Age-related differences in functional connectivity associated with pain modulation.

Growing evidence suggests that aging is associated with impaired endogenous pain modulation, and that this likely underlies the increased transition from acute to chronic pain in older individuals. Resting-state functional connectivity (rsFC) offers a valuable tool to examine the neural mechanisms behind these age-related changes in pain modulation. RsFC studies generally observe decreased within-network connectivity due to aging, but its relevance for pain modulation remains unknown. We compared rsFC within a set of brain regions involved in pain modulation between young and older adults and explored the relationship with the efficacy of distraction from pain. This revealed several age-related increases and decreases in connectivity strength. Importantly, we found a significant association between lower pain relief and decreased strength of three connections in older adults, namely between the periaqueductal gray and right insula, between the anterior cingulate cortex (ACC) and right insula, and between the ACC and left amygdala. These findings suggest that the functional integrity of the pain control system is critical for effective pain modulation, and that its function is compromised by aging.

Unraveling the Left-Right Judgment Task in Chronic Low Back Pain: Insights Through Behavioral, Electrophysiological, Motor Imagery, and Bodily Disruption Perspectives.

Bodily disruptions have been consistently demonstrated in individuals with chronic low back pain. The performance on the left-right judgment task has been purposed as an indirect measure of the cortical proprioceptive representation of the body. It has been suggested to be dependent on implicit motor imagery, although the available evidence is conflicting. Hence, the aim of this case-control observational study was to examine the performance (accuracy and reaction times) and event-related potentials while performing the left-right judgment task for back and hand images in individuals with chronic low back pain versus healthy controls, along with its relationship with self-reported measurements and quantitative sensory testing. While self-reported data suggested bodily disruptions in the chronic low back pain sample, this was not supported by quantitative sensory testing. Although both groups displayed the same performance, our results suggested an increased attentional load on participants with chronic low back pain to achieve equal performance, measured by a higher N1 peak amplitude in occipital electrodes, especially when the effect of contextual images arises. The absence of differences in the reaction times for the left-right judgment task between both groups, along with inconsistencies in self-reported and quantitative sensory testing data, could question the involvement of implicit motor imagery in solving the task. In conclusion, our results suggest disrupted attentional processing in participants with chronic low back pain to solve the left-right judgment task. PERSPECTIVE: Although there are no differences in the performance of the left-right judgment task (hits, reaction times) between chronic low back pain patients and controls, the analysis of event-related potentials revealed that patients require a higher cognitive load, measured by N1 peak amplitude.

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.

Better Executive Functions Are Associated With More Efficient Cognitive Pain Modulation in Older Adults: An fMRI Study.

Growing evidence suggests that aging is associated with less efficient endogenous pain modulation as demonstrated by reduced conditioned pain modulation, and that these changes may be mediated by differences in frontal functioning. Yet, little is known about potential age-related changes in cognitive pain modulation, such as distraction from pain. In a first session, 30 healthy young (19-35 years) and 30 healthy older (59-82 years) adults completed a battery of neuropsychological tests. In a second session, we acquired functional brain images while participants completed a working memory task with two levels of cognitive load (high vs. low) and concurrently received individually adjusted heat stimuli (warm vs. painful). In both age groups, completing the high load task was associated with a significant reduction in the perceived intensity and unpleasantness of painful stimuli and a reduction in activation of brain regions involved in pain processing. Group comparisons revealed that young adults showed a stronger de-activation of brain regions involved in pain processing during the high load vs. the low load task, such as the right insula, right mid cingulate cortex and left supramarginal gyrus, compared to older adults. Older adults, on the other hand, showed an increased activation in the anterior cingulate cortex during the high load vs. low load task, when compared to young adults. Covariate analyses indicated that executive functions significantly predicted neural pain modulation in older adults: Better executive functions were associated with a more pronounced de-activation of the insula, thalamus and primary somatosensory cortex and increased activation of prefrontal regions during the high vs. low load task. These findings suggest that cognitive pain modulation is altered in older age and that the preservation of executive functions may have beneficial effects on the efficacy of distraction from pain.

An Educational and Exercise Mobile Phone-Based Intervention to Elicit Electrophysiological Changes and to Improve Psychological Functioning in Adults With Nonspecific Chronic Low Back Pain (BackFit App): Nonrandomized Clinical Trial.

