Processing capacity in chronic pain patients: a visual event-related potentials study

Potential mechanisms underlying the accelerated cognitive decline in people with chronic low back pain: A scoping review

A growing body of evidence has shown that people with chronic low back pain (CLBP) demonstrate significantly greater declines in multiple cognitive domains than people who do not have CLBP. Given the high prevalence of CLBP in the ever-growing aging population that may be more vulnerable to cognitive decline, it is important to understand the mechanisms underlying the accelerated cognitive decline observed in this population, so that proper preventive or treatment approaches can be developed and implemented. The current scoping review summarizes what is known regarding the potential mechanisms underlying suboptimal cognitive performance and cognitive decline in people with CLBP and discusses future research directions. Five potential mechanisms were identified based on the findings from 34 included studies: (1) altered activity in the cortex and neural networks; (2) grey matter atrophy; (3) microglial activation and neuroinflammation; (4) comorbidities associated with CLBP; and (5) gut microbiota dysbiosis. Future studies should deepen the understanding of mechanisms underlying this association so that proper prevention and treatment strategies can be developed.

Cerebral processing of emotions in phantom eye pain patients: An event related potential study

Purpose

Phantom eye pain (PEP) is a major clinical problem after eye removal with no standard treatment protocol to date. As pain is a multidimensional experience associated with emotional and cognitive components, this study aimed to explore the possible neuropsychological mechanisms of PEP in a perspective of emotional cognition, in order to provide a basis for clinical treatment.

Methods

Visual oddball event-related potentials (ERPs) under different external emotional stimuli (Disgust, Fear, Sadness, Happiness, Erotica and Neutral) were tested in 12 patients and 12 healthy volunteers. Participants' affective states were measured with the Mood Disorder Questionnaire (MDQ), the Hypomania Checklist-32 (HCL-32), and the Plutchik-van Praag Depression Inventory (PVP). The amplitudes and latencies of N1, P2, N2 and P3 components were analyzed by three-way ANOVA, i.e., group (2) ​× ​emotion (6) ​× ​electrode (3). Multiple comparisons were performed using Bonferroni's test.

Results

Longer N1 latencies, increased N1 amplitudes; shorter P2 latencies under Disgust and Happiness, decreased P2 amplitudes; shorter N2 latencies under Erotica, increased N2 amplitudes were found in patients compared with controls. There was no main effect of group or interaction effect on P3 latencies and P3 amplitudes. The MDQ and HCL-32 scores were lower, and the N1 latencies under Sadness were negatively correlated with PVP scores in patients.

Conclusions

PEP patients showed reversed patterns in exogenous attention allocation and enhanced involuntary attention to emotional stimuli compared with controls. This study demonstrated cortical processing of emotions in PEP patients and could provide a basis for developing emotional intervention therapy.

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.

Within-day rhythms of pain and cognitive function in people with and without fibromyalgia: synchronous or syncopated?

ABSTRACT

Cognitive dysfunction is a common fibromyalgia (FM) symptom and can impact on the daily lives of those affected. We investigated whether within-day pain intensity ratings were associated with contemporaneous objective and subjective measures of cognitive function and whether within-day increases in pain intensity preceded increases in cognitive dysfunction or vice versa. Inclusion of a non-FM group allowed us to examine whether effects were specific to FM. Fifty people with FM and 50 non-FM controls provided 7 days of data. Cognitive tests (processing speed and working memory) and ecological momentary assessments (pain intensity and self-reported cognitive functioning) were conducted ×5/day. Three-level multilevel models examined contemporaneous and within-day 1-lag pain intensity-cognitive functioning associations. Interaction terms assessed possible moderating effects of FM status. Momentary increase in pain was associated with increased self-reported cognitive dysfunction, more strongly so for those with FM (B = 0.27, 95% confidence interval 0.22-0.32; non-FM B = 0.17, 95% confidence interval 0.10-0.23). For the FM group, higher pain was associated with longer processing speed; for the non-FM group, higher pain was associated with shorter processing speed. Pain increase did not precede change in subjective or objective cognitive function in the FM group, but reduction in working memory preceded increase in pain intensity. This finding warrants further research attention and, if replicated, could hold prognostic and/or therapeutic potential.

