Brain mechanisms of social touch-induced analgesia in females

The relation between longing for touch and the implicit evaluation of images of touch

Longing for touch (LFT) refers to the discrepancy between the amount of touch that is desired and received. Previous studies have suggested that LFT might influence the perception of touch, but the results are conflicting. These studies also have relied exclusively on subjective and explicit measures, which can be prone to several biases. To circumvent these biases, the current study uses a novel implicit association test (IAT) to assess how LFT is associated with the perception of touch. In this version of the IAT, target stimuli consisted of images of people touching and images of people that did not depict touch. Seventy-two people without neurological, psychological or skin-related disorders participated in the study. After completing the IAT, the explicit wanting and liking of the target stimuli was assessed. LFT was measured with two visual analogue scales. In line with our expectations, LFT was significantly and positively associated with the explicit evaluation of images of touch. However, there was no relation between LFT and performance on the IAT. It is possible that the current version of the IAT primarily assessed implicit liking, while deprivation of touch may be more strongly associated with (implicit) wanting. Additional research is needed to further investigate this. The implications of these results and other directions for future research are discussed.

The effect of online social support on experimental pain

Ample evidence shows that in-person social support can alleviate both acute and chronic pain complaints. However, less is known about the effectiveness of online social support. Disparities in availability of and access to in-person social support could make online social support a promising and cost-effective alternative. To this end we aimed to compare the effects of online versus in-person social support on pain induced with a cold-pressor task (CPT). Specifically, 62 pain-free female participants immersed their feet in cold water (1) alone, (2) in the physical presence of a supportive other, (3) while chatting with the supportive other online, and (4) while chatting online with a stranger, in a randomized order. We assessed self-reported pain intensity, pain unpleasantness, and threat value of pain, as well as pain tolerance (i.e. immersion time) and heart rate. Overall, pain intensity and unpleasantness ratings were higher in the alone condition compared to the other conditions. A similar pattern was found in pain tolerance, but the differences were not statistically significant. Heart rate increased during the CPT but was highest in the in-person support condition. Moreover, recovery after cold water immersion was slower in the alone condition compared to the other conditions. In sum, interaction with a supportive other or a stranger, be it online or in-person, led to a reduction in acute pain compared to being alone. This study presents initial evidence that online interaction with others might be an effective alternative to in-person social support in order to reduce acute pain in women. PERSPECTIVE: Online and in-person social support were equally effective in reducing acute experimental cold-pressor pain compared to being alone. There was no difference between social support from strangers or a supportive other.

Longing for touch and the vicarious perception of CT-optimal touch in clinical outpatients

Longing for touch (LFT) can be defined as a discrepancy between the amount of touch that is desired and received. Previous studies have shown that LFT is prevalent in non-clinical populations, and that it is associated with an altered perception of CT-optimal touch. However, little is known about the prevalence and potential perceptual consequences of LFT in clinical populations. It is important to investigate this given the complicated relation with social touch that is often observed in these populations. We therefore assessed LFT in 69 clinical outpatients and 136 control participants in this study. Two videos were used to evaluate the vicarious perception of CT-optimal (3 cm/s) and CT non-optimal touch (30 cm/s). LFT was found to be more prevalent and severe in clinical outpatients. While patients also reported a lower frequency of touch, their subjective touch wish did not differ significantly from control participants. The increased LFT of the patients therefore seems to be primarily driven by an absence of touch, rather than a stronger need for touch. In both groups, LFT was positively associated with the vicarious pleasantness perception of CT-optimal and CT non-optimal touch. This provides further support for the hypothesis that LFT enhances the hedonic value of social touch. Taken together, these results provide valuable new insights into the experience and perception of social touch in clinical populations.

Skin-to-skin holding in relation to white matter connectivity in infants born preterm

Background and Objectives

Preterm birth is associated with altered white matter development and long-term neurodevelopmental impairments. Skin-to-skin care (kangaroo care) has well-documented benefits for physiological stability and bonding, but its association with neonatal brain structure remains unclear. This study explored the association between in-hospital skin-to-skin care and neonatal white matter microstructure in frontal and limbic pathways that are linked to stress regulation and socio-emotional development, processes potentially influenced by affective touch during skin-to-skin care.

Methods

This retrospective study analyzed electronic medical records and diffusion MRI data collected from 86 preterm infants (<32 weeks gestational age) in a single NICU. Skin-to-skin care exposure was quantified as total duration (minutes/instance) and rate (minutes/day) of sessions. Diffusion MRI scans obtained before hospital discharge assessed mean diffusivity (MD) and fractional anisotropy (FA) in the cingulate, anterior thalamic radiations (ATR), and uncinate fasciculus. Hierarchical regression models examined associations between skin-to-skin care and white matter microstructure, adjusting for gestational age, health acuity, postmenstrual age at scan, and MRI coil type. Sensitivity analyses controlled for socioeconomic status and NICU visitation frequency.

Results

Skin-to-skin care duration was positively associated with MD in the cingulate (B = 0.002, p = 0.016) and ATR (B = 0.002, p = 0.020). Skin-to-skin care rate was also positively linked to MD in the ATR (B = 0.040, p = 0.041). Skin-to-skin care duration and rate were not associated with FA in the cingulate but skin-to-skin duration and rate were negatively associated with FA in the ATR (duration: B = -0.001, p = 0.020; rate: B = -0.017, p = 0.008). No significant associations were found for the uncinate fasciculus. Findings remained robust after adjusting for socioeconomic status and visitation frequency.

Discussion

This study provides novel evidence linking in-hospital experiences of skin-to-skin care to neonatal white matter development. These findings have important implications for understanding how family-centered neuroprotective practices, such as skin-to-skin care, may affect brain development to improve long-term developmental outcomes.

Research Progress on Neural Processing of Hand and Forearm Tactile Sensation: A Review Based on fMRI Research

Tactile perception is one of the important ways through which humans interact with the external environment. Similar to the neural processing in visual and auditory systems, the neural processing of tactile information is a complex procedure that transforms this information into sensory signals. Neuroimaging techniques, such as functional Magnetic Resonance Imaging (fMRI), provide compelling evidence indicating that different types of tactile signals undergo independent or collective processing within multiple brain regions. This review focuses on fMRI studies employing both task-based (block design or event-related design) and resting-state paradigms. These studies use general linear models (GLM) to identify brain regions activated during touch processing, or employ functional connectivity(FC) analysis to examine interactions between brain regions, thereby exploring the neural mechanisms underlying the central nervous system's processing of various aspects of tactile sensation, including discriminative touch and affective touch. The discussion extends to exploring changes in tactile processing patterns observed in certain disease states. Recognizing the analogy between pain and touch processing patterns, we conclude by summarizing the interaction between touch and pain. Currently, fMRI-based studies have made significant progress in the field of tactile neural processing. These studies not only deepen our understanding of tactile perception but also provide new perspectives for future neuroscience studies.

Different ways to reach the same goal: Are the analgesic effects of different types of tactile stimuli similar?

BACKGROUND

Tactile-induced analgesia (TIA) is a phenomenon in which different types of tactile stimulation alleviate pain via different mechanisms including empathy. As TIA plays an essential role in therapeutic situations and clinical conditions, it is crucial to determine whether specific tactile stimulations confer distinct benefits.

METHODS

Fifty-two subjects (31 females; 21-47 years) were exposed to four distinct experimental conditions involving three types of touch provided within a simulated supportive therapeutic setting. First, a contact heat (70 s) at a pain intensity of 60/100 Numerical Pain Scale (NPS) was applied to the forearm. The pain stimulus was then given simultaneously with vibration, gentle stroking, or handholding in random order. Pain ratings were reported at 5 and 65 s of each stimulation. Given the role of empathy in TIA, we also assessed the levels of empathy experienced by the subjects and the experimenter.

