The sensory and affective components of pain: are they differentially modifiable dimensions or inseparable aspects of a unitary experience? A systematic review

Low-intensity transcranial ultrasound stimulation and its regulatory effect on pain

Transcranial ultrasound stimulation is an emerging non-invasive neuromodulation technology with the advantages of deep tissue penetration, high spatial resolution, and minimal side effects. Low intensity transcranial ultrasound stimulation (LITUS) has been shownto bea promising neuromodulation treatment for psychiatric and neurological disorders. Notably, significant progress has been made recently in both the application of LITUS in pain disorders and the elucidation of its analgesic mechanisms. This review provides an overview of LITUS and its state-of-the-art mechanisms, including cavitation, mechanical, and thermal effects. We summarize studies spanning from animal models to human trials, highlighting the analgesic effects of transcranial ultrasound stimulation on pain-related neural pathways. Furthermore, we explore potential analgesic mechanisms, such as the suppression of neural activity in the ascending pain pathway and other associated processes.Lastly, we discuss the potential of LITUS for future integrative treatments of chronic pain and psychomotor disorders, as well as its broader therapeutic applications.

From didactic explanations to co-design, sequential art and embodied learning: challenges, criticisms and future directions of patient pain education

Pain Neuroscience Education (PNE) emerged over two decades ago in response to the incoherence between evidence-based pain management strategies, and consumer and clinician understandings of "how pain works". Many clinical trials have investigated the effects of PNE either as a standalone intervention or embedded within a more complex care package, with mixed results. A range of research methods have been used to explore the inconsistent effects of PNE. Together they (i) identify significant shortcomings and limitations of PNE and (ii) raise the possibility that gaining a broadly scientifically accurate understanding of "how pain works" may be critical for subsequent pain and disability improvements. Both learnings strongly suggest that we need to do better. Extensive research incorporating several interest-holders has led to updated content and language and criticisms of both are addressed. The method of PNE has also been updated, with integration of educational frameworks, teaching strategies and tactics, patient resources and clinical tools that all aim to promote the likelihood that patients will learn key concepts and operationalise them to improve their pain, function and quality of life. Pain Science Education is used to differentiate the new approach from PNE.

Individual differences in response to repeated painful stimulation: Habituation, sensitization, and nocebo effects

The present study analyzes habituation, sensitization, and nocebo effects based on individual differences in response to painful stimulation. Habituation and sensitization to pain show two opposite patterns that may occur during repeated painful stimulation. Negative expectations such as a nocebo manipulation have been shown to increase pain ratings, but it is unclear to what extent they can influence habituation and sensitization to pain. In this preregistered study, we investigate the effects of repeated painful stimulation across time with pain intensity and unpleasantness ratings, individual differences in the response trajectories, and the impact of a nocebo manipulation in the context of habituation and sensitization response subgroups. We included 60 participants (26 male, 34 female, age 18-60) who received repeated painful electrical stimulation across four runs. Half of the participants received a negative verbal expectation (i.e., nocebo manipulation) after the third run. Participants provided both intensity and unpleasantness ratings after each stimulus. The results demonstrated large individual variability in responses. On the group level, participants showed sensitization to pain which decreased across runs. Individual slopes across and within-runs varied greatly, starting with mostly sensitization and ending with habituation profiles. Habituation of pain intensity and unpleasantness was highly correlated. The nocebo manipulation resulted in a significant nocebo effect, demonstrating a large increase in pain and unpleasantness ratings. In summary, this study showed large individual differences and the impact of a nocebo manipulation on the background of different response profiles. PERSPECTIVE: Repeated painful stimulation resulted in patterns of habituation and sensitization, with large individual variability that differed for across and within-run analyses. Pain intensity and unpleasantness ratings were highly correlated. A nocebo manipulation demonstrated increased intensity and unpleasantness reports, even after habituation and sensitization patterns were established.

Effects of a Secondary Cognitive Task on Psychological and Stretch Performance

Extensive research supports the positive effects of stretching on joint flexibility. During stretching, an individual's perceptions of stretch-related discomfort and pain negatively influence affective response. This study examined the effects of a dissociative attentional strategy on performance and perception during stretching. To induce dissociation, participants completed a secondary cognitive task (mental math) during passive and active static stretching. Participants (n = 16) stretched in the following conditions: (1) active-mental math, (2) active-control, (3) passive-mental math, and (4) passive-control. Participants completed conditions in a block randomized order (i.e. Latin Square Design). MANOVA of range of motion (ROM) did not support an interaction of stretch and cognitive load condition or a main effect of cognitive load. However, there was a significant effect of stretch condition on pleasantness and a significant effect of cognitive load on perceived stretch intensity and pleasantness. Passive stretching resulted in a greater ROM, reduced perceived stretch intensity, and increased pleasantness compared to active stretching. The introduction of a secondary cognitive task resulted in no significant change to ROM, but did result in reduced perception of stretch intensity and increased pleasantness. Conclusion: These findings provide evidence that dissociation during static stretch can reduce perceived stretch intensity without reduction in ROM. This effect exists even during active stretching, with the added benefit of improved ROM.

Severity of Pain at Admission and Development of Symptoms of Anxiety and Depression: A Study of Burn Patients at a Tertiary Healthcare Facility in Ghana

Background Burns remain a global public health concern and one of the major causes of painful injury, which impacts patients physically and psychologically. Pain causes more suffering in the acute stage and rehabilitation in burn patients, which is associated with anxiety, depression, and post-traumatic stress disorder that can lead to long-term consequences, which negatively affects the quality of life (QoL) of the patient.  Objective This study aimed to determine the influence of the severity of pain at admission on the development of symptoms of anxiety and depression among burn patients within the first week of admission. Methods An analytical cross-sectional study was conducted among adult burn patients at the Burns Centre of the Korle-Bu Teaching Hospital. Patients' demographic and clinical characteristics, such as age, cause of burns, degree of burns, and percentage of total body surface area (TBSA), were recorded. Hospital Anxiety and depression scale (HADS) was used to assess anxiety and depression symptoms, while the Visual Analog Scale (VAS) was used to evaluate the intensity of pain. Simple linear regression was used to determine the influence of the severity of pain at admission on symptoms of anxiety and depression. Results Sixty-five adult inpatients were enrolled, with a mean age of 35.9 years. About 92% presented with severe pain, and two-thirds developed severe anxiety (66.2%) or depressive (67.7%) symptoms. The mean (±SD) anxiety symptoms, depression symptoms, and pain scores were 11.4(±2.7), 11.8(±3.4), and 8.5(±1.6), respectively. Mean anxiety symptom scores were significantly different between the age groups, %TBSA, and severity of pain. Mean depression symptom scores were significantly different between the severity of pain and the cause of burn injury. There was a significant positive relationship between the severity of pain on admission and the level of depression and anxiety symptoms. Conclusion Patients with burn injury present with severe pain at admission, and the majority develop significant anxiety and depressive symptoms within the first week of admission. The intensity of pain at admission is significantly associated with the level of anxiety and depression.

Pain and the Brain: A Systematic Review of Methods, EEG Biomarkers, Limitations, and Future Directions

Background: Pain is prevalent in almost all populations and may often hinder visual, auditory, tactile, olfactory, and taste perception as it alters brain neural processing. The quantitative methods emerging to define pain and assess its effects on neural functions and perception are important. Identifying pain biomarkers is one of the initial stages in developing such models and interventions. The existing literature has explored chronic and experimentally induced pain, leveraging electroencephalograms (EEGs) to identify biomarkers and employing various qualitative and quantitative approaches to measure pain. Objectives: This systematic review examines the methods, participant characteristics, types of pain states, associated pain biomarkers of the brain's electrical activity, and limitations of current pain studies. The review identifies what experimental methods researchers implement to study human pain states compared to human control pain-free states, as well as the limitations in the current techniques of studying human pain states and future directions for research. Methods: The research questions were formed using the Population, Intervention, Comparison, Outcome (PICO) framework. A literature search was conducted using PubMed, PsycINFO, Embase, the Cochrane Library, IEEE Explore, Medline, Scopus, and Web of Science until December 2024, following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines to obtain relevant studies. The inclusion criteria included studies that focused on pain states and EEG data reporting. The exclusion criteria included studies that used only MEG or fMRI neuroimaging techniques and those that did not focus on the evaluation or assessment of neural markers. Bias risk was determined by the Newcastle-Ottawa Scale. Target data were compared between studies to organize the findings among the reported results. Results: The initial search resulted in 592 articles. After exclusions, 24 studies were included in the review, 6 of which focused on chronic pain populations. Experimentally induced pain methods were identified as techniques that centered on tactile perception: thermal, electrical, mechanical, and chemical. Across both chronic and stimulated pain studies, pain was associated with decreased or slowing peak alpha frequency (PAF). In the chronic pain studies, beta power increases were seen with pain intensity. The functional connectivity and pain networks of chronic pain patients differ from those of healthy controls; this includes the processing of experimental pain. Reportedly small sample sizes, participant comorbidities such as neuropsychiatric disorders and peripheral nerve damage, and uncontrolled studies were the common drawbacks of the studies. Standardizing methods and establishing collaborations to collect open-access comprehensive longitudinal data were identified as necessary future directions to generalize neuro markers of pain. Conclusions: This review presents a variety of experimental setups, participant populations, pain stimulation methods, lack of standardized data analysis methods, supporting and contradicting study findings, limitations, and future directions. Comprehensive studies are needed to understand the pain and brain relationship deeper in order to confirm or disregard the existing findings and to generalize biomarkers across chronic and experimentally induced pain studies. This requires the implementation of larger, diverse cohorts in longitudinal study designs, establishment of procedural standards, and creation of repositories. Additional techniques include the utilization of machine learning and analyzing data from long-term wearable EEG systems. The review protocol is registered on INPLASY (# 202520040).

