The Subjective Experience of Pain: An FMRI Study of Percept-Related Models and Functional Connectivity

Causal interactions in brain networks predict pain levels in trigeminal neuralgia

Trigeminal neuralgia (TN) is a highly debilitating facial pain condition. Magnetic resonance imaging (MRI) is the main method for generating insights into the central mechanisms of TN pain in humans. Studies have found both structural and functional abnormalities in various brain structures in TN patients as compared with healthy controls. Whereas studies have also examined aberrations in brain networks in TN, no studies have to date investigated causal interactions in these brain networks and related these causal interactions to the levels of TN pain. We recorded fMRI data from 39 TN patients who either rested comfortably in the scanner during the resting state session or tracked their pain levels during the pain tracking session. Applying Granger causality to analyze the data and requiring consistent findings across the two scanning sessions, we found 5 causal interactions, including: (1) Thalamus → dACC, (2) Caudate → Inferior temporal gyrus, (3) Precentral gyrus → Inferior temporal gyrus, (4) Supramarginal gyrus → Inferior temporal gyrus, and (5) Bankssts → Inferior temporal gyrus, that were consistently associated with the levels of pain experienced by the patients. Utilizing these 5 causal interactions as predictor variables and the pain score as the predicted variable in a linear multiple regression model, we found that in both pain tracking and resting state sessions, the model was able to explain ∼36 % of the variance in pain levels, and importantly, the model trained on the 5 causal interaction values from one session was able to predict pain levels using the 5 causal interaction values from the other session, thereby cross-validating the models. These results, obtained by applying novel analytical methods to neuroimaging data, provide important insights into the pathophysiology of TN and could inform future studies aimed at developing innovative therapies for treating TN.

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

AIM

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

METHOD

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

RESULTS

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

CONCLUSION

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

Habituation to pain: self-report, electroencephalography, and functional magnetic resonance imaging in healthy individuals. A scoping review and future recommendations

ABSTRACT

Habituation to pain is a fundamental learning process and important adaption. Yet, a comprehensive review of the current state of the field is lacking. Through a systematic search, 63 studies were included. Results address habituation to pain in healthy individuals based on self-report, electroencephalography, or functional magnetic resonance imaging. Our findings indicate a large variety in methods, experimental settings, and contexts, making habituation a ubiquitous phenomenon. Habituation to pain based on self-report studies shows a large influence of expectations, as well as the presence of individual differences. Furthermore, widespread neural effects, with sometimes opposing effects in self-report measures, are noted. Electroencephalography studies showed habituation of the N2-P2 amplitude, whereas functional magnetic resonance imaging studies showed decreasing activity during painful repeated stimulation in several identified brain areas (cingulate cortex and somatosensory cortices). Important considerations for the use of terminology, methodology, statistics, and individual differences are discussed. This review will aid our understanding of habituation to pain in healthy individuals and may lead the way to improving methods and designs for personalized treatment approaches in chronic pain patients.

Antecedents of patient health engagement in the radiotherapy service (evidence from Indonesia)

Background

Private radiotherapy (RT) facilities in emerging countries are growing with cancer incidence. Private healthcare providers must provide better care based on patient perspectives to reach more patients.

Aim

This study investigated the relationship between antecedents of patient health engagement (PHE) with revisit intention (RVI) and intent to recommend (ITR) in private RT facilities.

Setting

The survey was conducted in a private hospital with a RT service in Central Java province, Indonesia.

Methods

A quantitative, cross-sectional design with a purposive sampling method was used. Patient questionnaire survey modified from validated self-administered radiotherapy experience (RTEQ) and PHE questionnaire were used to collect data. Partial least squares-structural equation modelling was used to analyse the data.

Results

In this study, 173 respondents consented to participate, which demonstrated that seven of the eight experience antecedents of PHE measured by reliable and valid RTEQ and were significantly related to PHE (p-value <0.05). At the same time, the degree of PHE has a significant relationship with RVI and ITR (p-value <0.05).

Conclusion

Patient informational needs elements from the patient experience, followed by situational repose, were shown to have a prominent relation to PHE. The management of private RT facilities needs to focus more on these elements to encourage PHE to establish hospital performance.

Contribution

The findings denote that six elements of RTEQ relate to PHE and further hospital outcomes. Hospital management could utilise this approach to improve the quality of care in RT facilities, specifically in private hospitals in emerging countries.

