The importance of context: when relative relief renders pain pleasant

Brain representations of affective valence and intensity in sustained pleasure and pain

Pleasure and pain are two fundamental, intertwined aspects of human emotions. Pleasurable sensations can reduce subjective feelings of pain and vice versa, and we often perceive the termination of pain as pleasant and the absence of pleasure as unpleasant. This implies the existence of brain systems that integrate them into modality-general representations of affective experiences. Here, we examined representations of affective valence and intensity in an functional MRI (fMRI) study (n = 58) of sustained pleasure and pain. We found that the distinct subpopulations of voxels within the ventromedial and lateral prefrontal cortices, the orbitofrontal cortex, the anterior insula, and the amygdala were involved in decoding affective valence versus intensity. Affective valence and intensity predictive models showed significant decoding performance in an independent test dataset (n = 62). These models were differentially connected to distinct large-scale brain networks-the intensity model to the ventral attention network and the valence model to the limbic and default mode networks. Overall, this study identified the brain representations of affective valence and intensity across pleasure and pain, promoting a systems-level understanding of human affective experiences.

Integration of Prior Expectations and Suppression of Prediction Errors During Expectancy-Induced Pain Modulation: The Influence of Anxiety and Pleasantness

Pain perception arises from the integration of prior expectations with sensory information. Although recent work has demonstrated that treatment expectancy effects (e.g., placebo hypoalgesia) can be explained by a Bayesian integration framework incorporating the precision level of expectations and sensory inputs, the key factor modulating this integration in stimulus expectancy-induced pain modulation remains unclear. In a stimulus expectancy paradigm combining emotion regulation in healthy male and female adults, we found that participants' voluntary reduction in anticipatory anxiety and pleasantness monotonically reduced the magnitude of pain modulation by negative and positive expectations, respectively, indicating a role of emotion. For both types of expectations, Bayesian model comparisons confirmed that an integration model using the respective emotion of expectations and sensory inputs explained stimulus expectancy effects on pain better than using their respective precision. For negative expectations, the role of anxiety is further supported by our fMRI findings that (1) functional coupling within anxiety-processing brain regions (amygdala and anterior cingulate) reflected the integration of expectations with sensory inputs and (2) anxiety appeared to impair the updating of expectations via suppressed prediction error signals in the anterior cingulate, thus perpetuating negative expectancy effects. Regarding positive expectations, their integration with sensory inputs relied on the functional coupling within brain structures processing positive emotion and inhibiting threat responding (medial orbitofrontal cortex and hippocampus). In summary, different from treatment expectancy, pain modulation by stimulus expectancy emanates from emotion-modulated integration of beliefs with sensory evidence and inadequate belief updating.

Expectancy of alcohol analgesia moderates perception of pain relief following acute alcohol intake

Although laboratory studies indicate alcohol reduces pain intensity and increases pain threshold, these effects likely do not completely explain perceived pain relief from alcohol intake. In this study, we tested expectancy of alcohol analgesia (EAA) as a moderator of subjective pain relief following oral alcohol challenge in individuals with and without chronic orofacial pain. Social drinkers (N = 48; 19 chronic pain; 29 pain-free controls) completed two testing sessions: alcohol administration (BrAC: 0.08 g/dL) and placebo. Alcohol expectancy (AE) was assessed using the EAA questionnaire and two 100-mm Visual Analogue Scales (VASs) regarding strength of belief that alcohol provides pain relief (AE VAS 1) or reduces pain sensitivity (AE VAS 2). Participants completed quantitative sensory testing (QST) involving application of pressure to the masseter insertion. Pain threshold (lbf; three repetitions) and pain intensity (4, 5, and 6 lbf; three repetitions each; 100-mm VAS) were collected. After each stimulus, participants rated perceived pain relief due to consumption of the study beverage (0-100 VAS). Higher EAA and AE VAS 1 ratings were associated with stronger perceived relief in the alcohol, but not placebo, condition. However, expectancy specifically related to reduction in pain sensitivity (AE VAS 2) was not associated with relief. Additionally, changes in pain threshold and intensity were not significantly correlated with perceived relief. Taken together, results suggest expectancy that alcohol provides pain relief is an important determinant of its negative reinforcing effects. Future studies should investigate challenging these expectancies as a means of reducing alcohol-related risk in people with pain. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Gender Differences in Pain Threshold, Unpleasantness, and Descending Pain Modulatory Activation Across the Adult Life Span: A Cross Sectional Study

The neurobiological underpinnings of gender differences in pain perception, and how these differences may be modified by age, are incompletely understood, placing patients at risk of suboptimal pain management. Using functional magnetic resonance imaging, we examined brain responses in the descending pain modulatory system (DPMS, specifically, dorsolateral prefrontal cortex, anterior cingulate cortex, insula, hypothalamus, amygdala, and periaqueductal gray, during an evoked pain task. We investigated the interaction of age and gender in our sample of healthy adults (27 females, 32 males, 30-86 years) on DPMS response. In a perceptually matched thermal pain paradigm, we investigated pain unpleasantness and neural responses for 3 heat pain percepts: just noticeable pain, weak pain, and moderate pain (MP). Females reported just noticeable pain at a lower temperature, but reported less unpleasantness at weak pain and MP percepts, compared to males. There was a significant age-by-gender interaction during moderate pain in the right anterior cingulate cortex and bilateral insula, such that, males had a stronger positive relationship between DPMS response and age compared to females in these regions. Our results indicate that differences in DPMS responses may explain some gender differences in pain perception and that this effect may change across the adult lifespan. PERSPECTIVE: Gender differences in pain have been well-documented but the brain mechanisms for these differences are still unclear. This article describes potential differences in brain functioning during different levels of pain that could explain differences in pain responses between men and women across the adult lifespan.

Identification of group differences in predictive anticipatory biasing of pain during uncertainty: preparing for the worst but hoping for the best

ABSTRACT

Pain anticipation during conditions of uncertainty can unveil intrinsic biases, and understanding these biases can guide pain treatment interventions. This study used machine learning and functional magnetic resonance imaging to predict anticipatory responses in a pain anticipation experiment. One hundred forty-seven participants that included healthy controls (n = 57) and individuals with current and/or past mental health diagnosis (n = 90) received cues indicating upcoming pain stimuli: 2 cues predicted high and low temperatures, while a third cue introduced uncertainty. Accurate differentiation of neural patterns associated with specific anticipatory conditions was observed, involving activation in the anterior short gyrus of the insula and the nucleus accumbens. Three distinct response profiles emerged: subjects with a negative bias towards high pain anticipation, those with a positive bias towards low pain anticipation, and individuals whose predictions during uncertainty were unbiased. These profiles remained stable over one year, were consistent across diagnosed psychopathologies, and correlated with cognitive coping styles and underlying insula anatomy. The findings suggest that individualized and stable pain anticipation occurs in uncertain conditions.

How Do Expectations Modulate Pain? A Motivational Perspective

Expectations can profoundly modulate pain experience, during which the periaqueductal gray (PAG) plays a pivotal role. In this article, we focus on motivationally evoked neural activations in cortical and brainstem regions both before and during stimulus administration, as has been demonstrated by experimental studies on pain-modulatory effects of expectations, in the hope of unraveling how the PAG is involved in descending and ascending nociceptive processes. This motivational perspective on expectancy effects on the perception of noxious stimuli sheds new light on psychological and neuronal substrates of pain and its modulation, thus having important research and clinical implications.

Sensory and emotional responses to deep pressure stimulation at myofascial trigger points: a pilot study

Objective

Although manual pressure, such as that used during a massage, is often associated with pain, it can simultaneously be perceived as pleasant when applied to certain body areas. We hypothesized that stimulation of myofascial trigger points (TPs) leads to simultaneous pain and pleasure. TPs are hyperirritable points located in the taut band of the skeletal muscle.

Method

In this study, we measured the muscle tone, muscle stiffness, and pressure pain threshold of TPs and control points in the left brachioradialis muscle of 48 healthy participants. We also applied deep compression to the two points and collected subjective data on pain, pleasantness, unpleasantness, and relief.