Nature exposure induces analgesic effects by acting on nociception-related neural processing

Nature exposure has numerous health benefits and might reduce self-reported acute pain. Given the multi-faceted and subjective quality of pain and methodological limitations of prior research, it is unclear whether the evidence indicates genuine analgesic effects or results from domain-general effects and subjective reporting biases. This preregistered neuroimaging study investigates how nature modulates nociception-related and domain-general brain responses to acute pain. Healthy participants (N = 49) receiving electrical shocks report lower pain when exposed to virtual nature compared to matched urban or indoor control settings. Multi-voxel signatures of pain-related brain activation patterns demonstrate that this subjective analgesic effect is associated with reductions in nociception-related rather than domain-general cognitive-emotional neural pain processing. Preregistered region-of-interest analyses corroborate these results, highlighting reduced activation of areas connected to somatosensory aspects of pain processing (thalamus, secondary somatosensory cortex, and posterior insula). These findings demonstrate that virtual nature exposure enables genuine analgesic effects through changes in nociceptive and somatosensory processing, advancing our understanding of how nature may be used to complement non-pharmacological pain treatment. That this analgesic effect can be achieved with easy-to-administer virtual nature exposure has important practical implications and opens novel avenues for research on the precise mechanisms by which nature impacts our mind and brain.

The impact of a virtual wound on pain sensitivity: insights into the affective dimension of pain

Background

The perception of pain is difficult to assess due to the complex combination of various components related to nociception, experience, and cognition. There are currently no biomarkers to assess the affective component of pain in healthy volunteers. Using Virtual Reality (VR), it may be possible to assess changes in pain perception when adding an affective component to painful stimulation.

Methods

In this two-visit feasibility study, we assess the effect of a simulated wound in VR on the electrical pain detection (PDT) and tolerance (PTT) threshold in 24 healthy male study participants. The VR simulation presented a copy of the research room from first person view. Prior to each VR assessment, study participants were primed by interacting with the VR environment. Two conditions were assessed: (1) VR-Wound: a burn-wound, smoke, and electrical sparks become visible and audible with increasing stimulus intensity, and (2) VR-neutral: no additional aspects. The PDT and PTT to electrical stimuli were recorded during both VR conditions and outside of VR. VAS-Questionnaires were used to assess unpleasantness and fear.

Results

The PDT decreased when a virtual wound is presented compared to a neutral condition. Study participants experienced the electrical stimulation as more painful and more intense during the wound simulation than during the neutral condition. The effect was more pronounced during the second visit.

Conclusion

VR enhanced the perception of pain, thereby providing new insights into the affective component of pain. Further testing of this methodology is warranted by performing a clinical study that evaluates drug effects on the affective component of pain.

Are Art-Based Interventions Effective in Improving Psychological Well-Being Among Informal Caregivers of Cancer Patients? A Systematic Review

Objectives: To systematically synthesize the current evidence on the effects of art-based interventions on improving anxiety, depression, stress, sleep, and well-being of cancer caregivers. Design: A systematic review. Methods: We searched PubMed, EMBASE, Web of Science, CINAHL, PsycINFO, and Cochrane Central Register of Controlled Trials databases from their inception up to April 2024. Studies exploring the effects of art-based interventions on the psychological symptoms of cancer caregivers were included. We did not restrict the publication to the particular study designs, including randomized controlled trials, quasiexperimental studies, and qualitative studies. Results: Fifteen studies of 607 participants were identified in this systematic review. Overall, the existing studies provided preliminary evidence to suggest that art-based interventions may benefit cancer caregivers in improving anxiety, depression, stress, caregiver burden, and quality of life. However, the relatively low quality of the current evidence limits the efficacy of these findings. Conclusions: According to the existing evidence, the therapeutic benefits of using art-based interventions for improving the psychological well-being of cancer caregivers are uncertain. More high-quality and well-designed studies are still required to confirm the psychological effectiveness of art-based interventions for cancer caregivers in the future.

Neuropsychiatric Manifestations of COVID-19 Disease and Post COVID Syndrome: The Role of N-acetylcysteine and Acetyl-L-carnitine

COVID-19 is associated with neuropsychiatric symptoms, such as anosmia, anxiety, depression, stress-related reactions, and psychoses. The illness can cause persistent cognitive impairment and "brain fog", suggesting chronic brain involvement. Clinical entities of ongoing symptomatic COVID-19 and Post COVID Syndrome (PCS) mainly present neuropsychiatric symptoms such as dysgeusia, headache, fatigue, anxiety, depression, sleep disturbances, and post-traumatic stress disorder. The pathophysiology of COVID-19-related brain damage is unclear, but it is linked to various mechanisms such as inflammation, oxidative stress, immune dysregulation, impaired glutamate homeostasis, glial and glymphatic damage, and hippocampal degeneration. Noteworthy is that the metabotropic receptor mGluR2 was discovered as a mechanism of internalisation of SARS-CoV-2 in Central Nervous System (CNS) cells. N-acetylcysteine (NAC) and acetyl-L-carnitine (ALC) are two supplements that have already been found effective in treating psychiatric conditions. Furthermore, NAC showed evidence in relieving cognitive symptomatology in PCS, and ALC was found effective in treating depressive symptomatology of PCS. The overlapping effects on the glutamatergic system of ALC and NAC could help treat COVID-19 psychiatric symptoms and PCS, acting through different mechanisms on the xc-mGluR2 network, with potentially synergistic effects on chronic pain and neuro-astrocyte protection. This paper aims to summarise the current evidence on the potential therapeutic role of NAC and ALC, providing an overview of the underlying molecular mechanisms and pathophysiology. It proposes a pathophysiological model explaining the effectiveness of NAC and ALC in treating COVID-19-related neuropsychiatric symptoms.

Pain is what you think: functional magnetic resonance imaging evidence toward a cognitive and affective approach for pain research

The sensory/discriminative domain of pain is often given more consideration than the cognitive and affective influences that ultimately make pain what it is: a highly subjective experience that is based on an individual's life history and experiences. While many investigations of the underlying mechanisms of pain have focused on solely noxious stimuli, few have compared somatosensory stimuli that cross the boundary from innocuous to noxious. Of those that have, there is little consensus on the similarities and differences in neural signaling across these sensory domains. The purpose of this study was to apply our established network connectivity analyses toward the goal of understanding the neural mechanisms behind sensory, cognitive, and affective responses to noxious and innocuous stimuli. Functional MRI data were collected from 19 healthy women and men that experienced warm and hot thermal stimuli across multiple trials. This is a within-subjects cross-sectional experimental study with repeated measures. Ratings of stimulus intensity and unpleasantness that were collected during each run confirmed significant perceptual differences between the two types of stimuli. Despite this finding, no group differences in network connectivity were found across conditions. When individual differences related to pain ratings were investigated, subtle differences were found in connectivity that could be attributed to sensory and association regions in the innocuous condition, and cognitive, affective, and autonomic regions in the pain condition. These results were reflected in the time-course data for each condition. Overall, signaling mechanisms for innocuous and noxious somatosensation are intricately linked, but pain-specific perception appears to be driven by our psychological and autonomic states.

From taboo to treatment: The emergence of psychedelics in the management of pain and opioid use disorder

The rise of psychedelics in contemporary medicine has sparked interest in their potential therapeutic applications. While traditionally associated with countercultural movements and recreational use, recent research has shed light on the potential benefits of psychedelics in various mental health conditions. In this review, we explore the possible role of psychedelics in the management of chronic pain and opioid use disorder (OUD), 2 critical areas in need of innovative treatment options. Pain control remains a significant clinical challenge, particularly for individuals with OUD and those who receive long-term opioid therapy who develop marked tolerance to opioid-induced analgesia. Despite the magnitude of this problem, there is a scarcity of controlled studies investigating pain management alternatives for these populations. Drawing from preclinical and human evidence, we highlight the potential of psychedelics to act on shared neurobiological substrates of chronic pain and OUD, potentially reversing pain- and opioid-induced neuroadaptations, such as central sensitization. We elaborate on the multifaceted dimensions of the pain experience (sensory, affective and cognitive) and their intersections that overlap with opioid-related phenomena (opioid craving and withdrawal), hypothesizing how these processes can be modulated by psychedelics. After summarizing the available clinical research, we propose mechanistic insights and methodological considerations for the design of future translational studies and clinical trials, building on a shared clinical and neurobiological understanding of chronic pain and OUD. Our intention is to provide timely perspectives that accelerate the development and exploration of novel therapeutics for chronic pain and OUD amidst the escalating opioid crisis.

