Learning to predict and control harmful events: chronic pain and conditioning

Disease-specific alterations in central fear network engagement during acquisition and extinction of conditioned interoceptive fear in inflammatory bowel disease

Interoceptive fear, which is shaped by associative threat learning and memory processes, plays a central role in abnormal interoception and psychiatric comorbidity in conditions of the gut-brain axis. Although animal and human studies support that acute inflammation induces brain alterations in the central fear network, mechanistic knowledge in patients with chronic inflammatory conditions remains sparse. We implemented a translational fear conditioning paradigm to elucidate central fear network reactivity in patients with quiescent inflammatory bowel disease (IBD), compared to patients with irritable bowel syndrome (IBS) and healthy controls (HC). Using functional magnetic resonance imaging, conditioned differential neural responses within regions of the fear network were analyzed during acquisition and extinction learning. In contrast to HC and IBS, IBD patients demonstrated distinctly altered engagement of key regions of the central fear network, including amygdala and hippocampus, during differential interoceptive fear learning, with more pronounced responses to conditioned safety relative to pain-predictive cues. Aberrant hippocampal responses correlated with chronic stress exclusively in IBD. During extinction, differential engagement was observed in IBD compared to IBS patients within amygdala, ventral anterior insula, and thalamus. No group differences were found in changes of cue valence as a behavioral measure of fear acquisition and extinction. Together, the disease-specific alterations in neural responses during interoceptive fear conditioning in quiescent IBD suggest persisting effects of recurring intestinal inflammation on central fear network reactivity. Given the crucial role of interoceptive fear in abnormal interoception, these findings point towards inflammation-related brain alterations as one trajectory to bodily symptom chronicity and psychiatric comorbidity. Patients with inflammatory conditions of the gut-brain axis may benefit from tailored treatment approaches targeting maladaptive interoceptive fear.

The fear-avoidance model as an embodied prediction of threat

The fear-avoidance model is a well-established framework in the understanding of persistent pain. It proposes a dichotomous path: either the context is interpreted as safe; there is no fear reaction and, therefore, the individual engages in active (positive) coping; or the context is interpreted as threatening, leading to a self-reinforcing vicious circle of fear and (negative) avoidance. We propose an embodied interpretation of this phenomenon employing the joint framework of predictive coding and active inference. The key idea is that multisensory integration of exteroceptive, proprioceptive, and interoceptive sensory inputs can lead to dysfunctional experiences of threat in nonthreatening situations. Threat inference can promote fear responses, maladaptive strategies (i.e., avoidance) and self-provides evidence for threat in associated or future contexts, or both. Under this treatment, the prediction of nonrealized threat becomes self-evidencing and context-invariant, and hence self-perpetuating. Safety cues are unable to attenuate the interpretation of the negative context as the dominant inference of the context is threatful and gains more precision and becomes resistant over time. Our model provides an explanation for the emergence of a dysfunctional fear response in the clinical setting despite apparent safety based on modern concepts from theoretical (computational) neuroscience.

Psychophysiologic symptom relief therapy for chronic back pain: hypothesis and trial rationale

Chronic pain syndromes affect over one-third of the US adult population and often lead to significant disability and a reduced quality of life. Despite their high prevalence, causal links between chronic pain syndromes and anatomic abnormalities are often not apparent. Most current chronic pain treatments provide modest, if any, relief. Thus, there is a pressing need to understand the causal mechanisms implicated in chronic pain as a means to develop more targeted interventions for improvement in clinical outcomes and reduction in morbidity and financial burden. In the present manuscript, we summarize the current literature on treatment for chronic pain, and hypothesize that non-specific chronic back pain (without a clear organic etiology, such as tumors, infections or fractures) is of psychophysiologic origin. Based on this hypothesis, we developed Psychophysiologic Symptom Relief Therapy (PSRT), a novel pain reduction intervention for understanding and treating chronic pain. In this manuscript, we provide the rationale for PSRT, which we have tested in a pilot trial with a subsequent larger randomized trial underway. In the proposed trial, we will evaluate whether non-specific chronic back pain can be treated by addressing the underlying stressors and psychological underpinnings without specific physical interventions.

Rewarding Approach Behaviour Attenuates the Return of Pain-Related Avoidance After Successful Extinction with Response Prevention

After successful exposure treatment for chronic pain, pain-related fear and avoidance may return, i.e., relapse may occur. This return of fear and avoidance may be modulated by various post-treatment factors. In this study, we aimed to investigate two potential factors that may affect return of fear and avoidance, i.e. cognitive load and rewarding approach behaviour. In an operant pain-related avoidance conditioning paradigm, healthy pain-free volunteers first learned to fear and avoid an arm-reaching movement that was often paired with painful electrocutaneous stimulation (T1), by performing alternative movements that were less often (T2) or never (T3) paired with pain. During extinction with response prevention, participants were only allowed to perform T1, and pain was omitted. To model relapse, two unexpected painful stimuli were presented (i.e., reinstatement manipulation), after which participants could freely choose among the three arm-reaching movements again. During test, the Low Load group performed an additional easy digit task, whereas the High Load group performed a more cognitively demanding digit task. The Reward group performed the demanding digit task, whilst being rewarded to perform T1. Results showed that pain-related fear and avoidance returned, irrespective of cognitive load imposed. When participants were rewarded to approach T1, however, the return of avoidance, but not fear, was attenuated. Our findings suggest that engaging in rewarding activities may facilitate the maintenance of treatment outcomes, and provide additional support to the growing body of literature indicating a divergent relationship between fear and avoidance. PERSPECTIVE: Results of this experiment suggest that engaging in rewarding activities may optimize exposure treatment for chronic pain, by dampening the return of pain-related avoidance - though not of pain-related fear - after extinction.

Pavlovian-to-instrumental transfer in individuals with chronic pain

Avoidance of pain has been argued to be key factor leading pain events to chronic disability. In this respect, research has focused on investigating the working mechanisms of avoidance's acquisition. Avoidance of painful stimuli has been traditionally studied using a combination of Pavlovian and Instrumental procedures. However, such approach seems to go against real-life scenarios where avoidance is commonly acquired more readily. Using a novel pain avoidance paradigm, we tested whether pain avoidance can be installed in absence of associations between a cue and pain omission, and whether such avoidance differs between pain patients and healthy controls. Participants first learned to avoid painful stimuli by pressing a grip bar. Then, they passively encountered pairings of one geometrical shape with pain and of another geometrical shape without pain. Lastly, participants encountered the geometrical shapes while being able to use the grip bar. Results showed that participants pressed the bar more vigorously when encountering the previously pain-related shape compared to the pain-unrelated shape. This effect did not seem to differ between pain patients and healthy control. Our study could inspire a new way in measuring avoidance in pain, possibly paving the way to better understanding how avoidance is installed in chronic pain.

Tackling Kinesiophobia in Chronic Shoulder Pain: A Case Report on the Combined Effect of Pain Education and Whole-Body Cryostimulation

BACKGROUND

Chronic shoulder pain may cause significant functional disability and reduced psychosocial well-being. Detailed Case Description: In this case, we propose the use of pain neuroscience education and whole-body cryostimulation (WBC) to treat a 64-year-old woman with severe functional limitations and chronic right shoulder pain. The aim was to overcome kinesiophobia and improve her motor function, autonomy, and quality of life. Functional and clinical assessments were conducted at admission, discharge, and at a one-month follow-up via phone call. The patient's global health, shoulder function, and quality of life showed improvement during hospitalisation and were maintained after one month.

DISCUSSION

Pain education is crucial in managing chronic shoulder pain, especially in addressing kinesiophobia and promoting positive patient outcomes. In this context, WBC was used as a supplementary treatment to traditional pain relief and exercise tolerance therapies. This can help individuals to participate more actively in their rehabilitation process, ultimately promoting functional recovery and an improved quality of life.

