Altered Psychophysiological Responses to the View of Others' Pain and Anger Faces in Fibromyalgia Patients

Measurement of event-related potentials from electroencephalography to evaluate emotional processing in Fibromyalgia Syndrome: A systematic review and meta-analysis

OBJECTIVE

The present systematic review and meta-analysis intended to: 1) determine the extent of abnormalities in emotional processing linked to emotional event-related potentials (ERPs) in Fibromyalgia Syndrome (FMS) and 2) integrate data from similar emotional tasks into a meta-analysis to clearly demonstrate the scientific and clinical value of measuring emotional ERPs by electroencephalography (EEG) in FMS.

METHODS

A systematic review and meta-analysis of studies comparing emotional processing indicated by ERPs in FMS patients and healthy controls was conducted. Fifteen articles were included in the systematic review after applying the eligibility criteria.

RESULTS

Nine articles demonstrated disturbances in emotional processing in FMS. These emotional disturbances were distributed over the whole range of ERP latencies, mainly over central, parietal, temporal and occipital areas. Despite of this, quantitative analysis revealed only significant differences in N250 and LPP/LPC between FMS patients and healthy controls, with smaller LPP/LPC and greater N250 seen in FMS.

DISCUSSION

N250 and LPP/LPC seem to be the ERPs with the greatest potential to determine emotional alterations in FMS. These ERPs are related to complex cognitive processes such as decoding features relevant to affect recognition (N250) as well differentiation between emotions, persistent engagement, conflict resolution or evaluation of emotional intensity (LPC/LPP). However, differences in task setup had an important impact on the variation of ERP outcomes. Systematization of protocols and tasks is indispensable for future studies.

Alpha-band oscillations and emotion: A review of studies on picture perception

Although alpha-band activity has long been a focus of psychophysiological research, its modulation by emotional value during picture perception has only recently been studied systematically. Here, we review these studies and report that the most consistent alpha oscillatory pattern indexing emotional processing is an enhanced desynchronization (ERD) over posterior sensors when viewing emotional compared with neutral pictures. This enhanced alpha ERD is not specific to unpleasant picture content, as previously proposed for other measures of affective response, but has also been observed for pleasant stimuli. Evidence suggests that this effect is not confined to the alpha band but that it also involves a desynchronization of the lower beta frequencies (8-20 Hz). The emotional modulation of alpha ERD occurs even after massive stimulus repetition and when emotional cues serve as task-irrelevant distractors, consistent with the hypothesis that evaluative processes are mandatory in emotional picture processing. A similar enhanced ERD has been observed for other significant cues (e.g., conditioned aversive stimuli, or in anticipation of a potential threat), suggesting that it reflects cortical excitability associated with the engagement of the motivational systems.

Pain and related suffering reduce attention toward others

BACKGROUND

It has been proposed that the expression of pain-related suffering may lead to an enhanced focus on oneself and reduced attention toward the external world. This study aimed at investigating whether experimentally induced painrelated suffering may lead persons to withdraw into themselves, causing a reduced focus on external stimuli as reflected by impaired performance in a facial recognition task and heightened perception of internal stimuli measured by interoceptive awareness.

METHODS

Thirty-two participants had to recognize different emotional facial expressions (neutral, sad, angry, happy), or neutral geometrical figures under conditions of no pain, low, and high prolonged pain intensities. Interoceptive accuracy was measured using a heartbeat-detection task prior to and following the pain protocol.

RESULTS

Males but not females were slower to recognize facial expressions under the condition of high painful stimulation compared to the condition of no pain. In both, male and female participants, the difficulty in recognizing another person's emotions from a facial expression was directly related to the level of suffering and unpleasantness experienced during pain. Interoceptive accuracy was higher after the pain experiment. However, neither the initial interoceptive accuracy nor the change were significantly related to the pain ratings.

CONCLUSIONS

Our results suggest that long-lasting and intense painful stimuli, which induce suffering, lead to attentional shifts leading to withdrawal from others. These findings contribute to a better understanding of the social dynamics of pain and pain-related suffering.

Pain E-motion Faces Database (PEMF): Pain-related micro-clips for emotion research

A large number of publications have focused on the study of pain expressions. Despite the growing knowledge, the availability of pain-related face databases is still very scarce compared with other emotional facial expressions. The Pain E-Motion Faces Database (PEMF) is a new open-access database currently consisting of 272 micro-clips of 68 different identities. Each model displays one neutral expression and three pain-related facial expressions: posed, spontaneous-algometer and spontaneous-CO2 laser. Normative ratings of pain intensity, valence and arousal were provided by students of three different European universities. Six independent coders carried out a coding process on the facial stimuli based on the Facial Action Coding System (FACS), in which ratings of intensity of pain, valence and arousal were computed for each type of facial expression. Gender and age effects of models across each type of micro-clip were also analysed. Additionally, participants' ability to discriminate the veracity of pain-related facial expressions (i.e., spontaneous vs posed) was explored. Finally, a series of ANOVAs were carried out to test the presence of other basic emotions and common facial action unit (AU) patterns. The main results revealed that posed facial expressions received higher ratings of pain intensity, more negative valence and higher arousal compared with spontaneous pain-related and neutral faces. No differential effects of model gender were found. Participants were unable to accurately discriminate whether a given pain-related face represented spontaneous or posed pain. PEMF thus constitutes a large open-source and reliable set of dynamic pain expressions useful for designing experimental studies focused on pain processes.

