chronic pain are discussed. We conclude this chapter with implications for treatments, with focus on behavioral interventions, sensory and motor trainings, and mirror and motor imagery trainings.

Subliminal emotional pictures are capable of modulating early cerebral responses to pain in fibromyalgia

Pain experience involves a complex relationship between sensory and both emotional and cognitive factors, which appear to be mediated by different neural pathways. Previous evidence has shown that whereas conscious processing of unpleasant stimuli enhances pain perception, the influence of emotions on pain under unaware conditions is much less known. The need to better characterise the relationship between pain processing and emotional factors is crucial for dealing with chronic pain conditions. Therefore, the present study aimed to explore the neural correlates relating to the influence of visual masking emotional stimulation on the processing of painful stimuli in chronic pain patients suffering from fibromyalgia (FM). Twenty FM and 22 healthy control (HC) women participated in the study. The experimental masking paradigm consisted of a rapid succession of two types of stimuli, where a masked picture (neutral, negative or pain-related) was followed by a laser stimulus (painful or not painful). LEP activity was recorded at sixty scalp electrodes. An LEP-amplitude approach was used to quantify the main cerebral waves linked to pain response. ANOVAs indicated that the posterior regions of the P1 component were sensitive to experimental manipulation (p<0.05). Specifically, FM patients showed higher amplitudes to painful stimuli preceded by pain-related pictures compared with painful trials preceded by other emotional pictures. The FM group also showed greater amplitudes than those in the HC group in P2a and P2b waves. In addition to the scalp data, at the neural level the posterior cingulate cortex, lingual gyrus and insular cortex showed higher activation in the FM group than in the HC group. Our findings show an early cerebral modulation of pain (as reflected by the P1) in FM patients, suggesting that only pain-related information, even when it is unconsciously perceived, is capable to enhance exogenous (automatic) attention, increasing the neural activity involved in processing painful stimulation. Further research is needed to fully understand unconscious emotional influences on pain in fibromyalgia.

Gamma oscillations in somatosensory cortex recruit prefrontal and descending serotonergic pathways in aversion and nociception

In humans, gamma-band oscillations in the primary somatosensory cortex (S1) correlate with subjective pain perception. However, functional contributions to pain and the nature of underlying circuits are unclear. Here we report that gamma oscillations, but not other rhythms, are specifically strengthened independently of any motor component in the S1 cortex of mice during nociception. Moreover, mice with inflammatory pain show elevated resting gamma and alpha activity and increased gamma power in response to sub-threshold stimuli, in association with behavioral nociceptive hypersensitivity. Inducing gamma oscillations via optogenetic activation of parvalbumin-expressing inhibitory interneurons in the S1 cortex enhances nociceptive sensitivity and induces aversive avoidance behavior. Activity mapping identified a network of prefrontal cortical and subcortical centers whilst morphological tracing and pharmacological studies demonstrate the requirement of descending serotonergic facilitatory pathways in these pain-related behaviors. This study thus describes a mechanistic framework for modulation of pain by specific activity patterns in the S1 cortex.

Gamma oscillations in somatosensory areas in humans correlate with pain perception and pain stimulus intensity, but could also reflect cognitive processes such as attention. Here the authors provide evidence in mice that these oscillations causally contribute to pain perception.

Positive symptoms and time perception in schizophrenia: A meta-analysis

Positive symptoms of schizophrenia may be related to distortions in time perception. To examine this issue, we conducted a meta-analysis to determine whether positive symptoms are associated with deficits in time processing performance. MEDLINE and Web of Science were searched from January 1980 through March 2017, and all related articles and their references were scrutinized to find relevant studies. Studies were selected if they included participants with a diagnosis of schizophrenia, and reported data from behavioral measures of interval timing (e.g. duration discrimination and temporal order judgement). The results indicated that positive symptoms of schizophrenia are related with overestimation of interval timing (i.e., acceleration of the “internal clock”), and suggest that time perception may be associated with psychosis.