CONCLUSION

The combination of cryostimulation, tailored physical exercises, pain education, manual therapy, and psychological support created a synergistic effect that addressed both the physical and psychological aspects of pain and kinesiophobia.

"The mere imagination scares me"-evidence for fear responses during mental imagery of pain-associated interoceptive sensations in adolescents with chronic pain

ABSTRACT

According to the bio-informational theory of emotion by Lang, mental imagery of fearful stimuli activates physiological and behavioural response systems, even in the absence of sensory input. We investigated whether instructed mental imagery of pain-associated (not painful) interoceptive sensations entails a threat value and elicits increased startle response, skin conductance level (SCL), and heart rate (HR) indicative of defensive mobilization in adolescents with chronic pain. Additionally, self-reported measures (fear, fear of pain, desire to avoid) were assessed. Adolescents (11-18 years) with chronic headache (CH, n = 46) or chronic abdominal pain (CAP, n = 29) and a control group (n = 28) were asked to imagine individualized pain-associated, neutral and standardized fear scripts. During pain-associated compared with neutral imagery, both pain groups showed higher mean HR, with CH also showing higher HR reactivity, while HR acceleration was not observed within control group. In contrast, during pain-associated compared with neutral imagery, startle response magnitude and SCL remained unchanged in all groups. Additionally, overall levels in self-reports were higher during pain-associated compared with neutral imagery, but significantly more pronounced in the pain groups compared with the control group. Results suggest that the mere imagination of pain-associated sensations elicits specific autonomic fear responses accompanied by increased self-reported fear in adolescents with chronic pain. The specific modulation of heart rate shed new light on our understanding of multimodal fear responses in adolescents with chronic pain and may help to refine paradigms to decrease fear of interoceptive sensations in chronic pain.

Investigating the Impact of Stress on Pain: A Scoping Review on Sense of Control, Social-Evaluative Threat, Unpredictability, and Novelty (STUN Model)

Background

Stress can have paradoxical effects on pain, namely hyperalgesia and hypoalgesia. Four situational characteristics activate the hypothalamic-pituitary-adrenal axis, leading to a physiological stress response: lacking Sense of control, social-evaluative Threat, Unpredictability and Novelty (STUN). This scoping review reports on the types of evidence published on the effects of STUN characteristics on pain outcomes.

Databases/Data Treatment

Searches of primary electronic databases were performed to identify articles published on adults between 1990 and 2021 that contained search terms on pain and stress/STUN characteristics. A total of 329 articles were included in the analysis.

Results

Only 3.3% of studies examined simultaneously >1 STUN component. Almost all observational studies (177/180) examined the association between perceived stress and pain without measuring physiological stress responses. Of the 130 experimental studies, 78 (60.0%) manipulated stressful characteristics through nociception, and only 38.5% assessed if/how stress manipulation impacted perceived stress.

Conclusion

There is a clear lack of integration of the characteristics that trigger a physiological stress response in the pain field. Only 3.3% of studies examined simultaneously more than one STUN component and there is an unequal attention given to individual components of the STUN framework. Recommendations for future research include selection of stress manipulations/measurements that are more precisely inducing/reflecting neurobiological mechanisms of stress responses to insure valid integration of scientific knowledge.

Beyond yellow flags: The Big-Five personality traits and psychologically informed musculoskeletal rehabilitation

BACKGROUND

Psychosocial variables are known to play an important role in musculoskeletal pain. Recent efforts incorporating psychological theory into rehabilitative medicine, as part of patient-centred care or psychologically informed physical therapy, have gained broader acceptance. The fear-avoidance model is the dominant psychosocial model and has introduced a variety of phenomena which assess psychological distress (i.e., yellow flags). Yellow flags, such as fear, anxiety and catastrophizing, are useful concepts for musculoskeletal providers but reflect a narrow range of psychological responses to pain.

OBJECTIVE

Clinicians lack a more comprehensive framework to understand psychological profiles of each patient and provide individualised care. This narrative review presents the case for applying personality psychology and the Big-Five trait model (extraversion, agreeableness, conscientiousness, neuroticism and openness to experience) to musculoskeletal medicine. These traits have strong associations with various health outcomes and provide a robust framework to understand patient emotion, motivation, cognition and behaviour.

KEY RESULTS

High conscientiousness is associated with positive health outcomes and health promoting behaviours. High neuroticism with low conscientiousness increases the odds of negative health outcomes. Extraversion, agreeableness and openness have less direct effects but have positive correlations with important health behaviours, including active coping, positive affect, rehabilitation compliance, social connection and education level.

CLINICAL APPLICATION

The Big-Five model offers an evidence-based way for MSK providers to better understand the personality of their patients and how it relates to health. These traits offer the potential for additional prognostic factors, tailored treatments and psychological intervention.

Psychometric validation of the French Multidimensional Chronic Asthenia Scale (MCAS) in a sample of 621 patients with chronic fatigue

BACKGROUND

Psychometric validation of the Multidimensional Chronic Asthenia Scale (MCAS) was conducted in order to provide an effective tool for assessing the health-related quality of life of French-speaking patients with chronic asthenia (CA).

METHODS

Items resulting from the initial formulation of the self-reported MCAS (along with other materials) were completed by French-speaking volunteers with inactive or active inflammatory bowel disease (IBD-I vs. IBD-A) or chronic fatigue syndrome (CFS). Responses from 621 participants (180 patients with IBD-A, 172 with IBD-I, 269 with CFS) collected in a single online survey were divided into three subsamples to test the construct validity of the MCAS (Step 1, N = 240), to confirm its factorial structure (Step 2, N = 204) and to explore its convergent-discriminant validity with the Fatigue Symptoms Inventory (FSI) and revised Piper Fatigue Scale (r-PFS, Step 3, N = 177).

RESULTS

Steps 1 and 2 showed that, as expected, MCAS has four dimensions: feeling of constraint (FoC), physical (PC), life (LC) and interpersonal consequences (IC), which are also related to the duration of CA (i.e., the longer it lasts, the more the dimensions are impacted). The results further showed that the MCAS is sensitive enough to capture between-group differences, with the CFS group being the most impaired, followed by IBD-A and IBD-I. While convergent-discriminant validity between the 4 factors of MCAS and FSI and r-PFS, respectively, was satisfactory overall, Step 3 also pointed to some limitations that call for future research (e.g., shared variances between the PC and IC dimensions of MCAS and behavioral dimension of r-PFS).

CONCLUSION

Despite these limitations, the MCAS clearly constitutes a promising tool for measuring quantitative differences (i.e., severity/intensity) in CA associated with various diseases, but also, and importantly, the clinically important differences in domains of its expression (i.e., qualitative differences).

Life is pain: Fibromyalgia as a nexus of multiple liability distributions

Fibromyalgia is a complex disease of unclear etiology that is complicated by difficulties in diagnosis, treatment, and clinical heterogeneity. To clarify this etiology, healthcare-based data are leveraged to assess the influences on fibromyalgia in several domains. Prevalence is less than 1% of females in our population register data, and about 1/10th that in males. Fibromyalgia often presents with co-occurring conditions including back pain, rheumatoid arthritis, and anxiety. More comorbidities are identified with hospital-associated biobank data, falling into three broad categories of pain-related, autoimmune, and psychiatric disorders. Selecting representative phenotypes with published genome-wide association results for polygenic scoring, we confirm genetic predispositions to psychiatric, pain sensitivity, and autoimmune conditions show associations with fibromyalgia, although these may differ by ancestry group. We conduct a genome-wide association analysis of fibromyalgia in biobank samples, which did not result in any genome-wide significant loci; further studies with increased sample size are necessary to identify specific genetic effects on fibromyalgia. Overall, fibromyalgia appears to have strong clinical and likely genetic links to several disease categories, and could usefully be understood as a composite manifestation of these etiological sources.

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.