Cognitive Reserve as a Protective Factor of Mental Health in Middle-Aged Adults Affected by Chronic Pain

Chronic pain is associated with worse mental health and cognitive impairment, which can be a cause or a consequence of brain structure and function alterations, e.g., maladaptive plasticity, antinociceptive system dysregulation. Cognitive reserve reflects the effectiveness of the internal connections of the brain and it has been shown to be a protective factor in brain damage, slowing cognitive aging or reducing the risk of mental health disorders. The current study explored the impact of chronic pain on psychosocial factors, mental health, and cognition. Furthermore, we aimed to examine the role of cognitive reserve in the relationship between mental health and chronic pain clinical characteristics in middle-aged adults. The study group consisted of 477 volunteers from the Barcelona Brain Health Initiative who completed online surveys on pain, mental health, cognitive reserve, and psychosocial factors (sleep and quality of life). We described the differences in sociodemographic data, psychosocial factors, mental health, and self-perceived cognitive impairment, and neuropsychological assessment, between participants reporting pain compared with those without pain, as well as the main characteristics of the chronic pain group. Finally, to study the role of cognitive reserve in the modulation of the relationship between chronic pain and mental health, we compared variables between subgroups of participants with high/low pain intensity and cognitive reserve. The results showed that chronic pain was reported by 45.5% of middle-aged adults. Our results revealed that participants with chronic pain were older and had worse health status than people without pain. The presence of chronic pain affected working memory, mental health, and daily life activities. Moreover, cognitive reserve moderated the influence of pain intensity on mental health, resulting in less mental health affection in people suffering from high pain intensity with high cognitive reserve. In conclusion, the construct of the cognitive reserve could explain differential susceptibility between chronic pain and its mental health association and be a powerful tool in chronic pain assessment and treatment, principally due to its modifiable nature.

Cognition and chronic pain: an analysis on community-dwelling elderly caregivers and non-caregivers

BACKGROUND

In recent years there has been an increasing number of elderly people who care for another elderly person in the same household. These elderly people are more susceptible to overload and the presence of chronic pain, while pain can negatively influence cognitive variables.

OBJECTIVE

To compare the performance and cognitive processing of elderly caregivers and non-caregivers with and without chronic pain.

METHODS

This was a cross-sectional study carried out among 149 elderly people divided into four groups that were matched according to sex, age and schooling. The tests used were a numerical pain assessment scale, the Brief Cognitive Screening Battery (BCSB), Addenbrooke's Cognitive Examination (ACER-R) and cognitive processing through event-related potentials (P300).

RESULTS

Statistically significant differences between participants with and without chronic pain were found with regard to attention/orientation (p=0.045) and visual-spatial skills (p=0.017), and in the total score (p=0.033). In the pain-free group, the caregivers showed better results than the non-caregivers. There were no effects between subjects or interactions (caregiving and pain factors) either on P300 amplitude or on P300 latency.

CONCLUSION

In general, it was observed that pain-free individuals presented better performance. No relationship was observed between the factors care and pain regarding cognitive performance.

Pain-dependent learning in healthy volunteers

A state-dependent learning paradigm was studied in which healthy adult volunteers studied/encoded and recalled information from short passages, neutral in their content, in one of the following conditions: (1) Pain during study-Pain during both recall sessions; (2) Pain during study-No Pain during both recall sessions; (3) No Pain during study-Pain during both recall sessions; and (4) No Pain during study-No Pain during both recall sessions. Pain was experimentally induced using the cold pressor technique. In this study, we looked at evidence for state-dependent learning when the context of learning is not emotionally driven, but neutral. The memory task consisted of encoding detailed information about short stories, then recalling as many details as possible 20 min and 48 hr later. The results indicated no occurrence of a state-dependent learning and retrieval effect in this sample: Participants in the pain-no pain and no pain-pain conditions did not significantly perform differently than participants in the pain-pain and no pain-no pain conditions. However, a main effect of the state during study/encoding was significant, suggesting that being in pain during study had a detrimental effect on performance on the memory tests regardless of the state at retrieval. These results oppose previous studies' findings and shed new light on possible implications in various research areas.

Short-Term Suppression of Somatosensory Evoked Potentials and Perceived Sensations in Healthy Subjects Following TENS

Transcutaneous electrical nerve stimulation (TENS) has been reported to alleviate pain in chronic pain patients. Currently, there is limited knowledge how TENS affects can cause cortical neuromodulation and lead to modulation of non-painful and painful sensations. Our aim was therefore to investigate the effect of conventional, high-frequency TENS on cortical activation and perceived sensations in healthy subjects. We recorded somatosensory evoked potentials (SEPs) and perceived sensations following high-frequency TENS (100 Hz) in 40 healthy subjects (sham and intervention group). The effect of TENS was examined up to an hour after the intervention phase, and results revealed significant cortical inhibition. We found that the magnitude of N100, P200 waves, and theta and alpha band power was significantly suppressed following the TENS intervention. These changes were associated with a simultaneous reduction in the perceived intensity and the size of the area where the sensation was felt. Although phantom limb pain relief previously has been associated with an inhibition of cortical activity, the efficacy of the present TENS intervention to induce such cortical inhibition and cause pain relief should be verified in a future clinical trial.