Abnormal visual cortex activity using functional magnetic resonance imaging in treatment resistant photophobia in Friedreich Ataxia

Purpose

Friedreich ataxia (FDRA) is a debilitating neurodegenerative disease that can have ophthalmological manifestations including visual dysfunction, nystagmus, and optic atrophy. However, severe photophobia has not been reported nor evaluated with functional magnetic resonance imaging (fMRI).

Methods

A 64-year-old white female with a 37-year history of FDRA presented to the eye clinic with worsening photophobia of 3 years. To measure her visual cortex activation and subjective responses during episodes of photophobia, she underwent event-related fMRI with light stimuli. In comparison, the same protocol was conducted in an individual with photophobia but without FDRA. After the fMRI, both patients were treated with 35 units of BoNT-A applied to the forehead.

Results

Analysis of visual cortex activity in response to light stimulus in the FDRA patient showed no correlation between blood oxygen level dependent (BOLD) activation and light stimuli in the first (r = -0.100, p = 0.235), and a weak negative correlation in the second half of the fMRI scan (r = -0.236 p = 0.004). In notable contrast, significant positive correlations were noted between visual cortex activity and the light stimulus (1st half: r = 0.742, p < 0.001, vs. 2nd half: r = 0.614, p < 0.001) in the comparator. Six weeks later, no improvement in photophobia was noted in either patient.

Conclusion and importance

Our study highlights photophobia as one potential ocular manifestation of FDRA and suggests that one underlying contributor may be a decoupled cortical neurovascular response to light. Our study provides novel information that may guide physiologic understanding and future treatments in this disease.

Pathophysiology of Pain and Mechanisms of Neuromodulation: A Narrative Review (A Neuron Project)

Pain serves as a vital innate defense mechanism that can significantly impact an individual's quality of life. Understanding the physiological effects of pain well plays an important role in developing novel pain treatments. Nociceptor neurons play a key role in pain and inflammation. Interactions between nociceptors and the immune system occur both at the site of injury and within the central nervous system. Modulating chemical mediators and nociceptor activity offers promising new approaches to pain management. Essentially, the sensory nervous system is essential for modulating the body's protective response, making it critical to understand these interactions to discover new pain treatment strategies. New innovations in neuromodulation have led to alternatives to opioids individuals with chronic pain with consequent improvement in disease-based treatment and nerve targeting. New neural targets from cellular and structural perspectives have revolutionized the field of neuromodulation. This narrative review aims to elucidate the mechanisms of pain transmission and processing, examine the characteristics and properties of nociceptors, and explore how the immune system influences pain perception. It further provides an updated overview of the physiology of pain and neuromodulatory mechanisms essential for managing acute and chronic pain. We assess the current understanding of different pain types, focusing on key molecules involved in each type and their physiological effects. Additionally, we compare painful and painless neuropathies and discuss the neuroimmune interactions involved in pain manifestation.

Sensory and affective dimensions in loudness perception: Insights from young adults

Traditional psychoacoustic measures often lack accuracy in diagnosing hyperacusis and other sound tolerance disorders, possibly due to their reliance on artificial stimuli and unidimensional scales. The aim of this study was to assess loudness across sensory and affective dimensions using natural sounds, drawing on pain research wherein intensity and unpleasantness are assessed separately. We hypothesized that similar distinctions apply to loudness perception. A total of 102 young adults with normal to mild hearing loss rated 32 sound stimuli (pleasant, unpleasant, neutral, and artificial) at 10 intensities (40 to 100 dBA) on sensory and affective scales. They also completed the Hyperacusis Questionnaire, the Noise Sensitivity Scale, and the Hospital Anxiety and Depression Scale. Mixed linear models indicated both correlations and dissociations between scales that varied according to intensity and valence. Louder stimuli were rated as more unpleasant, but only at high intensities. On the sensory scale, sounds were perceived as louder with increasing intensity; however, at low to moderate intensities, pleasant and neutral sounds were rated as louder, whereas at higher intensities, artificial and unpleasant stimuli were rated as louder. On the affective scale, the perception of unpleasantness also increased with intensity, but less steeply. At high intensities, artificial stimuli were rated similarly to unpleasant stimuli. Noise sensitivity scores predicted louder and more unpleasant ratings, whereas depression scores were associated with softer and less pleasant perceptions. This study highlights the need for multidimensional approaches in audiology and suggests that the integration of sensory and affective scales with natural stimuli may improve the diagnosis and treatment of sound tolerance disorders.

Multimodal benefits of hypnosis on pain, mental health, sleep, and quality of life in patients with chronic pain related to fibromyalgia: A randomized, controlled, blindly-evaluated trial

BACKGROUND AND PURPOSE

Fibromyalgia is a chronic syndrome marked by intense musculoskeletal pain often refractory to pharmacological treatment. Although studies have shown that hypnosis improves fibromyalgia pain, gaps in experimental design limit their reliability. This work aimed to evaluate the effects of hypnosis on pain, mental health, sleep, and quality of life in participants with fibromyalgia chronic pain.

METHODS

In this prospective, parallel, randomized, controlled, blindly-evaluated trial, participants of both sexes (n = 49) diagnosed with fibromyalgia and with moderate to severe chronic pain attended 8 weekly 1-h sessions with a hypnotherapist. For the hypnosis group (n = 24), sessions consisted in induction of hypnotic trance followed by suggestions to promote analgesia. For the control group (n = 25), sessions consisted in casual unscripted conversation. Participants were assessed at baseline (7 days before), post-intervention (7 days after), and follow-up (3 months after). The primary outcome was pain intensity. The secondary outcomes were the sensory and affective dimensions of pain; pain unpleasantness; pain catastrophizing; anxiety and depression; sleep quality; fibromyalgia impact; and quality of life.

RESULTS

Hypnosis significantly reduced pain scores both at post-intervention and follow-up in comparison with baseline. The analgesic effect of hypnosis combined with pharmacological treatment lasted for at least 3 months and was superior to analgesia promoted by first- and second-line pharmacological treatment alone. Hypnosis significantly improved all parameters evaluated as secondary outcomes both at post-intervention and follow-up without inducing adverse events.

CONCLUSION

Our results corroborate that clinical hypnosis is an effective and feasible tool for managing chronic pain and other symptoms of fibromyalgia.

Advances and challenges in neuroimaging-based pain biomarkers

Identifying neural biomarkers of pain has long been a central theme in pain neuroscience. Here, we review the state-of-the-art candidates for neural biomarkers of acute and chronic pain. We classify these potential neural biomarkers into five categories based on the nature of their target variables, including neural biomarkers of (1) within-individual perception, (2) between-individual sensitivity, and (3) discriminability for acute pain, as well as (4) assessment and (5) prospective neural biomarkers for chronic pain. For each category, we provide a synthesized review of candidate biomarkers developed using neuroimaging techniques including functional magnetic resonance imaging (fMRI), structural magnetic resonance imaging (sMRI), and electroencephalography (EEG). We also discuss the conceptual and practical challenges in developing neural biomarkers of pain. Addressing these challenges, optimal biomarkers of pain can be developed to deepen our understanding of how the brain represents pain and ultimately help alleviate patients' suffering and improve their well-being.

Diminished pain sensitivity mediates the relationship between psychopathic traits and reduced learning from pain

Individuals with elevated psychopathic traits exhibit decision-making deficits linked to a failure to learn from negative outcomes. We investigated how reduced pain sensitivity affects reinforcement-based decision-making in individuals with varying levels of psychopathic traits, as measured by the Self-Report Psychopathy Scale-Short Form. Using computational modelling, we estimated the latent cognitive processes in a community non-offender sample (n = 111) that completed a task with choices leading to painful and non-painful outcomes. Higher psychopathic traits were associated with reduced pain sensitivity and disturbances in reinforcement learning from painful outcomes. In a Structural Equation Model, a superordinate psychopathy factor was associated with a faster return to original stimulus-outcome associations as pain tolerance increased. This provides evidence directly linking reduced pain sensitivity and learning from painful outcomes with elevated psychopathic traits. Our results offer insights into the computational mechanisms of maladaptive decision-making in psychopathy and antisocial behavior.

