Effects of a force production task and a working memory task on pain perception

The biobehavioural pain and movement questionnaire (BioPMovQ): development and psychometric validation of a new questionnaire

Objective

The purpose of this research was to design and psychometrically validate a new instrument (the Biobehavioural Pain and Movement Questionnaire/BioPMovQ), which assesses the relationship between pain and various factors related to motor behaviour from a biobehavioural perspective.

Methods

A mixed-method design combining a qualitative study with an observational and cross-sectional study was employed to develop (content validity) and psychometrically validate (construct validity, reliability and concurrent/discriminant validity) a new instrument. A total of 200 patients with chronic musculoskeletal pain were recruited.

Results

According to the exploratory factor analysis, the final version of the BioPMovQ consists of 16 items distributed across 4 subscales (1, disability, 2, self-efficacy for physical activity; 3, movement avoidance behaviours; and 4, self-perceived functional ability), all with an eigen value greater than 1, explaining 55.79% of the variance. The BioPMovQ showed high internal consistency (Cronbach's α = 0.82; McDonald's ω = 0.83). The intraclass correlation coefficient was 0.86 (95% confidence interval 0.76 to 0.91), which was considered to demonstrate excellent test-retest reliability. The standard error of measurement and minimal detectable change were 3.43 and 8.04 points, respectively. No floor or ceiling effects were identified. There was a positive, significant and moderate magnitude correlation with the Graded Chronic Pain Scale (r = 0.54), kinesiophobia (r = 0.60), pain catastrophising (r = 0.44) and chronic pain self-efficacy (r = -0.31).

Conclusion

The BioPMovQ showed good psychometric properties. Based on the findings of this study, the BioPMovQ can be used in research and clinical practice to assess patients with chronic musculoskeletal pain.

Effects of Isometric Quadriceps Muscle Exercise with Visual and Auditory Feedback at 1 Year after Total Knee Arthroplasty

OBJECTIVE

To examine the effect of isometric quadriceps exercises with visual and auditory feedback after total knee arthroplasty (TKA).

METHODS

The sample included 41 patients from our previous study who could be followed up for 1 year after TKA. Patients in the intervention group performed isometric quadriceps exercises with visual and auditory feedback using the quadriceps training machine from the 2nd to the 14th day after TKA, whereas those in the control group underwent standard postoperative rehabilitation (without visual or auditory feedback during isometric quadriceps exercises) in the hospital. Patients were evaluated for pain intensity, timed up and go test (TUG) score, 10-m gait speed, 6-minute walking distance (6MWD), and the Western Ontario and McMaster University Osteoarthritis Index (WOMAC) score 1 year after TKA. Additionally, exercise habits and responses to the International Physical Activity Questionnaire (IPAQ) were investigated.

RESULTS

Pain intensity was significantly lower in the intervention group than in the control group. Greater improvements in the TUG test scores, 10-m gait speed, 6MWD, and WOMAC scores were observed in the intervention group. Walking activity, as recorded by the IPAQ, and the proportion of patients with exercise habits were significantly higher in the intervention group than in the control group.

CONCLUSIONS

These results suggest that performing isometric quadriceps exercise with visual and auditory feedback using the quadriceps training machine has good effects, such as pain reduction, physical function improvement, exercise tolerance, and increased physical activity at 1 year after TKA.

Neutral auditory words immediately followed by painful electric shock may show reduced next-day recollection

In this study, we investigated the effect of experimentally delivered acute pain on memory. Twenty-five participants participated in experimental sessions on consecutive days. The first session involved a categorization task to encourage memory encoding. There were two conditions, presented in randomized order, in which participants listened to a series of words, which were repeated three times. In one condition, one-third of the word items were immediately followed by a painful electrical shock. This word-shock pairing was consistent across repetition and the pain-paired items were presented unpredictably. In the other condition, all word items were not associated with pain. Response times over these repeated presentations were assessed for differences. Explicit memory was tested the following day, employing a Remember-Know assessment of word recognition, with no shocks employed. We found evidence that recollection may be reduced for pain-paired words, as the proportion of correct Remember responses (out of total correct responses) was significantly lower. There were no significant reductions in memory for non-pain items that followed painful stimulation after a period of several seconds. Consistent with the experience of pain consuming working memory resources, we theorize that painful shocks interrupt memory encoding for the immediately preceding experimental items, due to a shift in attention away from the word item.