A narrative exploration of identity in adults with de novo scoliosis

Adult de novo scoliosis is a chronic health condition characterised by a curvature in the ageing spine. It can cause debilitating back pain and significant visible differences. Yet there has been very limited research on the psychological effects of this condition, particularly around identity. Therefore, we undertook semi-structured interviews to explore the ways in which individuals with scoliosis understood their identity. Findings from narrative analysis highlight the ways in which individuals negotiate their identity in relation to their social roles, their ability to control their condition and things around them, the extent to which their condition is visible and the extent to which they experienced physical pain from their condition. This article concludes by highlighting the relationship between identity and scoliosis and offers practical implications and suggestions for future research.

Virtual reality to understand pain-associated approach behaviour: a proof-of-concept study

Pain-associated approach and avoidance behaviours are critically involved in the development and maintenance of chronic pain. Empirical research suggests a key role of operant learning mechanisms, and first experimental paradigms were developed for their investigation within a controlled laboratory setting. We introduce a new Virtual Reality paradigm to the study of pain-related behaviour and investigate pain experiences on multiple dimensions. The paradigm evaluates the effects of three-tiered heat-pain stimuli applied contingent versus non-contingent with three types of arm movements in naturalistic virtual sceneries. Behaviour, self-reported pain-related fear, pain expectancy and electrodermal activity were assessed in 42 healthy participants during an acquisition phase (contingent movement-pain association) and a modification phase (no contingent movement-pain association). Pain-associated approach behaviour, as measured by arm movements followed by a severe heat stimulus, quickly decreased in-line with the arm movement-pain contingency. Slower effects were observed in fear of movement-related pain and pain expectancy ratings. During the subsequent modification phase, the removal of the pain contingencies modified all three indices. In both phases, skin conductance responses resemble the pattern observed for approach behaviour, while skin conductance levels equal the pattern observed for the self-ratings. Our findings highlight a fast reduction in approach behaviour in the face of acute pain and inform about accompanying psychological and physiological processes. We discuss strength and limitations of our paradigm for future investigations with the ultimate goal of gaining a comprehensive understanding of the mechanisms involved in chronic pain development, maintenance, and its therapy.

Visual feedback manipulation in virtual reality to influence pain-free range of motion. Are people with non-specific neck pain who are fearful of movement more susceptible?

BACKGROUND

Movement-evoked pain may have a protective or learned component, influenced by visual cues which suggest that the person is moving towards a position that may be perceived as threatening. We investigated whether visual feedback manipulation in virtual reality (VR) had a different effect on cervical pain-free range of motion (ROM) in people with fear of movement.

METHOD

In this cross-sectional study, seventy-five people with non-specific neck pain (i.e., neck pain without a specific underlying pathology) rotated their head until the onset of pain, while wearing a VR-headset. Visual feedback about the amount of movement was equal, 30% smaller or 30% larger than their actual rotation. ROM was measured using the VR-headset sensors. The effect of VR manipulation in fearful (N = 19 using the Tampa Scale for Kinesiophobia (TSK) and N = 18 using the Fear Avoidance Beliefs Questionnaire-physical activity (FABQpa)) and non-fearful (N = 46; non-fearful on both scales) people was compared using mixed-design ANOVAs.

RESULTS

Fear of movement, influenced the effect of visual feedback manipulation on cervical pain-free ROM (TSK: p = 0.036, ղp2 = 0.060; FABQpa: p = 0.020, ղp2 = 0.077); a greater amplitude of pain-free movement was found when visual feedback reduced the perceived rotation angle compared to the control condition (TSK: p = 0.090, ղp2 = 0.104; FABQpa: p = 0.030, ղp2 = 0.073). Independent of the presence of fear, visual feedback manipulation reduced the cervical pain-free ROM in the overstated condition (TSK: p< 0.001, ղp2 = 0.195; FABQpa: p<0.001, ղp2 = 0.329).

DISCUSSION

Cervical pain-free ROM can be influenced by visual perception of the amount of rotation and people with fear of movement seem to be more susceptible to this effect. Further research in people with moderate/severe fear is needed to determine whether manipulating visual feedback may have clinical applicability to make patients aware that ROM may be influenced more by fear than tissue pathology.

Fear Learning in Genital Pain: Toward a Biopsychosocial, Ecologically Valid Research and Treatment Model

Although fear learning mechanisms are implicated in the development, maintenance, exacerbation, and reduction of genital pain, systematic research on how fear of genital pain emerges, spreads, persists, and reemerges after treatment is lacking. This paper provides an overview of the literature on pain-related fear, integrates the ideas on learning and sexual arousal responding, and specifies the pathways through which compromised learning may contribute to the development and persistence of genital pain. In order to refine theories of genital pain and optimize treatments, we need to adopt a biopsychosocial framework to pain-related fear learning and uncover potential moderators that shape individual trajectories. This involves examining the role of physiological processes, subjective experiences, as well as partner and relational cues in fear acquisition, excessive generalization and impaired safety learning, extinction of fear, counterconditioning, and return of fear. Recent methodological advances in fear conditioning and sex research are promising to enable more symptom-specific and ecologically valid experimental paradigms.

Neuromuscular adaptations to experimentally induced pain in the lumbar region: systematic review and meta-analysis

ABSTRACT

Experimental pain models are frequently used to understand the influence of pain on the control of human movement. In this systematic review, we assessed the effects of experimentally induced pain in the lumbar region of healthy individuals on trunk muscle activity and spine kinematics. Databases were searched from inception up to January 31, 2022. In total, 26 studies using either hypertonic saline injection (n = 19), heat thermal stimulation (n = 3), nociceptive electrical stimulation (n = 3), or capsaicin (n = 1) were included. The identified adaptations were task dependent, and their heterogeneity was partially explained by the experimental pain model adopted. Meta-analyses revealed an increase of erector spinae activity (standardized mean difference = 0.71, 95% confidence interval [CI] = 0.22-1.19) during full trunk flexion and delayed onset of transversus abdominis to postural perturbation tasks (mean difference = 25.2 ms, 95% CI = 4.09-46.30) in the presence of pain. Low quality of evidence supported an increase in the activity of the superficial lumbar muscles during locomotion and during voluntary trunk movements during painful conditions. By contrast, activity of erector spinae, deep multifidus, and transversus abdominis was reduced during postural perturbation tasks. Reduced range of motion of the lumbar spine in the presence of pain was supported by low quality of evidence. Given the agreement between our findings and the adaptations observed in clinical populations, the use of experimental pain models may help to better understand the mechanisms underlying motor adaptations to low back pain.

Fear-Avoidance Beliefs Are Associated with Pain Intensity and Shoulder Disability in Adults with Chronic Shoulder Pain: A Cross-Sectional Study

Shoulder pain is one of the most common musculoskeletal conditions, and for people over 40 years old, it represents the musculoskeletal pain with the greatest impact on quality of life. Psychological factors, such as fear-avoidance beliefs, are associated with musculoskeletal pain, and several studies suggest that they can influence various treatment outcomes. Our objective was to explore the cross-sectional association between fear-avoidance beliefs and shoulder pain intensity and disability in subjects with chronic shoulder pain. A cross-sectional study was conducted, and 208 participants with chronic unilateral subacromial shoulder pain were recruited. The shoulder pain and disability index assessed pain intensity and disability. The Spanish fear-avoidance components scale assessed the presence of fear-avoidance beliefs. The association between fear-avoidance beliefs and pain intensity and disability was analyzed by means of multiple linear regression models and proportional odds models, reporting odds ratios and 95% confidence intervals. Shoulder and pain disability scores were significantly associated with fear-avoidance beliefs (p < 0.0001, adjusted R-square 0.93, multiple linear regression). There was no evidence of an association between sex and age in this study. The regression coefficient for shoulder pain intensity and disability score was 0.67446. The proportional odds model showed an odds ratio of 1.39 (1.29-1.50) for shoulder pain intensity and disability total score. This study suggests that greater levels of fear-avoidance beliefs are associated with greater levels of shoulder pain and disability in adults with chronic shoulder pain.

