How expectations influence pain

Assessing the influence of non-ischaemic A-fiber conduction blockade on offset analgesia: an experimental study

Offset analgesia (OA) is believed to reflect the efficiency of the endogenous pain modulatory system. However, the underlying mechanisms are still being debated. Previous research suggested both, central and peripheral mechanisms, with the latter involving the influence of specific A-delta-fibers. Therefore, this study aimed to investigate the influence of a non-ischaemic A-fiber conduction blockade on the OA response in healthy participants. A total of 52 participants were recruited for an A-fiber conduction blockade via compression of the superficial radial nerve. To monitor fiber-specific peripheral nerve conduction capacity, quantitative sensory testing was performed continuously. Before, during and after the A-fiber block, an individualized OA-paradigm was applied to the dorsum of both hands (blocked and control side were randomized). Pain intensity of each heat stimulus was evaluated by an electronic visual analogue scale. A successful A-fiber conduction blockade was achieved in thirty participants. Offset analgesia has been verified within time (before, during, after blockade), and condition (blocked and control side) (p < 0.01, d > 0.5). Repeated measurements ANOVA showed no significant interaction effects between OA within condition and time (p = 0.24, η²p = 0.05). Hence, no significant effect of A-fiber blockade was detected on OA during noxious heat stimulation. The results suggest that peripheral A-fiber afferents may play a minor role in OA compared to alternative central mechanisms or other fibers. However, further studies are needed to substantiate a central rather than peripheral influence on OA. PERSPECTIVE: This article presents the observation of offset analgesia before, during and after a successful A-fiber conduction blockade in healthy volunteers. A better understanding of the mechanisms of offset analgesia and endogenous pain modulation in general may help to explain the underlying aspects of pain disorders.

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.

Expectation of pain and relief: A dynamical model of the neural basis for pain-trauma co-morbidity

Posttraumatic Stress Disorder (PTSD) is highly co-morbid with chronic pain conditions. When present, PTSD significantly worsens chronic pain outcomes. Likewise, pain contributes to a more severe PTSD as evidenced by greater disability, more frequent use of harmful opioid analgesics and increased pain severity. The biomechanism behind this comorbidity is incompletely understood, however recent work strongly supports the widely-accepted role of expectation, in the entanglement of chronic pain and trauma symptoms. This work has shown that those with trauma have a maladaptive brain response while expecting stress and pain, whereas those with chronic pain may have a notable impairment in brain response while expecting pain relief. This dynamical expectation model of the interaction between neural systems underlying expectation of pain onset (traumatic stress) and pain offset (chronic pain) is biologically viable and may provide a biomechanistic insight into pain-trauma comorbidity. These predictive mechanisms work through interoceptive pathways in the brain critically the insula cortex. Here we highlight how the neural expectation-related mechanisms augment the existing models of pain and trauma to better understand the dynamics of pain and trauma comorbidity. These ideas will point to targeted complementary clinical approaches, based on mechanistically separable neural biophenotypes for the entanglement of chronic pain and trauma symptoms.

Nocebo hyperalgesia and other expectancy-related factors in daily fibromyalgia pain: Combining experimental and electronic diary methods

OBJECTIVE

Expectancies are known to shape pain experiences, but it remains unclear how different types of expectancies contribute to daily pain fluctuations in fibromyalgia. This combined experimental and diary study aims to provide insights into how experimentally-derived nocebo hyperalgesia and other, diary-derived, expectancy-related factors are associated with each other and with daily pain in fibromyalgia.

METHODS

Forty-one female patients with fibromyalgia first participated in a lab procedure measuring nocebo hyperalgesia magnitude, then filled out an electronic diary 3 times a day over 3 weeks regarding the expectancy-related factors of pain expectancy, anxiety, optimism, and pain-catastrophizing thoughts, and current pain intensity.

RESULTS

Our results indicate that experimentally-induced nocebo hyperalgesia was not significantly related to diary-assessed expectancy-related factors and did not predict daily fibromyalgia pain. Higher levels of the self-reported expectancy-related factors pain expectancy and pain catastrophizing, but not anxiety and optimism, predicted moment-to-moment pain increases in fibromyalgia, after controlling for current pain, moment-of-day and all other expectancy-related factors.

CONCLUSION

Our exploratory research findings indicate that self-reported expectancy-related factors, particularly pain expectancy and pain catastrophizing, are potentially more relevant for predicting daily pain experience than experimentally-induced nocebo hyperalgesia. Further translation of nocebo hyperalgesia is needed from experimental to Ecological Momentary Assessment research. Our findings imply that targeting the decrease in pain expectancy and catastrophizing thoughts e.g., via Cognitive Behavioral Therapy, have potential for improving daily pain levels in fibromyalgia.

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.

Spatial summation of pain is associated with pain expectations: Results from a home-based paradigm

The purpose of this study was to reproduce the previously observed spatial summation of pain effect (SSp) using non-laboratory procedures and commercial equipment. An additional aim was to explore the association between expectations and SSp. The Cold Pressor Task (CPT) was used to induce SSp. Healthy participants (N = 68) immersed their non-dominant hands (divided into 5 segments) into cold water (CPT). Two conditions were used 1) gradual hand immersion (ascending condition) and 2) gradual hand withdrawal (descending condition). Pain intensity was measured on a Visual Analogue Scale (VAS). Psychological factors, such as the participants' expectations of pain intensity were also measured on a VAS. Results showed significant SSp (χ2(4) = 116.90, p < 0.001), reproduced with non-laboratory equipment in a home-based set-up. Furthermore, two novel findings were observed: i) there was a significant correlation between expectations and perceived pain, indicating a link between pain expectations and SSp, ii) spatial summation increased with the increase in duration exposure to the noxious stimulus (Wald χ2(8) = 80.80, p < 0.001). This study suggests that SSp is associated with pain expectations and can be formed by a mixture of excitatory and inhibitory mechanisms potentially driven by temporal characteristics of neural excitation. Moreover, this study proposes a new feasible way to induce SSp using a home-based set-up.

Top-down threat bias in pain perception is predicted by higher segregation between resting-state networks

Top-down processes such as expectations have a strong influence on pain perception. Predicted threat of impending pain can affect perceived pain even more than the actual intensity of a noxious event. This type of threat bias in pain perception is associated with fear of pain and low pain tolerance, and hence the extent of bias varies between individuals. Large-scale patterns of functional brain connectivity are important for integrating expectations with sensory data. Greater integration is necessary for sensory integration; therefore, here we investigate the association between system segregation and top-down threat bias in healthy individuals. We show that top-down threat bias is predicted by less functional connectivity between resting-state networks. This effect was significant at a wide range of network thresholds and specifically in predefined parcellations of resting-state networks. Greater system segregation in brain networks also predicted higher anxiety and pain catastrophizing. These findings highlight the role of integration in brain networks in mediating threat bias in pain perception.

The promises and pitfalls of seizure phenomenology

The typical adult patient presenting with a first seizure has a normal clinical examination, uninformative investigations, and often has no witness to their episode. The assessing clinician, therefore, has one primary source of information to guide their assessment; the patient's experience. However, seizure phenomenology - the subjective seizure experience - has received relatively less attention by researchers than objective semiology or investigations. This essay reviews the clinical importance of seizure phenomenology, and the challenges clinicians face in eliciting accurate and clinically relevant descriptions of ictal experience. I conclude by discussing tools that clinicians may use to support the clinical application of seizure phenomenology, and exploring the subjectivity of epilepsy more broadly.

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.