Result

Greater muscle stiffness was observed in the TPs versus control points (t = 6.55, p < 0.001), and the pain threshold was significantly lower in the TPs (t = -6.21, p < 0.001). Unpleasantness ratings after deep compression were significantly lower in the TPs compared with control points (t = -2.68, p < 0.05). Participants experienced greater relief at the TPs compared with control points (t = 2.01, p < 0.05), although the perceived pain did not differ between the two types of points.

Conclusion

We compared the properties of TPs and control points, and found that deep compression at TPs was associated with higher muscle tone and stiffness, lower unpleasantness ratings, and higher relief ratings compared with the control points. These findings suggest that, at least for some TPs, pain and pleasantness are simultaneously elicited by deep pressure stimulation.

On the interplay between pain observation, guilt and shame proneness and honesty

Seeing others in pain can stimulate powerful socio-emotional responses. Does it also make us more moral? In two laboratory experiments, we examined the interplay between pain observation, self-reported guilt and shame, subjective perceptions of pain intensity, and subsequent honest behavior. Watching a confederate perform a moderately painful (vs. non-painful) task did not affect honest behavior in a subsequent die-roll task. Independent of pain observation, there was a positive relationship between self-reported guilt proneness and shame proneness and honesty. More specifically, individuals who are more prone to feeling guilt -and to a lesser extent shame- behaved more honestly. Furthermore, we found weak support for the hypothesis that greater perceived pain (rather than objective pain) is associated with less cheating. We call for further research in the interconnections between perceived pain, guilt, shame, and moral behavior.

A parahippocampal-sensory Bayesian vicious circle generates pain or tinnitus: a source-localized EEG study

Pain and tinnitus share common pathophysiological mechanisms, clinical features, and treatment approaches. A source-localized resting-state EEG study was conducted in 150 participants: 50 healthy controls, 50 pain, and 50 tinnitus patients. Resting-state activity as well as functional and effective connectivity was computed in source space. Pain and tinnitus were characterized by increased theta activity in the pregenual anterior cingulate cortex, extending to the lateral prefrontal cortex and medial anterior temporal lobe. Gamma-band activity was increased in both auditory and somatosensory cortex, irrespective of the pathology, and extended to the dorsal anterior cingulate cortex and parahippocampus. Functional and effective connectivity were largely similar in pain and tinnitus, except for a parahippocampal-sensory loop that distinguished pain from tinnitus. In tinnitus, the effective connectivity between parahippocampus and auditory cortex is bidirectional, whereas the effective connectivity between parahippocampus and somatosensory cortex is unidirectional. In pain, the parahippocampal-somatosensory cortex is bidirectional, but parahippocampal auditory cortex unidirectional. These modality-specific loops exhibited theta-gamma nesting. Applying a Bayesian brain model of brain functioning, these findings suggest that the phenomenological difference between auditory and somatosensory phantom percepts result from a vicious circle of belief updating in the context of missing sensory information. This finding may further our understanding of multisensory integration and speaks to a universal treatment for pain and tinnitus-by selectively disrupting parahippocampal-somatosensory and parahippocampal-auditory theta-gamma activity and connectivity.

Modulation of aversive value coding in the vertebrate and invertebrate brain

Avoiding potentially dangerous situations is key for the survival of any organism. Throughout life, animals learn to avoid environments, stimuli or actions that can lead to bodily harm. While the neural bases for appetitive learning, evaluation and value-based decision-making have received much attention, recent studies have revealed more complex computations for aversive signals during learning and decision-making than previously thought. Furthermore, previous experience, internal state and systems level appetitive-aversive interactions seem crucial for learning specific aversive value signals and making appropriate choices. The emergence of novel methodologies (computation analysis coupled with large-scale neuronal recordings, neuronal manipulations at unprecedented resolution offered by genetics, viral strategies and connectomics) has helped to provide novel circuit-based models for aversive (and appetitive) valuation. In this review, we focus on recent vertebrate and invertebrate studies yielding strong evidence that aversive value information can be computed by a multitude of interacting brain regions, and that past experience can modulate future aversive learning and therefore influence value-based decisions.

Do We Have Structure, Process and Outcomes to Support Cannabis as Supportive Therapy in Cancer?

Cannabis is becoming more popular and more available in the United States. It has been approved for use by multiple states for various conditions and several states now allow recreational cannabis. We explore the structure of cannabis distribution, the process of acquisition, outcomes, and the safety of cannabis in the United States.

Altered brain activities in mesocorticolimbic pathway in primary dysmenorrhea patients of long-term menstrual pain

Background

Patients with primary dysmenorrhea (PDM) often present with abnormalities other than dysmenorrhea including co-occurrence with other chronic pain conditions and central sensitization. Changes in brain activity in PDM have been demonstrated; however, the results are not consistent. Herein, this study probed into altered intraregional and interregional brain activity in patients with PDM and expounded more findings.

Methods

A total of 33 patients with PDM and 36 healthy controls (HCs) were recruited and underwent a resting-state functional magnetic resonance imaging scan. Regional homogeneity (ReHo) and mean amplitude of low-frequency fluctuation (mALFF) analysis were applied to compare the difference in intraregional brain activity between the two groups, and the regions with ReHo and mALFF group differences were used as seeds for functional connectivity (FC) analysis to explore the difference of interregional activity. Pearson's correlation analysis was conducted between rs-fMRI data and clinical symptoms in patients with PDM.

Results

Compared with HCs, patients with PDM showed altered intraregional activity in a series of brain regions, including the hippocampus, the temporal pole superior temporal gyrus, the nucleus accumbens, the pregenual anterior cingulate cortex, the cerebellum_8, the middle temporal gyrus, the inferior temporal gyrus, the rolandic operculum, the postcentral gyrus and the middle frontal gyrus (MFG), and altered interregional FC mainly between regions of the mesocorticolimbic pathway and regions associated with sensation and movement. The anxiety symptoms are correlated with the intraregional activity of the right temporal pole superior temporal gyrus and FC between MFG and superior frontal gyrus.

Conclusion

Our study showed a more comprehensive method to explore changes in brain activity in PDM. We found that the mesocorticolimbic pathway might play a key role in the chronic transformation of pain in PDM. We, therefore, speculate that the modulation of the mesocorticolimbic pathway may be a potential novel therapeutic mechanism for PDM.

Neurosurgical Treatment of Pain

The aim of this review is to draw attention to neurosurgical approaches for treating chronic and opioid-resistant pain. In a first chapter, an up-to-date overview of the main pathophysiological mechanisms of pain has been carried out, with special emphasis on the details in which the surgical treatment is based. In a second part, the principal indications and results of different surgical approaches are reviewed. Cordotomy, Myelotomy, DREZ lesions, Trigeminal Nucleotomy, Mesencephalotomy, and Cingulotomy are revisited. Ablative procedures have a limited role in the management of chronic non-cancer pain, but they continues to help patients with refractory cancer-related pain. Another ablation lesion has been named and excluded, due to lack of current relevance. Peripheral Nerve, Spine Cord, and the principal possibilities of Deep Brain and Motor Cortex Stimulation are also revisited. Regarding electrical neuromodulation, patient selection remains a challenge.

Tonic pain alters functional connectivity of the descending pain modulatory network involving amygdala, periaqueductal gray, parabrachial nucleus and anterior cingulate cortex

INTRODUCTION

Resting state functional connectivity (FC) is widely used to assess functional brain alterations in patients with chronic pain. However, reports of FC accompanying tonic pain in pain-free persons are rare. A network we term the Descending Pain Modulatory Network (DPMN) is implicated in healthy and pathologic pain modulation. Here, we evaluate the effect of tonic pain on FC of specific nodes of this network: anterior cingulate cortex (ACC), amygdala (AMYG), periaqueductal gray (PAG), and parabrachial nuclei (PBN).

METHODS

In 50 pain-free participants (30F), we induced tonic pain using a capsaicin-heat pain model. functional MRI measured resting BOLD signal during pain-free rest with a 32°C thermode and then tonic pain where participants experienced a previously warm temperature combined with capsaicin. We evaluated FC from ACC, AMYG, PAG, and PBN with correlation of self-report pain intensity during both states. We hypothesized tonic pain would diminish FC dyads within the DPMN.