Generalization of pain-related avoidance behavior based on de novo categorical knowledge

ABSTRACT

People with chronic pain often fear and avoid movements and activities that were never paired with pain. Safe movements may be avoided if they share some semantic relationship with an actual pain-associated movement. This study investigated whether pain-associated operant responses (movements) can become categorically associated with perceptually dissimilar responses, thus motivating avoidance of new classes of safe movements-a phenomenon known as category-based avoidance generalization. Using a robotic arm, 2 groups were trained to categorize arm movements in different ways. Subsequently, the groups learned through operant conditioning that an arm movement from one of the categories was paired with a high probability of pain, whereas the others were paired with either a medium probability of pain or no pain (acquisition phase). Self-reported pain-related fear and pain expectancy were collected as indices of fear learning. During a final generalization test phase, the movements categorically related to those from the acquisition phase were made available but in the absence of pain. Results showed that the generalization of outcome measures depended on the categorical connections between arm movements, ie, the groups avoided and feared the novel generalization movement categorically related to the pain-associated acquisition movement, depending on how they had previously learned to categorize the movements. This suggests that operant pain-related avoidance can generalize to safe behaviors, which are not perceptually, but categorically, similar to a pain-associated behavior. This form of pain-related avoidance generalization is problematic because category-based relations can be extremely wide reaching and idiosyncratic. Thus, category-based generalization of operant pain-related avoidance merits further investigation.

Pavlovian-to-Instrumental Transfer across Mental Disorders: A Review

A mechanism known as Pavlovian-to-instrumental transfer (PIT) describes a phenomenon by which the values of environmental cues acquired through Pavlovian conditioning can motivate instrumental behavior. PIT may be one basic mechanism of action control that can characterize mental disorders on a dimensional level beyond current classification systems. Therefore, we review human PIT studies investigating subclinical and clinical mental syndromes. The literature prevails an inhomogeneous picture concerning PIT. While enhanced PIT effects seem to be present in non-substance-related disorders, overweight people, and most studies with AUD patients, no altered PIT effects were reported in tobacco use disorder and obesity. Regarding AUD and relapsing alcohol-dependent patients, there is mixed evidence of enhanced or no PIT effects. Additionally, there is evidence for aberrant corticostriatal activation and genetic risk, e.g., in association with high-risk alcohol consumption and relapse after alcohol detoxification. In patients with anorexia nervosa, stronger PIT effects elicited by low caloric stimuli were associated with increased disease severity. In patients with depression, enhanced aversive PIT effects and a loss of action-specificity associated with poorer treatment outcomes were reported. Schizophrenic patients showed disrupted specific but intact general PIT effects. Patients with chronic back pain showed reduced PIT effects. We provide possible reasons to understand heterogeneity in PIT effects within and across mental disorders. Further, we strengthen the importance of reliable experimental tasks and provide test-retest data of a PIT task showing moderate to good reliability. Finally, we point toward stress as a possible underlying factor that may explain stronger PIT effects in mental disorders, as there is some evidence that stress per se interacts with the impact of environmental cues on behavior by selectively increasing cue-triggered wanting. To conclude, we discuss the results of the literature review in the light of Research Domain Criteria, suggesting future studies that comprehensively assess PIT across psychopathological dimensions.

To Calibrate or not to Calibrate? A Methodological Dilemma in Experimental Pain Research

To calibrate or not to calibrate? This question is raised by almost everyone designing an experimental pain study with supra-threshold stimulation. The dilemma is whether to individualize stimulus intensity to the pain threshold / supra-threshold pain level of each participant or whether to provide the noxious stimulus at a fixed intensity so that everyone receives the identical input. Each approach has unique pros and cons which need to be considered to i) accurately design an experiment, ii) enhance statistical inference in the given data and, iii) reduce bias and the influence of confounding factors in the individual study e.g., body composition, differences in energy absorption and previous experience. Individualization requires calibration, a procedure already irritating the nociceptive system but allowing to match the pain level across individuals. It leads to a higher variability of the stimulus intensity, thereby influencing the encoding of "noxiousness" by the central nervous system. Results might be less influenced by statistical phenomena such as ceiling/floor effects and the approach does not seem to rise ethical concerns. On the other hand, applying a fixed (standardized) intensity reduces the problem of intensity encoding leading to a large between-subjects variability in pain responses. Fixed stimulation intensities do not require pre-exposure. It can be proposed that one method is not preferable over another, however the choice depends on the study aim and the desired level of external validity. This paper discusses considerations for choosing the optimal approach for experimental pain studies and provides recommendations for different study designs. PERSPECTIVE: To calibrate pain or not? This dilemma is related to almost every experimental pain research. The decision is a trade-off between statistical power and greater control of stimulus encoding. The article decomposes both approaches and presents the pros and cons of either approach supported by data and simulation experiment.

Study protocol and methods for Easing Pelvic Pain Interventions Clinical Research Program (EPPIC): a randomized clinical trial of brief, low-intensity, transdiagnostic cognitive behavioral therapy vs education/support for urologic chronic pelvic pain syndrome (UCPPS)

Background

Urologic chronic pelvic pain syndrome (UCPPS) encompasses several common, costly, diagnoses including interstitial cystitis/bladder pain syndrome and chronic prostatitis/chronic pelvic pain syndrome that are poorly understood and inadequately treated with conventional medical therapies. Behavioral strategies, recommended as a first-line treatment for managing symptoms, are largely inaccessible, time and labor intensive, and technically complex. The Easing Pelvic Pain Interventions Clinical Research Program (EPPIC) is a clinical trial examining the efficacy of low-intensity cognitive behavioral therapy (Minimal Contact CBT or MC-CBT) for UCPPS and its durability 3 and 6 months post treatment. Additional aims include characterizing the operative processes (e.g., cognitive distancing, context sensitivity, coping flexibility, repetitive negative thought) that drive MC-CBT-induced symptom relief and pre-treatment patient variables that moderate differential response.

Methods

UCPPS patients (240) ages 18–70 years, any gender, ethnicity, and race, will be randomized to 4-session MC-CBT or a credible, non-specific education comparator (EDU) that controls for the generic effects from simply going to treatment. Efficacy assessments will be administered at pre-treatment, 2 weeks, and 3 and 6 months post treatment-week acute phase. A novel statistical approach applied to micro-analytic mediator assessment schedule will permit the specification of the most effective CBT component(s) that drive symptom relief.

Discussion

Empirical validation of a low-intensity self-management therapy transdiagnostic in scope has the potential to improve the health of chronic pelvic pain patients refractory to medical therapies, reduce social and economic costs, conserve health care resources, as well as inform evidence-based practice guidelines. Identification of change mechanisms and moderators of treatment effects can provide proactive patient-treatment matching fundamental to goals of personalized medicine.

Trial Registration

Clinicaltrials.gov NCT05127616. Registered on 9/19/21.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06554-9.

Impaired pain-related threat and safety learning in patients with chronic back pain

ABSTRACT

Pain-related learning mechanisms likely play a key role in the development and maintenance of chronic pain. Previous smaller-scale studies have suggested impaired pain-related learning in patients with chronic pain, but results are mixed, and chronic back pain (CBP) particularly has been poorly studied. In a differential conditioning paradigm with painful heat as unconditioned stimuli, we examined pain-related acquisition and extinction learning in 62 patients with CBP and 61 pain-free healthy male and female volunteers using valence and contingency ratings and skin conductance responses. Valence ratings indicate significantly reduced threat and safety learning in patients with CBP, whereas no significant differences were observed in contingency awareness and physiological responding. Moreover, threat learning in this group was more impaired the longer patients had been in pain. State anxiety was linked to increased safety learning in healthy volunteers but enhanced threat learning in the patient group. Our findings corroborate previous evidence of altered pain-related threat and safety learning in patients with chronic pain. Longitudinal studies exploring pain-related learning in (sub)acute and chronic pain are needed to further unravel the role of aberrant pain-related learning in the development and maintenance of chronic pain.