Orofacial Pain and Dentistry Management: Guidelines for a More Comprehensive Evidence-Based Approach

Orofacial pain represents one of the most common health problems that negatively affects the activities of daily living. However, the mechanisms underlying these conditions are still unclear, and their comprehensive management is often lacking. Moreover, even if pain is a common symptom in dentistry, differential diagnostic procedures are needed to exclude other pain origins. Misinterpretation of the pain origin, in fact, can lead to misdiagnosis and to subsequent mismanagement. Pain in the orofacial area is the most common reason for patients to visit the dentist, but this area is complex, and the pain could be associated with the hard and soft tissues of the head, face, oral cavity, or to a dysfunction of the nervous system. Considering that the origins of orofacial pain can be many and varied, a thorough assessment of the situation is necessary to enable the most appropriate diagnostic pathway to be followed to achieve optimal clinical and therapeutic management.

Dysfunctional Activation of the Dorsolateral Prefrontal Cortex During Pain Anticipation Is Associated With Altered Subsequent Pain Experience in Fibromyalgia Patients

The ability to accurately predict pain is an adaptive feature in healthy individuals. However, in chronic pain, this mechanism may be selectively impaired and can lead to increased anxiety and excessive avoidance behavior. Recently, we reported the first data demonstrating brain activation in fibromyalgia (FM) patients during conditioned pain responses, in which FM patients revealed a tendency to form new pain-related associations rather than extinguishing irrelevant ones. The aim of the present study was to extend our previous analysis, to elucidate potential neural divergences between subjects with FM (n = 65) and healthy controls (HCs) (n = 33) during anticipatory information (ie, prior to painful stimulus onset). Using functional magnetic resonance imaging (fMRI), the current analyses include 1) a congruently cued paradigm of low and high pain predictive cues, followed by 2) an incongruently cued paradigm where low and high pain predictive cues were followed by an identical mid-intensity painful pressure. During incongruently cued high-pain associations, FM exhibited reduced left dorsolateral prefrontal cortex (dlPFC) activation compared to HCs, which was followed by an altered subsequent pain experience in FM, as patients continued to rate the following painful stimuli as high, even though the pressure had been lowered. During congruently cued low pain anticipation, FM exhibited decreased right dlPFC activation compared to HCs, as well as decreased brain connectivity between brain regions implicated in cognitive modulation of pain (dlPFC) and nociceptive processing (primary somatosensory cortex/postcentral gyrus [S1] and supplementary motor area [SMA]/midcingulate cortex [MCC]). These results may reflect an important feature of validating low pain expectations in HCs and help elucidate behavioral reports of impaired safety processing in FM patients. PERSPECTIVE: FM exhibited a stronger conditioned pain response for high-pain associations, which was associated with reduced dlPFC activation during the incongruent trial. During (congruent and incongruent) low pain associations, FM dlPFC brain activation remained indifferent. Imbalances in threat and safety pain perception may be an important target for psychotherapeutic interventions.

Post-injury pain and behaviour: a control theory perspective

Injuries of various types occur commonly in the lives of humans and other animals and lead to a pattern of persistent pain and recuperative behaviour that allows safe and effective recovery. In this Perspective, we propose a control-theoretic framework to explain the adaptive processes in the brain that drive physiological post-injury behaviour. We set out an evolutionary and ethological view on how animals respond to injury, illustrating how the behavioural state associated with persistent pain and recuperation may be just as important as phasic pain in ensuring survival. Adopting a normative approach, we suggest that the brain implements a continuous optimal inference of the current state of injury from diverse sensory and physiological signals. This drives the various effector control mechanisms of behavioural homeostasis, which span the modulation of ongoing motivation and perception to drive rest and hyper-protective behaviours. However, an inherent problem with this is that these protective behaviours may partially obscure information about whether injury has resolved. Such information restriction may seed a tendency to aberrantly or persistently infer injury, and may thus promote the transition to pathological chronic pain states.

Adding tactile feedback increases avatar ownership and makes virtual reality more effective at reducing pain in a randomized crossover study

Severe pain is a widespread health problem in need of novel treatment approaches. In the current study we used real water to give virtual objects (i.e., animated virtual water) more realistic physical properties (wet liquid qualities). Healthy volunteers aged 18-34 participated in a within-subject randomized study comparing participants' worst pain during brief thermal stimuli with (1) No Immersive Virtual Reality (VR), versus (2) during VR + no tactile feedback versus (3) VR + real water (with tactile feedback from co-located real objects). Tactile feedback significantly decreased pain intensity (VR analgesia, p < 0.01), compared to VR with no tactile feedback, and compared to No VR (baseline). Tactile feedback made the virtual water feel significantly more real, increased participant's sense of presence, and both VR conditions were distracting (significantly reduced accuracy on an attention demanding task). As a non-pharmacologic analgesic, mixed reality reduced pain by 35% in the current study, comparable to the analgesia from a moderate dose of hydromorphone in previous published experimental studies. Tactile feedback also significantly increased avatar embodiment, the participants illusion of ownership of the virtual hands, which has potential to improve the effectiveness of avatar therapy for chronic pain in future studies. Mixed reality should be tested as treatment in pain patients.

Local brain oscillations and interregional connectivity differentially serve sensory and expectation effects on pain

Pain emerges from the integration of sensory information about threats and contextual information such as an individual's expectations. However, how sensory and contextual effects on pain are served by the brain is not fully understood so far. To address this question, we applied brief painful stimuli to 40 healthy human participants and independently varied stimulus intensity and expectations. Concurrently, we recorded electroencephalography. We assessed local oscillatory brain activity and interregional functional connectivity in a network of six brain regions playing key roles in the processing of pain. We found that sensory information predominantly influenced local brain oscillations. In contrast, expectations exclusively influenced interregional connectivity. Specifically, expectations altered connectivity at alpha (8 to 12 hertz) frequencies from prefrontal to somatosensory cortex. Moreover, discrepancies between sensory information and expectations, i.e., prediction errors, influenced connectivity at gamma (60 to 100 hertz) frequencies. These findings reveal how fundamentally different brain mechanisms serve sensory and contextual effects on pain.

Red induces hyperalgesia and white induces hypoalgesia regardless of pain modality

Colors are an important factor that influences different aspects of people's lives. However, little is known about the effects of colors on pain. This preregistered study aimed to investigate whether the type of pain affects the impact of colors on pain intensity. 74 participants were randomly divided into 2 groups according to the type of pain: electrical or thermal. In both groups, pain stimuli of the same intensity were preceded by different colors. Participants rated the pain intensity induced by each pain stimulus. Additionally, pain expectations related to each color were rated at the beginning and the end of the procedure. A significant effect of color on pain intensity ratings was found. Pain was most intense in both groups after red, whereas the lowest ratings were given after white. A similar pattern of results was observed for pain expectations. Expectations also correlated with and were found to be a predictor of experienced pain for white, blue, and green. The study shows that white can reduce, while red can alter the experienced pain. Moreover, it shows that the effect of colors is affected to a greater extent by the pain expectations rather than the pain modality. We conclude that the way colors influence pain broadens the current knowledge on effects of colors on human behavior and could help in the future both patients and practitioners.

Pain-related opioidergic and dopaminergic neurotransmission: Dual meta-Analyses of PET radioligand studies

Molecular mechanisms of the interaction between opioidergic and dopaminergic processing during pain-related experiences in the human brain are still incompletely understood. This is partially due to the invasive nature of the available techniques to visualize and measure metabolic activity. Positron Emission Tomography (PET) radioligand studies using radioactive substances are still the only available modality to date that allows for the investigation of the molecular mechanisms in the human brain. The most commonly studied PET radiotracers are [11C]-carfentanil (CFN) and [11C]- or [18F]-diprenorphine (DPN), which bind to opioid receptors, and [11C]-raclopride (RAC) and [18F]-fallypride (FAL) tracers, which bind to dopamine receptors. The current meta-analysis examines pain-related studies that used aforementioned opioid and dopamine radioligands in an effort to consolidate the available data into the most likely activated regions. Our primary goal was to identify regions of shared opioid/dopamine neurotransmission during pain-related experiences using within-subject approach. Seed-based d Mapping (SDM) analysis of previously published voxel coordinate data showed that opioidergic activations were strongest in the bilateral caudate, thalamus, right putamen, cingulate gyrus, midbrain, inferior frontal gyrus, and left superior temporal gyrus. The dopaminergic studies showed that the bilateral caudate, thalamus, right putamen, cingulate gyrus, and left putamen had the highest activations. We were able to see a clear overlap between opioid and dopamine activations in a majority of the regions during pain-related experiences, though there were some unique areas of dopaminergic activation such as the left putamen. Regions unique to opioidergic activation included the midbrain, inferior frontal gyrus, and left superior temporal gyrus. Here we provide initial evidence for the functional overlap between opioidergic and dopaminergic processing during aversive states in humans.