BACKGROUND: Concomitant psychological and cognitive impairments modulate nociceptive processing and contribute to chronic low back pain (CLBP) maintenance, poorly correlated with radiological findings. Clinical practice guidelines recommend self-management and multidisciplinary educational and exercise-based interventions. However, these recommendations are based on self-reported measurements, which lack evidence of related electrophysiological changes. Furthermore, current mobile health (mHealth) tools for self-management are of low quality and scarce evidence. Thus, it is necessary to increase knowledge on mHealth and electrophysiological changes elicited by current evidence-based interventions. OBJECTIVE: The aim of this study is to investigate changes elicited by a self-managed educational and exercise-based 4-week mHealth intervention (BackFit app) in electroencephalographic and electrocardiographic activity, pressure pain thresholds (PPTs), pain, disability, and psychological and cognitive functioning in CLBP versus the same intervention in a face-to-face modality. METHODS: A 2-arm parallel nonrandomized clinical trial was conducted at the University of the Balearic Islands (Palma, Spain). A total of 50 patients with nonspecific CLBP were assigned to a self-managed group (23/50, 46%; mean age 45.00, SD 9.13 years; 10/23, 43% men) or a face-to-face group (27/50, 54%; mean age 48.63, SD 7.54 years; 7/27, 26% men). The primary outcomes were electroencephalographic activity (at rest and during a modified version of the Eriksen flanker task) and heart rate variability (at rest), PPTs, and pressure pain intensity ratings. The secondary outcomes were pain, disability, psychological functioning (mood, anxiety, kinesiophobia, pain catastrophizing, and fear-avoidance beliefs), and cognitive performance (percentage of hits and reaction times). RESULTS: After the intervention, frequency analysis of electroencephalographic resting-state data showed increased beta-2 (16-23 Hz; 0.0020 vs 0.0024; P=.02) and beta-3 (23-30 Hz; 0.0013 vs 0.0018; P=.03) activity. In addition, source analyses revealed higher power density of beta (16-30 Hz) at the anterior cingulate cortex and alpha (8-12 Hz) at the postcentral gyrus and lower power density of delta (2-4 Hz) at the cuneus and precuneus. Both groups also improved depression (7.74 vs 5.15; P=.01), kinesiophobia (22.91 vs 20.87; P=.002), activity avoidance (14.49 vs 12.86; P<.001), helplessness (6.38 vs 4.74; P=.02), fear-avoidance beliefs (35 vs 29.11; P=.03), and avoidance of physical activity (12.07 vs 9.28; P=.01) scores, but there was an increase in the disability score (6.08 vs 7.5; P=.01). No significant differences between the groups or sessions were found in heart rate variability resting-state data, electroencephalographic data from the Eriksen flanker task, PPTs, subjective ratings, or cognitive performance. CONCLUSIONS: Both intervention modalities increased mainly beta activity at rest and improved psychological functioning. Given the limitations of our study, conclusions must be drawn carefully and further research will be needed. Nevertheless, to the best of our knowledge, this is the first study reporting electroencephalographic changes in patients with CLBP after an mHealth intervention. TRIAL REGISTRATION: ClinicalTrials.gov NCT04576611; https://clinicaltrials.gov/ct2/show/NCT04576611.

Anterior Cingulate Cortex Activity During Rest Is Related to Alterations in Pain Perception in Aging.

Alterations in the affective component of pain perception are related to the development of chronic pain and may contribute to the increased vulnerability to pain observed in aging. The present study analyzed age-related changes in resting-state brain activity and their possible relation to an increased pain perception in older adults. For this purpose, we compared EEG current source density and fMRI functional-connectivity at rest in older (n = 20, 66.21 ± 3.08 years) and younger adults (n = 21, 20.71 ± 2.30 years) and correlated those brain activity parameters with pain intensity and unpleasantness ratings elicited by painful stimulation. We found an age-related increase in beta2 and beta3 activity in temporal, frontal, and limbic areas, and a decrease in alpha activity in frontal areas. Moreover, older participants displayed increased functional connectivity in the anterior cingulate cortex (ACC) and the insula with precentral and postcentral gyrus. Finally, ACC beta3 activity was positively correlated with pain intensity and unpleasantness ratings in older, and ACC-precentral/postcentral gyrus connectivity was positively correlated with unpleasantness ratings in older and younger participants. These results reveal that ACC resting-state hyperactivity is a stable trait of brain aging and may underlie their characteristic altered pain perception.