Altered recognition of fearful and angry facial expressions in women with fibromyalgia syndrome: an experimental case-control study

Evidence relative to facial emotion recognition and the role played by alexithymia in fibromyalgia syndrome is rare and heterogeneous. In this work, we investigated this ability in fibromyalgia investigating the implicit behaviour in the facial emotion recognition task, focusing on fear and anger. Twenty women with fibromyalgia and twenty healthy women as controls performed a facial emotion recognition of fearful and angry expressions. Their implicit behaviour was scored in accordance with the redundant target effect. The level of alexithymic traits through a standard psychological questionnaire and its effect on behavioral performance were also assessed. Participants affected by fibromyalgia reported a lower level of accuracy in recognizing fearful and angry expressions, in comparison with the controls. Crucially, such a difference was not explained by the different levels of alexithymic traits between groups. Our results agreed with some previous evidence suggesting an altered recognition of others' emotional facial expressions in fibromyalgia syndrome. Considering the role of emotion recognition on social cognition and psychological well-being in fibromyalgia, we underlined the crucial role of emotional difficulties in the onset and maintenance of the symptoms life-span.

Electrophysiological indices of pain expectation abnormalities in fibromyalgia patients

Fibromyalgia is a chronic pain syndrome characterized by dysfunctional processing of nociceptive stimulation. Neuroimaging studies have pointed out that pain-related network functioning seems to be altered in these patients. It is thought that this clinical symptomatology may be maintained or even strengthened because of an enhanced expectancy for painful stimuli or its forthcoming appearance. However, neural electrophysiological correlates associated with such attentional mechanisms have been scarcely explored. In the current study, expectancy processes of upcoming laser stimulation (painful and non-painful) and its further processing were explored by event-related potentials (ERPs). Nineteen fibromyalgia patients and twenty healthy control volunteers took part in the experiment. Behavioral measures (reaction times and subjective pain perception) were also collected. We manipulated the pain/no pain expectancy through an S1–S2 paradigm (cue-target). S1 (image: triangle or square) predicted the S2 appearance (laser stimulation: warmth or pinprick sensation). Laser stimuli were delivered using a CO₂ laser device. Temporal and spatial principal component analyses were employed to define and quantify the ERP component reliability. Statistical analyses revealed the existence of an abnormal pattern of pain expectancy in patients with fibromyalgia. Specifically, our results showed attenuated amplitudes at posterior lCNV component in anticipation of painful stimulation that was not found in healthy participants. In contrast, although larger P2 amplitudes to painful compared to innocuous events were shown, patients did not show any amplitude change in this laser-evoked response as a function of pain predictive cues (as occurred in the healthy control group). Additionally, analyses of the subjective perception of pain and reaction time indicated that laser stimuli preceded by pain cues were rated as more painful than those signaling non-pain expectancy and were associated with faster responses. Differences between groups were not found. The present findings suggest the presence of dysfunction in pain expectation mechanisms in fibromyalgia that eventually may make it difficult for patients to correctly interpret signs that prevent pain symptoms. Furthermore, the abnormal pattern in pain expectancy displayed by fibromyalgia patients could result in ineffective pain coping strategies. Understanding the neural correlates of pain processing and its modulatory factors is crucial to identify treatments for chronic pain syndromes.

Central nervous activity during an emotional Stroop task in fibromyalgia syndrome

Fibromyalgia syndrome (FMS) is a chronic condition of widespread pain accompanied by symptoms like depression, fatigue and cognitive impairments. In addition to central nervous pain sensitization, emotional dysregulation may be involved in FMS pathogenesis. This study investigated emotional influences on cognitive processing in FMS. Event-related potentials and theta oscillations were recorded during an emotional Stroop task including positive, negative, and neutral adjectives in 36 FMS patients and 35 controls. Patients had larger P3 amplitudes and greater theta power than controls, independent of the emotional word content. In patients, but not controls, negative words were associated with a larger late positive component (LPC) amplitude than positive words. No group difference was seen for P1, early posterior negativity or N4. Reaction times (RTs) were longer in patients than controls, independent of emotional word content. The P3 and theta oscillation findings suggest greater cognitive effort and attentional mobilization in FMS, which is needed to overcome the reduction of attentional resources resulting from central nervous pain sensitization. Although RTs do not support attentional bias in FMS, emotional modulation of the LPC amplitude may reflect preferential central nervous processing of negative information, which could contribute to pain and affective symptoms characterizing FMS. ACCESS TO RESEARCH DATA: The research data of the study are available to the public via the Open Science Framework repository (OSF: https://osf.io/tsyre/).