RESULTS

Handholding and vibration conditions were associated with a more rapid decrease in pain ratings compared to pain-alone (B values: handholding = -150.94 vs. pain-alone = -99.38, p = 0.01; vibration = -163.54 vs. pain-alone = -99.38, p < 0.001). Higher levels of the experimenter's empathy toward the subjects were associated with greater pain alleviation during vibration vs. pain-alone condition (B values: vibration = -56.42 vs. B pain-alone = -9.57, p = 0.04).

CONCLUSIONS

Vibration's potent analgesic effects may be attributed to its multi-channel analgesic mechanisms, including the therapist's empathy toward the participant. On the other hand, for handholding establishing an empathic interaction should be considered in a therapeutic setting to enhance its analgesic efficacy.

SIGNIFICANCE

This article explores the effectiveness of touch-based pain relief methods and their association with empathetic therapeutic interactions. The study emphasizes the significance of positive therapeutic interactions in facilitating tactile-induced analgesia.

Handholding reduces the recovery of threat memories and magnifies prefrontal hemodynamic responses

Human touch is a powerful means of social and affective regulation, promoting safety behaviors. Yet, despite its importance across human contexts, it remains unknown how touch can promote the learning of new safety memories and what neural processes underlie such effects. The current study used measures of peripheral physiology and brain activity to examine the effects of interpersonal touch during safety learning (extinction) on the recovery of previously learned threat. We observed that handholding during extinction significantly reduced threat recovery, which was reflected in enhanced prefrontal hemodynamic responses. This effect was absent when learners were instructed to hold a rubber ball, independent of the presence of their partners. Our findings indicate that social touch contributes to safety learning, potentially influencing threat memories via prefrontal circuitry.

Motivation and Pleasure Deficits Undermine the Benefits of Social Affiliation in Psychosis

In psychotic disorders, motivation and pleasure (MAP) deficits are associated with decreased affiliation and heightened functional impairment. We leveraged a transdiagnostic sample enriched for psychosis and a multi-method approach to test the hypothesis that MAP deficits undermine the stress-buffering benefits of affiliation. Participants completed the Social Affiliation Enhancement Task (SAET) to cultivate affiliation with an experimental partner. Although the SAET increased perceived affiliation and mood, individuals with greater negative symptoms derived smaller emotional benefits from the partners, as indexed by self-report and facial behavior. We then used the Handholding fMRI paradigm, which combines threat-anticipation with affiliative physical contact, to determine whether MAP deficits undermine the social regulation of distress. Individuals with greater MAP deficits showed diminished neural 'benefits'-reduced dampening of threat-elicited activation-from affiliative touch in key frontoparietal nodes of the Dorsal Attention Network. In short, MAP symptoms disrupt the emotional and neuroregulatory benefits of affiliation.

The effects of parental presence on amygdala and mPFC activation during fear conditioning: An exploratory study

Learning safe versus dangerous cues is crucial for survival. During development, parents can influence fear learning by buffering their children's stress response and increasing exploration of potentially aversive stimuli. Rodent findings suggest that these behavioral effects are mediated through parental presence modulation of the amygdala and medial prefrontal cortex (mPFC). Here, we investigated whether similar parental modulation of amygdala and mPFC during fear learning occurs in humans. Using a within-subjects design, behavioral (final N = 48, 6-17 years, mean = 11.61, SD = 2.84, 60% females/40% males) and neuroimaging data (final N = 39, 6-17 years, mean = 12.03, SD = 2.98, 59% females/41% males) were acquired during a classical fear conditioning task, which included a CS+ followed by an aversive noise (US; 75% reinforcement rate) and a CS-. Conditioning occurred once in physical contact with the participant's parent and once alone (order counterbalanced). Region of interest analyses examined the unconditioned stress response by BOLD activation to the US (vs. implicit baseline) and learning by activation to the CS+ (vs. CS-). Results showed that during US presentation, parental presence reduced the centromedial amygdala activity, suggesting buffering of the unconditioned stress response. In response to learned stimuli, parental presence reduced mPFC activity to the CS+ (relative to the CS-), although this result did not survive multiple comparisons' correction. These preliminary findings indicate that parents modulate amygdala and mPFC activity during exposure to unconditioned and conditioned fear stimuli, potentially providing insight into the neural mechanisms by which parents act as a social buffer during fear learning. RESEARCH HIGHLIGHTS: This study used a within-participant experimental design to investigate how parental presence (vs. absence) affects youth's neural responses in a classical fear conditioning task. Parental presence reduced the youth's centromedial amygdala activation to the unconditioned stimulus (US), suggesting parental buffering of the neural unconditioned response (UR). Parental presence reduced the youth's mPFC activation to a conditioned threat cue (CS+) compared to a safety cue (CS-), suggesting possible parental modulation of fear learning.

Brain-to-brain synchrony increased during interpersonal touch in romantic lovers: an EEG-based hyperscanning study

BACKGROUND

Interpersonal touch is an essential element of human social life. It's unclear whether the neural patterns of interpersonal touch are specific to intimate relationships or generally apply to other social relationships. Romantic lovers are typically intimate and have a high level of interpersonal touch. Currently, researchers focused on the neurobiological basis and neural processes of romantic love.

METHODS

110 participants finished two resting-state blocks, no-handholding and handholding conditions, with Electroencephalogram (EEG). We aimed to explore the differences in the brain-brain synchrony pattern of interpersonal touch between romantic lovers and strangers by calculating dynamic interpersonal functional connectivity (dIFC) via EEG-based hyperscanning.

RESULTS

Our results supported that the neural processing of interpersonal touch is a dynamic process. At first half, both groups tended to adapt, and then interpersonal touch increased the dIFC between romantic lovers and decreased the dIFC between strangers. Finally, we employed Support Vector Machine (SVM) to classify EEG signals into two different relationships. SVM recognized two relationships with an accuracy of 71% and 0.77 AUC of ROC at the first half, a 73% accuracy and 0.8 AUC of ROC at the second half.

CONCLUSIONS

Our study indicates that interpersonal touch may have different meanings between romantic lovers and strangers. Specifically, interpersonal touch enhances the dIFC between romantic lovers while reducing the dIFC between strangers. The research has important implications for planning touch-based interventions in social and medical care.

The effects of C-tactile stimulation on temporal summation of second pain: A study of the central and peripheral neural correlates

Affective touch is mediated by specialized receptors sensitive to gentle and slow touch called C-tactile afferents (CT). The activation of these receptors has shown promise in reducing subjective pain ratings, however, how this type of touch can affect central sensitization processes is poorly studied. This work aimed to investigate if affective touch is able to modulate pain sensitization and its electrophysiological correlates during Temporal Summation of Second Pain (TSSP), a phenomenon characterized by an increase in pain perception due to repeated noxious stimuli. Thirty-seven participants underwent a TSSP protocol involving three conditions: TSSP alone, TSSP during vibrotactile stimulation, and TSSP during CT stimulation (administered with a brush mounted in a robot arm). We measured subjective pain ratings, electroencephalographic (N2-P2 complex) and electrocardiographic activity during these conditions. Participants reported a significantly lower increase of pain during CT stimulation compared to vibrotactile stimulation, but not to TSSP alone. In addition, TSSP was reduced when administered in the ipsilateral arm compared to the other somatosensory stimulation. Subjective reports of attention towards painful stimuli, amplitude of the N2-P2 complex, and heart rate were also reduced during CT stimulation. Conclusion: Our results indicated that the activation of CT receptors may reduce sensitization compared to other types of somatosensory stimulation, which is possibly related to the reduction of the attention devoted to nociceptive stimulation. Our results suggest that activation of CT receptors may alleviate the occurrence of central pain sensitization.