Comparing objective cognitive impairments in patients with peripheral neuropathic pain or fibromyalgia

Existing studies on cognitive impairments in chronic pain do not investigate peripheral neuropathic pain (PNP) or compare pain conditions in a satisfactory manner. Here we aimed to compare executive dysfunctions in PNP patients with fibromyalgia (FM) and healthy controls (HC). Patients who self-reported cognitive impairments were assessed according to criteria for PNP or FM. Seventy-three patients met criteria and completed testing on executive functioning and IQ measures. We also included twenty matched healthy controls. Regression models controlling for age, sex and IQ, tested associations between group category (PNP, FM or HC) and outcomes. If a substantial association was detected, we followed up with head-to-head comparisons between PNP and FM. Multivariate regression models then tested associations between executive functioning and pain type, controlling for significant confounders. Results from head-to-head comparison between pain conditions showed significant differences on years lived with pain (FM > PNP), the use of anticonvulsants (PNP > FM) and use of analgesics (PNP > FM). When controlled for all significant differences, PNP patients had significantly lower scores on an attention-demanding cued-recall task compared to FM. Poor performance on attention-demanding cued-recall task was associated with PNP, which translate into problems with retaining fast-pace or advanced information.

Neuronal Correlates of Cognitive Control Are Altered in Women With Endometriosis and Chronic Pelvic Pain

Endometriosis is a debilitating women's health condition and is the most common cause of chronic pelvic pain. Impaired cognitive control is common in chronic pain conditions, however, it has not yet been investigated in endometriosis. The aim of this study was to explore the neuronal correlates of cognitive control in women with endometriosis. Using a cross-sectional study design with data collected at a single time-point, event-related potentials were elicited during a cued continuous performance test from 20 women with endometriosis (mean age = 28.5 ± 5.2 years) and 20 age- and gender-matched controls (mean age = 28.5 ± 5.2 years). Event-related potential components were extracted and P3 component amplitudes were derived with temporal principal components analysis. Behavioral and ERP outcomes were compared between groups and subjective pain severity was correlated with ERP component amplitudes. No significant behavioral differences were seen in task performance between the groups (all p > 0.094). Target P3b (all p < 0.034) and SW (all p < 0.040), and non-target early P3a (eP3a; all p < 0.023) and late P3a (lP3a; all p < 0.035) amplitudes were smaller for the endometriosis compared to the healthy control group. Lower non-target eP3a (p < 0.001), lP3a (p = 0.013), and SW (p = 0.019) amplitudes were correlated with higher pain severity scores. Findings suggest that endometriosis-associated chronic pelvic pain is linked to alterations in stimulus-response processing and inhibitory control networks, but not impaired behavioral performance, due to compensatory neuroplastic changes in overlapping cognitive control and pain networks.

Performance of healthy persons under pain in different cognitive load tasks: An event-related potential study on experimental pain individuals

OBJECTIVE

This study aims to determine how brain activities underlying task with different cognitive load would be modulated by the painful state using electroencephalography.

METHODS

The pain state was established by spraying capsaicin on subjects' left inner forearm. A total of 20 experimental pain subjects and 20 matched nonpain controls underwent cognitive tasks with electroencephalogram recording. We collected and analyzed behavioral and event-related potential (ERP) data.

RESULTS

High cognitive tasks exhibited significantly longer response times and lower accuracies than low-load tasks. The experimental pain group displayed a significantly lower accuracy than the control group. In addition, the experimental pain group showed no significance between high and low cognitive tasks in early ERP components (amplitude of N1, P2, N2, and early part of late positive potential), whereas the control group exhibited significance between different load tasks. Furthermore, we observed a delay peak energy for delta and theta oscillation in Fz 500-800 ms after the onset for pain persons and high cognitive load tasks.

CONCLUSIONS

Inadequate early attention modulation, along with delayed peak energy for brain oscillation (delta and theta), could be accountable for a worse performance in cognitive tasks in the experimental pain group. Thus, cognitive load is a highly considerable factor. Overall, this study offers more insights into how healthy population works with cognitive tasks under pain neurologically.