Chronic neuropathic pain is more than a perception: Systems and methods for an integral characterization

The management of chronic neuropathic pain remains a challenge, because pain is subjective, and measuring it objectively is usually out of question. However, neuropathic pain is also a signal provided by maladaptive neuronal activity. Thus, the integral management of chronic neuropathic pain should not only rely on the subjective perception of the patient, but also on objective data that measures the evolution of neuronal activity. We will discuss different objective and subjective methods for the characterization of neuropathic pain. Additionally, the gaps and proposals for an integral management of chronic neuropathic pain will also be discussed. The current management that relies mostly on subjective measures has not been sufficient, therefore, this has hindered advances in pain management and clinical trials. If an integral characterization is achieved, clinical management and stratification for clinical trials could be based on both questionnaires and neuronal activity. Appropriate characterization may lead to an increased effectiveness for new therapies, and a better quality of life for neuropathic pain sufferers.

Altered electromyographic responses to emotional and pain information in awake bruxers: case-control study

OBJECTIVES

This study aims to investigate how emotional information and pain-related information affect the activity of the masticatory muscles in participants with awake bruxism and controls.

MATERIAL AND METHODS

Different videos and texts, with positive, negative, and neutral valence or related to pain, were presented to a sample of university students, while their electromyographic (EMG) activity around the masseter muscle and their skin conductance were recorded. Two groups were selected, with 24 subjects each: one group of subjects with definitive awake bruxism (confirmed by posterior EMG activity) who also suffered from moderate jaw discomfort, and another group of subjects without bruxism.

RESULTS

The results demonstrated that the subjects with definitive awake bruxism displayed greater muscular activity when presented videos and texts with negative valence, especially when related to pain, than the non-bruxist group.

CONCLUSIONS

This study supports the idea that persons with bruxism who also suffer moderate levels of jaw discomfort present greater bruxism activity when watching pain-related stimuli, and to a lesser extent when watching negative stimuli.

CLINICAL RELEVANCE

The increased muscular activity induced by negative and pain-related information might contribute to pain exacerbation and perpetuation in persons with bruxism who suffer from discomfort.

The Link between Fibromyalgia Syndrome and Anger: A Systematic Review Revealing Research Gaps

Anger has been associated with increased pain perception, but its specific connection with Fibromyalgia Syndrome (FMS) has not yet been established in an integrated approach. Therefore, the present systematic review focuses on exploring this connection, and based on this connection, delimiting possible gaps in the research, altogether aimed at improving FMS clinical intervention and guiding future research lines. Anger is considered a basic negative emotion that can be divided into two dimensions: anger-in (the tendency to repress anger when it is experienced) and anger-out (the leaning to express anger through verbal or physical means). The current systematic review was performed based on the guidelines of the PRISMA and Cochrane Collaborations. The Prospective Register of Systematic Reviews (PROSPERO) international database was forehand used to register the review protocol. The quality of chosen articles was assessed and the main limitations and research gaps resulting from each scientific article were discussed. The search included PubMed, Scopus, and Web of Science databases. The literature search identified 13 studies eligible for the systematic review. Levels of anger-in have been shown to be higher in FMS patients compared to healthy participants, as well as patients suffering from other pain conditions (e.g., rheumatoid arthritis). FMS patients had also showed higher levels of state and trait anxiety, worry and angry rumination than other chronic pain patients. Anger seems to amplify pain especially in women regardless FMS condition but with a particularly greater health-related quality of life´s impact in FMS patients. In spite of the relevance of emotions in the treatment of chronic pain, including FMS, only two studies have proposed intervention programs focus on anger treatment. These two studies have observed a positive reduction in anger levels through mindfulness and a strength training program. In conclusion, anger might be a meaningful therapeutic target in the attenuation of pain sensitivity, and the improvement of the general treatment effects and health-related quality of life in FMS patients. More intervention programs directed to reduce anger and contribute to improve well-being in FMS patients are needed.

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.

Facial Emotion Recognition in Obesity and in Fibromyalgia: A Systematic Review

Facial emotion recognition (FER) is extensively investigated in psychological sciences in healthy individuals and clinical conditions. In this paper, we analyzed those studies in which FER was assessed in the case of obesity or fibromyalgia, in relation to the levels of alexithymia. Crucially, these two conditions frequently co-occur; however, no study has explored FER considering both fibromyalgia and obesity. Studies were identified using the electronic search engine of PubMed. The last research was run on 23 July 2021. Two independent lists were generated for the two clinical conditions. Six records were reviewed about obesity, while three records about fibromyalgia. The evidence relative to FER in obesity was not conclusive, whereas the evidence about an altered FER in fibromyalgia seemed more straightforward. Moreover, the role of alexithymia on FER in these clinical conditions was not extensively investigated. In our discussion, we highlighted those factors that should be carefully addressed in investigating FER in these clinical conditions. Moreover, we underlined methodological criticisms that should be overcome in future research.