Recovery expectations can be assessed with single-item measures: findings of a systematic review and meta-analysis on the role of recovery expectations on return-to-work outcomes after musculoskeletal pain conditions

ABSTRACT

The objective of this systematic review is to quantify the association between recovery expectations and return-to-work outcomes in adults with musculoskeletal pain conditions. In addition, this review has the second objective to compare the predictive utility of single-item and multi-item recovery expectation scales on return-to-work outcomes. Relevant articles were selected from Embase, PsycINFO, PubMed, Cochrane, and manual searches. Studies that assessed recovery expectations as predictors of return-to-work outcomes in adults with musculoskeletal pain conditions were eligible. Data were extracted on study characteristics, recovery expectations, return-to-work outcomes, and the quantitative association between recovery expectations and return-to-work outcomes. Risk of bias was assessed using the Effective Public Health Practice Project. Odds ratios were pooled to examine the effects of recovery expectations on return-to-work outcomes. Chi-square analyses compared the predictive utility of single-item and multi-item recovery expectation scales on return-to-work outcomes. Thirty studies on a total of 28,741 individuals with musculoskeletal pain conditions were included in this review. The odds of being work disabled at follow-up were twice as high in individuals with low recovery expectations (OR = 2.06 [95% CI 1.20-2.92] P < 0.001). Analyses also revealed no significant differences in the predictive value of validated and nonvalidated single-item measures of recovery expectations on work disability (χ 2 = 1.68, P = 0.19). There is strong evidence that recovery expectations are associated with return-to-work outcomes. The results suggest that single-item measures of recovery expectations can validly be used to predict return-to-work outcomes in individuals with musculoskeletal pain conditions.

The role of expectations, control and reward in the development of pain persistence based on a unified model

Chronic, or persistent pain affects more than 10% of adults in the general population. This makes it one of the major physical and mental health care problems. Although pain is an important acute warning signal that allows the organism to take action before tissue damage occurs, it can become persistent and its role as a warning signal thereby inadequate. Although per definition, pain can only be labeled as persistent after 3 months, the trajectory from acute to persistent pain is likely to be determined very early and might even start at the time of injury. The biopsychosocial model has revolutionized our understanding of chronic pain and paved the way for psychological treatments for persistent pain, which routinely outperform other forms of treatment. This suggests that psychological processes could also be important in shaping the very early trajectory from acute to persistent pain and that targeting these processes could prevent the development of persistent pain. In this review, we develop an integrative model and suggest novel interventions during early pain trajectories, based on predictions from this model.

A developmental shift in habituation to pain in human neonates

Habituation to recurrent non-threatening or unavoidable noxious stimuli is an important aspect of adaptation to pain. Neonates, especially if preterm, are exposed to repeated noxious procedures during their clinical care. They can mount strong behavioral, autonomic, spinal, and cortical responses to a single noxious stimulus; however, it is not known whether the developing nervous system can adapt to the recurrence of these inputs. Here, we used electroencephalography to investigate changes in cortical microstates (representing the complex sequential processing of noxious inputs) following two consecutive clinically required heel lances in term and preterm infants. We show that stimulus repetition dampens the engagement of initial microstates and associated behavioral and autonomic responses in term infants, while preterm infants do not show signs of habituation. Nevertheless, both groups engage different longer-latency cortical microstates to each lance, which is likely to reflect changes in higher-level stimulus processing with repeated stimulation. These data suggest that while both age groups are capable of encoding contextual differences in pain, the preterm brain does not regulate the initial cortical, behavioral, and autonomic responses to repeated noxious stimuli. Habituation mechanisms to pain are already in place at term age but mature over the equivalent of the last trimester of gestation and are not fully functional in preterm neonates.

Evidence for dopaminergic involvement in endogenous modulation of pain relief

Relief of ongoing pain is a potent motivator of behavior, directing actions to escape from or reduce potentially harmful stimuli. Whereas endogenous modulation of pain events is well characterized, relatively little is known about the modulation of pain relief and its corresponding neurochemical basis. Here, we studied pain modulation during a probabilistic relief-seeking task (a 'wheel of fortune' gambling task), in which people actively or passively received reduction of a tonic thermal pain stimulus. We found that relief perception was enhanced by active decisions and unpredictability, and greater in high novelty-seeking trait individuals, consistent with a model in which relief is tuned by its informational content. We then probed the roles of dopaminergic and opioidergic signaling, both of which are implicated in relief processing, by embedding the task in a double-blinded cross-over design with administration of the dopamine precursor levodopa and the opioid receptor antagonist naltrexone. We found that levodopa enhanced each of these information-specific aspects of relief modulation but no significant effects of the opioidergic manipulation. These results show that dopaminergic signaling has a key role in modulating the perception of pain relief to optimize motivation and behavior.

A comparison of interactive immersive virtual reality and still nature pictures as distraction-based analgesia in burn wound care

PURPOSE

Non-pharmacologic adjuncts to opioid analgesics for burn wound debridement enhance safety and cost effectiveness in care. The current study explored the feasibility of using a custom portable water-friendly immersive VR hardware during burn debridement in adults, and tested whether interactive VR would reduce pain more effectively than nature stimuli viewed in the same VR goggles.

METHODS

Forty-eight patients with severe burn injuries (44 adults and 4 children) had their burn injuries debrided and dressed in a wet wound care environment on Study Day 1, and 13 also participated in Study Day 2.

INTERVENTION

The study used a within-subject design to test two hypotheses (one hypothesis per study day) with the condition order randomized. On Study Day 1, each individual (n = 44 participants) spent 5 min of wound care in an interactive immersive VR environment designed for burn care, and 5 min looking at still nature photos and sounds of nature in the same VR goggles. On Study Day 2 (n = 12 adult participants and one adolescent from Day 1), each participant spent 5 min of burn wound care with no distraction and 5 min of wound care in VR, using a new water-friendly VR system. On both days, during a post-wound care assessment, participants rated and compared the pain they had experienced in each condition. OUTCOME MEASURES ON STUDY DAYS 1 AND 2: Worst pain during burn wound care was the primary dependent variable. Secondary measures were ratings of time spent thinking about pain during wound care, pain unpleasantness, and positive affect during wound care.

RESULTS

On Study Day 1, no significant differences in worst pain ratings during wound care were found between the computer-generated world (Mean = 71.06, SD = 26.86) vs. Nature pictures conditions (Mean = 68.19, SD = 29.26; t < 1, NS). On secondary measures, positive affect (fun) was higher, and realism was lower during computer-generated VR. No significant differences in pain unpleasantness or "presence in VR" between the two conditions were found, however. VR VS. NO VR. (STUDY DAY 2): Participants reported significantly less worst pain when distracted with adjunctive computer generated VR than during standard wound care without distraction (Mean = 54.23, SD = 26.13 vs 63.85, SD = 31.50, t(11) = 1.91, p < .05, SD = 17.38). In addition, on Study Day 2, "time spent thinking about pain during wound care" was significantly less during the VR condition, and positive affect was significantly greater during VR, compared to the No VR condition.

CONCLUSION

The current study is innovative in that it is the first to show the feasibility of using a custom portable water-friendly immersive VR hardware during burn debridement in adults. However, contrary to predictions, interactive VR did not reduce pain more effectively than nature stimuli viewed in the same VR goggles.