The locus coeruleus noradrenergic system gates deficits in visual attention induced by chronic pain

Despite years of research on pain comorbidity with affective disorders and cognitive deficits, it is still unclear how deficit in attention co-occurs with chronic pain. It is likely that altered neuroplasticity and or dysregulated neurotransmitters induced by chronic pain, at which pain and cognitive processing systems overlap, may have a negative effect on cognitive processing such as attention. One of the main common networks involved in attentional and pain processing is the noradrenergic system originating from the locus coeruleus (LC). We hypothesized that heightened noradrenaline release from LC induced by chronic pain could cause a deficit in visual attention. For this purpose, performance on the 5-choice serial reaction time test (5-CSRTT) was tested in animals with and without a chronic constriction injury and a selective depletion of noradrenaline in the LC. In addition, pain sensitivity was measured via mechanical allodynia and thermal hyperalgesia. We found that the increase in pain sensitivity following chronic pain correlates with a decline in executive functions as measured by 5-CSRTT. This was true in conditions of both low and high attentional demand. Interestingly, a selective depletion of noradrenaline in LC improved the attentional deficits caused by chronic pain. We argue that changes to the noradrenergic system originating in LC can improve deficits in visual attention induced by chronic pain. Deficit in attention is a common comorbidity among patients with chronic pain which adversely affects them in their family and work lives. Patients struggle with functional impairment due to pain, and deficite in attention adds to this dysfunction. Our findings identify the NE-LC system as a key mediator between chronic pain and the attentional deficits associated with this. This finding calls for further investigations concerning treatments related to the noradrenergic system to reduce the malicious effects of chronic pain.

A comprehensive literature review of chronic pain and memory

Chronic pain patients often complain of their "poor memory" and numerous studies objectively confirmed such difficulties in reporting working memory (WM) and long-term memory (LTM) dysfunctions. This paper provides a comprehensive review of the literature on memory impairment in chronic pain (CP) patients. Twenty-four observational studies evaluating WM or/and LTM in a chronic pain group and a control group were included in this review. Results showed that studies consistently reported a moderate decline, in both WM and LTM performances in CP patients. Even if CP patients complained about forgetfulness, objective measurements did not permit to conclude to a long-term storage impairment. CP patients exhibited more specifically encoding or retrieving difficulties compared to controls. Results showed that chronic pain selectively impacted the most attention-demanding memory processes, such as working memory and recollection in long-term memory. Results also demonstrated that CP patients exhibited a memory bias directed towards painful events compared to control subjects. Several authors have suggested that CP could be a maladaptive consequence of memory mechanisms. The long-lasting presence of pain continuously reinforces aversive emotional associations with incidental events. The inability to extinguish this painful memory trace could explain the chronic persistence of pain even when the original injury has disappeared. A major concern is the need to extricate pain-related cognitive effects from those resulting from all the co-morbidities associated with CP which both have a deleterious effect on cognitive function.

The Relationship Between Chronic Pain and Neurocognitive Function: A Systematic Review

OBJECTIVE

Understanding the relationship between chronic pain and neurocognition has important implications for the assessment and treatment of patient experiencing pain. This paper provides an overview of the current literature examining the neurocognition-chronic pain relationship and suggests future avenues of research, along with a discussion of clinical implications of the literature findings. Consideration of potential moderators and mediators of this relationship, as well as a brief discussion of the importance of future research in special populations at particular risk for these problems, are also a focus of this paper.

METHODS

This systematic review summarizes the findings of clinical studies in which neurocognitive performance was measured in chronic pain samples. A literature search led to the inclusion of 53 articles in the review.

RESULTS

Studies of neurocognitive performance in clinical chronic pain samples support a relationship between chronic pain and neurocognitive abnormalities, particularly on tests of memory, attention, and processing speed, with mixed data regarding executive functioning.

DISCUSSION

Several factors may moderate or mediate the relationship between chronic pain and neurocognitive functioning, including mood symptoms, medication side effects, and intensity and/or chronicity of pain. Limitations in the literature include a paucity of methodologically rigorous studies controlling for confounding variables (eg, opioid analgesia) and a limited number of studies examining the relationship between chronic pain and traumatic brain injury (a potential precipitant of both pain and neurocognitive impairment). Nonetheless, findings from the existing literature have significant clinical implications, including for populations with heightened risk of both pain and neurocognitive disorders.

Effect of chronic opioid therapy on actual driving performance in non-cancer pain patients

RATIONALE

Chronic non-cancer pain (CNCP) is a major health problem. Patients are increasingly treated with chronic opioid therapy (COT). Several laboratory studies have demonstrated that long-term use of opioids does not generally impair driving related skills. But there is still a lack of studies investigating on-the-road driving performance in actual traffic.

OBJECTIVES

The present study assessed the impact of COT on road-tracking and car-following performance in CNCP patients.

METHODS

Twenty CNCP patients, long-term treated with stable doses of opioid analgesics, and 19 healthy controls conducted standardized on-the-road driving tests in normal traffic. Performance of controls with a blood alcohol concentration (BAC) of 0.5 g/L was used as a reference to define clinically relevant changes in driving performance.