Electroencephalographic evidence of unconscious and conscious attentional bias in people with functional gastrointestinal disorders: A pilot study

Debate continues as to whether an attentional bias towards threat displayed by sufferers of functional gastrointestinal disorders (FGIDs) is conscious and, thus, more amenable to change through psychological therapy. We compared the amplitudes of early (unconscious) and later (conscious) electroencephalographic (EEG) event-related potentials following silent reading of symptom-related, emotionally neutral, and emotionally negative nouns across two participant groups: 30 female FGID-sufferers who met diagnostic criteria for irritable bowel syndrome or functional dyspepsia, and 30 female healthy controls. Analogous indices based on alpha desynchronization were also examined, as were correlations between the EEG-based indices and a range of psychosocial variables. FGID-sufferers displayed marginally significantly higher occipital EPN amplitudes for all nouns, indicating marginally higher levels of unconscious attention in the task. FGID-sufferers also displayed, for negative as compared to neutral nouns, significantly lower central N400 amplitudes indicative of higher conscious attention. The result was only apparent in post-hoc pairwise comparisons, however. Uniquely among FGID-sufferers, central N400 was strongly negatively correlated with a range of negative psychosocial traits and states. The findings provide preliminary evidence of hypervigilance to general (as opposed to symptom-specific) threat among FGID-sufferers. Amidst concerns over Type I error, recommendations are made for fine-tuning the operationalisation of unconscious and conscious attentional bias in this population.

Fibromyalgia Detection Based on EEG Connectivity Patterns

Objective: The identification of a complementary test to confirm the diagnosis of FM. The diagnosis of fibromyalgia (FM) is based on clinical features, but there is still no consensus, so patients and clinicians might benefit from such a test. Recent findings showed that pain lies in neuronal bases (pain matrices) and, in the long term, chronic pain modifies the activity and dynamics of brain structures. Our hypothesis is that patients with FM present lower levels of brain activity and therefore less connectivity than controls. Methods: We registered the resting state EEG of 23 patients with FM and compared them with 23 control subjects’ resting state recordings from the PhysioBank database. We measured frequency, amplitude, and functional connectivity, and conducted source localization (sLORETA). ROC analysis was performed on the resulting data. Results: We found significant differences in brain bioelectrical activity at rest in all analyzed bands between patients and controls, except for Delta. Subsequent source analysis provided connectivity values that depicted a distinct profile, with high discriminative capacity (between 91.3–100%) between the two groups. Conclusions: Patients with FM show a distinct neurophysiological pattern that fits with the clinical features of the disease.

Central nervous activity during implicit processing of emotional face expressions in fibromyalgia syndrome

OBJECTIVE

Fibromyalgia syndrome (FMS) is characterized by chronic widespread pain accompanied by symptoms like fatigue, insomnia, depression, anxiety and cognitive impairments. In addition to central nervous pain sensitization, emotional dysregulation may be involved in FMS pathogenesis. This study investigated central nervous correlates of affective and attentional processing in FMS using an implicit task.

METHODS

Event-related potentials (ERPs) of the EEG were recorded in 25 FMS patients and 37 healthy controls while they had to name the frame color of pictures displaying emotional expressions (angry, painful, happy, neutral). The actual picture had to be ingored. Symptoms of pain, depression and anxiety were also assessed.

RESULTS

Patients exhibited smaller P2 and late positive potential (LPP) amplitudes, and a greater N250 amplitude, than controls. The N250 amplitude varied according to the emotional expressions displayed in patients, but not in controls. No group differences arose for the P1 or N170 amplitudes. Patients had longer reaction times and made more errors on the task; task performance was more closely related to pain severity than to other symptoms.

CONCLUSION

The reduced P2 and LPP amplitudes indicate deficient short-term mobilization of attentional resources and sustained attention in FMS; the greater N250 amplitude may reflect greater engagement in the decoding of complex facial features, which is necessary to compensate for attentional impairments. Affective modulation of the N250 suggests that the neural mechanisms underlying complex visual processes are particularly susceptible to emotional influences in FMS. The behavioral data confirm attentional deficits in the disorder and implicate clinical pain therein.

Different Electrophysiological Responses to Pain-Related Visual Stimuli Between Fibromyalgia and Chronic low Back Pain Women: A Pilot Case-Control Study

BACKGROUND

Fibromyalgia is a chronic pain syndrome which occurs in the absence of an organic damage, whom causes is still unclear. Aims of this pilot study were to investigate the neural correlates of fibromyalgia in response to pain-related visual stimuli and explore the psychological differences among fibromyalgia, chronic low back pain (CLBP) and healthy conditions.