Neural dynamics of pain modulation by emotional valence

Definitions of human pain acknowledge at least two dimensions of pain, affective and sensory, described as separable and thus potentially differentially modifiable. Using electroencephalography, we investigated perceptual and neural changes of emotional pain modulation in healthy individuals. Painful electrical stimuli were applied after presentation of priming emotional pictures (negative, neutral, positive) and followed by pain intensity and unpleasantness ratings. We found that perceptual and neural event-related potential responses to painful stimulation were significantly modulated by emotional valence. Specifically, pain unpleasantness but not pain intensity ratings were increased when pain was preceded by negative compared to neutral or positive pictures. Amplitudes of N2 were higher when pain was preceded by neutral compared to negative and positive pictures, and P2 amplitudes were higher for negative compared to neutral and positive pictures. In addition, a hierarchical regression analysis revealed that P2 alone and not N2, predicted pain perception. Finally, source analysis showed the anterior cingulate cortex and the thalamus as main spatial clusters accounting for the neural changes in pain processing. These findings provide evidence for a separation of the sensory and affective dimensions of pain and open new perspectives for mechanisms of pain modulation.

Can electroencephalography (EEG) identify the different dimensions of pain in fibromyalgia? A pilot study

BACKGROUND

Electroencephalography (EEG) is a promising tool for identifying the physiological biomarkers of fibromyalgia (FM). Evidence suggests differences in power band and density between individuals with FM and healthy controls. EEG changes appear to be associated with pain intensity; however, their relationship with the quality of pain has not been examined. We aimed to investigate whether abnormal EEG in the frontal and central points of the 10-20 EEG system in individuals with FM is associated with pain's sensory-discriminative and affective-motivational dimensions. The association between EEG and the two dimensions of emotional disorders (depression and anxiety) was also investigated.

METHODS

In this cross-sectional pilot study, pain experience (pain rating index [PRI]) and two dimensions of emotional disorders (depression and anxiety) were assessed using the McGill Pain Questionnaire (PRI-sensory and PRI-affective) and Hospital Anxiety and Depression Scale (HADS), respectively. In quantitative EEG analysis, the relative spectral power of each frequency band (delta, theta, alpha, and beta) was identified in the frontal and central points during rest.

RESULTS

A negative correlation was found between the relative spectral power for the delta bands in the frontal (r= -0.656; p = 0.028) and central points (r= -0.624; p = 0.040) and the PRI-affective scores. A positive correlation was found between the alpha bands in the frontal (r = 0.642; p = 0.033) and central points (r = 0.642; p = 0.033) and the PRI-affective scores. A negative correlation between the delta bands in the central points and the anxiety subscale of the HADS (r = -0.648; p = 0.031) was detected.

CONCLUSION

The affective-motivational dimension of pain and mood disorders may be related to abnormal patterns of electrical activity in patients with FM.

TRIAL REGISTRATION

Retrospectively registered on ClinicalTrials.gov (NCT05962658).

Harnessing Children's Picture Books to Socialize Children About Pain and Injury: A Qualitative Study

Pain experiences are common during childhood (eg, "everyday" pain, vaccine injections) and are powerful opportunities for children to learn about pain and injury. These experiences likely inform fundamental and life-long beliefs about pain. There is scant research investigating the sociocultural contexts in which children learn about pain and injury. One unexplored context is the shared reading of picture books (eg, between parents/caregivers and children). In this study, we investigated whether shared reading of picture books that included depictions of pain and/or injury prompted parent/caregiver-child interactions. If interactions were observed, we explored what those interactions entailed. Twenty parents/caregivers (8 men, 12 women) and their children (n = 27; 10 boys, 17 girls) were recruited from libraries in South Australia. Parent/caregiver-child families chose from 8 books (7 fiction, 1 nonfiction) with varying amounts of pain/injury-related content. Shared reading interactions were video recorded, transcribed, and analyzed alongside analysis of the picture books using reflexive thematic analysis. Pain/injury-related interactions were observed between parents/caregivers and children during shared reading of picture books. Qualitative analyses generated 1 main theme and 3 subthemes. Findings identified that shared reading presented an opportunity for children's understanding of pain and injury to be socialized through discussion of characters' experiences. This included teaching children about pain and injury, as well as promoting empathy and emotional attunement toward characters who were depicted as being in pain. Finally, parents/caregivers often responded with observable/expressed amusement if pain/injury was depicted in a light-hearted or unrealistic way. Overall, shared reading of picture books presents an untapped opportunity to socialize children about pain and injury. PERSPECTIVE: Shared reading of picture books that have depictions of pain and/or injury can prompt parent/caregiver-child interactions about pain and injury. These interactions present critical opportunities that can be harnessed to promote children's learning of adaptive pain-related concepts and behaviors during a critical developmental period.

Unpacking the relationship between Big Five personality traits and experimental pain: A systematic review and meta-analysis

Pain is essential for survival, but individual responses to painful stimuli vary, representing a complex interplay between sensory, cognitive, and affective factors. Individual differences in personality traits and in pain perception covary but it is unclear which traits play the most significant role in understanding the pain experience and whether this depends on pain modality. A systematic search identified 1534 records (CINAHL, MEDLINE, PsycInfo, PubMed and Web of Science), of which 22 were retained and included in a systematic review. Only studies from the pressure pain domain (n=6) could be compared in a formal meta-analysis to evaluate the relationship between Big Five traits and experimental pain. Pressure pain tolerance correlated positively with Extraversion and negatively with Neuroticism with a trivial effect size (<0.1). While these findings suggest personality might be only weakly related to pain in healthy individuals, we emphasize the need to consider standardization, biases, and adequate sample sizes in future research, as well as additional factors that might affect experimental pain sensitivity.

Propofol Alleviates Anxiety-Like Behaviors Associated with Pain by Inhibiting the Hyperactivity of PVNCRH Neurons via GABAA Receptor β3 Subunits

Pain, a comorbidity of anxiety disorders, causes substantial clinical, social, and economic burdens. Emerging evidence suggests that propofol, the most commonly used general anesthetic, may regulate psychological disorders; however, its role in pain-associated anxiety is not yet described. This study investigates the therapeutic potential of a single dose of propofol (100 mg kg-1) in alleviating pain-associated anxiety and examines the underlying neural mechanisms. In acute and chronic pain models, propofol decreased anxiety-like behaviors in the elevated plus maze (EPM) and open field (OF) tests. Propofol also reduced the serum levels of stress-related hormones including corticosterone, corticotropin-releasing hormone (CRH), and norepinephrine. Fiber photometry recordings indicated that the calcium signaling activity of CRH neurons in the paraventricular nucleus (PVNCRH) is reduced after propofol treatment. Interestingly, artificially activating PVNCRH neurons through chemogenetics interfered with the anxiety-reducing effects of propofol. Electrophysiological recordings indicated that propofol decreases the activity of PVNCRH neurons by increasing spontaneous inhibitory postsynaptic currents (sIPSCs). Further, reducing the levels of γ-aminobutyric acid type A receptor β3 (GABAAβ3) subunits in PVNCRH neurons diminished the anxiety-relieving effects of propofol. In conclusion, this study provides a mechanistic and preclinical rationale to treat pain-associated anxiety-like behaviors using a single dose of propofol.

The effect of different pain characteristics on jaw functional limitations in patients with temporomandibular disorders

BACKGROUND

Patients with painful temporomandibular disorders (TMD) more often experience jaw functional limitations. The study of jaw functional limitations should be primarily focused on painful TMD.

OBJECTIVES

The impact of TMD pain characteristics (source, chronicity and intensity) on jaw functional limitations were evaluated using Jaw Functional Limitation Scale (JFLS).

METHODS

This cross-sectional study reviewed the dental records and self-report questionnaires of patients with painful TMD. The pain source, chronicity and intensity were evaluated to study the TMD pain characteristics. The jaw functional limitations were analysed using the Thai version of the JFLS.

RESULTS

A total of 176 patients with painful TMD were included in this study. The jaw functional limitations were affected only by pain intensity. Patients with TMD with severe pain intensity had significantly higher jaw functional limitations than those with mild-to-moderate pain intensity (p < .05). A significant association was observed between pain intensity and jaw functional limitations (p < .05). Mastication was highly restricted by pain intensity (odd ratio = 1.39, 95% confidence interval = 1.16-1.67).

CONCLUSION

The present study found a significant effect of TMD pain intensity on jaw functional limitations. Patients with severe TMD pain intensity were more likely to experience jaw functional limitations, particularly mastication limitation. Management focusing on reduction of pain intensity may improve jaw functions in patients with TMD.

Influence of psychometric and sleep quality features on painful mechanical sensitivity and pain modulation in patients with temporomandibular disorders

Investigating the collective impact of psychometric properties and sleep quality on pain sensitivity in temporomandibular disorder (TMD) patients could improve clinical management strategies.

OBJECTIVE

Assessing whether combined psychometric properties and sleep quality impact painful mechanical sensitivity and pain modulation in TMD patients.