RESULTS

Standard Deviation of Lateral Position (SDLP), a measure of road-tracking control, was 2.57 cm greater in CNCP patients than in sober controls. This difference failed to reach statistical significance in a superiority test. Equivalence testing indicated that the 95% CI around the mean SDLP change was equivalent to the SDLP change seen in controls with a BAC of 0.5 g/L and did not include zero. When corrected for age differences between groups the 95% CI widened to include both the alcohol reference criterion and zero. No difference was found in car-following performance.

CONCLUSIONS

Driving performance of CNCP patients did not significantly differ from that of controls due to large inter-individual variations. Hence in clinical practice determination of fitness to drive of CNCP patients who receive opioid treatments should be based on an individual assessment.

A Brain Signature to Differentiate Acute and Chronic Pain in Rats

The transition from acute pain to chronic pain entails considerable changes of patients at multiple levels of the nervous system and in psychological states. An accurate differentiation between acute and chronic pain is essential in pain management as it may help optimize analgesic treatments according to the pain state of patients. Given that acute and chronic pain could modulate brain states in different ways and that brain states could greatly shape the neural processing of external inputs, we hypothesized that acute and chronic pain would show differential effects on cortical responses to non-nociceptive sensory information. Here by analyzing auditory-evoked potentials (AEPs) to pure tones in rats with acute or chronic pain, we found opposite influences of acute and chronic pain on cortical responses to auditory inputs. In particular, compared to no-pain controls, the N100 wave of rat AEPs was significantly enhanced in rats with acute pain but significantly reduced in rats with chronic pain, indicating that acute pain facilitated cortical processing of auditory information while chronic pain exerted an inhibitory effect. These findings could be justified by the fact that individuals suffering from acute or chronic pain would have different vigilance states, i.e., the vigilance level to external sensory stimuli would be increased with acute pain, but decreased with chronic pain. Therefore, this auditory response holds promise of being a brain signature to differentiate acute and chronic pain. Instead of investigating the pain system per se, the study of pain-induced influences on cortical processing of non-nocicpetive sensory information might represent a potential strategy to monitor the progress of pain chronification in clinical applications.

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.

Effect of environment on the long-term consequences of chronic pain

Much evidence from pain patients and animal models shows that chronic pain does not exist in a vacuum but has varied comorbidities and far-reaching consequences. Patients with long-term pain often develop anxiety and depression and can manifest changes in cognitive functioning, particularly with working memory. Longitudinal studies in rodent models also show the development of anxiety-like behavior and cognitive changes weeks to months after an injury causing long-term pain. Brain imaging studies in pain patients and rodent models find that chronic pain is associated with anatomical and functional alterations in the brain. Nevertheless, studies in humans reveal that lifestyle choices, such as the practice of meditation or yoga, can reduce pain perception and have the opposite effect on the brain as does chronic pain. In rodent models, studies show that physical activity and a socially enriched environment reduce pain behavior and normalize brain function. Together, these studies suggest that the burden of chronic pain can be reduced by nonpharmacological interventions.

Cognitive dysfunction associated with pain and quality of life in chronic rhinosinusitis

BACKGROUND

Cognitive dysfunction and its relationship to both pain and disease-specific quality of life (QOL) in chronic rhinosinusitis (CRS) have not been investigated previously. We sought to analyze the correlations of pain and disease-specific QOL with cognitive function in CRS.

METHODS

Adults with CRS were prospectively enrolled in a cross-sectional study. Participants' cognitive function was assessed using the Cognitive Failures Questionnaire. Pain was characterized using the Short-Form McGill Pain Questionnaire (SF-MPQ) and the Brief Pain Inventory Short Form. Disease-specific QOL was ascertained using the Rhinosinusitis Disability Index (RSDI) and 22-item Sinonasal Outcome Test (SNOT-22). Disease severity was assessed using nasal endoscopy and computed tomography. Bivariate correlations of pain and cognitive dysfunction, disease-specific QOL, and clinical measures of disease severity were ascertained.

RESULTS

In patients with CRS (n = 70) there was a significant correlation between cognitive dysfunction and pain severity scores (Spearman's correlation [R(s)] = 0.321, p < 0.01). A similar correlation was identified with pain interference (R(s) = 0.317, p < 0.01) and cognitive dysfunction scores. This is mirrored by a significant correlation between another measure of pain severity, the SF-MPQ and cognitive dysfunction (R(s) = 0.498, p < 0.01). In patients with CRS there was a significant correlation between disease-specific QOL scores and cognitive function scores as measured by the SNOT-22 (R(s) = 0.395, p < 0.01) and the RSDI (R(s) = 0.528, p < 0.01).

CONCLUSION

In patients with CRS, increasing pain and worse QOL are associated with cognitive dysfunction. Possible mechanisms for this cognitive dysfunction include differential neural activation secondary to chronic pain and/or the sequela of a chronic inflammatory state.