Social Determinants and Consequences of Pain: Toward Multilevel, Intersectional, and Life Course Perspectives

Despite wide endorsement of a biopsychosocial framework for pain, social aspects of pain remain rarely addressed in the context of pain prevention and management. In this review, we aim to 1) examine the broad scope of social determinants and consequences of pain and their interactions across multiple levels of organization, and 2) provide a framework synthesizing existing concepts and potential areas for future work on social aspects of pain, drawing upon socioecological, intersectional, and life course approaches. Integrating interdisciplinary theory and evidence, we outline pathways through which multilevel social factors and pain may affect each other over time. We also provide a brief summary of intrapersonal aspects of pain, which are thought to operate at the interface between individuals and the social context. Progressing from micro- to macrolevel factors, we illustrate how social determinants of pain can directly or indirectly contribute to pain experiences, expression, risk, prognosis, and impact across populations. We consider 1) at the interpersonal level, the roles of social comparison, social relatedness, social support, social exclusion, empathy, and interpersonal conflict; 2) at the group or community level, the roles of intimacy groups, task groups, social categories, and loose associations; and 3) at the societal level, the roles of political, economic, and cultural systems, as well as their policies and practices. We present examples of multilevel consequences of pain across these levels and discuss opportunities to reduce the burden and inequities of pain by expanding multilevel social approaches in pain research and practice. PERSPECTIVE: Despite wide endorsement of a biopsychosocial framework for pain, social aspects of pain are often unclearly defined, hindering their use in pain prevention, management, and research. We summarize the scope of social aspects of pain and provide a framework synthesizing existing concepts and potential areas for future work.

Verbal Support From a Stranger Reduces the Development of Mechanical Hypersensitivity: Behavioral and Neurophysiological Evidence

Hand-holding reduces experimentally induced acute pain and buffers against the development of mechanical secondary hypersensitivity, an indirect proxy of central sensitization. Here, we tested if verbal support from a stranger, a common occurrence in clinical contexts, exerts the same effects. In this preregistered study, 44 healthy female participants were assigned to an alone or support group whereby a supportive female stranger encouraged them through the painful procedure leading to secondary mechanical hypersensitivity. Mechanical hypersensitivity was measured via self-reports and by the size of the anteroposterior and mediolateral spread of mechanical hypersensitivity. We investigated the moderating role of attachment style on self-reports and the effects of support on skin conductance level, salivary cortisol, and pinprick-evoked potentials. We also tested whether theta/beta ratio in the resting-state electroencephalogram predicted mechanical hypersensitivity. Self-reported ratings and the late part of the pinprick-evoked potentials were reduced in the support group, but the spread of mechanical hypersensitivity was not. Attachment anxiety and avoidance moderated the self-reported intensity such that individuals with higher attachment anxiety and avoidance scores reported lower intensity ratings in the support group. No significant effect of the verbal support was observed on skin conductance level and salivary cortisol. The theta/beta ratio did not predict the extent of hypersensitivity. Our data indicate that, in women, verbal support during intense pain leading to hypersensitivity is effective on some behavioral outcomes, but altogether the lack of group differences in cortisol, self-reported stress, and skin conductance does not provide strong support for the stress-buffering hypothesis. PERSPECTIVE: Verbal support by a stranger during a painful procedure leading to secondary mechanical hypersensitivity attenuated the development of some measures of mechanical hypersensitivity and associated neural responses in healthy female participants. No evidence was found for the role of stress. DATA AVAILABILITY: The authors will make all data available upon request.

A Hypothalamic Perspective of Human Socioemotional Behavior

Historical evidence from stimulation and lesion studies in animals and humans demonstrated a close association between the hypothalamus and typical and atypical socioemotional behavior. A central hypothalamic contribution to regulation of socioemotional responses was also provided indirectly by studies on oxytocin and arginine vasopressin. However, a limited number of studies have so far directly investigated the contribution of the hypothalamus in human socioemotional behavior. To reconsider the functional role of the evolutionarily conserved hypothalamic region in regulating human social behavior, here I provide a synthesis of neuroimaging investigations showing that the hypothalamus is involved in multiple and diverse facets of human socioemotional behavior through widespread functional interactions with other cortical and subcortical regions. These neuroimaging findings are then integrated with recent optogenetics studies in animals demonstrating that the hypothalamus plays a more active role in eliciting socioemotional responses and is not simply a downstream effector of higher-level brain systems. Building on the aforementioned evidence, the hypothalamus is argued to substantially contribute to a continuum of human socioemotional behaviors promoting survival and preservation of the species that extends from exploratory and approaching responses facilitating social bonding to aggressive and avoidance responses aimed to protect and defend formed relationships.

Choice enhances touch pleasantness

We value what we choose more than what is imposed upon us. Choice-induced preferences are extensively demonstrated using behavioural and neural methods, mainly involving rewarding objects such as money or material goods. However, the impact of choice on experiences, especially in the realm of affective touch, remains less explored. In this study, we specifically investigate whether choice can enhance the pleasure derived from affective touch, thereby increasing its intrinsic rewarding value. We conducted an experiment in which participants were being touched by an experimenter and asked to rate how pleasant their experience of touch was. They were given either a choice or no choice over certain touch stimulus variables which differed in their relevance: some were of low relevance (relating to the colour of the glove that the experimenter would use to touch them), while others were of high relevance (relating to the location on their arm where they would be stroked). Before and during touching, pupillometry was used to measure the level of arousal. We found that having a choice over aspects of tactile stimuli-especially those relevant to oneself-enhanced the pleasant perception of the touch. In addition, having a choice increases arousal in anticipation of touch. Regardless of how relevant it is to the actual tactile stimulus, allowing one to choose may positively enhance a person's perception of the physical contact they receive.

Out of touch? How trauma shapes the experience of social touch - Neural and endocrine pathways

Trauma can shape the way an individual experiences the world and interacts with other people. Touch is a key component of social interactions, but surprisingly little is known about how trauma exposure influences the processing of social touch. In this review, we examine possible neurobiological pathways through which trauma can influence touch processing and lead to touch aversion and avoidance in trauma-exposed individuals. Emerging evidence indicates that trauma may affect sensory touch thresholds by modulating activity in the primary sensory cortex and posterior insula. Disturbances in multisensory integration and oxytocin reactivity combined with diminished reward-related and anxiolytic responses may induce a bias towards negative appraisal of touch contexts. Furthermore, hippocampus deactivation during social touch may reflect a dissociative state. These changes depend not only on the type and severity of the trauma but also on the features of the touch. We hypothesise that disrupted touch processing may impair social interactions and confer elevated risk for future stress-related disorders.

Towards a Real-Life Understanding of the Altered Functional Behaviour of the Default Mode and Salience Network in Chronic Pain: Are People with Chronic Pain Overthinking the Meaning of Their Pain?