[Physical exercise impact on variables related to emotional and functional well-being in older adults]. / Impacto del ejercicio físico en variables relacionadas con el bienestar emocional y funcional en adultos mayores.

BACKGROUND AND AIM: The benefits of the physical exercise in aging, and specially in frailty, have been associated with reduced risk of mortality, chronic disease, and cognitive and functional impairments. Multi-component training, which combines strength, endurance, balance, and gait training, represents the most beneficial kind of physical exercise in older adults. METHODS: Given the effectiveness of the multi-component training, a physical exercise program «Actívate¼ (based on the methodology Vivifrail), with the focus on «active aging¼, was conducted in the present study. Forty-nine older adults over 60 years participated in this program. RESULTS: The physical exercise intervention led to a reduction in diastolic blood pressure, pain threshold and sleep disturbances (e. g. hypersomnia) (t ≥ 2.72, p < 0.01), as well as an increase of walking speed (t = 7.84, p ≤ 0.001). Further, quality of life factors (GENCAT scale), like emotional well-being, personal development, physical well-being, self-determination, and social inclusion, were greater after intervention (t ≥ -2.06, p < 0.05). CONCLUSIONS: These findings underline the benefits of multi-component training in functionality of older adults, and further, provide relevant aspects about the modulation of pain perception, sleep disturbances, social factors and physical and emotional well-being. Physical exercise programs such as «Actívate¼ should be promoted, in order to encourage healthy lifestyle habits, in the older adults' population.

Intact pain modulation through manipulation of controllability and expectations in aging.

BACKGROUND: Pain expectation and controllability can modulate pain processing. However, little is known about age-related effects on these cognitive factors involved in pain control. This study assessed age-related brain changes associated with pain expectation and controllability. METHODS: 17 healthy older adults (9 men; 65.65 ± 4.34 years) and 18 healthy younger adults (8 men; 20.56 ± 5.56 years) participated in the study. Pain evoked potentials and pain ratings were recorded while participants received painful electrical stimuli under two different conditions of pain controllability over the intensity of the stimulation (self-controlled vs. computer controlled) and two conditions of pain expectations (high vs. low pain). RESULTS: Although the intensity of the painful stimulation was kept constant, all participants showed reduced pain perception in the controllable and low pain expectancy conditions. However, older participants showed reduced amplitudes of pain evoked potentials in the time window between 150 and 500 ms after stimulus onset as compared to younger participants. Moreover, younger participants showed greater negative amplitudes from 80 to 150 ms after stimulus onset for uncontrollable versus controllable pain. CONCLUSIONS: These results suggest that although cognitive pain modulation is preserved during ageing, neural processing of pain is reduced in older adults. SIGNIFICANCE: This research describes the impact of age on cognitive pain modulation evoked by the manipulation of pain controllability and pain expectations. Our findings constitute a first step in the understanding of the greater vulnerability of older individuals to chronic pain. Moreover, we show that older adults can benefit from cognitive pain control mechanisms to increase the efficacy of pain treatments.

Acute Effects of a Brief Physical Exercise Intervention on Somatosensory Perception, Lumbar Strength, and Flexibility in Patients with Nonspecific Chronic Low-Back Pain.

BACKGROUND: Evidence-based clinical guidelines consider physical exercise one of the best nonpharmacological interventions for low-back pain (LBP), but it is necessary to clarify the exercise-induced hypoalgesia effect of different modalities of exercise in chronic pain populations. PURPOSE: This study focused on exploring acute changes in tactile and pressure-pain perception and lumbar strength and flexibility in patients with nonspecific chronic LBP (NSCLBP) after performing one of three 20-minute physical exercise modalities. METHODS: A total of 81 patients with NSCLBP were pseudorandomly distributed into three groups of 20-minute physical exercise - 1) aerobic (n=21, mean age 42±9.72 years, nine men), 2) stretching (n=21, mean age 40±11.37 years, ten men), and 3) strengthening (n=20, mean age 35.80±11.56 years, ten men) - and 4) a control group (n=19, mean age 38.64±10.24 years, eight men), and completed self-reported questionnaires during the same period. Tactile and pressure-pain thresholds and isometric lumbar muscle endurance and flexibility were assessed before and after this brief exercise-based intervention. RESULTS: All groups were comparable in terms of sociodemographic and clinical data, cardiovascular capacity, and self-reported data onphysical disability, mood, motivation, psychological response to stimulus properties of physical exercise, and physical activity enjoyment. Our analyses revealed higher tactile sensitivity (p<0.001) and pressure-pain thresholds (p<0.001) at the forefinger than other body locations. We also found lower pain sensitivity (p=0.010) and pressure pain-intensity ratings (p=0.001) and higher lumbar flexibility (p<0.001) after intervention. After calculation of absolute pre-post differences, higher tactile sensitivity was observed at the gluteus medius muscle than the erector spinal muscle only after aerobic intervention (p=0.046). CONCLUSION: These results add some evidence about different modalities of exercise-induced hypoalgesia in NSCLBP. However, the fact that we also found improvements in the control group limits our conclusions.