Decreased activation of cingulo-frontal-parietal cognitive/attention network during an attention-demanding task in patients with chronic low back pain

INTRODUCTION

Attention deficits have been repeatedly reported via neuropsychological assessment in previous literature in patients with chronic low back pain (CLBP). However, there are few functional neuroimaging studies of patients with CLBP during attention processing, and the exact underlying neural mechanisms are yet to be elucidated.

METHODS

We used functional magnetic resonance imaging (fMRI) to measure the function of the cingulo-frontal-parietal (CFP) cognitive/attention network while performing a multi-source interference task (MSIT) in patients with CLBP. Thirty-six patients with CLBP and 36 healthy controls were included in this study. The fMRI data were analyzed with the FSL-FEAT software.

RESULTS

Our results indicated that patients with CLBP showed significantly less activation in the CFP network including the right dorsolateral prefrontal cortex, the dorsal anterior cingulate cortex, and bilateral superior parietal cortex during attention-demanding (MSITinterference > MSITcontrol) trials compared to the healthy controls. A significant negative correlation was found between the scores of the visual analog scale for pain and activation of the right prefrontal cortex during performing the MSIT in patients with CLBP.

CONCLUSION

Our study provides in vivo imaging evidence of abnormal CFP network function during attention-demanding condition in patients with CLBP, which might reflect partly an adaptation/maladaptation of the brain to the chronic pain states.

Intrinsic brain network abnormalities in migraines without aura revealed in resting-state fMRI

BACKGROUND

Previous studies have defined low-frequency, spatially consistent intrinsic connectivity networks (ICN) in resting functional magnetic resonance imaging (fMRI) data which reflect functional interactions among distinct brain areas. We sought to explore whether and how repeated migraine attacks influence intrinsic brain connectivity, as well as how activity in these networks correlates with clinical indicators of migraine.

METHODS/PRINCIPAL FINDINGS

Resting-state fMRI data in twenty-three patients with migraines without aura (MwoA) and 23 age- and gender-matched healthy controls (HC) were analyzed using independent component analysis (ICA), in combination with a "dual-regression" technique to identify the group differences of three important pain-related networks [default mode network (DMN), bilateral central executive network (CEN), salience network (SN)] between the MwoA patients and HC. Compared with the HC, MwoA patients showed aberrant intrinsic connectivity within the bilateral CEN and SN, and greater connectivity between both the DMN and right CEN (rCEN) and the insula cortex - a critical region involving in pain processing. Furthermore, greater connectivity between both the DMN and rCEN and the insula correlated with duration of migraine.

CONCLUSIONS

Our findings may provide new insights into the characterization of migraine as a condition affecting brain activity in intrinsic connectivity networks. Moreover, the abnormalities may be the consequence of a persistent central neural system dysfunction, reflecting cumulative brain insults due to frequent ongoing migraine attacks.

Reactivity in pain-free subjects and a clinical pain population: evaluation of the Kohn Reactivity Scale-dutch Version

BACKGROUND

Patients with pain are more reactive to various types of sensations, not limited to pain alone. A potential useful instrument to assess reactivity is the Kohn Reactivity Scale (KRS). This study examines the psychometric characteristics of the KRS-Dutch version and its ability to differentiate between subjects with and without pain.

METHODS

Internal consistency, convergent validity, and test-retest reliability of the Dutch translation of the KRS were assessed in 321 pain-free control subjects and different subgroups of this sample. Subsequently, reactivity scores were compared between the pain-free subjects and 291 pain patients who were referred to a pain clinic for treatment.

RESULTS

Reliability analyses indicated good internal consistency (α ≥ 0.77) and high test-retest reliability (intraclass correlation = 0.95) of the KRS in the control subjects. Validity analyses yielded positive correlations of the KRS with related constructs like pain vigilance and awareness (r = 0.37), symptom severity (r = 0.29), and the personality characteristic neuroticism (r = 0.20). Pain patients had overall significantly higher KRS scores than the pain-free subjects indicating increased reactivity, particularly for the patients with medically unexplained pain.

CONCLUSIONS

These findings indicate that the KRS is a useful instrument to screen for reactivity in pain patients, which may be of particular relevance for those suffering from medically unexplained pain.

Executive and attentional functions in chronic pain: does performance decrease with increasing task load?

BACKGROUND

Diminished executive function and attentional control has been reported in chronic pain patients. However, the precise pattern of impairment in these aspects of cognition in chronic pain remains unclear. Moreover, a decline in psychomotor speed could potentially influence executive and attentional control performance in pain patients.

OBJECTIVE

To examine different aspects of executive and attentional control in chronic pain together with the confounding role of psychomotor slowing.