Alike, But Not Quite: Comparing the Generalization of Pain-Related Fear and Pain-Related Avoidance

Pain-related fear and -avoidance crucially contribute to pain chronification. People with chronic pain may adopt costly avoidance strategies above and beyond what is necessary, aligning with experimental findings of excessive fear generalization to safe movements in these populations. Furthermore, recent evidence suggests that, when avoidance is costly, it can dissociate from fear. Here, we investigated whether concurrently measured pain-related fear and costly avoidance generalization correspond in one task. We also explored whether healthy participants avoid excessively despite associated costs, and if avoidance would decrease as a function of dissimilarity from a pain-associated movement. In a robotic arm-reaching task, participants could avoid a low-cost, pain-associated movement trajectory (T+), by choosing a high-cost non-painful movement trajectory (T-), at opposite ends of a movement plane. Subsequently, in the absence of pain, we introduced three movement trajectories (G1-3) between T+ and T-, and one movement trajectory on the side of T- opposite to T+ (G4), linearly increasing in costs from T+ to G4. Avoidance was operationalized as maximal deviation from T+, and as trajectory choice. Fear learning was measured using self-reported pain-expectancy, pain-related fear, and startle eye-blink electromyography. Self-reports generalized, both decreasing with increasing distance from T+. In contrast, all generalization trajectories were chosen equally, suggesting that avoidance-costs and previous pain balanced each other out. No effects emerged in the electromyography. These results add to a growing body of literature showing that (pain-related) avoidance, especially when costly, can dissociate from fear, calling for a better understanding of the factors motivating, and mitigating, disabling avoidance. PERSPECTIVE: This article presents a comparison of pain-related fear- and avoidance generalization, and an exploration of excessive avoidance in healthy participants. Our findings show that pain-related avoidance can dissociate from fear, especially when avoidance is costly, calling for a better understanding of the factors motivating and mitigating disabling avoidance.

The chronic disease helplessness survey: developing and validating a better measure of helplessness for chronic conditions

Supplemental Digital Content is Available in the Text.

Introduction:

Learned helplessness develops with prolonged exposure to uncontrollable stressors and is therefore germane to individuals living with pain or other poorly controlled chronic diseases. This study has developed a helplessness scale for chronic conditions distinct from previous scales that blur the conceptualization of control constructs. Extant measures commonly examine controllability, not the three pillars of helplessness identified by Maier and Seligman (1976): cognitive, emotional, and motivational/motor deficits.

Methods:

Individuals who self-report a chronic pain condition (N = 350) responded to a Chronic Disease Helplessness Survey (CDHS) constructed to capture cognitive, motivational/motor, and emotion deficits. Exploratory factor analysis (EFA; N = 200) and confirmatory factor analysis (CFA; N = 150) were performed. The CDHS was assessed for convergent and discriminant validity.

Results:

A three-factor solution corresponding to cognitive, emotional, and motivational/motor factors was identified by EFA. The solution exhibited sufficient model fit and each factor had a high degree of internal consistency. The CDHS was significantly associated with greater pain intensity and interference, PCS helplessness, lower perceived pain control, and lower general self-efficacy. Individuals with diabetes generally experience greater control strategies over daily symptoms (e.g., diet, oral medications, and insulin) than patients with chronic pain and in this study displayed significantly lower CDHS scores compared to individuals with chronic pain, demonstrating discriminant validity.

Conclusions:

This study provides preliminary evidence that the three-factor CDHS is a psychometrically sound measure of helplessness in individuals with chronic pain.

Shoulder pain across more movements is not related to more rotator cuff tendon findings in people with chronic shoulder pain diagnosed with subacromial pain syndrome

Supplemental Digital Content is Available in the Text. Neither the number nor severity of rotator cuff tendons reported as abnormal was associated with the pain occurrence across clinically relevant arm movements.

Introduction:

People with chronic shoulder pain commonly report pain during arm movements in daily-life activities. Pain related to movement is commonly viewed as an accurate representation of tissue damage. Thus, when a person reports pain across a variety of movements, this is often understood as indicative of greater damage.

Objectives:

We aimed to investigate if movement-related pain that occurs across a wider variety of movements was associated with the number or severity of rotator cuff tendons reported as abnormal on a magnetic resonance imaging (MRI). To answer this question, this study was designed in 3 phases.

Methods:

We recruited 130 individuals with chronic shoulder pain diagnosed with subacromial pain syndrome. First, a list of daily functional activities commonly reported as painful by people with chronic shoulder pain was generated from 3 well-established outcome measures with 30 individuals and a measurement tool was developed with data from further 100 individuals, which demonstrated to have acceptable content validity, construct validity, internal consistency, interrater reliability, and structural validity. Multiple linear regression was then used to evaluate the hypotheses of the study. A direct acyclic graph was used to select variables for linear regression modelling.

Results:

There was no association between movement-related pain occurrence across movements and the MRI findings.

Conclusion:

Our study provides evidence that neither the number of rotator cuff tendons reported as abnormal nor the severity of each tendon imaging finding were associated with pain occurrence across movements and activities commonly perceived as painful by people with chronic shoulder pain.

Neural and behavioral correlates of human pain avoidance in participants with and without episodic migraine

ABSTRACT

The innate motivation to avoid pain can be disrupted when individuals experience uncontrollable stress, such as pain. This can lead to maladaptive behaviors, including passivity, and negative affect. Despite its importance, motivational aspects of pain avoidance are understudied in humans and their neural mechanisms vastly unknown. Rodent models suggest an important role of the periaqueductal gray, but it is unknown whether it subserves a similar role in humans. Furthermore, it is unclear whether pain avoidance is associated with individual differences in pain coping. Using functional magnetic resonance imaging, networks underlying pain avoidance behavior were examined in 32 participants with and without episodic migraine. Pain avoidance behavior was assessed using an adaptation of the incentive delay task. In each trial of the task, participants tried to avoid a painful stimulus and receive a nonpainful one instead while the difficulty to succeed varied across trials (3 difficulty levels: safe, easy, and difficult). After unsuccessful pain avoidance on the preceding trial, participants showed reduced pain avoidance behavior, especially in the difficult condition. This reduction in behavior was associated with higher helplessness scores only in participants with migraine. Higher helplessness in participants with migraine was further correlated with a stronger decrease in activation of cortical areas associated with motor behavior, attention, and memory after unsuccessful pain avoidance. Of these areas, specifically posterior parietal cortex activation predicted individual's pain avoidance behavior on the next trial. The results link individual pain coping capacity to patterns of neural activation associated with altered pain avoidance in patients with migraine.

Heart Rate Variability and Pain Sensitivity in Chronic Low Back Pain Patients Exposed to Passive Viewing of Photographs of Daily Activities

OBJECTIVE

Investigation if emotional reactivity by measuring heart rate variability (HRV) and pressure pain sensitivity during a passive visualization task in participants with chronic low back pain (CLBP).

MATERIALS AND METHODS

This case-control study was composed of 47 participants with CLBP and 47 asymptomatic participants. Both groups were submitted to a passive visualization task using 27 pictures from PHODA (Photograph Series of Daily Activities). HRV frequency domains were measured before, during, and after the task. Pressure pain threshold and pain intensity were also measured before and after the task.

RESULTS

The adjusted mean difference was statistically significant for HRV frequency domains during the visualization task, including low frequency [-5.92; 95% confidence interval (CI)=-9.60 to -2.23], high frequency (-0.71; 95% CI=-1.02 to -0.39), and low-frequency/high-frequency ratio (8.82; 95% CI=5.19 to 12.45). Pressure pain threshold decreased after the task in the CLBP group in all body sites, and pain intensity increased (-0.8; 95% CI=-1.16 to -0.39).