MATERIALS AND METHODS

A cross-sectional study using secondary data analysis of 77 TMD patients and 101 controls. All participants completed questionnaires characterizing their psychometric profile (anxiety, depression, stress and catastrophizing) and sleep quality, alongside psychophysical tests for painful mechanical sensory (mechanical pain threshold (MPT), pressure pain threshold (PPT), and wind-up ratio (WUR)) and conditioned pain modulation (CPM). Participants were grouped into "High distress" or "Low distress" categories based on psychometric properties and sleep quality using hierarchical cluster and k-means analyses. Multiple linear regression evaluated the influence of TMD, age, and the distress cluster on MPT, WUR, PPT, and CPM in masseter and thenar muscles. Differences were statistically significant when p < 0.05.

RESULTS

The presence of TMD was the strongest predictor of mechanical painful sensitivity in the trigeminal region (MPT[F(3,174) = 51.902;p < .001;R2 = .463]; TMD presence (β = -.682) / PPT[F(3,174) = 15.573;p < .001;R2 = .198] TMD presence (β = -.452), and extra-trigeminal (MPT[F(3,174) = 35.897;p < .001;R2 = .382] TMD (β = -.647) / CPM [F(3,174) = 4.106;p < .05;R2 = .050] TMD presence (β = .197). Furthermore, neither the high distress group nor the low distress group were able to significantly influence the variation of the values of any of the psychophysical variables evaluated (p > .05).

CONCLUSIONS

There is not a significant influence of impairment clusters based on psychological variables and sleep quality on painful mechanical sensitivity and pain modulation, regardless of the presence of TMD.

CLINICAL RELEVANCE

This outcome suggests that psychosocial factors and sleep quality may not play a decisive role in the sensory-discriminative aspect of pain, particularly concerning painful TMD.

Effects of functional polymorphisms of opioid receptor mu 1 and catechol-O-methyltransferase on the neural processing of pain

AIM

Pain is reconstructed by brain activities and its subjectivity comes from an interplay of multiple factors. The current study aims to understand the contribution of genetic factors to the neural processing of pain. Focusing on the single-nucleotide polymorphism (SNP) of opioid receptor mu 1 (OPRM1) A118G (rs1799971) and catechol-O-methyltransferase (COMT) val158met (rs4680), we investigated how the two pain genes affect pain processing.

METHOD

We integrated a genetic approach with functional neuroimaging. We extracted genomic DNA information from saliva samples to genotype the SNP of OPRM1 and COMT. We used a percept-related model, in which two different levels of perceived pain intensities ("low pain: mildly painful" vs "high pain: severely painful") were employed as experimental stimuli.

RESULTS

Low pain involves a broader network relative to high pain. The distinct effects of pain genes were observed depending on the perceived pain intensity. The effects of low pain were found in supramarginal gyrus, angular gyrus, and anterior cingulate cortex (ACC) for OPRM1 and in middle temporal gyrus for COMT. For high pain, OPRM1 affected the insula and cerebellum, while COMT affected the middle occipital gyrus and ACC.

CONCLUSION

OPRM1 primarily affects sensory and cognitive components of pain processing, while COMT mainly influences emotional aspects of pain processing. The interaction of the two pain genes was associated with neural patterns coding for high pain and neural activation in the ACC in response to pain. The proteins encoded by the OPRM1 and COMT may contribute to the firing of pain-related neurons in the human ACC, a critical center for subjective pain experience.

Advancing women's pelvic floor muscle function diagnosis: the EFSMAP examination and its reliability evaluation

BACKGROUND

The accurate diagnosis of pelvic floor muscle impairments is essential. The plethora of terms and the lack of evidence to support widely used pelvic floor muscle function (PFMF) measurements hinder diagnostic labels.

OBJECTIVE

To structure an examination of PFMF using visual observation and digital palpation and terms consistent with the ICF terminology, and to test its intra and interrater reliability/agreement.

METHODS

A panel of 9 physical therapists applied Delphi method to structure the PFMF exam under ICF terminology and to verify its measurements reproducibility. For reliability and agreement, a convenience sample of women aged 51.2 ± 14.7 years had the sensitivity to pressure, pain, muscle tone, involuntary movement reaction, control of voluntary movement (contraction/relaxation), coordination, strength, and endurance examined by two raters, in the same day for interrater (n = 40), and one week apart, for intrarater reliability (n = 25). Percent agreement, linear weighted kappa, intraclass correlation coefficient, and Bland-Altman's limits of agreement were calculated (alpha = 0.05).

RESULTS

Four round Delphi discussion structured the PFMF exam, named EFSMAP (Exame das Funções Sensoriais e Motoras do Assoalho Pélvico/Examination of Pelvic Floor Sensory and Motor Functions), set a list of concepts and instructions targeted at reproducibility and established PFMF diagnostic labels. Reliability, except for pain and tone, were moderate to excellent (Kw= 0.67-1.0 and ICC=0.48-0.82). Agreement was substantial for most PFMF features (0.64-1.00), except pain.

CONCLUSIONS

The EFSMAP was successfully developed as a valid and reliable exam to be used in research and clinical practice; it provides labels for the diagnosis of pelvic floor muscle impairments. It might be easily adopted worldwide as it uses ICF terminology.

The white matter characteristic of the genu of corpus callosum coupled with pain intensity and negative emotion scores in patients with trigeminal neuralgia: a multivariate analysis

Background

Trigeminal neuralgia (TN) is a chronic neuropathic pain disorder that not only causes intense pain but also affects the psychological health of patients. Since TN pain intensity and negative emotion may be grounded in our own pain experiences, they exhibit huge inter-individual differences. This study investigates the effect of inter-individual differences in pain intensity and negative emotion on brain structure in patients with TN and the possible pathophysiology mechanism underlying this disease.

Methods

T1 weighted magnetic resonance imaging and diffusion tensor imaging scans were obtained in 46 patients with TN and 35 healthy controls. All patients with TN underwent pain-related and emotion-related questionnaires. Voxel-based morphometry and regional white matter diffusion property analysis were used to investigate whole brain grey and white matter quantitatively. Innovatively employing partial least squares correlation analysis to explore the relationship among pain intensity, negative emotion and brain microstructure in patients with TN.

Results

Significant difference in white matter integrity were identified in patients with TN compared to the healthy controls group; The most correlation brain region in the partial least squares correlation analysis was the genus of the corpus callosum, which was negatively associated with both pain intensity and negative emotion.

Conclusion

The genu of corpus callosum plays an important role in the cognition of pain perception, the generation and conduction of negative emotions in patients with TN. These findings may deepen our understanding of the pathophysiology of TN.

Botulinum Toxin for Pain Relief in Cancer Patients: A Systematic Review of Randomized Controlled Trials

Cancer pain is one of the most disabling symptoms complained by cancer patients, with a crucial impact on physical and psychological well-being. Botulinum neurotoxins (BoNTs) type A and B have emerged as potential interventions for chronic pain; however, their role in these patients is still debated. Thus, this systematic review of randomized controlled trials aimed at assessing the effects of BoNT treatment for cancer pain to guide physicians in an evidence-based approach integrating BoNT in cancer care. Out of 5824 records, 10 RCTs satisfied our eligibility criteria and were included in the present work for a total of 413 subjects with several cancer types (breast, head and neck, esophageal, and thoracic/gastric cancers). While some studies demonstrated significant pain reduction and improved quality of life post-BoNT-A injections, outcomes across different cancer types were inconclusive. Additionally, several effects were observed in functioning, dysphagia, salivary outcomes, esophageal strictures, gastric emptying, and expansions. This review emphasizes the need for further standardized research to conclusively establish the efficacy of BoNT in comprehensive cancer pain management.

Microglial STING activation alleviates nerve injury-induced neuropathic pain in male but not female mice

Microglia, resident immune cells in the central nervous system, play a role in neuroinflammation and the development of neuropathic pain. We found that the stimulator of interferon genes (STING) is predominantly expressed in spinal microglia and upregulated after peripheral nerve injury. However, mechanical allodynia, as a marker of neuropathic pain following peripheral nerve injury, did not require microglial STING expression. In contrast, STING activation by specific agonists (ADU-S100, 35 nmol) significantly alleviated neuropathic pain in male mice, but not female mice. STING activation in female mice leads to increase in proinflammatory cytokines that may counteract the analgesic effect of ADU-S100. Microglial STING expression and type I interferon-ß (IFN-ß) signaling were required for the analgesic effects of STING agonists in male mice. Mechanistically, downstream activation of TANK-binding kinase 1 (TBK1) and the production of IFN-ß, may partly account for the analgesic effect observed. These findings suggest that STING activation in spinal microglia could be a potential therapeutic intervention for neuropathic pain, particularly in males.