METHODS

Neuropsychological tests of sustained attention, planning ability, inhibition and mental flexibility were administered to 34 participants with chronic pain and 32 control participants.

RESULTS

Compared with the controls, participants with chronic pain took longer to complete tests of sustained attention and mental flexibility, but did not perform worse on inhibition or planning tasks. The decreased performance on the mental flexibility task likely reflects a reduction in psychomotor speed. The pattern of performance on the sustained attention task reveals a specific decline in attention, indicated by a disproportionate decline in performance with an increase in task duration and by increased fluctuations in attention during task performance. No additional effect was noted of pain intensity, pain duration, pain catastrophizing, depressive symptoms, reduced sleep because of the pain or opioid use.

CONCLUSIONS

Executive and attention functions are not uniformly affected in chronic pain. At least part of the previously reported decline in executive function in this group may reflect psychomotor slowing. Overall, limited evidence was found that executive and attention performance is indeed lower in chronic pain. Therefore, it can be concluded that in chronic pain sustained attention performance is diminished while mental flexibility, planning and inhibition appear to be intact.

Effective treatment of chronic low back pain in humans reverses abnormal brain anatomy and function

Chronic pain is associated with reduced brain gray matter and impaired cognitive ability. In this longitudinal study, we assessed whether neuroanatomical and functional abnormalities were reversible and dependent on treatment outcomes. We acquired MRI scans from chronic low back pain (CLBP) patients before (n = 18) and 6 months after (spine surgery or facet joint injections; n = 14) treatment. In addition, we scanned 16 healthy controls, 10 of which returned 6 months after the first visit. We performed cortical thickness analysis on structural MRI scans, and subjects performed a cognitive task during the functional MRI. We compared patients and controls, as well as patients before versus after treatment. After treatment, patients had increased cortical thickness in the left dorsolateral prefrontal cortex (DLPFC), which was thinner before treatment compared with controls. Increased DLPFC thickness correlated with the reduction of both pain and physical disability. Additionally, increased thickness in primary motor cortex was associated specifically with reduced physical disability, and right anterior insula was associated specifically with reduced pain. Left DLPFC activity during an attention-demanding cognitive task was abnormal before treatment, but normalized following treatment. These data indicate that functional and structural brain abnormalities-specifically in the left DLPFC-are reversible, suggesting that treating chronic pain can restore normal brain function in humans.

Academic aptitude as a predictor of headache proneness during college: could headache be an outcome of low test scores?

BACKGROUND

Academic work as well as compensated employment has been found adversely associated with frequent headache; headache remains a costly disorder to the person and to society. However, little is known of factors--other than prior headache complaints--that may predict headache frequency over extended periods of time. Based on previous research, effortful task engagement appears to be a contributing factor to headache onset. This suggests that relatively stable attributes that are likely to affect effort expenditure may predict headache frequency over long intervals.

PURPOSE

The goal of this study was to evaluate the predictability of headache proneness in college-attending students by college aptitude tests administered in high school.

METHODS

Five hundred undergraduate students enrolled in a large public, urban university completed a number of questionnaires. Official admissions records of the college aptitude tests ACT (an acronym for the original test name, the American College Testing), SAT (the Scholastic Aptitude Test), and GPA (grade point average) were obtained and compared to the report of headache frequency.

RESULTS

The ACT test mathematics predicted headache proneness in the hypothesized direction, while the ACT English test provided conflicting data; some evidence of gender differences was suggested.

CONCLUSION

While nearly all research on headache and work effectiveness has considered headache to be a cause of reduced efficiency or productivity, this study suggests that a factor which presumably affects the ease of work completion (e.g., scholastic aptitude) may predict headache, at least in some cases within the "work" environment of academia.

Low-frequency BOLD fluctuations demonstrate altered thalamocortical connectivity in diabetic neuropathic pain

Background

In this paper we explored thalamocortical functional connectivity in a group of eight patients suffering from peripheral neuropathic pain (diabetic pain), and compared it with that of a group of healthy subjects. We hypothesized that functional interconnections between the thalamus and cortex can be altered after years of ongoing chronic neuropathic pain.

Results

Functional connectivity was studied through a resting state functional magnetic resonance imaging (fMRI) paradigm: temporal correlations between predefined regions of interest (primary somatosensory cortex, ventral posterior lateral thalamic nucleus, medial dorsal thalamic nucleus) and the rest of the brain were systematically investigated. The patient group showed decreased resting state functional connectivity between the thalamus and the cortex.

Conclusion

This supports the idea that chronic pain can alter thalamocortical connections causing a disruption of thalamic feedback, and the view of chronic pain as a thalamocortical dysrhythmia.