Generalized hypervigilance in fibromyalgia: Normal interoceptive accuracy, but reduced self-regulatory capacity

OBJECTIVE

The factors underlying the aetiology of fibromyalgia (FM) are largely unknown. According to the generalized hypervigilance hypothesis (GHH), FM patients show excessive attention towards pain stimuli and other sensory events, thereby increasing pain perception and dysfunctional behaviour. We tested this notion by assessing interoceptive accuracy (IA) in FM patients and matched healthy controls. We also tested the hypothesis that FM is characterized by reduced self-regulatory capacity as indexed by heart rate variability (HRV).

METHODS

47 FM patients (M_age=45.5, 39 females) and 45 healthy controls (M_age=44.9, 37 females) completed several self-report scales (Body Vigilance Scale, Depression Anxiety Stress Scales, Pain Catastrophizing Scale). To derive HRV, heart rate was monitored under resting conditions; for the assessment of IA participants performed a heartbeat tracking task in which they were asked to silently count their heartbeats.

RESULTS

FM patients reported higher body vigilance than healthy controls, but there were no group differences in IA. FM patients had lower HRV compared with healthy controls. HRV did not predictor IA.

CONCLUSION

In conclusion, our findings do not support the hypothesis of generalized hypervigilance in FM patients. Patients reported a heightened focus on bodily sensations, which was not reflected in IA. It may be that hypervigilance is not a general and stable characteristic but is rather context dependent and modality-specific.

Experimental hypervigilance changes the intensity/unpleasantness ratio of pressure sensations: evidence for the generalized hypervigilance hypothesis

Patients with chronic pain conditions such as fibromyalgia often demonstrate hypervigilance-undue alertness for unpleasant or threatening bodily sensations-as well as enhancement of these sensations. The generalized hypervigilance hypothesis (GHH) of Rollman and colleagues asserts that hypervigilance leads to this perceptual amplification. However, cause-and-effect relationships are difficult to establish in studies using a quasi-experimental design. In the present study, we sought to address this issue by attempting to induce hypervigilance experimentally, in one of two groups to which young, healthy adults had been randomly assigned. Those in the experimental group wrote about the flu and practiced counting their own blinks, breaths, and heartbeats; those in the control group wrote about a neutral topic and counted innocuous lights and sounds. Next, both groups rated the intensity and unpleasantness of pressure sensations (ranging from mild to painful) caused by a series of applications of a weighted rod to the forearm. The intensity/unpleasantness ratio of these ratings was significantly greater in the experimental group, suggesting that induced hypervigilance had caused perceptual amplification that generalized to pressure sensations, which had not been part of the experimental manipulation. Psychometric measures of anxiety and catastrophizing were equivalent in the two groups, indicating that the experimental manipulation operated via attentional rather than emotional changes. The results support the GHH.

Top-down and bottom-up modulation of pain-induced oscillations

Attention is an important factor that is able to strongly modulate the experience of pain. In order to differentiate cortical mechanisms underlying subject-driven (i.e., top-down) and stimulus-driven (bottom-up) modes of attentional pain modulation, we recorded electric brain activity in healthy volunteers during painful laser stimulation while spatial attention and stimulus intensity were systematically varied. The subjects’ task was to evaluate the pain intensity at the attended finger, while ignoring laser stimuli delivered to the other finger. Top-down (attention) and bottom up (intensity) influences differed in their effects on oscillatory response components. Attention towards pain induced a decrease in alpha and an increase in gamma band power, localized in the insula. Pain intensity modulated delta, alpha, beta and gamma band power. Source localization revealed stimulus driven modulation in the cingulate gyrus (CG) and somatosensory areas for gamma power changes. Our results indicate that bottom-up and top-down modes of processing exert different effects on pain-induced slow and fast oscillatory activities. Future studies may examine pain-induced oscillations using this paradigm to test for altered attentional pain control in patients with chronic pain.