Perspectives on approaching pain management in patients with dementia

This paper presents a review of the latest literature and guidance regarding the assessment and management of pain in older adults with dementia. The size and nature of the problem will be presented, in terms of the increasing aging population across the globe and potential for a significant increase in adults with dementia, along with the reduction in younger counterparts who will be available to provide care in the future. We will present the latest recommendations regarding how to assess pain and which tools are recommended for use underpinned by the strongest evidence. Finally, we will present the findings of the latest national (UK) guidelines for the management of pain. Recommendations will be made for future research and clinical practice.

Mindfulness intervention effect on endometriosis-related pain dimensions and its mediator role on stress and vitality: a path analysis approach

Endometriosis-related pain is supposedly mainly responsible for generating psychological stress and deteriorating the quality of life. However, the interaction between these factors has not been investigated, considering its multidimensional nature and through the path of effects of psychosocial approaches. The present study aims to investigate the effect of a brief mindfulness-based intervention (bMBI) on pain dimensions and its mediator role on psychological stress and QoL-Vitality improvement. A secondary analysis of a pilot randomized controlled trial using a series of parallel and serial mediators was carried out. The results showed that bMBI improves the sensory (B = -6.09 [-9.81, -2.52], β = -0.42) and affective (B = -3.40 [-5.02, -1.80], β = -0.47) pain. The bMBI effect on psychological stress reduction was mediated by these changes in sensory (B = -2.81 [-6.06, -0.41], β = -0.21) and affective (B = -1.97 [-5.07, -0.17], β = -0.15) pain. Serial sensory pain and psychological stress reduction (B = 2.27 [0.11, 5.81], β = -0.09) mediated the bMBI effect on quality of life vitality. Meditation training promotes additional improvement in affective and sensory pain characteristics through which psychological stress is reduced. The sensory pain dimension must be positively impacted in combination with psychological stress for the bMBI improves women's vitality. Adding a psychosocial intervention like meditation training to the standard treatment plan may be required for some women to achieve the needed changes to restore well-being.

Insights into pain distraction and the impact of pain catastrophizing on pain perception during different types of distraction tasks

Introduction

Distraction is commonly used to reduce pain, but the effectiveness of distractions remains inconclusive. Studies have shown that pain catastrophizing could modulate the effectiveness of distraction strategies. The present study aimed to compare various distraction tasks, then control for pain catastrophizing, and examine how this relationship varies with pain intensity and unpleasantness across different distraction tasks.

Methods

Forty-one pain-free participants (aged 27.00 ± 5.41) were recruited for a cross-sectional study. Four types of distraction (cognitive, sensory, emotional, and social) were presented, while moderate pain intensity was induced by electrical stimulation. Before starting the experiment, moderate pain intensity was individually calibrated as six on the Numerical Pain Rating Scale (NRS) to control individual differences in pain sensitivity. Each participant performed all four distraction tasks in a random order. NRS measured pain assessment. Pain catastrophizing was measured by the Pain Catastrophizing Scale (PCS). A repeated measure ANCOVA was conducted to examine the effects of pain dimensions during distraction tasks as a within-subject and pain catastrophizing as a covariate factor.

Results

A significant difference was observed in the pain intensity and unpleasantness during cognitive distraction. After controlling for PCS, there were diverse associations between PCS and pain intensity across distinct distraction tasks: social vs. sensory, and cognitive vs. sensory distraction. A consistent pattern in pain unpleasantness emerged with minor variations. This interaction underscored notable distinctions between social vs. sensory and emotional distractions, as well as between cognitive vs. sensory and emotional distractions. However, only the correlation in social distraction remained significant in both pain dimensions.

Discussion

Our findings reveal that the link between PCS and pain dimensions varies across different distraction tasks, suggesting diverse interactions. Particularly, social distraction, characterized by both emotional and cognitive states, proves beneficial with lower PCS scores; however, this advantage diminishes as PCS scores increase.

Development, refinement, and validation of an equine musculoskeletal pain scale

Musculoskeletal disease is a common cause of chronic pain that is often overlooked and inadequately treated, impacting the quality of life of humans and horses alike. Lameness due to musculoskeletal pain is prevalent in horses, but the perception of pain by owners is low compared with veterinary diagnosis. Therefore, this study aims to establish and validate a pain scale for chronic equine orthopaedic pain that is user-friendly for horse owners and veterinarians to facilitate the identification and monitoring of pain in horses. The newly developed musculoskeletal pain scale (MPS) was applied to 154 horses (mean age 20 ± 6.4 years SD) housed at an equine sanctuary, of which 128 (83%) suffered from chronic orthopaedic disease. To complete the MPS, the horses were observed and videotaped from a distance while at rest in their box or enclosure. In addition, they received a complete clinical and orthopaedic exam. The need for veterinary intervention to address pain (assessed and executed by the sanctuary independent from this study) was used as a longitudinal health outcome to determine the MPS's predictive validity. To determine the interrater agreement, the MPS was scored for a randomly selected subset of 30 horses by six additional blinded raters, three equine veterinary practitioners, and three experienced equestrians. An iterative process was used to refine the tool based on improvements in the MPS's correlation with lameness evaluated at the walk and trot, predictive validity for longitudinal health outcomes, and interrater agreement. The intraclass correlation improved from 0.77 of the original MPS to 0.88 of the refined version (95% confidence interval: 0.8-0.94). The refined MPS correlated significantly with lameness at the walk (r = 0.44, p = 0.001) and trot (r = 0.5, p < 0.0001). The refined MPS significantly differed between horses that needed veterinary intervention (mean MPS = 8.6) and those that did not (mean MPS = 5.0, p = 0.0007). In summary, the MPS showed good interrater repeatability between expert and lay scorers, significant correlation with lameness at the walk and trot, and good predictive validity for longitudinal health outcomes, confirming its ability to identify horses with orthopaedic health problems.

Graph theory analysis reveals an assortative pain network vulnerable to attacks

The neural substrate of pain experience has been described as a dense network of connected brain regions. However, the connectivity pattern of these brain regions remains elusive, precluding a deeper understanding of how pain emerges from the structural connectivity. Here, we employ graph theory to systematically characterize the architecture of a comprehensive pain network, including both cortical and subcortical brain areas. This structural brain network consists of 49 nodes denoting pain-related brain areas, linked by edges representing their relative incoming and outgoing axonal projection strengths. Within this network, 63% of brain areas share reciprocal connections, reflecting a dense network. The clustering coefficient, a measurement of the probability that adjacent nodes are connected, indicates that brain areas in the pain network tend to cluster together. Community detection, the process of discovering cohesive groups in complex networks, successfully reveals two known subnetworks that specifically mediate the sensory and affective components of pain, respectively. Assortativity analysis, which evaluates the tendency of nodes to connect with other nodes that have similar features, indicates that the pain network is assortative. Finally, robustness, the resistance of a complex network to failures and perturbations, indicates that the pain network displays a high degree of error tolerance (local failure rarely affects the global information carried by the network) but is vulnerable to attacks (selective removal of hub nodes critically changes network connectivity). Taken together, graph theory analysis unveils an assortative structural pain network in the brain that processes nociceptive information. Furthermore, the vulnerability of this network to attack presents the possibility of alleviating pain by targeting the most connected brain areas in the network.

A systematic review of the added value of perioperative pain neuroscience education

OBJECTIVE

To identify and summarize evidence about the benefits of perioperative pain neuroscience education (PNE) on pain-related and psychosocial outcomes.

METHODS

Included were reports written in English that carried out PNE or its synonyms; perioperative period; aged ≥ 18 years; interventional studies and observational studies. Secondary studies, conference abstracts, and editorials were excluded. There was no time limitation.

INFORMATION SOURCES

PubMed, Virtual Health Library, Cochrane Library, and Science Direct. Search: June 20th 2023. The risk of bias was assessed using the Joanna Briggs Institute checklists, and synthesis followed the recommendations of the Synthesis Without Meta-analysis (SWiM) guideline. Register: Center for Open Science website (10.17605/OSF.IO/ZTNEJ).

RESULTS

The sample consisted of 18 reports. For pain outcomes, it was not possible to attribute PNE benefits because ten reports found improvements in both intervention and control groups. For psychosocial outcomes, fourteen reports found benefits for PNE groups. All the analyzed reports showed low risk of bias.

CONCLUSION

PNE had additional benefits beyond those obtained with conventional treatment for psychosocial outcomes.

PRACTICAL IMPLICATIONS

Due to the lack of evidence, it was not possible to indicate the clinical use of PNE. It is suggested that further studies are needed aimed at clarifying the possible benefits.