Short-Term Effects of Isometric Quadriceps Muscle Exercise with Auditory and Visual Feedback on Pain, Physical Function, and Performance after Total Knee Arthroplasty: A Randomized Controlled Trial

Severe acute pain after total knee arthroplasty (TKA) may cause delay in muscle strength and functional recovery, and it is a risk factor for chronic postoperative pain. Although pharmacological approaches are the typical firstline to treat acute pain; recently, nonpharmacological approaches such as exercise have been increasingly applied. The purpose of this investigation was to evaluate the effects of a rehabilitation program involving isometric quadriceps exercise with auditory and visual feedback to improve the short-term outcome after TKA. Sixty-two patients, planning a primary unilateral TKA, were randomly assigned to either an intervention group (n = 31) involving isometric quadriceps exercise with auditory and visual feedback in usual rehabilitation after TKA or a control group (n = 31) involving a standardized program for TKA. Patients in the intervention group performed the isometric quadriceps muscle exercise using the Quadriceps Training Machine from 2 to 14 days after TKA instead of the traditional quadriceps sets. Pain intensity, isometric knee extension strength, range of motion, timed up and go test (TUG), 10-m gait speed, 6-minute walking distance, the Western Ontario and McMaster University Osteoarthritis index (WOMAC), the hospital anxiety and depression scale, and the pain catastrophizing scale were assessed before TKA (baseline) and 1 to 3 weeks after TKA. Pain intensity significantly decreased in the intervention group than in the control group at 1 (p = 0.005), 2 (p = 0.002), and 3 (p = 0.010) weeks after TKA. Greater improvements in TUG (p = 0.036), 10-m gait speed (p = 0.047), WOMAC total score (p = 0.017), pain (p = 0.010), and function (p = 0.028) 3 weeks after TKA were observed in the intervention group. These results suggest that isometric quadriceps exercises with auditory and visual feedback provided early knee pain relief, possibly leading to better improvements in physical performance, and patient's perception of physical function in the early stages of postoperative TKA. Further studies should investigate whether this short-term effect is sustainable.

When Less Is More: Investigating Factors Influencing the Distraction Effect of Virtual Reality From Pain

Virtual reality (VR) is a powerful method of redirecting attention away from pain. Yet, little is known about which factors modulate the size of this distraction effect. The aim of this study was to investigate the role of cognitive load and inter-individual differences in the cognitive and affective domain on heat pain thresholds during a VR game. Ninety healthy participants (mean age ± SD: 23.46 ± 3.28; 50% identified as male and 50% as female) played a low and high load version of a VR game while heat pain thresholds and heart rate were recorded. The effects of cognitive load were assessed by computing the difference in pain thresholds between the high and low load condition for each participant. In addition, we computed the difference in heart rate variability (HRV) measures between both conditions to explore whether these would be correlated with the difference in heat pain thresholds. Prior to the VR session, participants completed questionnaires about their emotional distress, pain-related cognitions, and different executive functioning tasks. Contrary to our expectations, not all participants benefitted from a higher load in terms of distraction from pain. Logistic regression analysis revealed that participants who reported more emotional distress were more likely to exhibit higher pain thresholds in the low relative to the high load condition. Accordingly, these participants tended to show marginally higher HRV in the low compared to the high load condition. Our study demonstrates that the potential benefits of an increased cognitive load in VR on pain sensitivity depends on individual differences in affective state.

Exercise-induced hypoalgesia after acute and regular exercise: experimental and clinical manifestations and possible mechanisms in individuals with and without pain

This review describes methodology used in the assessment of the manifestations of exercise-induced hypoalgesia in humans and previous findings in individuals with and without pain. Possible mechanisms and future directions are discussed.

Exercise and physical activity is recommended treatment for a wide range of chronic pain conditions. In addition to several well-documented effects on physical and mental health, 8 to 12 weeks of exercise therapy can induce clinically relevant reductions in pain. However, exercise can also induce hypoalgesia after as little as 1 session, which is commonly referred to as exercise-induced hypoalgesia (EIH). In this review, we give a brief introduction to the methodology used in the assessment of EIH in humans followed by an overview of the findings from previous experimental studies investigating the pain response after acute and regular exercise in pain-free individuals and in individuals with different chronic pain conditions. Finally, we discuss potential mechanisms underlying the change in pain after exercise in pain-free individuals and in individuals with different chronic pain conditions, and how this may have implications for clinical exercise prescription as well as for future studies on EIH.