Chronic pain is a source of substantial physical and psychological suffering, yet a clear understanding of the pathogenesis of chronic pain is lacking. Repeated studies have reported an altered behaviour of the salience network (SN) and default mode network (DMN) in people with chronic pain, and a majority of these studies report an altered behaviour of the dorsal ventromedial prefrontal cortex (vmPFC) within the anterior DMN. In this topical review, we therefore focus specifically on the role of the dorsal vmPFC in chronic pain to provide an updated perspective on the cortical mechanisms of chronic pain. We suggest that increased activity in the dorsal vmPFC may reflect maladaptive overthinking about the meaning of pain for oneself and one's actions. We also suggest that such overthinking, if negative, may increase the personal "threat" of a given context, as possibly reflected by increased activity in, and functional connectivity to, the anterior insular cortex within the SN.

CT-optimal touch and chronic pain experience in Parkinson's Disease; An intervention study

One of the most underdiagnosed and undertreated non-motor symptoms of Parkinson's Disease is chronic pain. This is generally treated with analgesics which is not always effective and can cause several side-effects. Therefore, new ways to reduce chronic pain are needed. Several experimental studies show that CT-optimal touch can reduce acute pain. However, little is known about the effect of CT-optimal touch on chronic pain. The aim of the current study is to investigate whether CT-optimal touch can reduce the chronic pain experience in Parkinson patients. In this intervention study, 17 Parkinson patients underwent three conditions; no touch, CT-optimal touch and CT non-optimal touch with a duration of one week each. During each touch week, participants received touch from their partners twice a day for 15 minutes. Results show that both types of touch ameliorate the chronic pain experience. Furthermore, it appears that it is slightly more beneficial to apply CT-optimal touch also because it is perceived as more pleasant. Therefore, we argue that CT-optimal touch might be used when immediate pain relief is needed. Importantly, this study shows that CT-optimal touch can reduce chronic pain in Parkinson's Disease and can be administered by a partner which makes it feasible to implement CT-optimal touch as daily routine.

The dual facilitatory and inhibitory effects of social pain on physical pain perception

Pain is a multi-dimensional phenomenon that encompasses both physical pain experienced physiologically and social pain experienced emotionally. The interactions between them are thought to lead to increased pain load. However, the effect of social pain on physical pain perception during interactions remains unclear. Four experiments were conducted merging physical and social pains to examine the behavioral pattern and neural mechanism of the effect of social pain on physical pain perception. Seemingly paradoxical effects of social pain were observed, which both facilitated and inhibited physical pain perception under different attention orientations. Brain imaging revealed that the posterior insula encoded the facilitatory effect, whereas the frontal pole engaged in the inhibitory effect. At a higher level, the thalamus further modulated both processes, playing a switch-like role under different concern statuses of social pain. These results provide direct evidence for the dual-pathway mechanism of the effect of social pain on physical pain.

IUPHAR review: Navigating the role of preclinical models in pain research

Chronic pain is a complex and challenging medical condition that affects millions of people worldwide. Understanding the underlying mechanisms of chronic pain is a key goal of preclinical pain research so that more effective treatment strategies can be developed. In this review, we explore nociception, pain, and the multifaceted factors that lead to chronic pain by focusing on preclinical models. We provide a detailed look into inflammatory and neuropathic pain models and discuss the most used animal models for studying the mechanisms behind these conditions. Additionally, we emphasize the vital role of these preclinical models in developing new pain-relief drugs, focusing on biologics and the therapeutic potential of NMDA and cannabinoid receptor antagonists. We also discuss the challenges of TRPV1 modulation for pain treatment, the clinical failures of neurokinin (NK)- 1 receptor antagonists, and the partial success story of Ziconotide to provide valuable lessons for preclinical pain models. Finally, we highlight the overall success and limitations of current treatments for chronic pain while providing critical insights into the development of more effective therapies to alleviate the burden of chronic pain.

The impact of the social context on the development of secondary hyperalgesia: an experimental study

ABSTRACT

Social support has been shown to reduce pain ratings and physiological responses to acute pain stimuli. Furthermore, this relationship is moderated by adult attachment styles. However, these effects have not been characterized in experimentally induced symptoms of chronic pain, such as secondary hyperalgesia (SH) which is characterized by an increased sensitivity of the skin surrounding an injury. We aimed to examine whether social support by handholding from a romantic partner can attenuate the development of experimentally induced SH. Thirty-seven women, along with their partners, participated in 2 experimental sessions 1 week apart. In both sessions, SH was induced using an electrical stimulation protocol. In the support condition, the partner was seated across from the participant holding the participant's hand during the electrical stimulation, whereas in the alone condition, the participant went through the stimulation alone. Heart rate variability was measured for both the participant as well as the partner before, during, and after the stimulation. We found that the width of the area of hyperalgesia was significantly smaller in the support condition. Attachment styles did not moderate this effect of social support on the area width. Increasing attachment avoidance was associated with both a smaller width of hyperalgesia and a smaller increase in the sensitivity on the stimulated arm. For the first time, we show that social support can attenuate the development of secondary hyperalgesia and that attachment avoidance may be associated with an attenuated development of secondary hyperalgesia.

The osteopath-parent-child triad in osteopathic care in the first 2 years of life: a qualitative study

Background

Enactivism and active inference are two important concepts in the field of osteopathy. While enactivism emphasizes the role of the body and the environment in shaping our experiences and understanding of the world, active inference emphasizes the role of action and perception in shaping our experiences and understanding of the world. Together, these frameworks provide a unique perspective on the practice of osteopathy, and how it can be used to facilitate positive change in patients. Since the neonatal period is a crucial time for development, osteopaths should aim to create a therapeutic relationship. Arguably, through participatory sense-making, osteopaths can help the baby build a generative model (with positive priors) to deal with stress and needs throughout their life.

Aim

Since the literature considers that interactions with the environment, which enact the patients' experiences, depending on contextual factors and communication between patient and caregiver, this research explored whether there is a correspondence between the indications in the literature and clinical practice in the management of the mother/parent-child dyad during osteopathic care on children aged 0 to 2 years old.

Methods

Semi-structured interviews were conducted with a purposive sample of nine osteopaths with experience in the field of pediatrics. Interviews were transcribed verbatim, and constructivist grounded theory was used to conceptualize, collect and analyze data. Codes and categories were actively constructed through an interpretive/constructionist paradigm.

Results

The core category was the idea of the pediatric osteopath as a support for the family, not only for the child. Four additional categories were identified: (1) Preparing a safe environment for both children and parents, (2) Communication, (3) Attachment and synchrony, and (4) Synchronization.

Conclusion

Through participatory sense-making, osteopaths manage contextual factors to establish an effective therapeutic alliance through the osteopath-parent-child triad to facilitate the construction of the child's internal generative model to promote healthy development. The therapeutic encounter is considered an encounter between embodied subjects, occurring within a field of affordances (ecological niche) that allows the interlocutors to actively participate in creating new meanings through interpersonal synchronization. Participatory sense-making and the establishment of a therapeutic alliance through the osteopath-parent-child triad are crucial to promote healthy development in the child.