RESULTS

Of all hypothesized FC dyads, only PAG and subgenual ACC was weakly altered during pain (F=3.34; p=0.074; pain-free>pain d=0.25). After pain induction sACC-PAG FC became positively correlated with pain intensity (R=0.38; t=2.81; p=0.007). Right PBN-PAG FC during pain-free rest positively correlated with subsequently experienced pain (R=0.44; t=3.43; p=0.001). During pain, this connection's FC was diminished (paired t=-3.17; p=0.0026). In whole-brain analyses, during pain-free rest, FC between left AMYG and right superior parietal lobule and caudate nucleus were positively correlated with subsequent pain. During pain, FC between left AMYG and right inferior temporal gyrus negatively correlated with pain. Subsequent pain positively correlated with right AMYG FC with right claustrum; right primary visual cortex and right temporo-occipitoparietal junction Conclusion: We demonstrate sACC-PAG tonic pain FC positively correlates with experienced pain and resting right PBN-PAG FC correlates with subsequent pain and is diminished during tonic pain. Finally, we reveal PAG- and right AMYG-anchored networks which correlate with subsequently experienced pain intensity. Our findings suggest specific connectivity patterns within the DPMN at rest are associated with subsequently experienced pain and modulated by tonic pain. These nodes and their functional modulation may reveal new therapeutic targets for neuromodulation or biomarkers to guide interventions.

Pain and the Triple Network Model

Acute pain is a physiological response that causes an unpleasant sensory and emotional experience in the presence of actual or potential tissue injury. Anatomically and symptomatically, chronic pathological pain can be divided into three distinct but interconnected pathways, a lateral “painfulness” pathway, a medial “suffering” pathway and a descending pain inhibitory circuit. Pain (fullness) can exist without suffering and suffering can exist without pain (fullness). The triple network model is offering a generic unifying framework that may be used to understand a variety of neuropsychiatric illnesses. It claims that brain disorders are caused by aberrant interactions within and between three cardinal brain networks: the self-representational default mode network, the behavioral relevance encoding salience network and the goal oriented central executive network. A painful stimulus usually leads to a negative cognitive, emotional, and autonomic response, phenomenologically expressed as pain related suffering, processed by the medial pathway. This anatomically overlaps with the salience network, which encodes behavioral relevance of the painful stimuli and the central sympathetic control network. When pain lasts longer than the healing time and becomes chronic, the pain- associated somatosensory cortex activity may become functionally connected to the self-representational default mode network, i.e., it becomes an intrinsic part of the self-percept. This is most likely an evolutionary adaptation to save energy, by separating pain from sympathetic energy-consuming action. By interacting with the frontoparietal central executive network, this can eventually lead to functional impairment. In conclusion, the three well-known pain pathways can be combined into the triple network model explaining the whole range of pain related co-morbidities. This paves the path for the creation of new customized and personalized treatment methods.

Endogenous opioids contribute to the feeling of pain relief in humans

Endogenous opioids mediate the pleasurable responses to positively reinforcing stimuli such as palatable food. Yet, the reduction or omission of a negative experience can also be rewarding (negative reinforcement). As such, pain relief leads to negative reinforcement and evokes a pleasant feeling in humans. Although it has been shown that the feeling of pleasure associated with positive reinforcement is at least partly mediated through endogenous opioids, it is currently unknown whether similar neurochemical mechanisms are involved in the pleasant feeling evoked by pain relief. In this study, 27 healthy participants completed 2 identical experimental sessions, 1 with placebo and 1 with naltrexone, an endogenous opioid antagonist. Pain relief was induced by superficial cooling after heat stimulation of capsaicin-sensitized skin. Participants rated the relief and pleasantness in response to the cooling. Endogenous opioid blockade by naltrexone decreased relief and pleasantness ratings compared with placebo (P = 0.0027). This study provides evidence that endogenous opioids play a role in mediating the pleasant feeling of pain relief in humans. Clinically, the rewarding nature of pain relief and its underlying mechanisms require consideration because of their potential reinforcing effects on behaviors that might be beneficial short-term but maladaptive long-term.

Decoding pain from brain activity

Pain is a dynamic, complex and multidimensional experience. The identification of pain from brain activity as neural readout may effectively provide a neural code for pain, and further provide useful information for pain diagnosis and treatment. Advances in neuroimaging and large-scale electrophysiology have enabled us to examine neural activity with improved spatial and temporal resolution, providing opportunities to decode pain in humans and freely behaving animals. This topical review provides a systematical overview of state-of-the-art methods for decoding pain from brain signals, with special emphasis on electrophysiological and neuroimaging modalities. We show how pain decoding analyses can help pain diagnosis and discovery of neurobiomarkers for chronic pain. Finally, we discuss the challenges in the research field and point to several important future research directions.

Are mind-body therapies effective for relieving cancer-related pain in adults? A systematic review and meta-analysis

OBJECTIVE

To assess whether mind-body therapies are effective for relieving cancer-related pain in adults, since at least one-third of adults with cancer are affected by moderate or severe pain.

METHODS

We searched for all randomized or quasi-randomized controlled trials that included adults (≥18 years) with cancer-related pain who were treated with mind-body therapies (mindfulness, hypnosis, yoga, guided imagery, and progressive muscle relaxation) in MEDLINE, Embase, CINAHL, Cochrane Central Register of Controlled Trials (CENTRAL), Science Citation Index, Web of Science, trials registers, and reference lists. The primary outcome was pain intensity. We calculated the standardized mean differences and 95% confidence intervals (CIs) and assessed the risk of bias.

RESULTS

We identified 40 primary studies involving a total of 3569 participants. The meta-analysis included 24 studies (2404 participants) and showed a significant effect of -0.39 (95% CI -0.62 to -0.16) with considerable heterogeneity (I²  = 86.3%, p < 0.001). After we excluded four "outlier" studies in sensitivity analyses, the effect size remained significant but weaker. There was a high risk of bias in all studies, for example, performance bias due to lack of participant blinding. Patients in multiple settings were included but many studies were of low quality.

CONCLUSIONS

Mind-body therapies may be effective in improving cancer pain, but the quality of the evidence is low. There is a need for further high-quality clinical trials.

The anatomy of pain and suffering in the brain and its clinical implications

Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage. Chronic pain, with a prevalence of 20-30 % is the major cause of human suffering worldwide, because effective, specific and safe therapies have yet to be developed. It is unevenly distributed among sexes, with women experiencing more pain and suffering. Chronic pain can be anatomically and phenomenologically dissected into three separable but interacting pathways, a lateral 'painfulness' pathway, a medial 'suffering' pathway and a descending pain inhibitory pathway. One may have pain(fullness) without suffering and suffering without pain(fullness). Pain sensation leads to suffering via a cognitive, emotional and autonomic processing, and is expressed as anger, fear, frustration, anxiety and depression. The medial pathway overlaps with the salience and stress networks, explaining that behavioural relevance or meaning determines the suffering associated with painfulness. Genetic and epigenetic influences trigger chronic neuroinflammatory changes which are involved in transitioning from acute to chronic pain. Based on the concept of the Bayesian brain, pain (and suffering) can be regarded as the consequence of an imbalance between the two ascending and the descending pain inhibitory pathways under control of the reward system. The therapeutic clinical implications of this simple pain model are obvious. After categorizing the working mechanisms of each of the available treatments (pain killers, psychopharmacology, psychotherapy, neuromodulation, psychosurgery, spinal cord stimulation) to 1 or more of the 3 pathways, a rational combination can be proposed of activating the descending pain inhibitory pathway in combination with inhibition of the medial and lateral pathway, so as to rebalance the pain (and suffering) pathways.