Pain, from perception to action: A computational perspective

Pain is driven by sensation and emotion, and in turn, it motivates decisions and actions. To fully appreciate the multidimensional nature of pain, we formulate the study of pain within a closed-loop framework of sensory-motor prediction. In this closed-loop cycle, prediction plays an important role, as the interaction between prediction and actual sensory experience shapes pain perception and subsequently, action. In this Perspective, we describe the roles of two prominent computational theories-Bayesian inference and reinforcement learning-in modeling adaptive pain behaviors. We show that prediction serves as a common theme between these two theories, and that each of these theories can explain unique aspects of the pain perception-action cycle. We discuss how these computational theories and models can improve our mechanistic understandings of pain-centered processes such as anticipation, attention, placebo hypoalgesia, and pain chronification.

Set and setting in microdosing: an oft-overlooked principle

RATIONALE

The use of psychedelics for medical and recreational purposes is rising. Contextual factors such as expectancy, intention, and sensory and social environment (set and setting) are widely recognized as moderating the effects of these substances. Nevertheless, clinical trials of microdosing - the ingestion of small, sub-hallucinogenic doses of psychedelics - rarely report their set and setting. This fact suggests that such factors are not considered important in the context of microdosing.

OBJECTIVE

This paper challenges this assumption and makes the case for the crucial relevance of set and setting in microdosing practice. Building on set and setting theory and placebo theory, we explain why set and setting are of crucial importance in the case of microdosing.

RESULTS

This reasoning helps elucidate the role of set and setting in determining the outcomes of microdosing and helps explain some of the contradictory results that have emerged in microdosing research in recent years.

CONCLUSION

Set and setting are important constructs to be considered especially in the context of microdosing psychedelics. By reporting set and setting, the results of microdosing research can be made more reliable and consistent.

Predictors of low and high opioid tablet consumption after inguinal hernia repair: an ACHQC opioid reduction task force analysis

PURPOSE

Prescribing and consumption of opioids remain highly variable. Using a national hernia registry, we aimed to identify patient and surgery specific factors associated with low and high opioid tablet consumption after inguinal hernia repair.

METHODS

This was a retrospective cross-sectional study evaluating patients undergoing elective inguinal hernia repair with 30-day follow-up and patient-reported opioid consumption from March 2019 to March 2021 using the Abdominal Core Health Quality Collaborative. Clinically significant patient demographics, comorbidities, operative details, quality-of-life measurements, and surgeon prescribing data were entered into a multivariable logistic regression model to identify statistically significant predictors of patients who took no opioid tablets or >10 tablets.

RESULTS

A total of 1937 patients were analyzed. Operations included 59% laparoscopic or robotic, 35% open mesh, and 6% open non-mesh repairs. Of these patients, 50% reported taking zero, 42% took 1-10, and 8% took ≥10 opioid tablets at 30-day follow-up. Patients who were older (OR 1.55, 95% CI 1.34-1.79, p-value <0.001), ASA ≤ 2 (OR 1.56, 95% CI 1.2-2.01, p-value <0.001), had no preoperative opioid use at baseline (OR 2.29, 95% CI 1.31-4.03, p-value = 0.004), had local anesthetic with general anesthesia (OR 1.39, 95% CI 1.0.5-1.85, p-value = 0.022), or prescribed <7 opioid tablets (OR 2.27, 95% CI 1.96-2.62, p-value <0.001) were more likely to take no opioid tablets.

CONCLUSION

Older, healthier, opioid naïve patients with local anesthetic administered during elective inguinal hernia repair are most likely to not require opioids. Surgeon prescribing-arguably the most modifiable factor-independently correlates with both low and high opioid consumption.

Computational and neural mechanisms of statistical pain learning

Pain invariably changes over time. These fluctuations contain statistical regularities which, in theory, could be learned by the brain to generate expectations and control responses. We demonstrate that humans learn to extract these regularities and explicitly predict the likelihood of forthcoming pain intensities in a manner consistent with optimal Bayesian inference with dynamic update of beliefs. Healthy participants received probabilistic, volatile sequences of low and high-intensity electrical stimuli to the hand during brain fMRI. The inferred frequency of pain correlated with activity in sensorimotor cortical regions and dorsal striatum, whereas the uncertainty of these inferences was encoded in the right superior parietal cortex. Unexpected changes in stimulus frequencies drove the update of internal models by engaging premotor, prefrontal and posterior parietal regions. This study extends our understanding of sensory processing of pain to include the generation of Bayesian internal models of the temporal statistics of pain.

Virtual Reality Animal Rescue World: Pediatric virtual reality analgesia during just noticeable pressure pain in children aged 2-10 years old (crossover design)

BACKGROUND AND AIMS

Excessive pain during medical procedures is a worldwide medical problem. Most scald burns occur in children under 6, who are often undermedicated. Adjunctive Virtual Reality (VR) distraction has been shown to reduce pain in children aged 6-17, but little is known about VR analgesia in young children. This study tests whether desktop VR (VR Animal Rescue World) can reduce the just noticeable pressure pain of children aged 2-10.

METHODS

A within-subject repeated measures design was used. With treatment order randomized, each healthy volunteer pediatric participant underwent brief cutaneous pressure stimuli under three conditions: (1) no distraction, (2) a verbal color naming task (no VR), and (3) a large TV-based desktop VR distraction. A hand-held Wagner pressure pain stimulation device was used to generate just noticeable pain sensations. Participants indicated when a steadily increasing non-painful pressure stimulus first turned into a painful pressure sensation (just noticeable pain).

RESULTS

A total of 40 healthy children participated (43% aged 2-5 years; and 57% aged 6-10 years). Compared to the no distraction condition, the 40 children showed significant VR analgesia (i.e., a significant reduction in pain sensitivity during the VR Animal Rescue World condition), t(39) = 9.83, p < 0.001, SD = 6.24. VR was also significantly more effective at reducing pain sensitivity vs. an auditory color naming task, t(39) = 5.42, p < 0.001, SD = 5.94. The subset of children aged 2-5 showed significant reductions in pain during VR. Children under 6 showed greater sensitivity to pain during no distraction than children aged 6-10.

CONCLUSION

During no distraction, children under 6 years old were significantly more sensitive to pain than children aged 6-10. Virtual reality (VR) significantly reduced the "just noticeable" pressure pain sensitivity of children in both age groups.

Electrophysiological indices of pain expectation abnormalities in fibromyalgia patients

Fibromyalgia is a chronic pain syndrome characterized by dysfunctional processing of nociceptive stimulation. Neuroimaging studies have pointed out that pain-related network functioning seems to be altered in these patients. It is thought that this clinical symptomatology may be maintained or even strengthened because of an enhanced expectancy for painful stimuli or its forthcoming appearance. However, neural electrophysiological correlates associated with such attentional mechanisms have been scarcely explored. In the current study, expectancy processes of upcoming laser stimulation (painful and non-painful) and its further processing were explored by event-related potentials (ERPs). Nineteen fibromyalgia patients and twenty healthy control volunteers took part in the experiment. Behavioral measures (reaction times and subjective pain perception) were also collected. We manipulated the pain/no pain expectancy through an S1–S2 paradigm (cue-target). S1 (image: triangle or square) predicted the S2 appearance (laser stimulation: warmth or pinprick sensation). Laser stimuli were delivered using a CO₂ laser device. Temporal and spatial principal component analyses were employed to define and quantify the ERP component reliability. Statistical analyses revealed the existence of an abnormal pattern of pain expectancy in patients with fibromyalgia. Specifically, our results showed attenuated amplitudes at posterior lCNV component in anticipation of painful stimulation that was not found in healthy participants. In contrast, although larger P2 amplitudes to painful compared to innocuous events were shown, patients did not show any amplitude change in this laser-evoked response as a function of pain predictive cues (as occurred in the healthy control group). Additionally, analyses of the subjective perception of pain and reaction time indicated that laser stimuli preceded by pain cues were rated as more painful than those signaling non-pain expectancy and were associated with faster responses. Differences between groups were not found. The present findings suggest the presence of dysfunction in pain expectation mechanisms in fibromyalgia that eventually may make it difficult for patients to correctly interpret signs that prevent pain symptoms. Furthermore, the abnormal pattern in pain expectancy displayed by fibromyalgia patients could result in ineffective pain coping strategies. Understanding the neural correlates of pain processing and its modulatory factors is crucial to identify treatments for chronic pain syndromes.