Altered neural oscillations within and between sensorimotor cortex and parietal cortex in chronic jaw pain

Pain perception is associated with priming of the motor system and the orienting of attention in healthy adults. These processes correspond with decreases in alpha and beta power in the sensorimotor and parietal cortices. The goal of the present study was to determine whether these findings extend to individuals with chronic pain. Individuals with chronic jaw pain and pain-free controls anticipated and experienced a low pain or a moderate pain-eliciting heat stimulus. Although stimuli were calibrated for each subject, stimulus temperature was not different between groups. High-density EEG data were collected during the anticipation and heat stimulation periods and were analyzed using independent component analyses, EEG source localization, and measure projection analyses. Direct directed transfer function was also estimated to identify frequency specific effective connectivity between regions. Between group differences were most evident during the heat stimulation period. We report three novel findings. First, the chronic jaw pain group had a relative increase in alpha and beta power and a relative decrease in theta and gamma power in sensorimotor cortex. Second, the chronic jaw pain group had a relative increase in power in the alpha and beta bands in parietal cortex. Third, the chronic jaw pain group had less connectivity strength in the beta and gamma bands between sensorimotor cortex and parietal cortex. Our findings show that the effect of chronic pain attenuates rather than magnifies neural responses to heat stimuli. We interpret these findings in the context of system-level changes in intrinsic sensorimotor and attentional circuits in chronic pain.

Functional brain activity during motor control and pain processing in chronic jaw pain

Changes in brain function in chronic pain have been studied using paradigms that deliver acute pain-eliciting stimuli or assess the brain at rest. Although motor disability accompanies many chronic pain conditions, few studies have directly assessed brain activity during motor function in individuals with chronic pain. Using chronic jaw pain as a model, we assessed brain activity during a precisely controlled grip force task and during a precisely controlled pain-eliciting stimulus on the forearm. We used multivariate analyses to identify regions across the brain whose activity together best separated the groups. We report 2 novel findings. First, although the parameters of grip force production were similar between the groups, the functional activity in regions including the prefrontal cortex, insula, and thalamus best separated the groups. Second, although stimulus intensity and pain perception were similar between the groups, functional activity in brain regions including the dorsal lateral prefrontal cortex, rostral ventral premotor cortex, and inferior parietal lobule best separated the groups. Our observations suggest that chronic jaw pain is associated with changes in how the brain processes motor and pain-related information even when the effector producing the force or experiencing the pain-eliciting stimulus is distant from the jaw. We also demonstrate that motor tasks and multivariate analyses offer alternative approaches for studying brain function in chronic jaw pain.

Pain-Related Suppression of Beta Oscillations Facilitates Voluntary Movement

Increased beta oscillations over sensorimotor cortex are antikinetic. Motor- and pain-related processes separately suppress beta oscillations over sensorimotor cortex leading to the prediction that ongoing pain should facilitate movement. In the current study, we used a paradigm in which voluntary movements were executed during an ongoing pain-eliciting stimulus to test the hypothesis that a pain-related suppression of beta oscillations would facilitate the initiation of a subsequent voluntary movement. Using kinematic measures, electromyography, and high-density electroencephalography, we demonstrate that ongoing pain leads to shorter reaction times without affecting the kinematics or accuracy of movement. Reaction time was positively correlated with beta power prior to movement in contralateral premotor areas. Our findings corroborate the view that beta-band oscillations are antikinetic and provide new evidence that pain primes the motor system for action. Our observations provide the first evidence that a pain-related suppression of beta oscillations over contralateral premotor areas leads to shorter reaction times for voluntary movement.

Automated classification of pain perception using high-density electroencephalography data

The translation of brief, millisecond-long pain-eliciting stimuli to the subjective perception of pain is associated with changes in theta, alpha, beta, and gamma oscillations over sensorimotor cortex. However, when a pain-eliciting stimulus continues for minutes, regions beyond the sensorimotor cortex, such as the prefrontal cortex, are also engaged. Abnormalities in prefrontal cortex have been associated with chronic pain states, but conventional, millisecond-long EEG paradigms do not engage prefrontal regions. In the current study, we collected high-density EEG data during an experimental paradigm in which subjects experienced a 4-s, low- or high-intensity pain-eliciting stimulus. EEG data were analyzed using independent component analyses, EEG source localization analyses, and measure projection analyses. We report three novel findings. First, an increase in pain perception was associated with an increase in gamma and theta power in a cortical region that included medial prefrontal cortex. Second, a decrease in lower beta power was associated with an increase in pain perception in a cortical region that included the contralateral sensorimotor cortex. Third, we used machine learning for automated classification of EEG data into low- and high-pain classes. Theta and gamma power in the medial prefrontal region and lower beta power in the contralateral sensorimotor region served as features for classification. We found a leave-one-out cross-validation accuracy of 89.58%. The development of biological markers for pain states continues to gain traction in the literature, and our findings provide new information that advances this body of work.NEW & NOTEWORTHY The development of a biological marker for pain continues to gain traction in literature. Our findings show that high- and low-pain perception in human subjects can be classified with 89% accuracy using high-density EEG data from prefrontal cortex and contralateral sensorimotor cortex. Our approach represents a novel neurophysiological paradigm that advances the literature on biological markers for pain.