Changes in brain gray matter due to repetitive painful stimulation

Using functional imaging, we recently investigated how repeated painful stimulation over several days is processed, perceived and modulated in the healthy human brain. Considering that activation-dependent brain plasticity in humans on a structural level has already been demonstrated in adults, we were interested in whether repeated painful stimulation may lead to structural changes of the brain. 14 healthy subjects were stimulated daily with a 20 min pain paradigm for 8 consecutive days, using structural MRI performed on days 1, 8, 22 and again after 1 year. Using voxel based morphometry, we are able to show that repeated painful stimulation resulted in a substantial increase of gray matter in pain transmitting areas, including mid-cingulate and somatosensory cortex. These changes are stimulation dependent, i.e. they recede after the regular nociceptive input is stopped. This data raises some interesting questions regarding structural plasticity of the brain concerning the experience of both acute and chronic pain.

Attention to painful stimulation enhances gamma-band activity and synchronization in human sensorimotor cortex

A number of cortical regions are involved in processing pain-related information. The SI and SII somatosensory cortices process mainly sensory discriminative attributes but also play an important role in recognition and memory of painful events. Regions such as SII and the posterior insula appear to be the first stations that house processes by which attention profoundly shapes both behavioral responses and subjective pain experience. We investigated the influence of directed attention on pain-induced oscillations and synchronization processes using magnetoencephalogram in combination with an oddball paradigm in 20 healthy subjects. The subject's task was to count rare painful electrical stimuli applied to one finger, while ignoring frequent stimuli at a different finger. A high detection ratio was observed for all blocks and subjects. Early evoked oscillations in the delta-band increased with higher stimulus intensity and directed attention, most prominently at contralateral sensorimotor sites. Furthermore, suppression and rebound of beta activity were observed after painful stimulation. Moreover, induced oscillatory activity in the high gamma-band increased with directed attention, an effect being significantly stronger for high compared with low stimulus intensity. Coupling analysis performed for this high gamma response revealed stronger functional interactions between ipsilateral and contralateral sites during attention. We conclude that pain-induced high-frequency activity in sensorimotor areas may reflect an attentional augmentation of processing, leading to enhanced saliency of pain-related signals and thus to more efficient processing of this information by downstream cortical centers.

The contribution of recollection and familiarity to recognition memory performance in chronic pain patients

This study examines the selective impact of chronic pain on memory functioning in a recognition task. Thirty chronic pain patients and 30 healthy control subjects performed a yes-no word recognition test. The contribution of recollection and familiarity to both groups' performance was compared by means of the Remember/Know (R/K) procedure, which distinguishes recognition based on the recollection of the encoding episode (R responses) and recognition accompanied by a feeling of familiarity (K responses). Chronic pain patients showed a decrease in recollection together with an increase in familiarity: indeed, they reported less R and more K responses than control subjects. This pattern of performance was not related to the overall recognition ability. These findings are consistent with the hypothesis of the attentional cost of chronic pain, suggesting a selective impact of chronic pain on the most attention-demanding cognitive processes, such as recollection. This study emphasises the relevance of specific procedures distinguishing the underlying components of memory functioning rather than solely global indicators.

Pain Enhances Functional Connectivity of a Brain Network Evoked by Performance of a Cognitive Task

Experimental and clinical evidence indicates that pain can affect cognitive processes, but the cortical networks involved in pain-cognition interactions are unclear. In this study, we determined the effect of pain on the activity of cortical areas involved in cognition acting as a whole (i.e., a network). Subjects underwent functional magnetic resonance imaging (fMRI) while engaged in an attention-demanding cognitive task (multisource interference task) of varying difficulty and simultaneously receiving painful stimuli at varying intensities. The control (baseline) condition was simple finger tapping that had minimal cognitive demands and without pain. Functional connectivity analysis revealed a cortical network consisting of two anti-correlated parts: a task-negative part (precuneus/posterior cingulate cortex, medial frontal and inferior parietal/temporal) the activity of which correlated negatively with the cognitive task and positively with the control baseline, and a task-positive part (inferior frontal, superior parietal, premotor, and anterior insula cortices) the activity of which correlated positively with the cognitive task and negatively with the baseline. Independent components analysis revealed these opposing networks were operating at a low frequency (0.03–0.08 Hz). The functional connectivity of the task-positive network was increased by cognitive demand and by pain. We suggest this attention-specific network balances the needs of general self-referential and environmental awareness versus focused attention to salient information. We postulate that pain affects cognitive ability by its reliance on this common attention-specific network. These data provide evidence that pain can modulate a network presumed to be involved in focused attention, suggesting a mechanism for the interference of pain on cognitive ability by the consumption of attentional resources.