Alterations in Neural Responses and Pain Perception in Older Adults During Distraction.

OBJECTIVE: Although it is acknowledged that pain may be modulated by cognitive factors, little is known about the effect of aging on these control processes. The present study investigated electroencephalographical correlates of pain processing and its cognitive modulation in healthy older individuals. METHODS: For this purpose, the impact of distraction on pain was evaluated in 21 young (9 men; 20.71 [2.30]) and 20 older (10 men; 66.80 [4.14]) adults. Participants received individually adjusted electrical pain stimuli in a high-distraction condition (one-back task) and in a low-distraction condition (simple letter response task). Pain-related evoked potentials and pain ratings were analyzed. RESULTS: Both groups rated pain as less intense (F(1,39) = 13.954, p < .001) and less unpleasant (F(1,39) = 10.111, p = .003) when it was experienced during the high- rather than the low-distraction condition. However, in comparison to younger participants, older adults gave higher unpleasantness ratings to painful stimulation (F(1,39) = 4.233, p = .046), accompanied by attenuated neural responses (N1-P1 and P3 amplitudes), regardless of the distraction condition (F(1,38) = 6.028 [p = .019] and F(1,38) = 6.669 [p = .014], respectively). CONCLUSIONS: Older participants felt pain relief through distraction, like younger participants. However, we also found that aging may enhance affective aspects of pain perception. Finally, our results show that aging is characterized by reduced neural processing of painful stimuli. This phenomenon could be related to the increased vulnerability of older participants to develop chronic pain.

Distraction from pain: The role of selective attention and pain catastrophizing.

BACKGROUND: Previous research has demonstrated the efficacy of cognitive engagement in reducing concurrent pain. However, little is known about the role of individual differences in inhibitory control abilities and negative pain-related cognitions in modulating the magnitude of this type of distraction from pain. METHODS: In a pain distraction paradigm, 41 participants completed a working memory task with both a demanding high load condition (2-back) and an easy low load condition (0-back), while receiving warm or painful thermal stimuli to their left forearm. To control for individual differences in sensitivity to pain and perceived task difficulty, nociceptive stimulus intensity and task speed were individually calibrated. Additionally, participants completed a set of cognitive inhibition tasks (flanker, go/nogo, Stroop) and questionnaires about negative pain-related cognitions (fear of pain, pain catastrophizing) prior to the distraction paradigm. RESULTS: As expected, engaging in the high load condition significantly reduced perceived intensity and unpleasantness of nociceptive stimuli, compared to the low load condition. The size of the distraction effect correlated significantly with better cognitive inhibition and selective attention abilities, as measured by the flanker task. A moderation analysis revealed a significant interaction between pain catastrophizing and performance in the flanker task in predicting the distraction effect size: Participants who performed well on the flanker task showed more pain reduction, but only when they were average to high pain catastrophizers. CONCLUSIONS: Selective attention abilities and pain catastrophizing seem to be important factors in explaining individual differences in the size of the analgesic response to a distractive task. SIGNIFICANCE: Understanding which factors influence the effectiveness of cognitive engagement in distracting from pain could help to optimize its therapeutic application in patient care. This study shows that a complex interplay of cognitive inhibition abilities, specifically selective attention, and negative pain-related cognitions, such as pain catastrophizing, modulate the magnitude of the distraction effect.

Age-Related Changes in Pain Perception Are Associated With Altered Functional Connectivity During Resting State.