Day-to-day hedonic and calming effects of opioids, opioid craving, and opioid misuse among patients with chronic pain prescribed long-term opioid therapy

ABSTRACT

Concerns have been raised regarding the misuse of opioids among patients with chronic pain. Although a number of factors may contribute to opioid misuse, research has yet to examine if the hedonic and calming effects that can potentially accompany the use of opioids contribute to opioid misuse. The first objective of this study was to examine the degree to which the hedonic and calming effects of opioids contribute to opioid misuse in patients with chronic pain. We also examined whether the hedonic and calming effects of opioids contribute to patients' daily levels of opioid craving, and whether these associations were moderated by patients' daily levels of pain intensity, catastrophizing, negative affect, or positive affect. In this longitudinal diary study, patients (n = 103) prescribed opioid therapy completed daily diaries for 14 consecutive days. Diaries assessed a host of pain, psychological, and opioid-related variables. The hedonic and calming effects of opioids were not significantly associated with any type of opioid misuse behavior. However, greater hedonic and calming effects were associated with heightened reports of opioid craving (both P's < 0.005). Analyses revealed that these associations were moderated by patients' daily levels of pain intensity, catastrophizing, and negative affect (all P's < 0.001). Results from this study provide valuable new insights into our understanding of factors that may contribute to opioid craving among patients with chronic pain who are prescribed long-term opioid therapy. The implications of our findings for the management of patients with chronic pain are discussed.

Neurocognitive Effects of Preceding Facial Expressions on Perception of Subsequent Emotions

In everyday life, individuals successively and simultaneously encounter multiple stimuli that are emotionally incongruent. Emotional incongruence elicited by preceding stimuli may alter emotional experience with ongoing stimuli. However, the underlying neural mechanisms of the modulatory influence of preceding emotional stimuli on subsequent emotional processing remain unclear. In this study, we examined self-reported and neural responses to negative and neutral pictures whose emotional valence was incongruent with that of preceding images of facial expressions. Twenty-five healthy participants performed an emotional intensity rating task inside a brain scanner. Pictures of negative and neutral scenes appeared, each of which was preceded by a pleasant, neutral, or unpleasant facial expression to elicit a degree of emotional incongruence. Behavioral results showed that emotional incongruence based on preceding facial expressions did not influence ratings of subsequent pictures' emotional intensity. On the other hand, neuroimaging results revealed greater activation of the right dorsomedial prefrontal cortex (dmPFC) in response to pictures that were more emotionally incongruent with preceding facial expressions. The dmPFC had stronger functional connectivity with the right ventrolateral prefrontal cortex (vlPFC) during the presentation of negative pictures that followed pleasant facial expressions compared to those that followed unpleasant facial expressions. Interestingly, increased functional connectivity of the dmPFC was associated with the reduced modulatory influence of emotional incongruence on the experienced intensity of negative emotions. These results indicate that functional connectivity of the dmPFC contributes to the resolution of emotional incongruence, reducing the emotion modulation effect of preceding information on subsequent emotional processes.

Association between pain, anxiety, and pain relief in patients receiving emergent endodontic treatment

OBJECTIVES

The experience of pain relief is closely associated with the affective-cognitive processing of hedonic value. Higher pain relief plays a key role in patients' satisfaction with treatment and higher motivation to receive treatment. Previous studies focused on pain and anxiety of endodontic treatment. However, the association between pain relief, pain, and anxiety has not been investigated.

MATERIALS AND METHODS

We investigated 35 patients (20 females and 15 males, with mean age 46.3 years old) with symptomatic irreversible pulpitis receiving emergent endodontic treatment. Pain-related experience, including pain relief, pain, and anxiety, was assessed before and after treatment, based on an 11-point numerical scale.

RESULTS

We found that before treatment, the expected pain relief (median score = 8) that one anticipated was positively correlated with the degree of pain reduction perceived after treatment (two-tailed rho = 0.51, p = 0.002). Expected pain relief was also positively correlated with the post-treatment relief (two-tailed rho = 0.76, p < 0.001) and the relief recalled after 6 weeks (two-tailed rho = 0.69, p < 0.001). Moreover, logistic regression models revealed that expected pain relief was a significant predictor of the subgroups of low vs. moderate scores of post-treatment pain (B =  - 1.06, p = 0.017) and anxiety (B =  - 1.60, p = 0.009), controlled for the condition of pre-treatment medication.

CONCLUSIONS

The current findings highlight that for patients with symptomatic irreversible pulpitis who received emergent endodontic treatment, their expected pain relief before treatment is a critical factor associated with pain reduction and post-treatment pain/anxiety.

CLINICAL RELEVANCE

Assessment of expected pain relief may be integrated into pre-treatment assessment for painful dental patients.

Training endogenous pain modulation: a preliminary investigation of neural adaptation following repeated exposure to clinically-relevant pain

Analgesic treatments that aim to eliminate pain display marginal success in relieving chronic pain and may increase pain vulnerability. Repeated exposure to pain may result in increased pain modulation via engagement of anti-nociceptive brain regions. It was hypothesized that repeated exposure to delayed onset muscle soreness (DOMS) would result in increased pain modulatory capacity (PMC) via functional neural adaptation. 23 healthy participants completed Baseline and Follow Up resting-state fMRI and quantitative sensory testing (QST) visits 40 days apart. Participants were randomized to two groups: A Repeated DOMS Group (RD Group) that received four, weekly DOMS inductions and a Control Group that received one baseline induction. Daily pain ratings were collected for seven days post-induction, as were quantitative sensory testing (QST) metrics at baseline and Follow Up. Regional functional connectivity (FC) was estimated among areas involved in pain modulation. Seed and network FC was estimated among areas involved in pain modulation and sensory processing. Changes in FC were compared between groups. The RD Group displayed significant reductions in post-DOMS pain ratings and significant changes in thermal QST measures. RD Group participants displayed greater adaptation in nucleus accumbens-medial prefrontal cortex (NAc-mPFC) FC and in sensorimotor network (SMN) connectivity with the dorsomedial, ventromedial, and rostromedial prefrontal cortices. Changes in SMN-PFC connectivity correlated with reductions in post-DOMS affective distress. Results suggest that repeated exposure to clinically-relevant pain results in adaptations among brain regions involved in pain modulation. Repeated exposure to clinically-relevant pain may serve as a mechanism to increase PMC via inhibition of emotional valuation of painful stimuli.

The neuroscience of positive emotions and affect: Implications for cultivating happiness and wellbeing

This review paper provides an integrative account regarding neurophysiological correlates of positive emotions and affect that cumulatively contribute to the scaffolding for happiness and wellbeing in humans and other animals. This paper reviews the associations among neurotransmitters, hormones, brain networks, and cognitive functions in the context of positive emotions and affect. Consideration of lifespan developmental perspectives are incorporated, and we also examine the impact of healthy social relationships and environmental contexts on the modulation of positive emotions and affect. The neurophysiological processes that implement positive emotions are dynamic and modifiable, and meditative practices as well as flow states that change patterns of brain function and ultimately support wellbeing are also discussed. This review is part of "The Human Affectome Project" (http://neuroqualia.org/background.php), and in order to advance a primary aim of the Human Affectome Project, we also reviewed relevant linguistic dimensions and terminology that characterizes positive emotions and wellbeing. These linguistic dimensions are discussed within the context of the neuroscience literature with the overarching goal of generating novel recommendations for advancing neuroscience research on positive emotions and wellbeing.

Benefits of Adding Gluteal Dry Needling to a Four-Week Physical Exercise Program in a Chronic Low Back Pain Population. A Randomized Clinical Trial

OBJECTIVE

To determine if adding dry needling to a four-week exercise program has an additional benefit compared with adding sham dry needling to the same exercise program in subjects with chronic low back pain.

DESIGN

Randomized clinical trial.

SETTING

Physiotherapy and Pain Clinic of Alcala University.

SUBJECTS

Forty-six patients with chronic low back pain.

METHODS

Subjects were randomized to two groups: the dry needling group (N = 23) or sham dry needling group (N = 23). Both groups received a four-week exercise program and before the exercise started a session of dry needling or sham dry needling. Pain (visual analog scale), disability (Roland-Morris Questionnaire), and fear avoidance beliefs (Fear Avoidance Beliefs Questionnaire) were assessed at baseline, after treatment, and at three-month follow-up. Pressure pain thresholds (algometer) were measured at baseline, after the dry needling or the sham dry needling, and after treatment.