DISCUSSION

Aversive environmental stimuli, such as visual cues, may generate defensive physiological reactions. HRV can provide a measure that reflects the perceptions of threat and safety in the environment. Participants with CLBP presented changes in sympathovagal balance during passive visualization of pictures of daily activities, higher pain sensitivity, and high pain intensity when they were exposed to a passive visualization task using pictures of daily living that may arouse fears of harm.

An attentional perspective on differential fear conditioning in chronic pain: The informational value of safety cues

Differences in fear conditioning between individuals suffering from chronic pain and healthy controls may indicate a learning bias that contributes to the acquisition and persistence of chronic pain. However, evidence from lab-controlled conditioning studies is sparse and previous experiments have produced inconsistent findings. Twenty-five participants suffering from chronic back pain and twenty-five controls not reporting chronic pain took part in a differential fear conditioning experiment measuring attention (eye tracking) and autonomic arousal (pupil dilation and skin conductance) elicited by visual cues predicting the presence or absence of electric shock. In contrast to the healthy control group, participants with chronic pain did not acquire differential autonomic responding to cues of threat and safety and specifically failed to acquire any attentional preference for the safety cue over irrelevant contextual cues (while such preference was intact for the threat cue). We present simulations of a reinforcement learning model to show how the pattern of data can be explained by assuming that participants with chronic pain might have experienced less positive emotion (relief) when the electric shock was absent following safety cues. Our model shows how this assumption can explain both, reduced differential responding to cues of threat and safety as well as less selective attention to the safety cue.

What is the link between migraine and psychiatric disorders? From epidemiology to therapeutics

The association between migraine and psychiatric disorders is well documented through numerous population-based studies. The results of these studies are coherent and show an increased risk of suffering from depression, bipolar disorders, numerous anxiety disorders, especially post-traumatic stress disorder. This raises the question of stress as a precipitating factor for migraine illness. Psychiatric comorbidity is even more frequent in chronic migraine than in episodic migraine patients. Many prospective studies have shown that psychiatric comorbidity could be considered as a risk factor for migraine chronicization. Psychiatric comorbidity is also responsible for an increase of the frequency of anti-migraine drug intake, a worsening of quality of life and a worsening of functional impairment. It is also responsible for an increase in the direct and indirect costs of migraine. The reason why psychiatric comorbidity is so high in migraineurs is not unambiguous. Multiple causal relationships and common etiological factors are linked. Recently, genome-wide association studies gave leads to a genetic common heritability between major depressive disorder and migraine. For clinicians, an important topic remains how to treat migraineurs with psychiatric comorbidity. These patients suffer frequently from severe migraine or refractory migraine. Antidepressant and anti-convulsive drugs can be useful, as well as psychological therapies. But moreover, it is of utmost importance to propose an integrated multidisciplinary approach to these difficult patients.

Imprecise Visual Feedback About Hand Location Increases a Classically Conditioned Pain Expectancy Effect

We tested the hypotheses that rendering sensory input about hand location imprecise increases a classically conditioned pain expectancy effect, increases generalization of the effect to novel locations and reduces extinction of the effect. Forty healthy volunteers performed movements with their right hand along predefined paths. Each path passed through 2 locations that were defined as either i) the conditioned stimulus (CS+; paired with a painful unconditioned stimulus), or ii) unpaired (CS-). During acquisition phase, participants watched their hand as they moved it. Participants were randomly allocated to an Imprecise group, for whom visual feedback of the hand was offset 30 to 50 mm from its true location, or a Precise group, for whom vision was not disrupted. In the test phase, participants moved their hands to 5 locations-the CS+, CS-, and 3 locations that lay between the 2 ("generalization stimuli"). Our primary hypothesis was supported-pain expectancy was greater at the CS+ location in the Imprecise group than in the Precise group (6.9 [SD = 1.9] vs 5.4 [SD = 2.5], P= .02). Pain expectancies generalized to novel locations similarly in both groups and there was no difference in extinction between groups. Our primary hypothesis was supported but our subsequent hypotheses were not. PERSPECTIVE: We conditioned pain expectancy at a certain location of one hand, even though most participants were unaware of the contingency. Conditioned pain expectancy was greater when sensory information about location was less precise. This adds support to the possibility that associative learning may play a role in the progression of an acute pain episode to a more generalized pain disorder.

When gut feelings teach the brain to fear pain: Context-dependent activation of the central fear network in a novel interoceptive conditioning paradigm

The relevance of contextual factors in shaping neural mechanisms underlying visceral pain-related fear learning remains elusive. However, benign interoceptive sensations, which shape patients' clinical reality, may context-dependently become conditioned predictors of impending visceral pain. In a novel context-dependent interoceptive conditioning paradigm, we elucidated the putative role of the central fear network in the acquisition and extinction of pain-related fear induced by interoceptive cues and pain-predictive contexts. In this fMRI study involving rectal distensions as a clinically-relevant model of visceroception, N = 27 healthy men and women underwent differential conditioning. During acquisition training, visceral sensations of low intensity as conditioned stimuli (CS) predicted visceral pain as unconditioned stimulus (US) in one context (Con⁺), or safety from pain in another context (Con^-). During extinction training, interoceptive CS remained unpaired in both contexts, which were operationalized as images of different rooms presented in the MRI scanner. Successful contextual conditioning was supported by increased negative valence of Con⁺ compared to Con^- after acquisition training, which resolved after extinction training. Although interoceptive CS were perceived as comparatively pleasant, they induced significantly greater neural activation of the amygdala, ventromedial PFC, and hippocampus when presented in Con⁺, while contexts alone did not elicit differential responses. During extinction training, a shift from CS to context differentiation was observed, with enhanced responses in the amygdala, ventromedial, and ventrolateral PFC to Con⁺ relative to Con^-, whereas no CS-induced differential activation emerged. Context-dependent interoceptive conditioning can turn benign interoceptive cues into predictors of visceral pain that recruit key regions of the fear network. This first evidence expands knowledge about learning and memory mechanisms underlying interoceptive hypervigilance and maladaptive avoidance behavior, with implications for disorders of the gut-brain axis.

Optimizing Long-term Outcomes of Exposure for Chronic Primary Pain from the Lens of Learning Theory

Exposure in vivo is a theory-driven and widely used treatment to tackle functional disability in people with chronic primary pain. Exposure is quite effective; yet, in line with exposure outcomes for anxiety disorders, a number of patients may not profit from it, or relapse. In this focus article, we critically reflect on the current exposure protocols in chronic primary pain, and provide recommendations on how to optimize them. We propose several adaptations that are expected to strengthen inhibitory learning and/or retrieval of the extinction memory, thus likely decreasing relapse. We summarize the limited, but emerging experimental data in the pain domain, and draw parallels with experimental evidence in the anxiety literature. Our reflections and suggestions pertain to the use of the fear hierarchy, reassurance, positive psychology interventions, exposure with a range of stimuli and within different contexts, and the use of safety behaviors during treatment, as well as associating the fear-inducing stimuli with novel outcomes. In addition, we reflect on the importance of specifically tackling (the return of) pain-related avoidance behavior with techniques such as disentangling fear from avoidance and reinforcing approach behaviors. Finally, we discuss challenges in the clinical application of exposure to improve functioning in chronic primary pain and possible avenues for future research. Perspectives: Inspired by recent advances in learning theory and its applications on the treatment of anxiety disorders, we reflect on the delivery of exposure treatment for chronic primary pain and propose strategies to improve its long-term outcomes.

Neural correlates of conditioned pain responses in fibromyalgia subjects indicate preferential formation of new pain associations rather than extinction of irrelevant ones

Supplemental Digital Content is Available in the Text.