Augmented pain-evoked primary sensorimotor cortex activation in adolescent girls with juvenile fibromyalgia

ABSTRACT

Juvenile fibromyalgia (JFM) is a chronic widespread pain condition that primarily affects adolescent girls. Previous studies have found increased sensitivity to noxious pressure in adolescents with JFM. However, the underlying changes in brain systems remain unclear. The aim of this study was to characterize pain-evoked brain responses and identify brain mediators of pain hypersensitivity in adolescent girls with JFM. Thirty-three adolescent girls with JFM and 33 healthy adolescent girls underwent functional magnetic resonance imaging scans involving noxious pressure applied to the left thumbnail at an intensity of 2.5 or 4 kg/cm 2 and rated pain intensity and unpleasantness on a computerized Visual Analogue Scale. We conducted standard general linear model analyses and exploratory whole-brain mediation analyses. The JFM group reported significantly greater pain intensity and unpleasantness than the control group in response to noxious pressure stimuli at both intensities ( P < 0.05). The JFM group showed augmented right primary somatosensory cortex (S1) activation to 4 kg/cm 2 (Z > 3.1, cluster-corrected P < 0.05), and the peak S1 activation magnitudes significantly correlated with the scores on the Widespread Pain Index ( r = 0.35, P = 0.048) with higher activation associated with more widespread pain. We also found that greater primary sensorimotor cortex activation in response to 4 kg/cm 2 mediated the between-group differences in pain intensity ratings ( P < 0.001). In conclusion, we found heightened sensitivity to noxious pressure stimuli and augmented pain-evoked sensorimotor cortex responses in adolescent girls with JFM, which could reflect central sensitization or amplified nociceptive input.

No effect of social interaction on experimental pain sensitivity: a randomized experimental study

ABSTRACT

Quantitative sensory testing (QST) is a commonly applied paradigm to investigate pain, which is a subjective experience influenced by a myriad of social and contextual factors. Therefore, it is important to consider the potential sensitivity of QST to the test setting and the social interaction that naturally is a part of it. This may particularly be the case in clinical settings where patients have something at stake. Therefore, we investigated differences in pain responses using QST in different test setups with varying degrees of human interaction. In a parallel three-armed randomized experimental study, we included 92 participants with low back pain and 87 healthy volunteers allocated to 1 of the 3 QST setups: 1 setup with manual tests performed by a human tester, 1 setup with automated tests performed by a robot and orally guided by a human tester, and 1 setup with automated tests performed solely by a robot without social interaction with a human tester. All 3 setups consisted of the same pain tests in the same order, including pressure pain threshold and cold pressor tests. We found no statistically significant differences between setups on the primary outcome of conditioned pain modulation nor any secondary QST outcomes. While this study is not without limitations, the results indicate that QST procedures are robust enough not to be influenced by social interaction to an appreciable degree.

Pain perception and physiological responses are modulated by active support from a romantic partner

As social animals, humans are strongly affected by social bonds and interpersonal interactions. Proximity and social support from significant others may buffer the negative outcomes of a painful experience. Several studies have investigated the role of romantic partners' support in pain modulation, mostly focusing on tactile support and showing its effectiveness in reducing pain perception. Nevertheless, no study so far has investigated the role of supportive speaking on pain modulation, nor has compared the effects of a tactile and vocal support within the same couples. The present study directly compared for the first time the efficacy of mere presence (Passive Support) and different forms of active (Touch, Voice, Touch + Voice) support from a romantic partner during a painful experience in a naturalistic setting. We assessed pain modulation in 37 romantic couples via both subjective (self-reported ratings) and physiological (skin conductance) measurements. We found that all three types of active support were equally more effective than passive support in reducing the painful experience at both subjective and physiological levels; interestingly, our results suggest that supportive speaking can reduce pain perception with respect to passive support to a similar extent as tactile support does. Overall, this study highlights the relevance of an active support in reducing pain perception, with active types of support being more effective than passive support, regardless of its specific modality.

Brain-to-brain mechanisms underlying pain empathy and social modulation of pain in the patient-clinician interaction

Social interactions such as the patient-clinician encounter can influence pain, but the underlying dynamic interbrain processes are unclear. Here, we investigated the dynamic brain processes supporting social modulation of pain by assessing simultaneous brain activity (fMRI hyperscanning) from chronic pain patients and clinicians during video-based live interaction. Patients received painful and nonpainful pressure stimuli either with a supportive clinician present (Dyadic) or in isolation (Solo). In half of the dyads, clinicians performed a clinical consultation and intake with the patient prior to hyperscanning (Clinical Interaction), which increased self-reported therapeutic alliance. For the other half, patient-clinician hyperscanning was completed without prior clinical interaction (No Interaction). Patients reported lower pain intensity in the Dyadic, relative to the Solo, condition. In Clinical Interaction dyads relative to No Interaction, patients evaluated their clinicians as better able to understand their pain, and clinicians were more accurate when estimating patients' pain levels. In Clinical Interaction dyads, compared to No Interaction, patients showed stronger activation of the dorsolateral and ventrolateral prefrontal cortex (dlPFC and vlPFC) and primary (S1) and secondary (S2) somatosensory areas (Dyadic-Solo contrast), and clinicians showed increased dynamic dlPFC concordance with patients' S2 activity during pain. Furthermore, the strength of S2-dlPFC concordance was positively correlated with self-reported therapeutic alliance. These findings support that empathy and supportive care can reduce pain intensity and shed light on the brain processes underpinning social modulation of pain in patient-clinician interactions. Our findings further suggest that clinicians' dlPFC concordance with patients' somatosensory processing during pain can be boosted by increasing therapeutic alliance.

Doctor trustworthiness influences pain and its neural correlates in virtual medical interactions

Trust is an important component of the doctor-patient relationship and is associated with improved patient satisfaction and health outcomes. Previously, we reported that patient feelings of trust and similarity toward their clinician predicted reductions in evoked pain in response to painful heat stimulations. In the present study, we investigated the brain mechanisms underlying this effect. We used face stimuli previously developed using a data-driven computational modeling approach that differ in perceived trustworthiness and superimposed them on bodies dressed in doctors' attire. During functional magnetic resonance imaging, participants (n = 42) underwent a series of virtual medical interactions with these doctors during which they received painful heat stimulation as an analogue of a painful diagnostic procedure. Participants reported increased pain when receiving painful heat stimulations from low-trust doctors, which was accompanied by increased activity in pain-related brain regions and a multivariate pain-predictive neuromarker. Findings suggest that patient trust in their doctor may have tangible impacts on pain and point to a potential brain basis for trust-related reductions in pain through the modulation of brain circuitry associated with the sensory-discriminative and affective-motivational dimensions of pain.

Social Touch Reduces Pain Perception—An fMRI Study of Cortical Mechanisms

Unmyelinated low-threshold mechanoreceptors (C-tactile, CT) in the human skin are important for signaling information about hedonic aspects of touch. We have previously reported that CT-targeted brush stroking by means of a robot reduces experimental mechanical pain. To improve the ecological validity of the stimulation, we developed standardized human–human touch gestures for signaling attention and calming. The attention gesture is characterized by tapping of the skin and is perceived as neither pleasant nor unpleasant, i.e., neutral. The calming gesture is characterized by slow stroking of the skin and is perceived as moderately to very pleasant. Furthermore, the attention (tapping) gesture is ineffective, whereas the calming (stroking) gesture is effective in activating CT-afferents. We conducted an fMRI study (n = 32) and capitalized on the previous development of touch gestures. We also developed an MR compatible stimulator for high-precision mechanical pain stimulation of the thenar region of the hand. Skin-to-skin touching (stroking or tapping) was applied and was followed by low and high pain. When the stroking gesture preceded pain, the pain was rated as less intense. When the tapping gesture preceded the pain, the pain was rated as more intense. Individual pain perception related to insula activation, but the activation was not higher for stroking than for tapping in any brain area during the stimulation period. However, during the evaluation period, stronger activation in the periaqueductal gray matter was observed after calming touch compared to after tapping touch. This finding invites speculation that human–human gentle skin stroking, effective in activating CT-afferents, reduced pain through neural processes involving CT-afferents and the descending pain pathway.