RESULTS

Both groups showed significant improvements for all variables. In the between-group comparison, the dry needling group improved significantly in pain at three-month follow-up and pressure pain thresholds at the end of treatment for all measures, and at three-month follow-up there was no improvement in gluteus medium.

CONCLUSIONS

In chronic low back patients, adding dry needling to a four-week exercise program has an additional benefit in pain and sensitivity compared with adding sham dry needling to the same exercise program.

Altered Interoceptive Perception and the Effects of Interoceptive Analgesia in Musculoskeletal, Primary, and Neuropathic Chronic Pain Conditions

Chronic pain (CP) severely disrupts the daily life of millions. Interoception (i.e., sensing the physiological condition of the body) plays a pivotal role in the aetiology and maintenance of CP. As pain is inherently an interoceptive signal, interoceptive frameworks provide important, but underutilized, approaches to this condition. Here we first investigated three facets of interoceptive perception in CP, compared with pain-free controls. We then introduce a novel interoceptive treatment and demonstrate its capacity to reduce pain severity in CP, potentially providing complementary analgesic treatments. Study 1 measured interoceptive accuracy, confidence and sensibility in patients (N = 60) with primary, secondary musculoskeletal, and neuropathic CP. Compared with matched controls, CP participants exhibited significantly lower interoceptive accuracy and interoceptive confidence. Pain severity was predicted positively by interoceptive accuracy, anxiety and depression, and negatively by interoceptive confidence. Study 2 tested a promising new interoceptive treatment for CP, in a single-blind between-subjects design (N = 51) with primary, secondary musculoskeletal, and neuropathic CP patients. The treatment specifically activates the C-Tactile system, by means of controlled stimulation of interoceptive unmyelinated afferents, at 3 cm/s with a force of 2.5 mN. This treatment led to significant pain reduction (mean 23%) in the CP treatment group after only 11 min, while CP controls who received comparable but non-interoceptive stimulation reported no change in pain intensity. These studies highlight the importance of interoceptive approaches to CP and demonstrate the potential of this novel method of C-Tactile stimulation to provide complementary analgesic treatments.

The impact of parental contact upon cortical noxious-related activity in human neonates

BACKGROUND

Neonates display strong behavioural, physiological and cortical responses to tissue-damaging procedures. Parental contact can successfully regulate general behavioural and physiological reactivity of the infant, but it is not known whether it can influence noxious-related activity in the brain. Brain activity is highly dependent upon maternal presence in animal models, and therefore this could be an important contextual factor in human infant pain-related brain activity.

METHODS

Global topographic analysis was used to identify the presence and inter-group differences in noxious-related activity in three separate parental contexts. EEG was recorded during a clinically required heel lance in three age and sex-matched groups of neonates (a) while held by a parent in skin-to-skin (n = 9), (b) while held by a parent with clothing (n = 9) or (c) not held at all, but in individualized care (n = 9).

RESULTS

The lance elicited a sequence of 4-5 event-related potentials (ERPs), including the noxious ERP (nERP), which was smallest for infants held skin-to-skin and largest for infants held with clothing (p=0.016). The nERP was then followed by additional and divergent long-latency ERPs (> 750 ms post-lance), not previously described, in each of the groups, suggesting the engagement of different higher level cortical processes depending on parental contact.

CONCLUSIONS

These results show the importance of considering contextual factors in determining infant brain activity and reveal the powerful influence of parental contact upon noxious-related activity across the developing human brain.

SIGNIFICANCE

This observational study found that the way in which the neonatal brain processes a noxious stimulus is altered by the type of contact the infant has with their mother. Specifically, being held in skin-to-skin reduces the magnitude of noxious-related cortical activity. This work has also shown that different neural mechanisms are engaged depending on the mother/infant context, suggesting maternal contact can change how a baby's brain processes a noxious stimulus.

The Bayesian brain in imbalance: Medial, lateral and descending pathways in tinnitus and pain: A perspective

Tinnitus and pain share similarities in their anatomy, pathophysiology, clinical picture and treatments. Based on what is known in the pain field, a heuristic model can be proposed for the pathophysiolgy of tinnitus. This heuristic pathophysiological model suggests that pain and tinnitus are the consequence of an imbalance between two pain/tinnitus evoking pathways, i.e., a lateral sensory pathway and a medial affective pathway, both of which are not balanced anymore by a pain/noise inhibitory pathway. Mechanistically, based on the Bayesian brain concept, it can be explained by a switch occuring under influence of the rostral to dorsal anterior cingulate cortex of its prior predictions, i.e., a reference resetting, in which the pain/tinnitus state is considered as the new reference state. This reference resetting is confirmed by the nucleus accumbens as part of the reward system and maintained by connectivity changes between the nucleus accumbens and the pregenual anterior cingulate cortex. As a consequence it can be suggested to treat pain/tinnitus via reconditioning, either surgically or non-surgically. The model can also be used to develop objective measures for tinnitus and pain via supervised machine learning.

Impact of physical therapists' instructions on function and the perception of post-dry needling soreness in mechanical cervical pain; a randomized clinical trial

BACKGROUND

To investigate the impact of physical therapists' instructions on the perception of post dry needling (DN) soreness and function in patients with mechanical neck pain.

METHODS

Seventy-five patients with neck pain were randomly assigned to three groups: "positive" group (n = 25) received positive verbal input; "negative" group (n = 25) received negative verbal input, and control group (n = 25) did not receive any input about post-needling soreness. All three groups received DN of a trigger point in the upper trapezius muscle. The subjective pain experience, pressure pain threshold (PPT), and neck disability Index (NDI) were assessed before and after DN.

RESULTS

Patients in all groups showed improvement in pain, PPT and NDI. There were no significant differences in pain (P = 0.41) and PPT (P = 0.68) in the positive and negative groups compared with the control group. Significant difference in function was seen with the NDI after DN of patients in the positive and negative groups compared with the control group (P = 0.011, standard error: 1.08-1.5).

CONCLUSION

Considering that the power of our study may be too low to draw more definitive conclusions, DN appears to be an effective technique to improve pain and mechanical hyperalgesia. The experience of post-needling soreness does not appear to influence the outcome of DN on pain, PPT, and NDI. Post-needling soreness does not seem to be a limiting factor in achieving acceptable outcomes, especially when clinicians offer DN within a therapeutic emphasizing a positive patient response. This study questions whether any treatments need to be offered to patients receiving DN.

Medial Orbitofrontal De-Activation During Tonic Cold Pain Stimulation: A fMRI Study Examining the Opponent-Process Theory

BACKGROUND

While the concomitant administration of painful and rewarding stimuli tends to reduce the perception of one another, recent evidence shows that pleasant pain relief is experience after the interruption of noxious stimuli. On neurobiological grounds, these opponent processes should translate into decreased activity in brain reward regions during nociceptive stimulation and increased activity in these regions after its interruption. While growing evidence supports the latter assumption, evidence is lacking in humans in support of the former.

METHODS

Twenty-six healthy individuals underwent a functional magnetic resonance imaging (fMRI) session during which they were administered a cold pain stimulation, using a novel paradigm which consisted in a cold gel applied on the right foot of participants.

RESULTS

After the interruption of noxious stimulation, participants experienced significant levels of pleasant pain relief. During cold pain stimulation, brain activations were observed in key regions of the pain matrix (eg, thalamus, primary somatosensory cortex and insula). Conversely, the medial orbitofrontal cortex was found to be de-activated. Medial orbitofrontal de-activations were negatively correlated with subclinical pain symptoms.

DISCUSSION

Our results show that a key brain reward region (eg, medial orbitofrontal cortex) is de-activated during cold pain stimulation, a result which is consistent with one of the central assumptions of the opponent-process theory. On methodological grounds, our results show that the cold gel applied to the foot can be used to trigger activations in the pain matrix, and that the interruption of the cold pressor test elicits significant levels of pleasant pain relief. fMRI studies on pain-reward interactions in chronic pain patients are warranted.