METHODS

After a clinical assessment, electrophysiological responses to pain-related visual stimuli were recorded using a 256-Hydrocel Geodesic-Sensor-Net. Event-related potentials (ERPs), standardised low-resolution electromagnetic tomography (sLORETA), and psychological (Symptom Checklist-90-Revised) data were analysed for a total sample of 23 women (5 healthy volunteers, 12 fibromyalgia patients, 6 CLBP patients).

RESULTS

The main finding was that fibromyalgia women reported a different brain response to pain-related visual stimuli on the frontal montage compared to women with CLBP (p = .028). Moreover, fibromyalgia women showed an increased activity mainly on the hippocampus (p = .003) and the posterior cingulate cortex (p ≤ .001) in response to algic stimuli compared to not algic ones. Lastly, these women presented higher scores on the somatization (p = .002), obsession-compulsion (p = .045), depression (p = .043) and positive symptom distress (p = .023) dimensions compared to the healthy women.

CONCLUSIONS

These preliminary results suggest that although the painful symptoms are similar, the central elaboration of pain could be different between women with fibromyalgia and those with CLBP. Moreover, these findings provide preliminary evidences about the great alert and the central sensitivity to pain-related information regarding fibromyalgia patients.

Emotional Influences on Cognitive Processing in Fibromyalgia Patients With Different Depression Levels: An Event-related Potential Study

OBJECTIVES

Comorbid symptoms in fibromyalgia (FM) syndrome, such as mood disorders and cognitive dysfunction, may lead to greater functional impairment than pain itself. This study aimed to unravel the modulating role of depression in response execution and inhibition in FM using an emotional go/no-go task.

MATERIALS AND METHODS

In total, 17 FM patients with low depression, 18 FM patients with high depression, and 18 pain-free controls were included. Pain, happy, and neutral faces were pseudorandomly presented, and participants were asked to respond to male faces (go trials) by pressing a button, and to inhibit their responses if female faces were presented (no-go trials).

RESULTS

FM patients with high depression showed lower positive affect scores, higher negative affect and pain vigilance scores, and slower reaction times, than FM patients with low depression and pain-free controls. Both subgroups of FM patients also rated pain faces as more arousing than pain-free controls. The lack of group differences in our electrophysiological data, neither in N200 nor in P300 amplitudes, seems to indicate that there was no significant impairment in response execution in response inhibition due to pain.

DISCUSSION

Taken together, these results add evidence to the notion that depression is associated with higher affective dysregulation and deficit of information-processing speed in FM. Furthermore, our data suggest that pain induces a bias to pain-related information, but the absence of significant group differences in event-related potential amplitudes, calculated with analyses of covariance (ANCOVA) (with pain intensity), seem to show that pain intensity is not a predictor for cognitive dysfunctions.

Influence of depressive feelings in the brain processing of women with fibromyalgia: An EEG study

Depression is one of the most common mental health problems which affects more than 10% of the global population. The prevalence of this disorder is higher in fibromyalgia patients. However, the influence of the combination of depression and fibromyalgia in the brain processing is poorly understood.To explore the modifications of EEG power spectrum in women with fibromyalgia when depressive feelings are elicited.Twenty eight women with fibromyalgia participated in this cross-sectional study. They were classified as women with depression or women without depression according to the score in the Geriatric Depression Scale. This questionnaire was used to elicit depression symptoms during the EEG recording. Analyses were performed with the standardized LOw Resolution Electric Tomography (sLORETA) software. Power spectrum were compared in the following frequency bands: delta, theta, alpha-1, alpha-2, beta-1, beta-2, and beta-3.Fibromyalgia patients with untreated depression showed a hypoactivation of the left hemisphere when compared with fibromyalgia patients without depression. In addition, when compared fibromyalgia patients without depression and women with both fibromyalgia and depression who were taking antidepressant medications, differences in EEG power spectrum in the studied frequency bands were not found.The current study contributes to the understanding on the influence of the combination of fibromyalgia and depression in the brain activity patterns. Patients with untreated depression showed a hypoactivation of the left hemisphere while eliciting depression symptoms. However, further research is needed, antidepressant medication might reduce the differences between patients with depression and those who do not suffer from depression symptoms.