Aging affects pain experience and brain functioning. However, how aging leads to changes in pain perception and brain functional connectivity has not yet been completely understood. To investigate resting-state and pain perception changes in old and young participants, this study employed region of interest (ROI) to ROI resting-state functional connectivity (rsFC) analysis of imaging data by using regions implicated in sensory and affective dimensions of pain, descending pain modulation, and the default-mode networks (DMNs). Thirty-seven older (66.86 ± 4.04 years; 16 males) and 38 younger healthy participants (20.74 ± 4.15 years; 19 males) underwent 10 min' eyes-closed resting-state scanning. We examined the relationship between rsFC parameters with pressure pain thresholds. Older participants showed higher pain thresholds than younger. Regarding rsFC, older adults displayed increased connectivity of pain-related sensory brain regions in comparison to younger participants: increased rsFC between bilateral primary somatosensory area (SI) and anterior cingulate cortex (ACC), and between SI(L) and secondary somatosensory area (SII)-(R) and dorsolateral prefrontal cortex (PFC). Moreover, decreased connectivity in the older compared to the younger group was found among descending pain modulatory regions: between the amygdala(R) and bilateral insula(R), thalamus(R), ACC, and amygdala(L); between the amygdala(L) and insula(R) and bilateral thalamus; between ACC and bilateral insula, and between periaqueductal gray (PAG) and bilateral thalamus. Regarding the DMN, the posterior parietal cortex and lateral parietal (LP; R) were more strongly connected in the older group than in the younger group. Correlational analyses also showed that SI(L)-SII(R) rsFC was positively associated with pressure pain thresholds in older participants. In conclusion, these findings suggest a compensatory mechanism for the sensory changes that typically accompanies aging. Furthermore, older participants showed reduced functional connectivity between key nodes of the descending pain inhibitory pathway.

Reduced brain processing of affective pictures in children with cerebral palsy.

Sensory and cognitive deficits are common comorbidities in children with cerebral palsy. This observational study examines if brain processing of affective information is also altered in children with cerebral palsy (CP) in comparison with typically developing peers (TDP). METHODS: Evoked-related potentials were recorded in 15 children with CP (age = 11.27 ± 4.53 yr, 6 girls) and 14 TDP (age = 10.14 ± 4.29 yr, 5 girls) when viewing pleasant, unpleasant and neutral pictures. The subjective perception of valence and arousal of each one of the pictures was examined. RESULTS: Children with CP showed a significant amplitude reduction of evoked potentials in the occipital region to the affective stimuli in early brain processing latencies (P100 and N200; all F > 2.9, all p < .05). Children with CP rated pictures with affective content (pleasant and unpleasant) as less arousing (F(2.25) = 46.71, p < .001), and neutral pictures as more pleasant, than their TDP (F(2.25) = 75.56, p < .001). CONCLUSION: The pictures with emotional content produce less activation, both at the behavioral and brain processing levels in children with CP. These differences were found in early latencies of brain processing which could be related to alterations in the detection of emotionally relevant stimuli.

Psychological, cognitive factors and contextual influences in pain and pain-related suffering as revealed by a combined qualitative and quantitative assessment approach.

Previous psychophysiological research suggests that pain measurement needs to go beyond the assessment of Pain Intensity and Unpleasantness by adding the evaluation of Pain-Related Suffering. Based on this three-dimensional approach, we attempted to elucidate who is more likely to suffer by identifying reasons that may lead individuals to report Pain and Pain-Related Suffering more than others. A sample of 24 healthy participants (age range 18-33) underwent four different sessions involving the evaluation of experimentally induced phasic and tonic pain. We applied two decision tree models to identify variables (selected from psychological questionnaires regarding pain and descriptors from post-session interviews) that provided a qualitative characterization of the degrees of Pain Intensity, Unpleasantness and Suffering and assessed the respective impact of contextual influences. The overall classification accuracy of the decision trees was 75% for Intensity, 77% for Unpleasantness and 78% for Pain-Related Suffering. The reporting of suffering was predominantly associated with fear of pain and active cognitive coping strategies, pain intensity with bodily competence conveying strength and resistance and unpleasantness with the degree of fear of pain and catastrophizing. These results indicate that the appraisal of the three pain dimensions was largely determined by stable psychological constructs. They also suggest that individuals manifesting higher active coping strategies may suffer less despite enhanced pain and those who fear pain may suffer even under low pain. The second decision tree model revealed that suffering did not depend on pain alone, but that the complex rating-related decision making can be shifted by situational factors (context, emotional and cognitive). The impact of coping and fear of pain on individual Pain-Related Suffering may highlight the importance of improving cognitive coping strategies in clinical settings.