Functional brain reconfiguration during sustained pain

Pain is constructed through complex interactions among multiple brain systems, but it remains unclear how functional brain networks are reconfigured over time while experiencing pain. Here, we investigated the time-varying changes in the functional brain networks during 20 min capsaicin-induced sustained orofacial pain. In the early stage, the orofacial areas of the primary somatomotor cortex were separated from other areas of the somatosensory cortex and integrated with subcortical and frontoparietal regions, constituting an extended brain network of sustained pain. As pain decreased over time, the subcortical and frontoparietal regions were separated from this brain network and connected to multiple cerebellar regions. Machine-learning models based on these network features showed significant predictions of changes in pain experience across two independent datasets (n = 48 and 74). This study provides new insights into how multiple brain systems dynamically interact to construct and modulate pain experience, advancing our mechanistic understanding of sustained pain.

Top-down threat bias in pain perception is predicted by intrinsic structural and functional connections of the brain

Top-down processes such as expectations play a key role in pain perception. In specific contexts, inferred threat of impending pain can affect perceived pain more than the noxious intensity. This biasing effect of top-down threats can affect some individuals more strongly than others due to differences in fear of pain. The specific characteristics of intrinsic brain characteristics that mediate the effects of top-down threat bias are mainly unknown. In this study, we examined whether threat bias is associated with structural and functional brain connectivity. The variability in the top-down bias was mapped to the microstructure of white matter in diffusion weighted images (DWI) using MRTrix3. Mean functional connectivity of five canonical resting state networks was tested for association with bias scores and with the identified DWI metrics. We found that the fiber density of the splenium of the corpus callosum was significantly low in individuals with high top-down threat bias (FWE corrected with 5000 permutations, p < 0.05). The mean functional connectivity within the language/memory and between language/memory and default mode networks predicted the bias scores. Functional connectivity within language memory networks predicted the splenium fiber density, higher pain catastrophizing and lower mindful awareness. Probabilistic tractography showed that the identified region in the splenium connected several sensory regions and high-order parietal regions between the two hemispheres, indicating the splenium's role in sensory integration. These findings demonstrate that individuals who show more change in pain with changes in the threat of receiving a stronger noxious stimulus have lower structural connectivity in the pathway necessary for integrating top-down cue information with bottom-up sensory information. Conversely, systems involved in memory recall, semantic and self-referential processing are more strongly connected in people with top-down threat bias.

Understanding Pain and Trauma Symptoms in Veterans From Resting-State Connectivity: Unsupervised Modeling

Trauma and posttraumatic stress are highly comorbid with chronic pain and are often antecedents to developing chronic pain conditions. Pain and trauma are associated with greater utilization of medical services, greater use of psychiatric medication, and increased total cost of treatment. Despite the high overlap in the clinic, the neural mechanisms of pain and trauma are often studied separately. In this study, resting-state functional magnetic resonance imaging (rs-fMRI) scans were completed among a diagnostically heterogeneous sample of veterans with a range of back pain and trauma symptoms. Using Group Iterative Multiple Model Estimation (GIMME), an effective functional connectivity analysis, we explored an unsupervised model deriving subgroups based on path similarity in a priori defined regions of interest (ROIs) from brain regions implicated in the experience of pain and trauma. Three subgroups were identified by patterns in functional connection and differed significantly on several psychological measures despite similar demographic and diagnostic characteristics. The first subgroup was highly connected overall, was characterized by functional connectivity from the nucleus accumbens (NAc), the anterior cingulate cortex (ACC), and the posterior cingulate cortex (PCC) to the insula and scored low on pain and trauma symptoms. The second subgroup did not significantly differ from the first subgroup on pain and trauma measures but was characterized by functional connectivity from the ACC and NAc to the thalamus and from ACC to PCC. The third subgroup was characterized by functional connectivity from the thalamus and PCC to NAc and scored high on pain and trauma symptoms. Our results suggest that, despite demographic and diagnostic similarities, there may be neurobiologically dissociable biotypes with different mechanisms for managing pain and trauma. These findings may have implications for the determination of appropriate biotype-specific interventions that target these neurological systems.

Participants with mildly-disabling chronic neck pain perform differently during explicit compared to implicit motor learning of a reaching task

Chronic musculoskeletal (CMSK) pain associated with musculoskeletal disorders like low back pain or neck pain are the leading causes of disability. While CMSK pain has the potential to negatively influence motor learning, there is limited research to understand the impact of CMSK on motor learning. In order to examine differences in motor learning between individuals with and without CMSK we modified a serial reaction time task to assess motor learning of a repetitive reaching task. The paradigm was used to assess both explicit and implicit motor learning. In a cross-sectional study design, seventeen participants with chronic neck pain (CNP) (5 males) and 21 controls (8 males) were recruited. In addition, physical, cognitive, sensorimotor, disability and pain assessments were used to examine differences between individuals with and without CNP. All participants with CNP were categorized as having mild disability. There was no difference in cognitive assessments and minimal differences in physical measures between groups. Examining motor learning, groups with and without CNP demonstrated similar outcomes in both explicit and implicit motor learning. There was one notable performance difference between groups in the reaching task, the group with CNP demonstrated slower reaching movements outward and inward during blocks without explicit information. This may suggest a cautious approach to movement with reduced explicit information. Findings from this study provide insight on motor learning in individuals with mildly-disabling CNP, further research is necessary to examine how instruction can impact peak performance in people with CMSK pain.

Effectiveness of a group intervention using pain neuroscience education and exercise in women with fibromyalgia: a pragmatic controlled study in primary care

BACKGROUND

Very positive effects have been described in the application of pain neuroscience education (PNE) to chronic pain and migraine. However, there are few data on the applicability of this therapeutic approach in actual clinical practice in a primary care (PC) setting. The aim of this study was to explore the efficacy in fibromyalgia (FM) of an intervention based on PNE and exercise compared to treatment as usual (TAU).

METHODS

Pragmatic nonrandomised controlled trial set in 5 healthcare centres and one physiotherapy centre in PC. Fifty-three women with FM (2010 American College of Rheumatology Diagnostic Criteria for Fibromyalgia) were studied, 35 in the intervention group (IG) and 18 in the control group (CG). The women in the IG were interviewed individually and then received 6 weekly sessions plus one review session (1 month later): those in the CG received their TAU. The subject assignation to the CG or the IG was determined according to their availability to attend the sessions. They all filled in several questionnaires (prior to and 1 year after the intervention) to evaluate the impact of FM in their daily lives, catastrophism, anxiety and depression, severity and impact of pain in daily personal performance and functional capacity.

RESULTS

The reductions (improvements) in the scores of all tests (baseline-final) were greater in the IG (p < 0.05) when adjusted for age and baseline values, with moderate or high effect size. After 1 year, 20% (CI - 1 to 42%) more women in the IG, compared to the CG, had a FIQ score < 39 (mild functional impairment). 17/38 (49%) women in the IG no longer met FM criteria at the end of follow-up.

CONCLUSIONS

An intervention based on PNE and exercise in patients with FM is feasible and seems effective in PC.

TRIAL REGISTRATION

The study was retrospectively registered at ClinicalTrials.gov (Trial Registration NCT04539171 ), on 04/09/2020.