Functional magnetic resonance imaging pain conditioning data suggest that fibromyalgia prioritizes updating their cerebral representation to forming new potential pain-related associations while simultaneously maintaining no longer relevant ones.

Behavioral studies have demonstrated aberrant safety processing in fibromyalgia subjects (FMSs) and suggested that patients accumulate new potential pain-related threats more effectively than extinguishing no longer relevant ones. The aim of the current study was to investigate the neural correlates of conditioned pain responses and their relationship with emotional distress in FMS (n = 67) and healthy controls (HCs, n = 34). Using functional magnetic resonance imaging, we traced conditioned pain responses to an identical moderately painful pressure (P30) depending on whether it was following a green (P30green) or a red (P30red) cue. The cues were previously associated with individually calibrated painful pressure stimuli of low and high intensity, corresponding to visual analogue scale 10 and 50 mm, respectively. Fibromyalgia subjects displayed increased P30green ratings over time, while P30red ratings remained elevated. Healthy controls adapted all pain ratings to resemble moderate pain. Fibromyalgia subjects exhibited increased activation for [P30green>P30red] in M1/anterior insula, whereas HC showed increased S2/mid-insula response to [P30red>P30green]. High pain catastrophizing scale (PCS) ratings in fibromyalgia (FM) covaried with heightened brain activation for [P30green] × PCS in left dorsolateral prefrontal cortex and medial prefrontal cortex/orbitofrontal cortex; and [P30green>P30red] × PCS in dorsal anterior cingulate cortex/mid-cingulate cortex; superior temporal pole, extending to anterior insula; bilateral thalamus; and posterior insula. Psychophysiological interaction analysis for FM [P30green>P30red] × PCS revealed a dissociation in functional connectivity between thalamus and bilateral inferior parietal lobe. In alignment with behavioral data, FMS displayed a cerebral response suggesting preferential formation of new pain-related associations while simultaneously maintaining no longer relevant ones. The opposite was observed in HC. Increased responses to pain-related threats in FM may contribute to dysfunctional pain-protective behaviors and disability.

Associative learning and extinction of conditioned threat predictors across sensory modalities

The formation and persistence of negative pain-related expectations by classical conditioning remain incompletely understood. We elucidated behavioural and neural correlates involved in the acquisition and extinction of negative expectations towards different threats across sensory modalities. In two complementary functional magnetic resonance imaging studies in healthy humans, differential conditioning paradigms combined interoceptive visceral pain with somatic pain (study 1) and aversive tone (study 2) as exteroceptive threats. Conditioned responses to interoceptive threat predictors were enhanced in both studies, consistently involving the insula and cingulate cortex. Interoceptive threats had a greater impact on extinction efficacy, resulting in disruption of ongoing extinction (study 1), and selective resurgence of interoceptive CS-US associations after complete extinction (study 2). In the face of multiple threats, we preferentially learn, store, and remember interoceptive danger signals. As key mediators of nocebo effects, conditioned responses may be particularly relevant to clinical conditions involving disturbed interoception and chronic visceral pain.

A picture is worth a thousand words: linking fibromyalgia pain widespreadness from digital pain drawings with pain catastrophizing and brain cross-network connectivity

ABSTRACT

Pain catastrophizing is prominent in chronic pain conditions such as fibromyalgia and has been proposed to contribute to the development of pain widespreadness. However, the brain mechanisms responsible for this association are unknown. We hypothesized that increased resting salience network (SLN) connectivity to nodes of the default mode network (DMN), representing previously reported pain-linked cross-network enmeshment, would be associated with increased pain catastrophizing and widespreadness across body sites. We applied functional magnetic resonance imaging (fMRI) and digital pain drawings (free-hand drawing over a body outline, analyzed using conventional software for multivoxel fMRI analysis) to investigate precisely quantified measures of pain widespreadness and the associations between pain catastrophizing (Pain Catastrophizing Scale), resting brain network connectivity (Dual-regression Independent Component Analysis, 6-minute multiband accelerated fMRI), and pain widespreadness in fibromyalgia patients (N = 79). Fibromyalgia patients reported pain in multiple body areas (most frequently the spinal region, from the lower back to the neck), with moderately high pain widespreadness (mean ± SD: 26.1 ± 24.1% of total body area), and high pain catastrophizing scale scores (27.0 ± 21.9, scale range: 0-52), which were positively correlated (r = 0.26, P = 0.02). A whole-brain regression analysis focused on SLN connectivity indicated that pain widespreadness was also positively associated with SLN connectivity to the posterior cingulate cortex, a key node of the DMN. Moreover, we found that SLN-posterior cingulate cortex connectivity statistically mediated the association between pain catastrophizing and pain widespreadness (P = 0.01). In conclusion, we identified a putative brain mechanism underpinning the association between greater pain catastrophizing and a larger spatial extent of body pain in fibromyalgia, implicating a role for brain SLN-DMN cross-network enmeshment in mediating this association.

Does muscular or mental fatigue have an influence on the nociceptive flexion reflex? A randomized cross-over study in healthy people

BACKGROUND

The nociceptive flexion reflex (NFR) is a spinally-mediated withdrawal reflex occurring in response to noxious stimuli and is used as an electrophysiological marker of spinal nociception. Although it is well-documented that the NFR is subject to powerful modulation of several personal factors, the effects of experimentally induced fatigue on the NFR have not yet been examined. Hence, this study aimed to characterize if and how fatigue affects spinal nociception in healthy adults.

METHODS

The NFR of 58 healthy people was measured prior to and following rest and two fatiguing tasks performed in randomized order. The NFR was elicited by transcutaneous electrical stimulation of the sural nerve and objectified by electromyographic recordings from the biceps femoris muscle. An isokinetic fatiguing protocol was used to induce localized muscle fatigue of the hamstrings. The modified incongruent Stroop-word task was used to provoke mental fatigue. A linear mixed model analysis was performed to assess the influence of fatigue on the NFR.

RESULTS

Low-to-moderate levels experimentally induced localized muscle and mental fatigue did not affect the NFR in healthy adults. These results suggest that descending pain inhibitory processes to dampen spinal nociception are resistant to the effects of localized muscle and mental fatigue.

CONCLUSIONS

The relative robustness of the NFR to fatigue may be beneficial in both clinical and research settings where the influence of confounders complicates interpretation. Furthermore, the findings possibly help enhance our understanding on why even demanding cognitive/physical exercise-based treatment programs form effective treatment strategies for patients with chronic pain.

SIGNIFICANCE

The present study unraveled that low-to-moderate levels experimentally induced localized muscle and mental fatigue did not affect the NFR. These results suggest that descending pain inhibitory processes to dampen spinal nociception are resistant to the effects of localized muscle and mental fatigue. This relative robustness of the NFR may be beneficial in a clinical setting in which the evaluation of spinal nociception that is unaffected by clinical symptoms of fatigue may be useful (e.g. chronic fatigue syndrome, cancer-related fatigue, etc.).

Will that hurt? A contingency learning task to assess pain-expectancy judgments for low back postures

BACKGROUND AND OBJECTIVES

Contingency learning, i.e. learning that a cue predicts the presence (or absence) of an event, is central to the formation of beliefs regarding painfulness of body postures. Such beliefs may spread to safe cues due to compromised learning (e.g., excessive generalization, impaired safety learning), prompting avoidance and leading to disability. Despite its importance, compromised learning about low back pain is underinvestigated. We propose a low back pain scenario contingency learning task for the investigation of back pain-related learning.

METHODS

Sixty healthy participants viewed pictures of an avatar in various back postures, and for each posture gave pain-expectancy judgments and viewed the verbal outcome (pain/no pain) for a fictive back pain patient. During acquisition, one posture was followed by pain (conditioned stimulus; CS+), whereas another was not (CS-). During generalization, unreinforced novel intermediate back postures (generalization stimuli; GSs) were tested. During extinction, only the CSs were presented, not followed by pain. During generalization of extinction, only the GSs were presented, not followed by pain.