Photic sensitization is mediated by cortico-accumbens pathway in rats with trigeminal neuropathic pain

Exposure to light stimuli may trigger or exacerbate perception of pain, also known as a common yet debilitating symptom of photophobia in patient with chronic orofacial pain. Mechanism underlying this phenomenon of photic sensitization in neuropathic condition remains elusive. Here, we found that rats developed hypersensitivity to normal light illumination after establishment of chronic constriction injury of infraorbital nerve (ION-CCI) model, which can be attenuated by blocking the exposure of photic stimulation. Additionally, this behavioral phenotype of light-sensitivity impairment was associated with overexpression of anterior cingulate cortex (ACC) c-fos positive neurons, enhancement of neural excitability in the ACC neurons and its excitatory synaptic transmission between nucleus accumbens (NAc). Optogenetic and chemogenic silencing of ACC-NAc pathway improved trigeminal sensitization in responses to light stimuli by decreasing spontaneous pain-like episodes in ION-CCI animals. In contrast, selective activation of ACC-to-NAc circuits enhanced photic hypersensitivity in dark environment. Thus, our data provided novel role of ACC and its projection to NAc in bidirectional modulation of photic sensation, which may contribute to the understanding of photic allodynia in trigeminal neuropathic pain status.

Photobiomodulation and vitamin B treatment alleviate both thermal and mechanical orofacial pain in rats

PURPOSE

The present study investigates the efficacy of Photobiomodulation (PBM) and Vitamin B Complex (VBC) to relieve pain, both in separately and combined (PBM and VBC).

METHODS

Rats with chronic constriction injury of the right infraorbital nerve (CCI-IoN) or Sham surgery were used. PBM was administered at a wavelength of 904 nm and energy density of 6.23 J/cm2 and VBC (containing B1, B6 and B12) subcutaneously, both separately and combined. Behavioral tests were performed to assess mechanical and thermal hypersensitivity before and after CCI and after PBM, VBC, or PBM + VBC. The expression of inflammatory proteins in the trigeminal ganglion and the immunohistochemical alterations of Periaqueductal Gray (PAG) astrocytes and microglia were examined following CCI and treatments.

RESULTS

All testeds treatments reversed the painful behavior. The decrease in pain was accompanied by a decrease of Glial Fibrillary Acidic Protein (GFAP), a specific astrocytic marker, and Ionized calcium-binding adaptor molecule 1 (Iba-1), a marker of microglia, and decreased expression of Transient Receptor Potential Vanilloid 1 (TRPV1), Substance P, and Calcitonin Gene-Related Peptide (CGRP) induced by CCI-IoN in PAG and Trigeminal ganglion. Furthermore, both treatments showed a higher expression of Cannabinoid-type 1 (CB1) receptor in the trigeminal ganglion compared to CCI-IoN rats. Our results show that no difference was observed between groups.

CONCLUSION

We showed that PBM or VBC regulates neuroinflammation and reduces inflammatory protein expression. However, the combination of PBM and VBC did not enhance the effectiveness of both therapies alone.

Botulinum toxin A decreases neural activity in pain-related brain regions in individuals with chronic ocular pain and photophobia

Introduction

To examine the effect of botulinum toxin A (BoNT-A) on neural mechanisms underlying pain and photophobia using functional magnetic resonance imaging (fMRI) in individuals with chronic ocular pain.

Methods

Twelve subjects with chronic ocular pain and light sensitivity were recruited from the Miami Veterans Affairs eye clinic. Inclusion criteria were: (1) chronic ocular pain; (2) presence of ocular pain over 1 week recall; and (3) presence of photophobia. All individuals underwent an ocular surface examination to capture tear parameters before and 4-6 weeks after BoNT-A injections. Using an event-related fMRI design, subjects were presented with light stimuli during two fMRI scans, once before and 4-6 weeks after BoNT-A injection. Light evoked unpleasantness ratings were reported by subjects after each scan. Whole brain blood oxygen level dependent (BOLD) responses to light stimuli were analyzed.

Results

At baseline, all subjects reported unpleasantness with light stimulation (average: 70.8 ± 32.0). Four to six weeks after BoNT-A injection, unpleasantness scores decreased (48.1 ± 33.6), but the change was not significant. On an individual level, 50% of subjects had decreased unpleasantness ratings in response to light stimulation compared to baseline ("responders," n = 6), while 50% had equivalent (n = 3) or increased (n = 3) unpleasantness ("non-responders"). At baseline, several differences were noted between responders and non-responders; responders had higher baseline unpleasantness ratings to light, higher symptoms of depression, and more frequent use of antidepressants and anxiolytics, compared to non-responders. Group analysis at baseline displayed light-evoked BOLD responses in bilateral primary somatosensory (S1), bilateral secondary somatosensory (S2), bilateral anterior insula, paracingulate gyrus, midcingulate cortex (MCC), bilateral frontal pole, bilateral cerebellar hemispheric lobule VI, vermis, bilateral cerebellar crus I and II, and visual cortices. BoNT-A injections significantly decreased light evoked BOLD responses in bilateral S1, S2 cortices, cerebellar hemispheric lobule VI, cerebellar crus I, and left cerebellar crus II. BoNT-A responders displayed activation of the spinal trigeminal nucleus at baseline where non-responders did not.

Discussion

BoNT-A injections modulate light-evoked activation of pain-related brain systems and photophobia symptoms in some individuals with chronic ocular pain. These effects are associated with decreased activation in areas responsible for processing the sensory-discriminative, affective, dimensions, and motor responses to pain.

Pain assessment tools for use in infants: a meta-review

BACKGROUND

Identifying pain in infants is challenging due to their inability to self-report pain, therefore the availability of valid and reliable means of assessing pain is critical.

OBJECTIVE

This meta-review sought to identify evidence that could guide the selection of appropriate tools in this vulnerable population.

METHODS

We searched Scopus, Medline, Embase, CINAHL, MIDRIS, EMCare and Google Scholar for eligible systematic reviews. Eligible reviews documented psychometric properties of available observational tools used to assess pain in infants.

RESULTS

A total of 516 reviews were identified of which 11 met our inclusion criteria. We identified 36 pain assessment tools (evaluated in 11 reviews) of which seven were reported in at least three reviews. The level of evidence reported on the psychometric properties of pain assessment tools varied widely ranging from low to good reliability and validity, whilst there are limited data on usability and clinical utility.

CONCLUSIONS

Currently, no observer administered pain assessment tool can be recommended as the gold standard due to limited availability and quality of the evidence that supports their validity, reliability and clinical utility. This meta-review attempts to collate the available evidence to assist clinicians to decide on what is the most appropriate tool to use in their clinical practice setting. It is important that researchers adopt a standard approach to evaluating the psychometric properties of pain assessment tools and evaluations of the clinical utility in order that the highest level of evidence can be used to guide tool selection.

Neurotechnology for Pain

Neurotechnologies for treating pain rely on electrical stimulation of the central or peripheral nervous system to disrupt or block pain signaling and have been commercialized to treat a variety of pain conditions. While their adoption is accelerating, neurotechnologies are still frequently viewed as a last resort, after many other treatment options have been explored. We review the pain conditions commonly treated with electrical stimulation, as well as the specific neurotechnologies used for treating those conditions. We identify barriers to adoption, including a limited understanding of mechanisms of action, inconsistent efficacy across patients, and challenges related to selectivity of stimulation and off-target side effects. We describe design improvements that have recently been implemented, as well as some cutting-edge technologies that may address the limitations of existing neurotechnologies. Addressing these challenges will accelerate adoption and change neurotechnologies from last-line to first-line treatments for people living with chronic pain.

Physical pain among Indigenous Peoples in Canada: a scoping review

PURPOSE

Pain is a multifaceted experience shaped by various factors including context of pain, previous life events, and ongoing ethnocultural circumstances. Moreover, the definition of pain is inconsistent across cultures. Western medicine views physical pain (e.g., associated with a bone fracture) and nonphysical mental pain (e.g., depression) as two distinct conditions. Indigenous perspectives are often more wholistic, encompassing mental, spiritual, emotional, and physical hurt. The subjective nature of pain invites ample opportunity for discrimination in both its assessment and management. As such, it is important to consider Indigenous perspectives of pain in research and clinical practice. To investigate which aspects of Indigenous pain knowledge are currently considered by Western research, we conducted a scoping review of the literature on pain in Indigenous Peoples of Canada.

SOURCE

In June 2021, we searched nine databases and downloaded 8,220 papers after removal of duplicates. Two independent reviewers screened abstracts and full-text articles.

PRINCIPLE FINDINGS

Seventy-seven papers were included in the analysis. Using grounded theory, five themes emerged: pain measures/scales (n = 7), interventions (n = 13), pharmaceuticals (n = 17), pain expression/experiences (n = 45), and pain conditions (n = 70).

CONCLUSION

This scoping review shows that there is a paucity of research on pain measurement in Indigenous Peoples of Canada. This finding is concerning in light of numerous studies reporting that Indigenous Peoples experience their pain as ignored, minimized, or disbelieved. Furthermore, a clear disconnect emerged between pain expression in Indigenous Peoples and assessment in medical professionals. We hope that this scoping review will serve to translate current knowledge to other non-Indigenous academics and to initiate meaningful collaboration with Indigenous partners. Future research led by Indigenous academics and community partners is critically needed to better address pain needs in Canada.