Virtual reality-based distraction for intravenous insertion-related distress in children: a study protocol for a randomised controlled trial

INTRODUCTION

Intravenous (IV) insertions are among the most performed procedures for children seeking medical care; they are often a painful and stressful experience for both children and their caregivers. Paediatric distress and pain that is inadequately treated may lead to a frightened and uncooperative child, repeated IV attempts and overall frustration with care for both the family and clinical team. We hypothesise that distraction via an immersive virtual reality (VR) experience may reduce the associated distress for children undergoing IV insertions.

METHODS AND ANALYSIS

This two-armed randomised controlled superiority trial will be conducted in a Canadian paediatric emergency department and will aim to enrol 80 children overall. Children will be randomised to receive either departmental standard of care alone or standard of care plus an immersive VR experience. Children 6-17 years of age who are undergoing IV insertion and have topical anaesthetic application will be considered for inclusion. Our primary objective is to compare the reduction of distress between the two study arms. The primary outcome will be the child's observed distress score as measured by the Observational Signs of Behavioral Distress-Revised tool. Secondary outcomes include the child's pain intensity and fear, parental anxiety, satisfaction with the IV procedure, as well as adverse events. Recruitment launched in September 2020 and is expected to end in March 2022.

ETHICS AND DISSEMINATION

This study has been approved by the Health Research Ethics Board (University of Alberta). Informed consent will be obtained from parents or guardians, and assent from children. Study data will be submitted for publication irrespective of results. This study is funded through a Women and Children's Health Research Institute Innovation grant. Purchase of the VR equipment was facilitated through a Stollery Children's Hospital Foundation small equipment grant.

TRIAL REGISTRATION NUMBER

NCT04291404Cite Now.

The association of affective state with the assimilation of daily pain expectancy and pain experience

ABSTRACT

Expectancies for pain and pain relief are central to experimental models of placebo analgesia and nocebo hyperalgesia, and are a promising target for clinical intervention in patients with chronic pain. Affective states may play an important role in modulating the degree to which expectancies influence pain, broadening the opportunities for intervention targets. However, findings to date have been mixed and mostly limited to laboratory designs. Few studies have examined the interplay of naturally occurring affective states, pain expectancies, and pain experiences in the course of daily life with chronic pain. In the present study, patients with temporomandibular disorder reported their daily pain expectancies and affective states each morning, and their daily pain experience each evening, over a two-week period. Multilevel modeling analyses revealed the association of morning pain expectancies with subsequent pain experiences was moderated by morning positive affective state (B=.04, SE=.02, t=2.00, p=.046), such that the congruent assimilation of a low pain expectancy with a low pain experience was starkest when morning positive affect was higher than usual. Relatedly, higher morning positive affect predicted greater odds of experiencing a match between pain expectancies and pain experience when the expectation was for low, but not high, pain levels (OR: 1.19, CI: 1.01-1.41, p=.03). Negative affect, in contrast, did not significantly influence the assimilation of high pain expectancies with high pain experiences. These findings extend prior experimental studies by showing that the association of daily pain expectancies with pain experience varies as a function of affective state.

An Exploratory Study on the Effectiveness of Virtual Reality Analgesia for Children and Adolescents with Kidney Diseases Undergoing Venipuncture

The current study evaluated the effectiveness of VR analgesia among pediatric and adolescent patients with kidney disease undergoing venipuncture. Patients at an Italian Children’s hospital (N = 82, age range 7–17 years) undergoing venipuncture were randomly assigned to a No VR group (non-medical conversation) vs. a Yes VR group (VR analgesia). After the procedure, patients gave 0–10 Verbal Numeric Pain Scale ratings. Compared with patients in the No VR Group, patients in the Yes VR group reported significantly lower “Pain intensity”(No VR mean = 2.74, SD = 2.76 vs. Yes VR mean = 1.56, SD = 1.83) and the VR group also rated “Pain unpleasantness” significantly lower than the No VR group (No VR mean = 2.41, SD = 0.94 vs. Yes VR mean = 1.17, SD = 1.80). Patients distracted with VR also reported having significantly more fun during the venipuncture procedure. No side effects emerged. In addition to reducing pain intensity, VR has the potential to make venipuncture a more fun and less unpleasant experience for children with CKD, as measured in the present study for the first time. Finally, in exploratory analyses, children aged 7–11 in the VR group reported 55% lower worst pain than control subjects in the same age range, whereas children aged 12 to 17 in the VR group only reported 35% lower worst pain than control subjects. Additional research and development using more immersive VR is recommended.

Distinct networks of periaqueductal gray columns in pain and threat processing

Noxious events that can cause physical damage to the body are perceived as threats. In the brainstem, the periaqueductal gray (PAG) ensures survival by generating an appropriate response to these threats. Hence, the experience of pain is coupled with threat signaling and interfaces in the dl/l and vlPAG columns. In this study, we triangulate the functional circuits of the dl/l and vlPAG by using static and time-varying functional connectivity (FC) in multiple fMRI scans in healthy participants (n=37, 21 female). The dl/l and vlPAG were activated during cue, heat, and rating periods when the cue signaled a high threat of experiencing heat pain and the incoming intensity of heat pain was low; responses were significantly lower after low threat cues. The two regions responded similarly to the cued conditions but showed prominent distinctions in the extent of FC with other brain regions. Thus, both static and time-varying FC showed significant differences in the functional circuits of dl/l and vlPAG in rest and task scans. The dl/lPAG consistently synchronized with the salience network, suggesting a role in threat detection, while the vlPAG exhibited more widespread synchronization and frequently connected with memory/language and sensory regions. Hence, these two PAG regions process heat pain when stronger pain is expected or when it is uncertain, and preferentially synchronize with distinct brain circuits in a reproducible manner. The dl/lPAG seems more directly involved in salience detection, while the vlPAG seems engaged in contextualizing threats.

Temporal–spectral signaling of sensory information and expectations in the cerebral processing of pain

Pain is not only shaped by sensory information but also by an individual’s expectations. Here, we investigated how commonly analyzed electroencephalography (EEG) responses to pain signal sensory information, expectations, and discrepancies thereof (prediction errors) in the processing of pain. Bayesian analysis confirmed that pain perception was shaped by objective sensory information and expectations. In contrast, EEG responses at different latencies (including the N1, N2, and P2 components) and frequencies (including alpha, beta, and gamma oscillations) were shaped by sensory information but not by expectations. Thus, EEG responses to pain are more involved in signaling sensory information than in signaling expectations or prediction errors. Expectation effects are obviously mediated by other brain mechanisms than the effects of sensory information on pain.

The perception of pain is shaped by somatosensory information about threat. However, pain is also influenced by an individual’s expectations. Such expectations can result in clinically relevant modulations and abnormalities of pain. In the brain, sensory information, expectations (predictions), and discrepancies thereof (prediction errors) are signaled by an extended network of brain areas which generate evoked potentials and oscillatory responses at different latencies and frequencies. However, a comprehensive picture of how evoked and oscillatory brain responses signal sensory information, predictions, and prediction errors in the processing of pain is lacking so far. Here, we therefore applied brief painful stimuli to 48 healthy human participants and independently modulated sensory information (stimulus intensity) and expectations of pain intensity while measuring brain activity using electroencephalography (EEG). Pain ratings confirmed that pain intensity was shaped by both sensory information and expectations. In contrast, Bayesian analyses revealed that stimulus-induced EEG responses at different latencies (the N1, N2, and P2 components) and frequencies (alpha, beta, and gamma oscillations) were shaped by sensory information but not by expectations. Expectations, however, shaped alpha and beta oscillations before the painful stimuli. These findings indicate that commonly analyzed EEG responses to painful stimuli are more involved in signaling sensory information than in signaling expectations or mismatches of sensory information and expectations. Moreover, they indicate that the effects of expectations on pain are served by brain mechanisms which differ from those conveying effects of sensory information on pain.