Emotion regulation and the salience network: a hypothetical integrative model of fibromyalgia

Fibromyalgia is characterized by widespread pain, fatigue, sleep disturbances and other symptoms, and has a substantial socioeconomic impact. Current biomedical and psychosocial treatments are unsatisfactory for many patients, and treatment progress has been hindered by the lack of a clear understanding of the pathogenesis of fibromyalgia. We present here a model of fibromyalgia that integrates current psychosocial and neurophysiological observations. We propose that an imbalance in emotion regulation, reflected by an overactive 'threat' system and underactive 'soothing' system, might keep the 'salience network' (also known as the midcingulo-insular network) in continuous alert mode, and this hyperactivation, in conjunction with other mechanisms, contributes to fibromyalgia. This proposed integrative model, which we term the Fibromyalgia: Imbalance of Threat and Soothing Systems (FITSS) model, should be viewed as a working hypothesis with limited supporting evidence available. We hope, however, that this model will shed new light on existing psychosocial and biological observations, and inspire future research to address the many gaps in our knowledge about fibromyalgia, ultimately stimulating the development of novel therapeutic interventions.

The brain-body disconnect: A somatic sensory basis for trauma-related disorders

Although the manifestation of trauma in the body is a phenomenon well-endorsed by clinicians and traumatized individuals, the neurobiological underpinnings of this manifestation remain unclear. The notion of somatic sensory processing, which encompasses vestibular and somatosensory processing and relates to the sensory systems concerned with how the physical body exists in and relates to physical space, is introduced as a major contributor to overall regulatory, social-emotional, and self-referential functioning. From a phylogenetically and ontogenetically informed perspective, trauma-related symptomology is conceptualized to be grounded in brainstem-level somatic sensory processing dysfunction and its cascading influences on physiological arousal modulation, affect regulation, and higher-order capacities. Lastly, we introduce a novel hierarchical model bridging somatic sensory processes with limbic and neocortical mechanisms regulating an individual's emotional experience and sense of a relational, agentive self. This model provides a working framework for the neurobiologically informed assessment and treatment of trauma-related conditions from a somatic sensory processing perspective.

A wearable soft robot that can alleviate the pain and fear of the wearer

Social soft robotics may provide a new solution for alleviating human pain and fear. Here, we introduce a hand-held soft robot that can be clenched by the wearer. The robot comprises small airbags that can be inflated to provide the wearer with a feeling of being clenched. We then conducted an in-depth study of 66 adults who participated in a pain research protocol using thermal stimulation to investigate the effect of wearing the robot on pain perception and fear of injections. Pain assessment scale scores for perceived pain decreased significantly [Formula: see text] when participants wore the robot compared with the baseline condition in which the robot was not worn. In addition, the saliva test results showed a downward trend in oxytocin level when the robot provided the wearer with haptic feedback via the inflation of the internal airbags in response to the wearer's clench. Furthermore, the negative psychological state of participants, as measured using the positive and negative affect scale, improved significantly when wearing the robot. We also revealed that the salivary cortisol level, an indicator of stress, decreased significantly across all participants at the end of the experiment. In addition, participants' fear of injections was significantly improved after participation in the experiment. These results suggest that the wearable soft robot may alleviate the human perception of pain and fear in during medical treatments, such as vaccinations.

Processing of pain by the developing brain: evidence of differences between adolescent and adult females

ABSTRACT

Adolescence is a sensitive period for both brain development and the emergence of chronic pain particularly in females. However, the brain mechanisms supporting pain perception during adolescence remain unclear. This study compares perceptual and brain responses to pain in female adolescents and adults to characterize pain processing in the developing brain. Thirty adolescent (ages 13-17 years) and 30 adult (ages 35-55 years) females underwent a functional magnetic resonance imaging scan involving acute pain. Participants received 12 ten-second noxious pressure stimuli that were applied to the left thumbnail at 2.5 and 4 kg/cm 2 , and rated pain intensity and unpleasantness on a visual analogue scale. We found a significant group-by-stimulus intensity interaction on pain ratings. Compared with adults, adolescents reported greater pain intensity and unpleasantness in response to 2.5 kg/cm 2 but not 4 kg/cm 2 . Adolescents showed greater medial-lateral prefrontal cortex and supramarginal gyrus activation in response to 2.5 kg/cm 2 and greater medial prefrontal cortex and rostral anterior cingulate responses to 4 kg/cm 2 . Adolescents showed greater pain-evoked responses in the neurologic pain signature and greater activation in the default mode and ventral attention networks. Also, the amygdala and associated regions played a stronger role in predicting pain intensity in adolescents, and activity in default mode and ventral attention regions more strongly mediated the relationship between stimulus intensity and pain ratings. This study provides first evidence of greater low-pain sensitivity and pain-evoked brain responses in female adolescents (vs adult women) in regions important for nociceptive, affective, and cognitive processing, which may be associated with differences in peripheral nociception.

The influence of social signals on the self-experience of pain: A neuroimaging review

Researchers in cognitive neuroscience have investigated extensively how psychological factors shape the processing and perception of pain using behavioral, physiological, and neuroimaging methods. However, social influences of pain, an essential part of biopsychosocial pain models, have received relatively little attention. This is particularly true for the neurobiological mechanisms underlying social modulations on pain. Therefore, this review discusses the findings of recent neuroimaging studies measuring the effects of social manipulations on pain perception (e.g., verbal and non-verbal social signals, social interaction style, conformity, social support, and sociocultural mediators). Finally, a schematic summary of the different social modulatory themes is presented.

Interaction Matters: The Effect of Touching the Social Robot PARO on Pain and Stress is Stronger When Turned ON vs. OFF

Social touch between humans, as well as between humans and animals, was previously found to reduce pain and stress. We previously reported that touching a social robot can also induce a reduction in pain ratings. However, it is unclear if the effect that touching a robot has on pain perception is due to its appearance and its pleasant touch, or due to its ability to socially interact with humans. In the current experiment, we aimed to assess the contribution of the interactive quality to pain perception. We assessed the effect of touching the social robot PARO on mild and strong pain ratings and on stress perception, on a total of 60 healthy young participants. The robot either interacted with participants (ON group, n = 30) or was turned off (OFF group, n = 30). Touching the robot induced a decrease in mild pain ratings (compared to baseline) only in the ON group while strong pain ratings decreased similarly in both the ON and the OFF groups. The decrease in mild pain ratings in the ON group was significantly greater in participants with a higher positive perception of the interaction with PARO. We conclude that part of the effect that touching the robot has on pain stems from its interactive features.

Therapeutic Alliance as Active Inference: The Role of Therapeutic Touch and Biobehavioural Synchrony in Musculoskeletal Care

Touch is recognised as crucial for survival, fostering cooperative communication, accelerating recovery, reducing hospital stays, and promoting overall wellness and the therapeutic alliance. In this hypothesis and theory paper, we present an entwined model that combines touch for alignment and active inference to explain how the brain develops "priors" necessary for the health care provider to engage with the patient effectively. We appeal to active inference to explain the empirically integrative neurophysiological and behavioural mechanisms that underwrite synchronous relationships through touch. Specifically, we offer a formal framework for understanding - and explaining - the role of therapeutic touch and hands-on care in developing a therapeutic alliance and synchrony between health care providers and their patients in musculoskeletal care. We first review the crucial importance of therapeutic touch and its clinical role in facilitating the formation of a solid therapeutic alliance and in regulating allostasis. We then consider how touch is used clinically - to promote cooperative communication, demonstrate empathy, overcome uncertainty, and infer the mental states of others - through the lens of active inference. We conclude that touch plays a crucial role in achieving successful clinical outcomes and adapting previous priors to create intertwined beliefs. The ensuing framework may help healthcare providers in the field of musculoskeletal care to use hands-on care to strengthen the therapeutic alliance, minimise prediction errors (a.k.a., free energy), and thereby promote recovery from physical and psychological impairments.