Neural and sociocultural mediators of ethnic differences in pain

Understanding ethnic differences in pain is important for addressing disparities in pain care. A common belief is that African Americans are hyposensitive to pain compared to Whites, but African Americans show increased pain sensitivity in clinical and laboratory settings. The neurobiological mechanisms underlying these differences are unknown. We studied an ethnicity- and gender-balanced sample of African Americans, Hispanics and non-Hispanic Whites using functional magnetic resonance imaging during thermal pain. Higher pain report in African Americans was mediated by discrimination and increased frontostriatal circuit activations associated with pain rating, discrimination, experimenter trust and extranociceptive aspects of pain elsewhere. In contrast, the neurologic pain signature, a neuromarker sensitive and specific to nociceptive pain, mediated painful heat effects on pain report largely similarly in African American and other groups. Findings identify a brain basis for higher pain in African Americans related to interpersonal context and extranociceptive central pain mechanisms and suggest that nociceptive pain processing may be similar across ethnicities.

Multiple Brain Networks Mediating Stimulus-Pain Relationships in Humans

The brain transforms nociceptive input into a complex pain experience comprised of sensory, affective, motivational, and cognitive components. However, it is still unclear how pain arises from nociceptive input and which brain networks coordinate to generate pain experiences. We introduce a new high-dimensional mediation analysis technique to estimate distributed, network-level patterns that formally mediate the relationship between stimulus intensity and pain. We applied the model to a large-scale analysis of functional magnetic resonance imaging data (N = 284), focusing on brain mediators of the relationship between noxious stimulus intensity and trial-to-trial variation in pain reports. We identify mediators in both traditional nociceptive pathways and in prefrontal, midbrain, striatal, and default-mode regions unrelated to nociception in standard analyses. The whole-brain mediators are specific for pain versus aversive sounds and are organized into five functional networks. Brain mediators predicted pain ratings better than previous brain measures, including the neurologic pain signature (Wager et al. 2013). Our results provide a broader view of the networks underlying pain experience, as well as novel brain targets for interventions.

Threat Prediction from Schemas as a Source of Bias in Pain Perception

Our sensory impressions of pain are generally thought to represent the noxious properties of an agent but can be influenced by the predicted level of threat. Predictions can be sourced from higher-order cognitive processes, such as schemas, but the extent to which schemas can influence pain perception relative to bottom-up sensory inputs and the underlying neural underpinnings of such a phenomenon are unclear. Here, we investigate how threat predictions generated from learning a cognitive schema lead to inaccurate sensory impressions of the pain stimulus. Healthy male and female participants first detected a linear association between cue values and stimulus intensity and rated pain to reflect the linear schema when compared with uncued heat stimuli. The effect of bias on pain ratings was reduced when prediction errors (PEs) increased, but pain perception was only partially updated when measured against stepped increases in PEs. Cognitive, striatal, and sensory regions graded their responses to changes in predicted threat despite the PEs (p < 0.05, corrected). Individuals with more catastrophic thinking about pain and with low mindfulness were significantly more reliant on the schema than on the sensory evidence from the pain stimulus. These behavioral differences mapped to variability in responses of the striatum and ventromedial prefrontal cortex. Thus, this study demonstrates a significant role of higher-order schemas in pain perception and indicates that pain perception is biased more toward predictions and less toward nociceptive inputs in individuals who report less mindfulness and more fear of pain.SIGNIFICANCE STATEMENT This study demonstrates that threat predictions generated from cognitive schemas continue to influence pain perception despite increasing prediction errors arising in pain pathways. Individuals first formed a cognitive schema of linearity in the relationship between the cued threat value and the stimulus intensity. Subsequently, the linearity was reduced gradually, and participants partially updated their evaluations of pain in relation to the stepped increases in prediction errors. Individuals who continued to rate pain based more on the predicted threat than on changes in nociceptive inputs reported high pain catastrophizing and less mindful-awareness scores. These two affects mapped to activity in the ventral and dorsal striatum, respectively. These findings direct us to a significant role of top-down processes in pain perception.

Pain-Evoked Reorganization in Functional Brain Networks

Recent studies indicate that a significant reorganization of cerebral networks may occur in patients with chronic pain, but how immediate pain experience influences the organization of large-scale functional networks is not yet well characterized. To investigate this question, we used functional magnetic resonance imaging in 106 participants experiencing both noxious and innocuous heat. Painful stimulation caused network-level reorganization of cerebral connectivity that differed substantially from organization during innocuous stimulation and standard resting-state networks. Noxious stimuli increased somatosensory network connectivity with (a) frontoparietal networks involved in context representation, (b) "ventral attention network" regions involved in motivated action selection, and (c) basal ganglia and brainstem regions. This resulted in reduced "small-worldness," modularity (fewer networks), and global network efficiency and in the emergence of an integrated "pain supersystem" (PS) whose activity predicted individual differences in pain sensitivity across 5 participant cohorts. Network hubs were reorganized ("hub disruption") so that more hubs were localized in PS, and there was a shift from "connector" hubs linking disparate networks to "provincial" hubs connecting regions within PS. Our findings suggest that pain reorganizes the network structure of large-scale brain systems. These changes may prioritize responses to painful events and provide nociceptive systems privileged access to central control of cognition and action during pain.

The Effects of Melatonin on the Descending Pain Inhibitory System and Neural Plasticity Markers in Breast Cancer Patients Receiving Chemotherapy: Randomized, Double-Blinded, Placebo-Controlled Trial

Background: Adjuvant chemotherapy for breast cancer (ACBC) has been associated with fatigue, pain, depressive symptoms, and disturbed sleep. And, previous studies in non-cancer patients showed that melatonin could improve the descending pain modulatory system (DPMS). We tested the hypothesis that melatonin use before and during the first cycle of ACBC is better than placebo at improving the DPMS function assessed by changes in the 0–10 Numerical Pain Scale (NPS) during the conditioned pain modulating task (CPM-task) (primary outcome). The effects of melatonin were evaluated in the following secondary endpoints: heat pain threshold (HPT), heat pain tolerance (HPTo), and neuroplasticity state assessed by serum brain-derived neurotrophic factor (BDNF), tropomyosin kinase receptor B, and S100B-protein and whether melatonin’s effects on pain and neuroplasticity state are due more so to its impact on sleep quality.

Methods: Thirty-six women, ages 18 to 75 years old, scheduled for their first cycle of ACBC were randomized to receive 20mg of oral melatonin (n = 18) or placebo (n = 18). The effect of treatment on the outcomes was analyzed by delta (Δ)-values (from pre to treatment end).

Results: Multivariate analyses of covariance revealed that melatonin improved the function of the DPMS. The Δ-mean (SD) on the NPS (0–10) during the CPM-task in the placebo group was −1.91 [−1.81 (1.67) vs. −0.1 (1.61)], and in the melatonin group was −3.5 [−0.94 (1.61) vs. −2.29 (1.61)], and the mean difference (md) between treatment groups was 1.59 [(95% CI, 0.50 to 2.68). Melatonin’s effect increased the HPTo and HPT while reducing the (Δ)-means of the serum neuroplasticity marker in placebo vs. melatonin. The Δ-BDNF is 1.87 (7.17) vs. −20.44 (17.17), respectively, and the md = 22.31 [(95% CI = 13.40 to 31.22)]; TrKB md = 0.61 [0.46 (0.17) vs. −0.15 (0.18); 95% CI = 0.49 to 0.73)] and S00B-protein md = −8.27[(2.89 (11.18) vs. −11.16 (9.75); 95% CI = −15.38 to −1.16)]. However, melatonin’s effect on pain and the neuroplastic state are not due to its effect on sleep quality.

Conclusions: These results suggest that oral melatonin, together with the first ACBC counteracts the dysfunction in the inhibitory DPMS and improves pain perception measures. Also, it shows that changes in the neuroplasticity state mediate the impact of melatonin on pain.

Clinical Trial Registration:www.ClinicalTrials.gov, identifier NCT03205033.