Quantitative Data for Transcutaneous Electrical Nerve Stimulation and Acupuncture Effectiveness in Treatment of Fibromyalgia Syndrome

Aim. To evaluate the effects of acupuncture and transcutaneous electric nerve stimulation (TENS) applications on the quantitative electroencephalography (qEEG) changes and to evaluate their therapeutic effects in patients with fibromyalgia syndrome (FMS). The study included 42 patients with FMS and 21 healthy volunteers. The patients were randomly assigned to two groups (n=21 in each) to undergo either TENS or acupuncture application. In both acupuncture and TENS groups, baseline electroencephalography (EEG) recording was performed for 10 min and, then, TENS or acupuncture was performed for 20 min, followed by another 10 min EEG recording. Baseline qEEG findings of FMS patients in the TENS and acupuncture groups were similar. Delta and theta powers over the frontal region of FMS patients were lower than controls. Theta powers of right posterior region were also lower than controls. In the TENS group, after the treatment, an increase was observed in the alpha power of the left anterior region as well as a decrease in pain scores. In the acupuncture group, an increase was determined in the alpha power of the right and left posterior regions as well as a decrease in pain score after the treatment. The power of low- and moderate-frequency waves on resting EEG was decreased in the patients with FMS. Decreased pain and increased inhibitor activity were found on qEEG after TENS and acupuncture applications. In conclusion, both TENS and acupuncture applications seem to be beneficial in FMS patients.

Pain Expressions and Inhibitory Control in Patients With Fibromyalgia: Behavioral and Neural Correlates

Fibromyalgia (FM) is a generalized chronic pain condition associated with a variety of symptoms, including altered cognitive and emotional processing. It has been proposed that FM patients show a preferential allocation of attention to information related to the symptoms of the disease, particularly to pain cues. However, the existing literature does not provide conclusive evidence on the presence of this attentional bias, and its effect on cognitive functions such as inhibitory control. To clarify this issue, we recorded the electroencephalographic activity of 31 women diagnosed with FM and 28 healthy women, while performing an emotional Go/NoGo task with micro-videos of pain, happy, and neutral facial expressions. We analyzed behavioral data, performed EEG time-frequency analyses, and obtained the event-related potentials (ERPs) N2 and P3 components in NoGo trials. A series of self-reports was also administered to evaluate catastrophic thinking and the main symptoms of fibromyalgia. Pain expressions were associated with longer reaction times and more errors, as well as with higher theta and delta power, and P3 amplitude to NoGo stimuli. Thus, behavioral and psychophysiological data suggest that increased attention to pain expressions impairs the performance of an inhibitory task, although this effect was similar in FM patients and healthy controls. N2 amplitude was modulated by type of facial expression (larger to pain faces), but only for the control group. This finding suggests that the presentation of pain faces might represent a smaller conflict for the patients, more used to encounter pain stimuli. No main group effects were found significant for N2 or P3 amplitudes, nor for time-frequency data. Using stimuli with greater ecological validity than in previous studies, we could not confirm a greater effect of attentional bias toward negative stimuli over inhibitory performance in patients with FM. Studying these effects allow us to better understand the mechanisms that maintain pain and develop intervention strategies to modify them.

Fear of pain and event-related potentials during exposure to image-cued somatosensory stimulation

Numerous behavior studies have assessed links of pain-related fear with biases in attention towards pain stimuli but considerably less is known about neural processes underlying such biases. To address this gap, event-related potentials (ERPs) were examined as 39 high pain-fearful (Hi-FOP) and 36 low pain-fearful (Lo-FOP) adults (1) viewed non-painful versus painful images and (2) subsequently received non-painful versus possibly painful somatosensory stimulation, respectively. The Hi-FOP group judged both non-painful and painful somatosensory stimulation to be more intense than Lo-FOP group members did. Hi-FOP group members also displayed smaller N1 amplitudes than Lo-FOP group members did during image presentations, regardless of image type. Finally, Lo-FOP group members exhibited larger P3 amplitudes when processing potentially painful somatosensory stimulation compared to non-painful stimulation while no such difference was observed in Hi-FOP group members. Overall results suggested that the pain-fearful tended to exaggerate the subjective intensity of potentially painful somatosensory stimuli but allocated comparatively fewer cognitive resources to processing such stimulation; arguably, this pattern perpetuates high fear of pain levels.

Alexithymia, not fibromyalgia, predicts the attribution of pain to anger-related facial expressions

BACKGROUND

Fibromyalgia (FM) is a syndrome characterized by chronic, widespread musculoskeletal pain, occurring predominantly in women. Previous studies have shown that patients with FM display a pattern of selective processing or cognitive bias which fosters the encoding of pain-related information. The present study tested the hypothesis of an increased attribution of pain to facial expressions of emotions (FEE), in patients with FM. As previous studies have shown that alexithymia influences the processing of facial expressions, independent of specific clinical conditions, we also investigated whether alexithymia, rather than FM per se, influenced attribution of pain to FEE.

METHODS

One hundred and twenty-three women (41 with FM, 82 healthy controls, HC) were enrolled in this cross-sectional case-control study. We adopted two pain-attribution tasks, the Emotional Pain Estimation and the Emotional Pain Ascription, both using a modified version of the Ekman 60 Faces Test. Psychological distress was assessed using the Hospital Anxiety and Depression Scale, and alexithymia was assessed using the Toronto Alexithymia Scale.

RESULTS

Patients with FM did not report increased attribution of pain to FEE. Alexithymic individuals demonstrated no specific problem in the recognition of basic emotions, but attributed significantly more pain to angry facial expression.