Dissociation between individual differences in self-reported pain intensity and underlying fMRI brain activation

Pain is an individual experience. Previous studies have highlighted changes in brain activation and morphology associated with within- and interindividual pain perception. In this study we sought to characterize brain mechanisms associated with between-individual differences in pain in a sample of healthy adolescent and adult participants (N = 101). Here we show that pain ratings varied widely across individuals and that individuals reported changes in pain evoked by small differences in stimulus intensity in a manner congruent with their pain sensitivity, further supporting the utility of subjective reporting as a measure of the true individual experience. Furthermore, brain activation related to interindividual differences in pain was not detected, despite clear sensitivity of the Blood Oxygenation Level-Dependent (BOLD) signal to small differences in noxious stimulus intensities within individuals. These findings suggest fMRI may not be a useful objective measure to infer reported pain intensity.

Functional Neuroimaging of Human Hypothalamus in Socioemotional Behavior: A Systematic Review

There exist extensive animal research and lesion studies in humans demonstrating a tight association between the hypothalamus and socioemotional behavior. However, human neuroimaging literature in this direction is still rather limited. In order to reexamine the functional role of this region in regulating human social behavior, we here provided a synthesis of neuroimaging studies showing hypothalamic activation during affiliative, cooperative interactions, and in relation to ticklish laughter and humor. In addition, studies reporting involvement of the hypothalamus during aggressive and antisocial interactions were also considered. Our systematic review revealed a growing number of investigations demonstrating that the evolutionary conserved hypothalamic neural circuity is involved in multiple and diverse aspects of human socioemotional behavior. On the basis of the observed heterogeneity of hypothalamus-mediated socioemotional responses, we concluded that the hypothalamus might play an extended functional role for species survival and preservation, ranging from exploratory and approaching behaviors promoting social interactions to aggressive and avoidance responses protecting and defending the established social bonds.

A multistudy analysis reveals that evoked pain intensity representation is distributed across brain systems

Information is coded in the brain at multiple anatomical scales: locally, distributed across regions and networks, and globally. For pain, the scale of representation has not been formally tested, and quantitative comparisons of pain representations across regions and networks are lacking. In this multistudy analysis of 376 participants across 11 studies, we compared multivariate predictive models to investigate the spatial scale and location of evoked heat pain intensity representation. We compared models based on (a) a single most pain-predictive region or resting-state network; (b) pain-associated cortical-subcortical systems developed from prior literature ("multisystem models"); and (c) a model spanning the full brain. We estimated model accuracy using leave-one-study-out cross-validation (CV; 7 studies) and subsequently validated in 4 independent holdout studies. All spatial scales conveyed information about pain intensity, but distributed, multisystem models predicted pain 20% more accurately than any individual region or network and were more generalizable to multimodal pain (thermal, visceral, and mechanical) and specific to pain. Full brain models showed no predictive advantage over multisystem models. These findings show that multiple cortical and subcortical systems are needed to decode pain intensity, especially heat pain, and that representation of pain experience may not be circumscribed by any elementary region or canonical network. Finally, the learner generalization methods we employ provide a blueprint for evaluating the spatial scale of information in other domains.

Affective touch perception and longing for touch during the COVID-19 pandemic

Interpersonal touch and affective touch play a crucial role in social interactions and have a positive influence on mental health. The social distancing regulations implemented during the COVID-19 pandemic have reduced the ability to engage in interpersonal touch. This could cause longing for touch, and it might subsequently alter the way in which affective touch is perceived. To investigate this, we conducted an online survey and included 1982 participants, which contained questions regarding the COVID-19 regulations, longing for touch, and the perceived pleasantness of affective and non-affective touch. Results showed that participants reported feelings of longing for touch. This significantly increased with the duration and severity of the COVID-19 regulations. In addition, participants who experienced more longing for touch rated videos of affective and non-affective touch as more pleasant. Current results provide insight in the impact of sudden and prolonged COVID-19 regulations and show that increasing the duration and severity of these regulations is associated with a higher desire for touch, which is associated with increased perceived pleasantness of observing touch.

The neurologic pain signature responds to nonsteroidal anti-inflammatory treatment vs placebo in knee osteoarthritis

Supplemental Digital Content is Available in the Text.

fMRI-based measures, validated for nociceptive pain, respond to acute osteoarthritis pain, are not sensitive to placebo, and are mild-to-moderately sensitive to naproxen.

Introduction:

Many drug trials for chronic pain fail because of high placebo response rates in primary endpoints. Neurophysiological measures can help identify pain-linked pathophysiology and treatment mechanisms. They can also help guide early stop/go decisions, particularly if they respond to verum treatment but not placebo. The neurologic pain signature (NPS), an fMRI-based measure that tracks evoked pain in 40 published samples and is insensitive to placebo in healthy adults, provides a potentially useful neurophysiological measure linked to nociceptive pain.

Objectives:

This study aims to validate the NPS in knee osteoarthritis (OA) patients and test the effects of naproxen on this signature.

Methods:

In 2 studies (50 patients, 64.6 years, 75% females), we (1) test the NPS and other control signatures related to negative emotion in knee OA pain patients; (2) test the effect of placebo treatments; and (3) test the effect of naproxen, a routinely prescribed nonsteroidal anti-inflammatory drug in OA.

Results:

The NPS was activated during knee pain in OA (d = 1.51, P < 0.001) and did not respond to placebo (d = 0.12, P = 0.23). A single dose of naproxen reduced NPS responses (vs placebo, NPS d = 0.34, P = 0.03 and pronociceptive NPS component d = 0.38, P = 0.02). Naproxen effects were specific for the NPS and did not appear in other control signatures.

Conclusion:

This study provides preliminary evidence that fMRI-based measures, validated for nociceptive pain, respond to acute OA pain, do not appear sensitive to placebo, and are mild-to-moderately sensitive to naproxen.

Therapeutic Alliance as Active Inference: The Role of Therapeutic Touch and Synchrony

Recognizing and aligning individuals' unique adaptive beliefs or "priors" through cooperative communication is critical to establishing a therapeutic relationship and alliance. Using active inference, we present an empirical integrative account of the biobehavioral mechanisms that underwrite therapeutic relationships. A significant mode of establishing cooperative alliances-and potential synchrony relationships-is through ostensive cues generated by repetitive coupling during dynamic touch. Established models speak to the unique role of affectionate touch in developing communication, interpersonal interactions, and a wide variety of therapeutic benefits for patients of all ages; both neurophysiologically and behaviorally. The purpose of this article is to argue for the importance of therapeutic touch in establishing a therapeutic alliance and, ultimately, synchrony between practitioner and patient. We briefly overview the importance and role of therapeutic alliance in prosocial and clinical interactions. We then discuss how cooperative communication and mental state alignment-in intentional communication-are accomplished using active inference. We argue that alignment through active inference facilitates synchrony and communication. The ensuing account is extended to include the role of (C-) tactile afferents in realizing the beneficial effect of therapeutic synchrony. We conclude by proposing a method for synchronizing the effects of touch using the concept of active inference.