Offset analgesia is associated with opposing modulation of medial versus dorsolateral prefrontal cortex activations: A functional near-infrared spectroscopy study

Offset analgesia is defined by a dramatic drop in perceived pain intensity with a relatively small decrease in noxious input. Although functional magnetic resonance imaging studies implicate subcortical descending inhibitory circuits during offset analgesia, the role of cortical areas remains unclear. The current study identifies cortical correlates of offset analgesia using functional near infrared spectroscopy (fNIRS). Twenty-four healthy volunteers underwent fNIRS scanning during offset (OS) and control (Con) heat stimuli applied to the forearm. After controlling for non-neural hemodynamic responses in superficial tissues, widespread increases in cortical oxygenated hemoglobin concentration were observed, reflecting cortical activation during heat pain. OS-Con contrasts revealed deactivations in bilateral medial prefrontal cortex (mPFC) and bilateral somatosensory cortex (SSC) associated with offset analgesia. Right dorsolateral prefrontal cortex (dlPFC) showed activation only during OS. These data demonstrate opposing cortical activation patterns during offset analgesia and support a model in which right dlPFC underlies ongoing evaluation of pain intensity change. With predictions of decreasing pain intensity, right dlPFC activation likely inhibits ascending noxious input via subcortical pathways resulting in SSC and mPFC deactivation. This study identifies cortical circuitry underlying offset analgesia and introduces the use of fNIRS to study pain modulation in an outpatient clinical environment.

Educational Intervention for Management of Acute Trauma Pain: A Proof-of-Concept Study in Post-surgical Trauma Patients

OBJECTIVE

Despite years of research and the development of countless awareness campaigns, the number of deaths related to prescription opioid overdose is steadily rising. Often, naive patients undergoing trauma-related surgery are dispensed opioids while in the hospital, resulting in an escalation to long-term opioid misuses. We explored the impact of an educational intervention to modify perceptions of opioid needs at the bedside of trauma inpatients in post-surgery pain management.

MATERIALS AND METHODS

Twenty-eight inpatients with acute post-surgical pain completed this proof-of-concept study adopting an educational intervention related to opioids and non-pharmacological strategies in the context of acute post-surgical pain. An education assessment survey was developed to measure pre- and post-education perceptions of opioid needs to manage pain. The survey statements encompassed the patient's perceived needs for opioids and other pharmacological and non-pharmacological therapeutics to manage acute pain. The primary outcome was the change in the patient's perceived need for opioids. The secondary (explorative) outcome was the change in Morphine Milligram Equivalents (MME) used on the day of the educational intervention while inpatients and prescribed at the time of the hospital discharge.

RESULTS

After the educational intervention, patients reported less agreement with the statement, "I think a short course of opioids (less than 5 days) is safe." Moreover, less agreement on using opioids to manage trauma-related pain was positively associated with a significant reduction in opioids prescribed at discharge after the educational intervention. The educational intervention might have effectively helped to cope with acute trauma-related pain while adjusting potential unrealistic expectancies about pain management and, more in general, opioid-related needs.

CONCLUSION

These findings suggest that trauma patients' expectations and understanding of the risks associated with the long-term use of opioids can be modified by a short educational intervention delivered by health providers during the hospitalization. Establishing realistic expectations in managing acute traumatic pain may empower patients with the necessary knowledge to minimize the potential of continuous long-term opioid use, opioid misuse, and the development of post-trauma opioid abuse and/or addiction.

Association of painful human immunodeficiency virus distal sensory polyneuropathy with aberrant expectation of pain relief: functional magnetic resonance imaging evidence

Mechanisms underlying chronic neuropathic pain associated with HIV-associated distal sensory polyneuropathy are poorly understood, yet 40% of those with distal neuropathy (or 20% of all people with HIV) suffer from this debilitating condition. Central pain processing mechanisms are thought to contribute to the development of HIV neuropathic pain, yet studies investigating central mechanisms for HIV neuropathic pain are few. Considering the motivational nature of pain, we aimed to examine the degree to which expectation of pain onset and expectation of pain offset are altered in sixty-one male patients with HIV-related distal sensory polyneuropathy with (N = 30) and without (N = 31) chronic neuropathic pain. By contrasting painful (foot) and non-painful (hand) sites between those with and without neuropathic pain, we could identify unique neural structures that showed altered activation during expectation of pain offset or relief. Our results showed no evidence for peripheral mechanisms evidenced by lack of significant between group differences in thermo-sensation, subjective pain response or epidermal nerve fibre density. Likewise, we found no significant differences between groups in subjective or brain mechanisms underlying the expectation of pain onset. Conversely, we found significant interaction within right anterior insula during expectation of pain offset in our study in that individuals in the pain group compared to the no-pain group exhibited increased anterior insula activation on the painful compared to the non-painful site. Our findings are consistent with abnormal processing of expectation of pain offset or abnormal pain relief-related mechanisms potentially due to increased emotional distress regarding the experience of chronic endogenous pain.

Brain circuits for pain and its treatment

[Figure: see text].

A social affective neuroscience lens on placebo analgesia

Pain is a fundamental experience that promotes survival. In humans, pain stands at the intersection of multiple health crises: chronic pain, the opioid epidemic, and health disparities. The study of placebo analgesia highlights how social, cognitive, and affective processes can directly shape pain, and identifies potential paths for mitigating these crises. This review examines recent progress in the study of placebo analgesia through affective science. It focuses on how placebo effects are shaped by expectations, affect, and the social context surrounding treatment, and discusses neurobiological mechanisms of placebo, highlighting unanswered questions and implications for health. Collaborations between clinicians and social and affective scientists can address outstanding questions and leverage placebo to reduce pain and improve human health.

How Pain Shapes Depression and Anxiety: A Hybrid Self-regulatory/Predictive Mind Perspective

Because many persons living with chronic pain achieve a relatively balanced lifestyle without experiencing functional disability, medical psychologists must explain the well-documented co-occurrence of pain complaints and DSM-5-disorders (including but not limited to depression and anxiety) in a significant subset of individuals. The question of differential resilience versus susceptibility has received modest theoretical and empirical attention, but remains open. In this review, I deconstruct the temporally extended pain adaptation process in order to address this vexing question, relying upon two complementary explanatory frames. The first is a motivational/cybernetic systems formulation labeled the Goal-Centered, Self-Regulatory, Automated Social Systems Psychology (GRASSP) model, erected upon feedback sensitive, goal-guided, hierarchically organized self-regulatory processes. Depression and anxiety presumably result from compromised regulatory functions undermining pain processing, goal pursuit, and everyday performance. The second perspective postulates a "Bayesian Brain"/"Predictive Mind" capable of unifying perception, action, and emotion via predictive processing. From a Bayesian perspective, predictive processing implies that our brains evolved to compare, without conscious direction, incoming environmental information against prior, model-based predictions in order to arrive at accurate perceptual representations of the world. Maladjustment results from failures of active inference. When applied to the perception of visceral information, the embodied process, termed interoceptive inference, can also yield pathogenic outcomes. The Bayesian model holds that depression and anxiety in individuals with pain result from error-prone (biased, rigid, or highly certain) prior evaluations of aversive feeling states and their relation to the external milieu. I consider how the hybrid conceptual framework advanced by the two models points to several novel and familiar avenues of intervention.

Hope, Optimism, and Clinical Pain: A Meta-Analysis

BACKGROUND

Generalized expectancies have been theorized to play key roles in pain-related outcomes, but the empirical findings have been mixed.

PURPOSE

The primary aim of this meta-analysis was to quantify the relationships between two of the most researched positive generalized expectancies (i.e., hope and optimism) and pain-related outcomes (i.e., pain severity, physical functioning, and psychological dysfunction) for those experiencing clinical pain.

METHODS

A total of 96 studies and 31,780 participants with a broad array of pain diagnoses were included in analyses, using random-effects models.