LIMITATIONS

Our study involved a relatively small sample size. The use of self-reported instruments might have led to underestimation of the presence of frank alexithymia in individuals having borderline cut-off scores.

CONCLUSIONS

Alexithymia, rather than FM per se, plays a key role in explaining the observed differences in pain attribution to anger-related facial expressions.

Diminished Interoceptive Awareness in Fibromyalgia Syndrome

Sensitivity to signals arising within the body (interoceptive awareness) has been implicated in emotion processing; interindividual differences in interoceptive awareness modulate both subjective and physiological indicators of emotional experience and the regulation of emotion-related behaviors. This study investigated interoceptive awareness in patients with fibromyalgia syndrome (FMS), a chronic pain condition accompanied by various affective symptoms. Interoceptive awareness was assessed in 45 FMS patients and 31 healthy individuals using a heartbeat perception task. Cognitive performance, comorbid psychiatric disorders and medication use were assessed as possible confounding variables. Concerning the primary outcome, patients exhibited markedly reduced heartbeat perception compared to healthy individuals. Moreover, there was an inverse relationship between interoceptive awareness and FMS symptom severity. Reduced interoceptive awareness may be involved in the affective aspects of FMS pathology. Poor access to bodily signals may restrict patients´ ability to integrate these signals during emotional processing, which, by extension, may preclude optimal emotional self-regulation.

Increased Low- and High-Frequency Oscillatory Activity in the Prefrontal Cortex of Fibromyalgia Patients

Recent human neuroimaging studies have suggested that fibromyalgia (FM), a chronic widespread pain disorder, exhibits altered thalamic structure and function. Since the thalamus has extensive reciprocal connection with the cortex, structural and functional thalamic alterations in FM might be linked to aberrant thalamocortical oscillation. This study investigated the presence of abnormal brain rhythmicity in low- and high-frequency bands during resting state in patients with FM and their relationship to clinical pain symptom. Spontaneous magnetoencephalography (MEG) activity was recorded in 18 females with FM and 18 age- and sex-matched healthy control (HC) subjects. The most remarkable finding was that FM patients had general increases in theta, beta and gamma power along with a slowing of the dominant alpha peak. Increased spectral powers in the theta-band were primarily localized to the left dorsolateral prefrontal (DLPFC) and orbitofrontal cortex (OFC). Beta and gamma over-activation were localized to insular, primary motor and primary and secondary somatosensory (S2) cortices, as well as the DLPFC and OFC. Furthermore, enhanced high-frequency oscillatory activities in the DLPFC and OFC were associated with higher affective pain scores in patients with FM. Our results demonstrate that FM patients feature enhanced low- and high-frequency oscillatory activity in the brain areas related to cognitive and emotional modulation of pain. Increased low- and high-frequency activity of the prefrontal cortex may contribute to persistent perception of pain in FM. Therapeutic intervention based on manipulating neural oscillation to restore normal thalamocortical rhythmicity may be beneficial to pain relief in FM.

Electroencephalographic Patterns in Chronic Pain: A Systematic Review of the Literature

The main objective of this study is to review and summarize recent findings on electroencephalographic patterns in individuals with chronic pain. We also discuss recent advances in the use of quantitative Electroencephalography (qEEG) for the assessment of pathophysiology and biopsychosocial factors involved in its maintenance over time. Data collection took place from February 2014 to July 2015 in PubMed, SciELO and PEDro databases. Data from cross-sectional studies and longitudinal studies, as well as clinical trials involving chronic pain participants were incorporated into the final analysis. Our primary findings related to chronic pain were an increase of theta and alpha EEG power at rest, and a decrease in the amplitude of evoked potentials after sensory stimulation and cognitive tasks. This review suggests that qEEG could be considered as a simple and objective tool for the study of brain mechanisms involved in chronic pain, as well as for identifying the specific characteristics of chronic pain condition. In addition, results show that qEEG probably is a relevant outcome measure for assessing changes in therapeutic studies.

Affective Modulation of Brain and Autonomic Responses in Patients With Fibromyalgia

OBJECTIVES

Emotional dysregulation and abnormal processing of affective information are thought to play a significant role for the maintenance of pain in fibromyalgia. The motivational priming hypothesis states that negative emotions could increase pain via activation of the aversive system, thus leading to an affective modulation of defensive reflexes. Nevertheless, little is known about peripheral and central correlates of affective reflex modulation in fibromyalgia.

METHODS

Thirty patients with fibromyalgia and 30 healthy individuals were asked to view three video clips from a self-perspective to induce specific mood states. Video clips consisted of the same virtual walk through different locations of a park under three affective environments (unpleasant, pleasant, and neutral). Startle eyeblink reflex and heart rate response elicited by abrupt startle noises, as well as heart rate variability and electroencephalography (EEG) oscillations were recorded when participants were passively viewing the virtual environments.