What Do Placebo and Nocebo Effects Have to Do With Health Equity? The Hidden Toll of Nocebo Effects on Racial and Ethnic Minority Patients in Clinical Care

A placebo effect is a positive clinical response to non-specific elements of treatment with a sham or inert replica of a drug, device, or surgical intervention. There is considerable evidence that placebo effects are driven by expectation of benefit from the intervention. Expectation is shaped by a patient's past experience, observations of the experience of others, and written, verbal, or non-verbal information communicated during treatment. Not surprisingly, expectation in the clinical setting is strongly influenced by the attitude, affect, and communication style of the healthcare provider. While positive expectations can produce beneficial effects, negative information and experiences can lead to negative expectations, and consequently negative or nocebo effects. Key components identified and studied in the placebo and nocebo literature intersect with factors identified as barriers to quality care in the clinical setting for Black patients and other patients of color, including poor patient-clinician communication, medical mistrust, and perceived discrimination. Thus, in the context of discrimination and bias, the absence of placebo and presence of nocebo-generating influences in clinical settings could potentially reinforce racial and ethnic inequities in clinical outcomes and care. Healthcare inequities have consequences that ripple through the medical system, strengthening adverse short- and long-term outcomes. Here, we examine the potential for the presence of nocebo effects and absence of placebo effects to play a role in contributing to negative outcomes related to unequal treatment in the clinical encounter.

Prescribing and Administering Opioid Doses Based Solely on Pain Intensity: Update of A Position Statement by the American Society for Pain Management Nursing

The foundation of safe and effective pain management is an individualized, comprehensive pain assessment that includes, but is not limited to, the intensity of pain if the patient is able to report it. An unforeseen consequence of the widespread use of pain intensity rating scales is the practice of prescribing specific doses of opioid analgesics based solely on specific pain intensity ratings. Many factors in addition to pain intensity influence opioid requirements. To date there is no research demonstrating that a specific opioid dose will relieve pain of a specific intensity in all patients or even in the same patient at different times. The official position of the American Society for Pain Management Nursing (ASPMN) maintains that the practice of prescribing doses of opioid analgesics based solely on pain intensity should be prohibited because it disregards the relevance of other essential elements of assessment and may contribute to untoward patient outcomes.

Investigating the specificity of the neurologic pain signature against breathlessness and finger opposition

ABSTRACT

Brain biomarkers of pain, including pain-predictive "signatures" based on brain activity, can provide measures of neurophysiological processes and potential targets for interventions. A central issue relates to the specificity of such measures, and understanding their current limits will both advance their development and explore potentially generalizable properties of pain to other states. Here, we used 2 data sets to test the neurologic pain signature (NPS), an established pain neuromarker. In study 1, brain activity was measured using high-field functional magnetic resonance imaging (7T fMRI, N = 40) during 5 to 25 seconds of experimental breathlessness (induced by inspiratory resistive loading), conditioned breathlessness anticipation, and finger opposition. In study 2, we assessed anticipation and breathlessness perception (3T, N = 19) under blinded saline (placebo) and remifentanil administration. The NPS responded to breathlessness, anticipation, and finger opposition, although no direct comparisons with painful events were possible. Local NPS patterns in anterior or midinsula, S2, and dorsal anterior cingulate responded to breathlessness and finger opposition and were reduced by remifentanil. Local NPS responses in the dorsal posterior insula did not respond to any manipulations. Therefore, significant global NPS activity alone is not specific for pain, and we offer insight into the overlap between NPS responses, breathlessness, and somatomotor demand.

The Interpersonal Neuroscience of Social Learning

The study of the brain mechanisms underpinning social behavior is currently undergoing a paradigm shift, moving its focus from single individuals to the real-time interaction among groups of individuals. Although this development opens unprecedented opportunities to study how interpersonal brain activity shapes behaviors through learning, there have been few direct connections to the rich field of learning science. Our article examines how the rapidly developing field of interpersonal neuroscience is (and could be) contributing to our understanding of social learning. To this end, we first review recent research extracting indices of brain-to-brain coupling (BtBC) in the context of social behaviors and, in particular, social learning. We then discuss how studying communicative behaviors during learning can aid the interpretation of BtBC and how studying BtBC can inform our understanding of such behaviors. We then discuss how BtBC and communicative behaviors collectively can predict learning outcomes, and we suggest several causative and mechanistic models. Finally, we highlight key methodological and interpretational challenges as well as exciting opportunities for integrating research in interpersonal neuroscience with social learning, and we propose a multiperson framework for understanding how interpersonal transmission of information between individual brains shapes social learning.

Recommendations for the Development of Socioeconomically-Situated and Clinically-Relevant Neuroimaging Models of Pain

Pain is a complex, multidimensional experience that emerges from interactions among sensory, affective, and cognitive processes in the brain. Neuroimaging allows us to identify these component processes and model how they combine to instantiate the pain experience. However, the clinical impact of pain neuroimaging models has been limited by inadequate population sampling - young healthy college students are not representative of chronic pain patients. The biopsychosocial approach to pain management situates a person's pain within the diverse socioeconomic environments they live in. To increase the clinical relevance of pain neuroimaging models, a three-fold biopsychosocial approach to neuroimaging biomarker development is recommended. The first level calls for the development of diagnostic biomarkers via the standard population-based (nomothetic) approach with an emphasis on diverse sampling. The second level calls for the development of treatment-relevant models via a constrained person-based (idiographic) approach tailored to unique individuals. The third level calls for the development of prevention-relevant models via a novel society-based (social epidemiologic) approach that combines survey and neuroimaging data to predict chronic pain risk based on one's socioeconomic conditions. The recommendations in this article address how we can leverage pain's complexity in service of the patient and society by modeling not just individuals and populations, but also the socioeconomic structures that shape any individual's expectations of threat, safety, and resource availability.

Getting in touch: A neural model of comforting touch

Comforting touch involves contact distress-alleviating behaviors of an observer towards the suffering of a target. A growing number of studies have investigated the effects of touch on pain attenuation, focusing on the (toucher), the target (comforted) or both. Here we synthesize findings of brain mechanisms underlying comforting touch in the target and toucher to propose an integrative brain model for understanding how touch attenuates distress. Building on evidence from the pain and distress literatures, our model applies interchangeably to pain and distress regulation. We describe comforting touch as a feedback-loop that begins with distress experienced by the target, triggering an empathic response in the toucher which in turn reduces distress in the target. This cycle is mediated by interactions between the neural circuits associated with touch perception, shared distress, emotion regulation and reward as well as brain-to-brain coupling in the observation-execution system. We conclude that formulating a model of comforting touch offers a mechanistic framework for understanding the effects of touch as well as other social interactions involving social support.

Touch and social support influence interpersonal synchrony and pain

Interpersonal touch and social support can influence physical health, mental well-being and pain. However, the mechanisms by which supportive touch promotes analgesia are not well understood. In Study 1, we tested how three kinds of social support from a romantic partner (passive presence, gentle stroking and handholding) affect pain ratings and skin conductance responses (SCRs). Overall, support reduced pain ratings in women, but not men, relative to baseline. Support decreased pain-related SCRs in both women and men. Though there were no significant differences across the three support conditions, effects were largest during handholding. Handholding also reduced SCRs in the supportive partner. Additionally, synchronicity in couples’ SCR was correlated with reductions in self-reported pain, and individual differences in synchrony were correlated with the partner’s trait empathy. In Study 2, we re-analyzed an existing dataset to explore fMRI activity related to individual differences in handholding analgesia effects in women. Increased activity in a distributed set of brain regions, including valuation-encoding frontostriatal areas, was correlated with lower pain ratings. These results may suggest that social support can reduce pain by changing the value of nociceptive signals. This reduction may be moderated by interpersonal synchrony and relationship dynamics.