RESULTS

Both hope and optimism had negative correlations with pain severity (hope: r = -.168, p < .001; optimism: r = -.157, p < .001), positive correlations with physical functioning (hope: r = .199, p < .001; optimism: r = .175, p < .001), and negative correlations with psychological dysfunction (hope: r = -.349, p = .001; optimism: r = -.430, p <.001).

CONCLUSION

The current findings suggest that hope and optimism are similarly associated with adaptive pain-related outcomes. Future research should examine the efficacy of interventions on hope and optimism in ameliorating the experience of clinical pain.

Exposure to an Immersive Virtual Reality Environment can Modulate Perceptual Correlates of Endogenous Analgesia and Central Sensitization in Healthy Volunteers

Virtual reality (VR) has been shown to produce analgesic effects during different experimental and clinical pain states. Despite this, the top-down mechanisms are still poorly understood. In this study, we examined the influence of both a real and sham (ie, the same images in 2D) immersive arctic VR environment on conditioned pain modulation (CPM) and in a human surrogate model of central sensitization in 38 healthy volunteers. CPM and acute heat pain thresholds were assessed before and during VR/sham exposure in the absence of any sensitization. In a follow-on study, we used the cutaneous high frequency stimulation model of central sensitization and measured changes in mechanical pain sensitivity in an area of heterotopic sensitization before and during VR/sham exposure. There was an increase in CPM efficiency during the VR condition compared to baseline (P < .01). In the sham condition, there was a decrease in CPM efficiency compared to baseline (P < .01) and the real VR condition (P < .001). Neither real nor sham VR had any effect on pain ratings reported during the conditioning period or on heat pain threshold. There was also an attenuation of mechanical pain sensitivity during the VR condition indicating a lower sensitivity compared to sham (P < .05). We conclude that exposure to an immersive VR environment has no effect over acute pain thresholds but can modulate dynamic CPM responses and mechanical hypersensitivity in healthy volunteers. PERSPECTIVE: This study has demonstrated that exposure to an immersive virtual reality environment can modulate perceptual correlates of endogenous pain modulation and secondary hyperalgesia in a human surrogate pain model. These results suggest that virtual reality could provide a novel mechanism-driven analgesic strategy in patients with altered central pain processing.

Interacting with virtual objects via embodied avatar hands reduces pain intensity and diverts attention

The current study introduces a new paradigm for exploring cognitive factors in pain. Interacting with virtual objects via embodied avatar hands increased the illusion of “being there” in the virtual world, increased VR analgesia for acute pain, and reduced accuracy on an attention demanding task. Twenty-four healthy volunteer college students participated in this within-subject randomized crossover design study. During Phase 1, each participant received brief thermal pain stimuli during interactive embodied avatar VR vs. passive VR (no avatar and no interactivity), VR treatment order randomized. After each pain stimulus, participants provided subjective 0–10 ratings of pain. Compared to the passive VR condition, during the interactive avatar VR, participants reported significant reductions in (1) worst pain, (2) pain unpleasantness, (3) time thinking about pain and (4). they had significantly more fun during the pain stimulus (p = .000 for each). During Phase 2, participants performed a divided attention task in each of the two VR conditions. Participants made significantly more errors on the divided attention task during the interactive avatar VR condition, compared to passive VR, implicating an attention mechanism for how virtual reality reduces pain and helping understand how VR influences pain perception.

Trial registration: NCT04245475. Date of registration: 29/01/2020.

Direct and mediated effects of treatment context on low back pain outcome: a prospective cohort study

OBJECTIVES

Contextual components of treatment previously associated with patient outcomes include the environment, therapeutic relationship and expectancies. Questions remain about which components are most important, how they influence outcomes and comparative effects across treatment approaches. We aimed to identify significant and strong contextual predictors of patient outcomes, test for psychological mediators and compare effects across three treatment approaches.

DESIGN

Prospective cohort study with patient-reported and practitioner-reported questionnaire data (online or paper) collected at first consultation, 2 weeks and 3 months.

SETTING

Physiotherapy, osteopathy and acupuncture clinics throughout the UK.

PARTICIPANTS

166 practitioners (65 physiotherapists, 46 osteopaths, 55 acupuncturists) were recruited via their professional organisations. Practitioners recruited 960 adult patients seeking treatment for low back pain (LBP).

PRIMARY AND SECONDARY OUTCOMES

The primary outcome was back-related disability. Secondary outcomes were pain and well-being. Contextual components measured were: therapeutic alliance; patient satisfaction with appointment systems, access, facilities; patients' treatment beliefs including outcome expectancies; practitioners' attitudes to LBP and practitioners' patient-specific outcome expectancies. The hypothesised mediators measured were: patient self-efficacy for pain management; patient perceptions of LBP and psychosocial distress.

RESULTS

After controlling for baseline and potential confounders, statistically significant predictors of reduced back-related disability were: all three dimensions of stronger therapeutic alliance (goal, task and bond); higher patient satisfaction with appointment systems; reduced patient-perceived treatment credibility and increased practitioner-rated outcome expectancies. Therapeutic alliance over task (η_p²=0.10, 95% CI 0.07 to 0.14) and practitioner-rated outcome expectancies (η_p²=0.08, 95% CI 0.05 to 0.11) demonstrated the largest effect sizes. Patients' self-efficacy, LBP perceptions and psychosocial distress partially mediated these relationships. There were no interactions with treatment approach.

CONCLUSIONS

Enhancing contextual components in musculoskeletal healthcare could improve patient outcomes. Interventions should focus on helping practitioners and patients forge effective therapeutic alliances with strong affective bonds and agreement on treatment goals and how to achieve them.

Reward processing as a common diathesis for chronic pain and depression

Pain disorders and psychiatric illness are strongly comorbid, particularly in the context of Major Depressive Disorder (MDD). While these disorders account for a significant amount of global disability, the mechanisms of their overlap remain unclear. Understanding these mechanisms is of vital importance to developing prevention strategies and interventions that target both disorders. Of note, brain reward processing may be relevant to explaining how the comorbidity arises, given pain disorders and MDD can result in maladaptive reward responsivity that limits reward learning, appetitive approach behaviours and consummatory response. In this review, we discuss this research and explore the possibility of reward processing deficits as a common diathesis to explain the manifestation of pain disorders and MDD. Specifically, we hypothesize that contextual physical or psychological events (e.g. surgery, divorce) in the presence of a reward impairment diathesis worsens symptoms and results in a negative feedback loop that increases the chronicity and probability of developing the other disorder. We also highlight the implications for treatment and provide a framework for future research.

Patient Expectancy Does Not Predict Success or Failure of Thermal Neurotomy for Persistent Zygapophysial and Sacroiliac Joint Pain

OBJECTIVE

The placebo effect is important in determining the outcome of the treatment of pain for which expectancy and context are the main contributors. The variable success of thermal neurotomy spinal pain procedures is often seen as evidence of the placebo effect. Conversely, proponents of pain procedures explain poorer outcomes by technical procedure deficiencies, including inadequate diagnosis. This cohort study set out to determine whether patient expectancy is a contributing factor in the outcome of thermal neurotomy to the cervical, thoracic, and lumbar zygapophysial and sacroiliac joints.

DESIGN

This single-practitioner, single-site retrospective analysis of prospectively gathered cohort data of 549 patients evaluated the impact of patient preprocedure expectancy (rated on a simple 0-10 or 0-4 numerical rating scale) on outcomes in a large consecutive series of patients who had undergone thermal neurotomy treatment between 2009 and 2019. In addition, a portion of patients were asked to what extent they hoped for or desired a good outcome.

RESULTS

Successful pain relief (≥75% reduction from baseline) was not associated with a higher preprocedure expectancy than were failed procedures. Hope and desire demonstrated no impact on the positive or negative impact of the procedure.

CONCLUSIONS

Altogether, patient expectation of outcome, hope, and desire are not associated with the outcome of effective pain relief by thermal neurotomy that has been performed to the appropriate and commonly available technical standards. Further work is needed to determine the influence of patient expectation across a range of pain intervention modalities.