RESULTS

Patients with fibromyalgia rated all environments as more negative and arousing than did healthy controls (p values < .05). Nevertheless, startle eyeblink reflex and heart rate response were lower in patients with fibromyalgia than in healthy controls when viewing all three environments (p values < .05). Patients with fibromyalgia also displayed lower heart rate variability, as well as higher EEG power (2-22 Hz) during all environments than did healthy controls (p values < .05).

CONCLUSIONS

Patients with fibromyalgia were characterized by relevant deficits in affective modulation of startle and cardiac responses, heart rate variability, and EEG power spectra in response to sustained induction of affective states. These findings suggest an alteration of emotional and attentional aspects of information processing at subjective, autonomic, and central nervous system levels.

Mutual influences of pain and emotional face processing

The perception of unpleasant stimuli enhances whereas the perception of pleasant stimuli decreases pain perception. In contrast, the effects of pain on the processing of emotional stimuli are much less known. Especially given the recent interest in facial expressions of pain as a special category of emotional stimuli, a main topic in this research line is the mutual influence of pain and facial expression processing. Therefore, in this mini-review we selectively summarize research on the effects of emotional stimuli on pain, but more extensively turn to the opposite direction namely how pain influences concurrent processing of affective stimuli such as facial expressions. Based on the motivational priming theory one may hypothesize that the perception of pain enhances the processing of unpleasant stimuli and decreases the processing of pleasant stimuli. This review reveals that the literature is only partly consistent with this assumption: pain reduces the processing of pleasant pictures and happy facial expressions, but does not - or only partly - affect processing of unpleasant pictures. However, it was demonstrated that pain selectively enhances the processing of facial expressions if these are pain-related (i.e., facial expressions of pain). Extending a mere affective modulation theory, the latter results suggest pain-specific effects which may be explained by the perception-action model of empathy. Together, these results underscore the important mutual influence of pain and emotional face processing.

The N170 and face perception in psychiatric and neurological disorders: A systematic review

OBJECTIVE

To systematically evaluate evidence for configural and affective face processing abnormalities as measured by the N170 and Vertex Positive Potential (VPP) event-related potential components, and analogous M170 magnetoencephalography (MEG) component, in neurological and psychiatric disorders.

METHODS

1251 unique articles were identified using PsychINFO and PubMed databases. Sixty-seven studies were selected for review, which employed various tasks to measure the N170, M170 or VPP; the 13 neurological/psychiatric conditions were Attention-Deficit Hyperactivity Disorder (ADHD), Alcohol Dependence, Alzheimer's Disease, Autism Spectrum Disorders (ASDs), Bipolar Disorder, Bulimia Nervosa, Fibromyalgia, Huntington's Disease, Major Depressive Disorder, Parkinson's Disease, Prosopagnosia, Schizophrenia and Social Phobia.

RESULTS

Smaller N170 and VPP amplitudes to faces compared to healthy controls were consistently reported in Schizophrenia but not in ASDs. In Schizophrenia N170 and VPP measures were not correlated with clinical symptoms. Findings from other disorders were highly inconsistent; however, reported group differences were almost always smaller amplitudes or slower latencies to emotional faces in disordered groups regardless of diagnosis.

CONCLUSIONS

Results suggest that N170/VPP abnormalities index non-specific facial affect processing dysfunction in these neurological and psychiatric conditions, reflecting social impairments being broadly characteristic of these groups.

SIGNIFICANCE

The N170 and analogous components hold promise as diagnostic and treatment monitoring biomarkers for social dysfunction.

Viewing pain and happy faces elicited similar changes in postural body sway

Affective facial expressions are potent social cues that can induce relevant physiological changes, as well as behavioral dispositions in the observer. Previous studies have revealed that angry faces induced significant reductions in body sway as compared with neutral and happy faces, reflecting an avoidance behavioral tendency as freezing. The expression of pain is usually considered an unpleasant stimulus, but also a relevant cue for delivering effective care and social support. Nevertheless, there are few data about behavioral dispositions elicited by the observation of pain expressions in others. The aim of the present research was to evaluate approach–avoidance tendencies by using video recordings of postural body sway when participants were standing and observing facial expressions of pain, happy and neutral. We hypothesized that although pain faces would be rated as more unpleasant than the other faces, they would provoke significant changes in postural body sway as compared to neutral facial expressions. Forty healthy female volunteers (mean age 25) participated in the study. Amplitude of forward movements and backward movements in the anterior-posterior and medial-lateral axes were obtained. Statistical analyses revealed that pain faces were the most unpleasant stimuli, and that both happy and pain faces were more arousing than neutral ones. Happy and pain faces also elicited greater amplitude of body sway in the anterior-posterior axes as compared with neutral faces. In addition, significant positive correlations were found between body sway elicited by pain faces and pleasantness and empathic ratings, suggesting that changes in postural body sway elicited by pain faces might be associated with approach and cooperative behavioral responses.