The Context of Values in Pain Control: Understanding the Price Effect in Placebo Analgesia

The experience of pain relief arises from physiological and psychological factors, and attributes such as the commercial features of analgesic treatments have been shown to influence placebo analgesia by affecting treatment expectations. Therefore, treatment valuation from price information should influence the placebo analgesic effect. This hypothesis was tested in a functional magnetic resonance imaging study in which healthy subjects were enrolled in a 2-day experiment. On day 1, the participants (n = 19) had treatment experiences with 2 different placebo creams during a conditioning session without receiving information on treatment price. On day 2, placebo analgesia was tested after providing price information (high vs low) while functional magnetic resonance imaging was performed. The results showed that the higher priced placebo treatment leads to enhanced pain relief. Placebo analgesia in response to the higher priced treatment was associated with activity in the ventral striatum, ventromedial prefrontal cortex, and ventral tegmental area. The behavioral results indicate that the experience of pain was influenced by treatment valuation from price. Our findings reveal that the context of values in pain control is associated with activity in expectation- and reward-related circuitry. PERSPECTIVE: Treatment with higher price was associated with enhanced placebo analgesia, and this effect was influenced by activities in expectation and reward processing brain areas. The context of value such as medical cost influences cognitive evaluation processes to modulate pain. Our study may help evaluate a patient's preference toward high-priced drugs.

Patients With Fibromyalgia Reporting Severe Pain but Low Impact of the Syndrome: Clinical and Pain-Related Cognitive Features

BACKGROUND

Fibromyalgia (FM) is a prevalent and highly disabling chronic pain syndrome. However, differences among patients regarding how pain impacts on daily life are remarkable. The main aim of this study was to identify clinical and pain-related cognitive variables characterizing patients reporting high adaptability despite experiencing severe chronic pain.

METHODS

Two hundred and eighty-three Spanish patients with FM with high levels of pain were classified into 2 groups: (1) those reporting low impact of the syndrome, and (2) those with moderate-to-high impact. Perceived stress, anxiety, and depressive symptoms along with pain catastrophizing, psychological inflexibility, and perceived control over pain were evaluated. Differences in sociodemographics, years with FM, past/current major depressive disorder comorbidity, and health-related economic costs (ie, medications, use of medical services, lost productivity due to sick leave) were also assessed. Stepwise logistic regression analyses predicting group membership from clinical variables and pain-related cognitive processes as predictors were performed.

RESULTS

Lower stress, anxiety, and depressive symptoms, along with reduced pain catastrophism, psychological inflexibility, and perceived control over pain, were found in the low-impact group. Significant predictors of group membership (low-impact vs. moderate-to-high impact) in regression analyses were "cognitive fusion" (psychological inflexibility), "helplessness" (pain catastrophizing), and depressive symptomatology, together with pain intensity and other FM symptoms.

CONCLUSIONS

The present study provides further evidence on resilience resources in chronic pain by identifying some variables (ie, reduced depressive symptomatology, pain catastrophizing, and psychological inflexibility) differentially characterizing a profile of patients with FM who are especially able to adapt to high levels of pain.

Composite Pain Biomarker Signatures for Objective Assessment and Effective Treatment

Pain is a subjective sensory experience that can, mostly, be reported but cannot be directly measured or quantified. Nevertheless, a suite of biomarkers related to mechanisms, neural activity, and susceptibility offer the possibility-especially when used in combination-to produce objective pain-related indicators with the specificity and sensitivity required for diagnosis and for evaluation of risk of developing pain and of analgesic efficacy. Such composite biomarkers will also provide improved understanding of pain pathophysiology.

Punishing the Self: Post-Traumatic Guilt Mediates the Link Between Trauma and Deficient Pain Modulation

Trauma survivors may suffer from post-traumatic stress disorder (PTSD), elevated post-traumatic guilt (PG), and alterations in the pain system. However, the association between PG and alterations in pain perception and modulation among trauma survivors has not been established, nor has the possible underlying role of PG. This longitudinal study investigated: 1) the unique contribution of PG in predicting pain perception and modulation, while controlling for PTSD symptoms; and 2) the mediating role of PG in explaining pain perception and modulation among torture survivors, above and beyond PTSD symptoms. Participants were 59 torture survivors and 44 age-matched controls. PG and PTSD symptoms were assessed in 2003 (T1). Heat-pain threshold, heat-pain tolerance, temporal summation of pain (TSP), and conditioned pain modulation (CPM) were measured 5 years later (T2). Torture survivors had elevated PG and PTSD symptoms, enhanced TSP, and reduced CPM, compared to controls. While PTSD predicted reduced pain tolerance and CPM, PG predicted increased pain tolerance. Moreover, PG mediated the associations between torture and (increased) pain threshold, pain tolerance, and TSP. It appears that PTSD and PG induce opposite effects on the pain modulation capacity of torture survivors, a dichotomy that may explain paradoxical pain responses among trauma survivors, as discussed. PERSPECTIVE: This longitudinal study sheds light on the possible mechanisms underlying variations in pain perception and modulation among trauma survivors. PTSD and PG each mediated opposing pain modulation profiles, suggesting that individual responses to trauma, rather than the trauma itself, influence pain responses.

Stopping or Decreasing Opioid Therapy in Patients on Chronic Opioid Therapy

With the rising concerns about long-term opioid use, particularly in patients with chronic noncancer pain, more and more patients are being considered for decreased doses or discontinuation of opioid therapy. This is a challenging clinical situation for both patient and clinician and should be presented in a shared decision-making model so that the patient understands the risks of opioid therapy and how the therapy will be discontinued. The patient should be aware of the long-range plan and its milestones. It is imperative that alternate pain control treatments be made available to the patient early, and that the patient never feels abandoned by the healthcare team. There can be many barriers in shared decision-making and multiple discussions between patient and provider may be required. Opioid use should not be decreased sharply or discontinued abruptly, but should be gradually decremented in a process known as tapering. Tapering should be systematic and planned in advance with the patient knowing the steps. Slow tapers (over months) are more comfortable for the patients but may not always be appropriate. There is guidance for planning the taper and the patient should be closely monitored throughout this process. If withdrawal symptoms occur, they can be managed, for example, with lofexidine. Patients should get full support as they explore new pain control options. For patients who have opioid use disorder, addiction counseling may be appropriate. Navigating opioid discontinuation can be slow work, but optimal results occur when the healthcare team works together and respectfully with the patient.

The role of hedonics in the Human Affectome

Experiencing pleasure and displeasure is a fundamental part of life. Hedonics guide behavior, affect decision-making, induce learning, and much more. As the positive and negative valence of feelings, hedonics are core processes that accompany emotion, motivation, and bodily states. Here, the affective neuroscience of pleasure and displeasure that has largely focused on the investigation of reward and pain processing, is reviewed. We describe the neurobiological systems of hedonics and factors that modulate hedonic experiences (e.g., cognition, learning, sensory input). Further, we review maladaptive and adaptive pleasure and displeasure functions in mental disorders and well-being, as well as the experience of aesthetics. As a centerpiece of the Human Affectome Project, language used to express pleasure and displeasure was also analyzed, and showed that most of these analyzed words overlap with expressions of emotions, actions, and bodily states. Our review shows that hedonics are typically investigated as processes that accompany other functions, but the mechanisms of hedonics (as core processes) have not been fully elucidated.

Assessment of experimental orofacial pain, pleasantness and unpleasantness via standardized psychophysical testing

BACKGROUND

Somatosensory assessment within the orofacial region may be performed using highly standardized quantitative sensory testing (QST). However, the function of the C-tactile (CT) afferent, a nerve fibre linked to the perception of pleasant touch, is usually not evaluated. Furthermore, the perception of unpleasantness is also rarely assessed, a dimension not only limited to a painful experience. Therefore, the primary aim was to apply standardized QST stimuli as well as standardized pleasant stimuli and evaluate their potential capacity for evocation of perceived pain, pleasant and unpleasant sensations in the facial region.

METHODS

Twenty-one female participants underwent QST as per the protocol derived from the German Research Network on Neuropathic Pain. For the first time, two modified protocols were used to investigate stimuli for perceived pleasantness and unpleasantness.