Pain and motor processing in the human cerebellum

Pain-related adaptations in movement require a network architecture that allows for integration across pain and motor circuits. Previous studies addressing this issue have focused on cortical areas such as the midcingulate cortex. Here, we focus on pain and motor processing in the human cerebellum. The goal of this study was to identify areas of activation in the cerebellum, which are common to pain and motor processing, and to determine whether the activation is limited to the superior and inferior cerebellar motor maps or extends into multimodal areas of the posterior cerebellum. Our observations identified overlapping activity in left and right lobules VI and VIIb during pain and motor processing. Activation in these multimodal regions persisted when pain and motor processes were combined within the same trial, and activation in contralateral left lobule VIIb persisted when stimulation was controlled for. Functional connectivity analyses revealed significant correlations in the BOLD time series between multimodal cerebellar regions and sensorimotor regions in the cerebrum including anterior midcingulate cortex, supplementary motor area, and thalamus. The current findings are the first to show multimodal processing in lobules VI and VIIb for motor control and pain processing and suggest that the posterior cerebellum may be important in understanding pain-related adaptations in motor control.

Nonlinear Effects of Noxious Thermal Stimulation and Working Memory Demands on Subjective Pain Perception

OBJECTIVE

A bidirectional relationship between working memory (WM) and acute pain has long been assumed, but equivocal evidence exists regarding this relationship. This study characterized the relationship between WM and acute pain processing in healthy individuals using an adapted Sternberg WM task.

DESIGN

Participants completed a Sternberg task while receiving noxious thermal stimulation. Participants received a pseudorandom presentation of four different temperatures (baseline temperatures and individually determined low-, medium-, and high-temperature stimuli) and four levels of Sternberg task difficulty (0-, 3-, 6-, and 9-letter strings).

SUBJECTS

Twenty-eight healthy participants were recruited from Stanford University and the surrounding community to complete this study.

RESULTS

A nonlinear interaction between intensity of thermal stimulation and difficulty of the Sternberg task was noted. Increased cognitive load from the Sternberg task resulted in increased perception of pain in low-intensity thermal stimulation but suppressed pain perception in high-intensity thermal stimulation. Thermal stimulation had no significant effect on participants' response time or accuracy on the Sternberg task regardless of intensity level.

CONCLUSIONS

Pain perception appears to decrease as a function of WM load only for sufficiently noxious stimuli. However, increasing noxious stimuli did not affect cognitive performance. These complex relationships may reflect a shared cognitive space that can become "overloaded" with input of multiple stimuli of sufficient intensity.

Dose-response effect of isometric force production on the perception of pain

Isometric contractions can influence the way that we perceive pain, but conclusions on the dose-response effect of force amplitude on pain perception are limited because previous studies have not held the duration of force contractions constant while varying force amplitude. To address this issue we designed an experiment that allowed us to accurately guide the amplitude of an isometric pinch grip force contraction on a trial-by-trial basis, while a thermal pain eliciting stimulus was simultaneously delivered for the same duration to the non-contracting hand. Our results show that an increase in the amplitude of force produced by one hand corresponded with a decrease in pain perception in the opposite hand. Our observations provide novel evidence that the centralized inhibitory response that underlies analgesia is sensitive to and enhanced by stronger isometric contractions.

Neuroimaging Evidence of Motor Control and Pain Processing in the Human Midcingulate Cortex

Human neuroimaging and virus-tracing studies in monkey predict that motor control and pain processes should overlap in anterior midcingulate cortex (aMCC), but there is currently no direct evidence that this is the case. We used a novel functional magnetic resonance imaging paradigm to examine brain activity while subjects performed a motor control task, experienced a pain-eliciting stimulus on their hand, and performed the motor control task while also experiencing the pain-eliciting stimulus. Our experiment produced 3 novel results. First, group-level analyses showed that when separate trials of motor control and pain processing were performed, overlapping functional activity was found in the same regions of aMCC, supplementary motor area (SMA), anterior insula, and putamen. Secondly, increased activity was found in the aMCC and SMA when motor control and pain processing occurred simultaneously. Thirdly, individual-level analyses showed that 93% of subjects engaged the same region of aMCC during separate trials of motor control and pain processing irrespective of differences in the sulcal/gyral morphology of the cingulate cortex across individuals. These observations provide direct evidence in humans that the same region of aMCC is engaged for motor control and pain processing.