Corrigendum: Inhibitory Control Impairment on Somatosensory Gating Due to Aging: An Event-Related Potential Study.

[This corrects the article DOI: 10.3389/fnhum.2018.00280.].

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.

Inhibitory Control Impairment on Somatosensory Gating Due to Aging: An Event-Related Potential Study.

The capacity to suppress irrelevant incoming input, termed sensory gating, is one of the most investigated inhibitory processes associated with cognitive impairments due to aging. The aim of this study was to examine the influence of aging on sensory gating by using somatosensory event-related potentials (ERPs) elicited by repetitive non-painful tactile stimulation (paired-pulsed task). Somatosensory ERPs were recorded in 20 healthy young adults and 20 healthy older adults while they received two identical pneumatic stimuli (S1 and S2) of 100 ms duration with an inter-stimulus interval of 550 ± 50 ms on both forefingers. The difference between the somatosensory ERPs amplitude elicited by S1 and S2 was computed as a sensory gating measure. The amplitude and the latency of P50, N100 and late positive complex (LPC) were analyzed as well as the source generators of the gating effect. Reduced sensory gating was found in older individuals for N100 at frontal and centro-parietal electrodes and for LPC at fronto-central electrodes. Source localization analyses also revealed a reduced current density during gating effect in the older group in frontal areas in N100 and LPC. Moreover, older individuals showed delayed latencies in N100. No significant gating effect differences were found between groups in P50. These findings suggest an age-related slowing of processing speed and a reduced efficiency of inhibitory mechanisms in response to repetitive somatosensory information during stimulus evaluation, and a preservation of processing speed and inhibitory control during early stimulus coding in aging.

Controllability and hippocampal activation during pain expectation in fibromyalgia syndrome.

To examine the role of perceived control in pain perception, fibromyalgia patients and healthy controls participated in a reaction time experiment under different conditions of pain controllability. No significant differences between groups were found in pain intensity and unpleasantness ratings. However, during the expectation of uncontrollable pain, patients compared to controls showed higher hippocampal activation. In addition, hippocampal activity during the pain expectation period predicted activation of the posterior cingulate cortex (PCC), precuneus and hippocampus during pain stimulation in fibromyalgia patients. The increased activation of the hippocampus during pain expectation and subsequent activation of the PCC/precuneus during the lack of control phase points towards an influence of pain perception through heightening of alertness and anxiety responses to pain in fibromyalgia patients.

Altered Dynamic of EEG Oscillations in Fibromyalgia Patients at Rest.

OBJECTIVE: Previous fMRI findings have shown that chronic pain patients display an altered activation and functional connectivity of the pain network. The aim of the present study was to analyze EEG dynamics in fibromyalgia patients (n = 20) and pain-free controls (n = 18) at rest. METHODS: Spectral power density, source current density, and intra- and inter-hemispheric coherence were analyzed from 64 EEG channels during 5-minutes eyes-closed rest. RESULTS: Results indicated that fibromyalgia patients displayed reduced power density of the delta EEG band (2-4 Hz) over right insula, right superior and middle temporal gyri as compared with pain-free controls. Fibromyalgia patients also exhibited greater power density than pain-free controls in two segments of the beta band (16-23 Hz and 23-30 Hz) over right middle frontal lobe and midcingulate gyrus. Pain duration in fibromyalgia patients was negatively correlated with delta power from right insula. Greater centro-parietal intra-hemispheric coherence was observed at the left hemisphere on theta (4-8 Hz), and beta-3 (23-30 Hz) frequency bands in fibromyalgia patients than in pain-free controls. Individual differences in depression, anxiety or negative affect did not account for these findings. CONCLUSIONS: Fibromyalgia leads to an altered dynamic of the brain network involved in the processing of pain even at rest. Furthermore ,: our results provide further support for the feasibility of resting-state EEG analyses as a clinical biomarker for the characterization of chronic pain states.