RESULTS

Participants expected pain more for the CS + than the CS- (differential acquisition) and generalized their pain-expectancy to the GS most similar to the CS+ (generalization). During extinction, pain-expectancy for the CS + decreased and generalized to the GS most similar to the CS+ (generalization of extinction).

LIMITATIONS

Future research should investigate generalizability of findings to clinical samples and consider the role of pre-existing pain threat beliefs.

CONCLUSIONS

This task is an easily applicable, non-invasive way to investigate the formation of back pain-related threat beliefs.

An experimental investigation into the mediating role of pain-related fear in boosting nocebo hyperalgesia

Nocebo hyperalgesia refers to increases in perceived pain that putatively result from negative expectations regarding a nocebo stimulus (eg, an inert treatment, compared with no treatment). The precise cognitive-emotional factors contributing to the origins of nocebo effects are poorly understood. We aimed to test the effects of experimentally induced pain-related fear on the acquisition and extinction of nocebo hyperalgesia in healthy participants (N = 72). Acquisition and extinction of nocebo hyperalgesia were compared between a group receiving standard nocebo conditioning (Control group) and 2 groups receiving distinct fear inductions: high intensity of pain stimulations (High-pain group) or a threat manipulation (High-threat group). During nocebo acquisition, the Control and High-threat groups were administered thermal pain stimulations of moderate intensity paired with sham electrical stimulation (nocebo trials), whereas high pain intensity was administered to the High-pain group. During extinction, equivalent pain intensities were administered across all trials. Pain-related fear was measured by eyeblink startle electromyography and self-report. Nocebo hyperalgesia occurred in all groups. Nocebo effects were significantly larger in the High-pain group than those in the Control group. This effect was mediated by self-reported fear, but not by fear-potentiated startle. Groups did not differ in the extinction rate. However, only the High-pain group maintained significant nocebo responses at the end of extinction. Anticipatory pain-related fear induced through a threat manipulation did not amplify nocebo hyperalgesia. These findings suggest that fear of high pain may be a key contributor to the amplification of nocebo hyperalgesia, only when high pain is experienced and not when it is merely anticipated.

Using Visual Feedback Manipulation in Virtual Reality to Influence Pain-Free Range of Motion in People with Nonspecific Neck Pain

Background

Based on associative learning theories it is hypothesized that pain might be a conditioned response. In people with musculoskeletal pain, the occurrence of movement‐induced pain might be a protective response, influenced by visual cues suggesting that the person is approaching a painful position. This study aimed to determine (1) whether the pain‐free range of motion (ROM) increased and decreased when visual feedback understated or overstated true rotation in people with neck pain and (2) whether this effect was more pronounced if pain was chronic.

Method

People with subacute and chronic nonspecific neck pain wore a VR‐headset and rotated their head to the left and right until the onset of pain. Visual feedback about the amount of movement was either equal, 20% less, or 20% greater than their actual rotation. Maximal pain‐free ROM was measured using the VR‐headset sensors. Data were analyzed using a mixed‐design ANOVA.

Results

There was no effect of visual feedback manipulation on pain‐free ROM (P = 0.13) and no interaction effect between the visual feedback condition and duration of pain (P = 0.86).

Discussion

The inability to influence pain‐free ROM by manipulating visual feedback in people with subacute or chronic neck pain does not support associative learning theories for the perception of neck pain.

Transition from acute to chronic pain: where cells, systems and society meet

Current treatments for chronic pain are often ineffective. At the same as searching for novel therapeutics, there is growing interest in preventing acute pain becoming chronic. While the field is still in its infancy, its knowledge base is increasingly expanding. Certainly, biomedical factors, for example, the type of tissue damage, are important but they are often not modifiable. Psychosocial risk factors (e.g., thoughts and beliefs about pain, mood, social support, workplace problems) are modifiable. There is an increasing body of research that cognitive behavioral therapy can prevent transition. Internet-based delivery of cognitive behavioral therapy improves access. Clinicians need to be aware that they may inadvertently promote pain chronification in their patients by what they say and do.

When Implicit Prosociality Trumps Selfishness: The Neural Valuation System Underpins More Optimal Choices When Learning to Avoid Harm to Others Than to Oneself

Humans learn quickly which actions cause them harm. As social beings, we also need to learn to avoid actions that hurt others. It is currently unknown whether humans are as good at learning to avoid others' harm (prosocial learning) as they are at learning to avoid self-harm (self-relevant learning). Moreover, it remains unclear how the neural mechanisms of prosocial learning differ from those of self-relevant learning. In this fMRI study, 96 male human participants learned to avoid painful stimuli either for themselves or for another individual. We found that participants performed more optimally when learning for the other than for themselves. Computational modeling revealed that this could be explained by an increased sensitivity to subjective values of choice alternatives during prosocial learning. Increased value sensitivity was further associated with empathic traits. On the neural level, higher value sensitivity during prosocial learning was associated with stronger engagement of the ventromedial PFC during valuation. Moreover, the ventromedial PFC exhibited higher connectivity with the right temporoparietal junction during prosocial, compared with self-relevant, choices. Our results suggest that humans are particularly adept at learning to protect others from harm. This ability appears implemented by neural mechanisms overlapping with those supporting self-relevant learning, but with the additional recruitment of structures associated to the social brain. Our findings contrast with recent proposals that humans are egocentrically biased when learning to obtain monetary rewards for self or others. Prosocial tendencies may thus trump egocentric biases in learning when another person's physical integrity is at stake.SIGNIFICANCE STATEMENT We quickly learn to avoid actions that cause us harm. As "social animals," we also need to learn and consider the harmful consequences our actions might have for others. Here, we investigated how learning to protect others from pain (prosocial learning) differs from learning to protect oneself (self-relevant learning). We found that human participants performed better during prosocial learning than during self-relevant learning, as they were more sensitive toward the information they collected when making choices for the other. Prosocial learning recruited similar brain areas as self-relevant learning, but additionally involved parts of the "social brain" that underpin perspective-taking and self-other distinction. Our findings suggest that people show an inherent tendency toward "intuitive" prosociality.

Impact of acute inflammation on the extinction of aversive gut memories

Impaired extinction of pain-related fear memories can lead to persistent or resurging fear of pain, contributing to the development and maintenance of chronic pain conditions. The mechanisms underlying maladaptive pain-related learning and memory processes remain incompletely understood, particularly in the context of interoceptive, visceral pain. Inflammation is known to interfere with learning and memory, but its effects on the extinction of pain-related fear memories have never been tested. In a randomized, double-blind, placebo-controlled study, we assessed the impact of experimental acute inflammation on the extinction and reinstatement of conditioned visceral pain-related fear. Forty healthy male volunteers underwent differential fear conditioning with visceral pain as clinically relevant unconditioned stimulus (US). Participants then received an intravenous injection of either 0.8 ng/kg lipopolysaccharide (LPS) as inflammatory stimulus or physiological saline as placebo, and extinction training was conducted at the peak of the inflammatory response. Extinction recall and reinstatement test were performed after overnight consolidation. Results showed that visceral pain represents an effective US, eliciting pronounced conditioned pain-related fear responses. Repeated unreinforced presentation of the pain-predictive cue during extinction training resulted in full extinction of the conditioned behavioral response. However, unexpected re-exposure to the US during reinstatement test resulted in return of fear. Despite pronounced LPS-induced effects on inflammatory markers, cortisol, and negative affect, we did not find evidence that acute inflammation resulted in altered fear extinction. The findings support the notion that visceral pain-related fear learning establishes a robust aversive memory trace that remains preserved during inhibitory learning, leaving a latent vulnerability for the return of fear. Inflammation during inhibitory learning did neither weaken nor further amplify this aversive memory trace, suggesting that it is rather resistant to acute inflammation-induced effects, at least in healthy individuals with no additional vulnerability factors.