RESULTS

Thermal stimuli provided separate thresholds for each sensation. From certain mechanical stimuli (e.g., vibration), overlap between the perceived sensations of pleasantness and unpleasantness was identified. It was not possible to evoke only an unpleasant sensation without a painful contribution, and both these sensations increased significantly when utilizing an increasing pinprick force (p < 0.011). Between dynamic stimuli, the brush was rated as significantly more pleasant than the cotton wool tip (p = 0.015). A quadratic model provided the best fit for velocity against mean pleasantness ratings (R²  = 0.62 ± 0.08), supporting previous CT afferent literature to some extent.

CONCLUSION

Stimuli were generally not isolated to one sensation, highlighting the multidimensional construct of stimulus perception and the need for scales to capture this.

SIGNIFICANCE

The battery of QST tests from the DFNS protocol has been modified to investigate pleasant and unpleasant sensations. This allows the evaluation of psychophysical properties across standardized dimensions to provide a thorough view of somatosensory function and to better understand the affective spectrum of somatosensory function.

Self-Criticism Impacts Emotional Responses to Pain

Nonsuicidal self-injury (NSSI) is associated with numerous negative outcomes (e.g., suicide attempts), making it a focus of great clinical concern. Yet, mechanisms reinforcing NSSI remain unclear. The benefits and barriers model proposes that NSSI engagement is determined by both benefits of and barriers to NSSI. Benefits include mood improvement, a function reported by most who engage in NSSI; barriers include a desire to avoid pain and bodily harm. Self-criticism is generally understood as a trait lowering desire to avoid pain and bodily harm, thus decreasing that specific barrier. However, recent research demonstrated that self-criticism may also increase NSSI benefits. Highly self-critical people may view NSSI and pain in the context of feeling deserving of pain and punishment-thus, pain may improve mood for self-critical individuals. We tested whether self-criticism impacted emotional responding to pain among adult females with (n = 44) and without (n = 65) NSSI histories. After a negative mood induction, participants rated their moods before, during, and after self-administered pain. In participants with and without NSSI histories, self-criticism was positively correlated with mood improvements during pain. Thus, regardless of NSSI history, self-criticism impacted emotional responses to pain. Together, results suggest that self-criticism may not only decrease an important NSSI barrier but also enhance NSSI benefits, specifically leading to more mood improvement during pain.

Altered prefrontal correlates of monetary anticipation and outcome in chronic pain

Chronic pain may alter both affect- and value-related behaviors, which represents a potentially treatable aspect of chronic pain experience. Current understanding of how chronic pain influences the function of brain reward systems, however, is limited. Using a monetary incentive delay task and functional magnetic resonance imaging (fMRI), we measured neural correlates of reward anticipation and outcomes in female participants with the chronic pain condition of fibromyalgia (N = 17) and age-matched, pain-free, female controls (N = 15). We hypothesized that patients would demonstrate lower positive arousal, as well as altered reward anticipation and outcome activity within corticostriatal circuits implicated in reward processing. Patients demonstrated lower arousal ratings as compared with controls, but no group differences were observed for valence, positive arousal, or negative arousal ratings. Group fMRI analyses were conducted to determine predetermined region of interest, nucleus accumbens (NAcc) and medial prefrontal cortex (mPFC), responses to potential gains, potential losses, reward outcomes, and punishment outcomes. Compared with controls, patients demonstrated similar, although slightly reduced, NAcc activity during gain anticipation. Conversely, patients demonstrated dramatically reduced mPFC activity during gain anticipation-possibly related to lower estimated reward probabilities. Further, patients demonstrated normal mPFC activity to reward outcomes, but dramatically heightened mPFC activity to no-loss (nonpunishment) outcomes. In parallel to NAcc and mPFC responses, patients demonstrated slightly reduced activity during reward anticipation in other brain regions, which included the ventral tegmental area, anterior cingulate cortex, and anterior insular cortex. Together, these results implicate altered corticostriatal processing of monetary rewards in chronic pain.

Effects of Positive and Negative Expectations on Human Pain Perception Engage Separate But Interrelated and Dependently Regulated Cerebral Mechanisms

Expectations substantially influence pain perception, but the relationship between positive and negative expectations remains unclear. Recent evidence indicates that the integration between pain-related expectations and prediction errors is crucial for pain perception, which suggests that aversive prediction error-associated regions, such as the anterior insular cortex (aIC) and rostral anterior cingulate cortex (rACC), may play a pivotal role in expectation-induced pain modulation and help to delineate the relationship between positive and negative expectations. In a stimulus expectancy paradigm combining fMRI in healthy volunteers of both sexes, we found that, although positive and negative expectations respectively engaged the right aIC and right rACC to modulate pain, their associated activations and pain rating changes were significantly correlated. When positive and negative expectations modulated pain, the right aIC and rACC exhibited opposite coupling with periaqueductal gray (PAG) and the mismatch between actual and expected pain respectively modulated their coupling with PAG and thalamus across individuals. Participants' certainty about expectations predicted the extent of pain modulation, with positive expectations involving connectivity between aIC and hippocampus, a region regulating anxiety, and negative expectations engaging connectivity between rACC and lateral orbitofrontal cortex, a region reflecting outcome value and certainty. Interestingly, the strength of these certainty-related connectivities was also significantly associated between positive and negative expectations. These findings suggest that aversive prediction-error-related regions interact with pain-processing circuits to underlie stimulus expectancy effects on pain, with positive and negative expectations engaging dissociable but interrelated neural responses that are dependently regulated by individual certainty about expectations.SIGNIFICANCE STATEMENT Positive and negative expectations substantially influence pain perception, but their relationship remains unclear. Using fMRI in a stimulus expectancy paradigm, we found that, although positive and negative expectations engaged separate brain regions encoding the mismatch between actual and expected pain and involved opposite functional connectivities with the descending pain modulatory system, they produced significantly correlated pain rating changes and brain activation. Moreover, participants' certainty about expectations predicted the magnitude of both types of pain modulation, with the underlying functional connectivities significantly correlated between positive and negative expectations. These findings advance current understanding about cognitive modulation of pain, suggesting that both types of pain modulation engage different aversive prediction error signals but are dependently regulated by individual certainty about expectations.

The effect of occipital nerve field stimulation on the descending pain pathway in patients with fibromyalgia: a water PET and EEG imaging study

Background

Fibromyalgia is a chronic disorder characterized by widespread musculoskeletal pain accompanied by fatigue, sleep, memory, and mood problems. Recently, occipital nerve field stimulation (ONS) has been proposed as an effective potential treatment for fibromyalgia-related pain. The aim of this study is to unravel the neural mechanism behind occipital nerve stimulation’s ability to suppress pain in fibromyalgia patients.

Materials and methods

Seven patients implanted with subcutaneous electrodes in the C2 dermatoma were enrolled for a Positron Emission Tomography (PET) H₂¹⁵O activation study. These seven patients were selected from a cohort of 40 patients who were part of a double blind, placebo-controlled study followed by an open label follow up at six months. The H₂¹⁵O PET scans were taken during both the “ON” (active stimulation) and “OFF” (stimulating device turned off) conditions. Electroencephalogram (EEG) data were also recorded for the implanted fibromyalgia patients during both the “ON” and “OFF” conditions.

Results

Relative to the “OFF” condition, ONS stimulation resulted in activation in the dorsal lateral prefrontal cortex, comprising the medial pain pathway, the ventral medial prefrontal cortex, and the bilateral anterior cingulate cortex as well as parahippocampal area, the latter two of which comprise the descending pain pathway. Relative deactivation was observed in the left somatosensory cortex, constituting the lateral pain pathway as well as other sensory areas such as the visual and auditory cortex. The EEG results also showed increased activity in the descending pain pathway. The pregenual anterior cingulate cortex extending into the ventral medial prefrontal cortex displayed this increase in the theta, alpha1, alpha2, beta1, and beta2 frequency bands.

Conclusion

PET shows that ONS exerts its effect via activation of the descending pain inhibitory pathway and the lateral pain pathway in fibromyalgia, while EEG shows activation of those cortical areas that could be responsible for descending inhibition system recruitment.

Trial Registration

This study is registered with ClinicalTrials.gov, number NCT00917176 (June 10, 2009).