Laser-Evoked Potentials in Fibromyalgia: The Influence of Greater Occipital Nerve Stimulation on Cerebral Pain Processing

OBJECTIVE

Fibromyalgia causes widespread musculo-skeletal pain in the four quadrants of the body. Greater occipital nerve stimulation has recently shown beneficial effects in fibromyalgia patients on pain, fatigue, and mood disorders. Laser-evoked potentials (LEPs) are used for research to understand the pathophysiological mechanisms of pain and to evaluate the effects of pain treatment. In fibromyalgia patients, LEPs tend to have a higher N2 amplitude, a tendency to shorter latencies, and patients have a lower pain threshold. Greater occipital nerve stimulation might exert a modulation of the medial pain pathways processing the affective motivational components of pain (unpleasantness) as well as the descending pain inhibitory pathways (reducing pain), both of which are contributing to the N2P2 peak.

MATERIALS AND METHODS

To test this hypothesis, the authors performed LEPs in a group of fibromyalgia patients with and without greater occipital nerve stimulation.

RESULTS

Occipital nerve stimulation does not alter the amplitudes of the LEP recordings, although a significant difference in latencies can be seen. More specifically, latencies of the N2P2 increased in the condition after stimulation, and especially at the Pz electrode.

CONCLUSION

Our results suggest Occipital Nerve Stimulation (ONS) induces a modification of the balance between antinociceptive pain inhibitory pathways and pain-provoking pathways.

Phasic and tonic pain differentially impact the interruptive function of pain

The interruptive effect of painful experimental stimulation on cognitive processes is a well-known phenomenon. This study investigated the influence of pain duration on the negative effects of pain on cognition. Thirty-four healthy volunteers performed a rapid serial visual presentation task (RSVP) in which subjects had to detect (visual detection task) and count the occurrence of a target letter (working memory task) in two separate sessions while being stimulated on the left volar forearm with either short (2 sec) or long (18 sec) painful heat stimuli of equal subjective intensity. The results show that subjects performed significantly worse in the long pain session as indexed by decreased detection and counting performance. Interestingly, this effect on performance was also observed during control trials of the long pain session in which participants did not receive any painful stimulation. Moreover, subjects expected long painful stimulation to have a greater impact on their performance and individual expectation correlated with working memory performance. These findings suggest that not only the length of painful stimulation but also its expected ability to impair cognitive functioning might influence the interruptive function of pain. The exact relevance of expectation for the detrimental effects of pain on cognitive processes needs to be explored in more detail in future studies.

Dopamine precursor depletion influences pain affect rather than pain sensation

Pain is a multidimensional experience, which includes sensory, cognitive, and affective aspects. Converging lines of evidence indicate that dopaminergic neurotransmission plays an important role in human pain perception. However, the precise effects of dopamine on different aspects of pain perception remain to be elucidated. To address this question, we experimentally decreased dopaminergic neurotransmission in 22 healthy human subjects using Acute Phenylalanine and Tyrosine Depletion (APTD). During APTD and a control condition we applied brief painful laser stimuli to the hand, assessed different aspects of pain perception, and recorded electroencephalographic responses. APTD-induced decreases of cerebral dopaminergic activity did not influence sensory aspects of pain perception. In contrast, APTD yielded increases of pain unpleasantness. The increases of unpleasantness ratings positively correlated with effectiveness of APTD. Our finding of an influence of dopaminergic neurotransmission on affective but not sensory aspects of phasic pain suggests that analgesic effects of dopamine might be mediated by indirect effects on pain affect rather than by direct effects on ascending nociceptive signals. These findings contribute to our understanding of the complex relationship between dopamine and pain perception, which may play a role in various clinical pain states.

Cognitive and emotional control of pain and its disruption in chronic pain

Chronic pain is one of the most prevalent health problems in our modern world, with millions of people debilitated by conditions such as back pain, headache and arthritis. To address this growing problem, many people are turning to mind-body therapies, including meditation, yoga and cognitive behavioural therapy. This article will review the neural mechanisms underlying the modulation of pain by cognitive and emotional states - important components of mind-body therapies. It will also examine the accumulating evidence that chronic pain itself alters brain circuitry, including that involved in endogenous pain control, suggesting that controlling pain becomes increasingly difficult as pain becomes chronic.