Differences in the neural basis and transcriptomic patterns in acute and persistent pain-related anxiety-like behaviors

Background

Both acute and persistent pain is associated with anxiety in clinical observations, but whether the underlying neural mechanisms differ is poorly understood.

Methods

We used formalin or complete Freund's adjuvant (CFA) to induce acute or persistent pain. Behavioral performance was assessed by the paw withdrawal threshold (PWT), open field (OF), and elevated plus maze (EPM) tests. C-Fos staining was used to identify the activated brain regions. Chemogenetic inhibition was further performed to examine the necessity of brain regions in behaviors. RNA sequencing (RNA-seq) was used to identify the transcriptomic changes.

Results

Both acute and persistent pain could lead to anxiety-like behavior in mice. The c-Fos expression indicates that the bed nucleus of the stria terminalis (BNST) is activated only in acute pain, whereas the medial prefrontal cortex (mPFC) is activated only in persistent pain. Chemogenetic manipulation reveals that the activation of the BNST excitatory neurons is required for acute pain-induced anxiety-like behaviors. In contrast, the activation of the prelimbic mPFC excitatory neurons is essential for persistent pain-induced anxiety-like behaviors. RNA-seq reveals that acute and persistent pain induces differential gene expression changes and protein-protein interaction networks in the BNST and prelimbic mPFC. The genes relevant to neuronal functions might underline the differential activation of the BNST and prelimbic mPFC in different pain models, and be involved in acute and persistent pain-related anxiety-like behaviors.

Conclusion

Distinct brain regions and gene expression patterns are involved in acute and persistent pain-related anxiety-like behaviors.

Connecting Circuits with Networks in Addiction Neuroscience: A Salience Network Perspective

Human neuroimaging has demonstrated the existence of large-scale functional networks in the cerebral cortex consisting of topographically distant brain regions with functionally correlated activity. The salience network (SN), which is involved in detecting salient stimuli and mediating inter-network communication, is a crucial functional network that is disrupted in addiction. Individuals with addiction display dysfunctional structural and functional connectivity of the SN. Furthermore, while there is a growing body of evidence regarding the SN, addiction, and the relationship between the two, there are still many unknowns, and there are fundamental limitations to human neuroimaging studies. At the same time, advances in molecular and systems neuroscience techniques allow researchers to manipulate neural circuits in nonhuman animals with increasing precision. Here, we describe attempts to translate human functional networks to nonhuman animals to uncover circuit-level mechanisms. To do this, we review the structural and functional connections of the salience network and its homology across species. We then describe the existing literature in which circuit-specific perturbation of the SN sheds light on how functional cortical networks operate, both within and outside the context of addiction. Finally, we highlight key outstanding opportunities for mechanistic studies of the SN.

The Efficacy of New Zealand Greenshell™ Mussel Powder Supplementation in Supporting Muscle Recovery Following Eccentric Exercise-Induced Muscle Damage in Healthy, Untrained Adult Males

Unaccustomed eccentric exercise results in muscle damage limiting physical performance for several days. This study investigated if Greenshell™ mussel (GSM) powder consumption expedited muscle recovery from eccentric exercise-induced muscle damage (EIMD). Methods: Twenty untrained adult men were recruited into a double-blind, placebo-controlled, cross-over study and were randomly assigned to receive the GSM powder or placebo treatment first. Participants consumed their allocated intervention for four weeks then completed a bench-stepping exercise that induced muscle damage to the eccentrically exercised leg. Muscle function, soreness and biomarkers of muscle damage, oxidative stress and inflammation were measured before exercise, immediately after exercise and 24, 48 and 72 h post exercise. GSM powder promoted muscle function recovery, significantly improving (p < 0.05) isometric and concentric peak torque at 48 h and 72 h post exercise, respectively. Participants on the GSM treatment had faster dissipation of soreness, with significant treatment × time interactions for affective (p = 0.007) and Visual Analogue Scale-assessed pain (p = 0.018). At 72 h, plasma creatine kinase concentrations in the GSM group were lower (p < 0.05) compared with the placebo group. This study provides evidence for GSM powder being effective in supporting muscle recovery from EIMD.

Multi-Region Microdialysis Imaging Platform Revealed Dorsal Raphe Nucleus Calcium Signaling and Serotonin Dynamics during Nociceptive Pain

In this research, we combined our ultralight micro-imaging device for calcium imaging with microdialysis to simultaneously visualize neural activity in the dorsal raphe nucleus (DRN) and measure serotonin release in the central nucleus of the amygdala (CeA) and the anterior cingulate cortex (ACC). Using this platform, we observed brain activity following nociception induced by formalin injection in the mouse’s hind paw. Our device showed that DRN fluorescence intensity increased after formalin injection, and the increase was highly correlated with the elevation in serotonin release in both the CeA and ACC. The increase in calcium fluorescence intensity occurred during the acute and inflammatory phases, which suggests the biphasic response of nociceptive pain. Furthermore, we found that the increase in fluorescence intensity was positively correlated with mouse licking behavior. Lastly, we compared the laterality of pain stimulation and found that DRN fluorescence activity was higher for contralateral stimulation. Microdialysis showed that CeA serotonin concentration increased only after contralateral stimulation, while ACC serotonin release responded bilaterally. In conclusion, our study not only revealed the inter-regional serotonergic connection among the DRN, the CeA, and the ACC, but also demonstrated that our device is feasible for multi-site implantation in conjunction with a microdialysis system, allowing the simultaneous multi-modal observation of different regions in the brain.

Optimising psychological treatment for pain after breast cancer: a factorial design study protocol in Denmark

INTRODUCTION

One in five breast cancer (BC) survivors are affected by persistent pain years after completing primary treatment. While the efficacy of psychological interventions for BC-related pain has been documented in several meta-analyses, reported effect sizes are generally modest, pointing to a need for optimisation. Guided by the Multiphase Optimization Strategy, the present study aims to optimise psychological treatment for BC-related pain by identifying active treatment components in a full factorial design.

METHODS AND ANALYSIS

The study uses a 2×3 factorial design, randomising 192 women with BC-related pain (18-75 years) to eight experimental conditions. The eight conditions consist of three contemporary cognitive-behavioural therapy components, namely: (1) mindful attention, (2) decentring, and (3) values and committed action. Each component is delivered in two sessions, and each participant will receive either zero, two, four or six sessions. Participants receiving two or three treatment components will be randomised to receive them in varying order. Assessments will be conducted at baseline (T1), session by session, every day for 6 days following the first session in each treatment component, at post-intervention (T2) and at 12-week follow-up (T3). Primary outcomes are pain intensity (Numerical Rating Scale) and pain interference (Brief Pain Inventory interference subscale) from T1 to T2. Secondary outcomes are pain burden, pain quality, pain frequency, pain catastrophising, psychological distress, well-being and fear of cancer recurrence. Possible mediators include mindful attention, decentring, and pain acceptance and activity engagement. Possible moderators are treatment expectancy, treatment adherence, satisfaction with treatment and therapeutic alliance.

ETHICS AND DISSEMINATION

Ethical approval for the present study was received from the Central Denmark Region Committee on Health Research Ethics (no: 1-10-72-309-40). Findings will be made available to the study funders, care providers, patient organisations and other researchers at international conferences, and published in international, peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Registry (NCT05444101).

Graph theory analysis reveals an assortative pain network vulnerable to attacks

The neural substrate of pain experience has been described as a dense network of connected brain regions. However, the connectivity pattern of these brain regions remains elusive, precluding a deeper understanding of how pain emerges from the structural connectivity. Here, we use graph theory to systematically characterize the architecture of a comprehensive pain network, including both cortical and subcortical brain areas. This structural brain network consists of 49 nodes denoting pain-related brain areas, linked by edges representing their relative incoming and outgoing axonal projection strengths. Sixty-three percent of brain areas in this structural pain network share reciprocal connections, reflecting a dense network. The clustering coefficient, a measurement of the probability that adjacent nodes are connected, indicates that brain areas in the pain network tend to cluster together. Community detection, the process of discovering cohesive groups in complex networks, successfully reveals two known subnetworks that specifically mediate the sensory and affective components of pain, respectively. Assortativity analysis, which evaluates the tendency of nodes to connect with other nodes with similar features, indicates that the pain network is assortative. Finally, robustness, the resistance of a complex network to failures and perturbations, indicates that the pain network displays a high degree of error tolerance (local failure rarely affects the global information carried by the network) but is vulnerable to attacks (selective removal of hub nodes critically changes network connectivity). Taken together, graph theory analysis unveils an assortative structural pain network in the brain processing nociceptive information, and the vulnerability of this network to attack opens up the possibility of alleviating pain by targeting the most connected brain areas in the network.