Functional Changes of White Matter Are Related to Human Pain Sensitivity during Sustained Nociception

Pain is considered an unpleasant perceptual experience associated with actual or potential somatic and visceral harm. Human subjects have different sensitivity to painful stimulation, which may be related to different painful response pattern. Excellent studies using functional magnetic resonance imaging (fMRI) have found the effect of the functional organization of white matter (WM) on the descending pain modulatory system, which suggests that WM function is feasible during pain modulation. In this study, 26 pain sensitive (PS) subjects and 27 pain insensitive (PIS) subjects were recruited based on cold pressor test. Then, all subjects underwent the cold bottle test (CBT) in normal (26 degrees temperature stimulating) and cold (8 degrees temperature stimulating) conditions during fMRI scan, respectively. WM functional networks were obtained using K-means clustering, and the functional connectivity (FC) was assessed among WM networks, as well as gray matter (GM)-WM networks. Through repeated measures ANOVA, decreased FC was observed between the GM-cerebellum network and the WM-superior temporal network, as well as the WM-sensorimotor network in the PS group under the cold condition, while this difference was not found in PIS group. Importantly, the changed FC was positively correlated with the state and trait anxiety scores, respectively. This study highlighted that the WM functional network might play an integral part in pain processing, and an altered FC may be related to the descending pain modulatory system.

Nociceptor-Macrophage Interactions in Apical Periodontitis: How Biomolecules Link Inflammation with Pain

Periradicular tissues have a rich supply of peripheral afferent neurons, also known as nociceptive neurons, originating from the trigeminal nerve. While their primary function is to relay pain signals to the brain, these are known to be involved in modulating innate and adaptive immunity by initiating neurogenic inflammation (NI). Studies have investigated neuroanatomy and measured the levels of biomolecules such as cytokines and neuropeptides in human saliva, gingival crevicular fluid, or blood/serum samples in apical periodontitis (AP) to validate the possible role of trigeminal nociceptors in inflammation and tissue regeneration. However, the contributions of nociceptors and the mechanisms involved in the neuro-immune interactions in AP are not fully understood. This narrative review addresses the complex biomolecular interactions of trigeminal nociceptors with macrophages, the effector cells of the innate immune system, in the clinical manifestations of AP.

One Year of Outpatient Dialectical Behavioral Therapy and Its Impact on Neuronal Correlates of Attachment Representation in Patients with Borderline Personality Disorder Using a Personalized fMRI Task

(1) Background: BPD is characterized by affect dysregulation, interpersonal problems, and disturbances in attachment, but neuroimaging studies investigating attachment representations in BPD are rare. No study has examined longitudinal neural changes associated with interventions targeting these impairments. (2) Methods: We aimed to address this gap by performing a longitudinal neuroimaging study on n = 26 patients with BPD treated with Dialectic Behavioral Therapy (DBT) and n = 26 matched healthy controls (HCs; post intervention point: n = 18 BPD and n = 23 HCs). For functional imaging, we applied an attachment paradigm presenting attachment related scenes represented in drawings paired with related neutral or personalized sentences from one's own attachment narratives. In a prior cross-sectional investigation, we identified increased fMRI-activation in the human attachment network, in areas related to fear response and the conflict monitoring network in BPD patients. These were especially evident for scenes from the context of loneliness (monadic pictures paired with individual narrative sentences). Here, we tested whether these correlates of attachment representation show a near-to-normal development over one year of DBT intervention. In addition, we were interested in possible associations between fMRI-activation in these regions-of-interest (ROI) and clinical scores. (3) Results: Patients improved clinically, showing decreased symptoms of borderline personality organization (BPI) and increased self-directedness (Temperament and Character Inventory, TCI) over treatment. fMRI-activation was increased in the anterior medial cingulate cortex (aMCC) and left amygdala in BPD patients at baseline which was absent after intervention. When investigating associations between scores (BPI, TCI) and functional activation, we found significant effects in the bilateral amygdala. In contrast, aMCC activation at baseline was negatively associated with treatment outcome, indicating less effective treatment effects for those with higher aMCC activation at baseline. (4) Conclusions: Monadic attachment scenes with personalized sentences presented in an fMRI setup are capable of identifying increased activation magnitude in BPD. After successful DBT treatment, these increased activations tend to normalize which could be interpreted as signs of a better capability to regulate intensive emotions in the context of "social pain" towards a more organized/secure attachment representation. Amygdala activation, however, indicates high correlations with pre-treatment scores; activation in the aMCC is predictive for treatment gain. Functional activation of the amygdala and the aMCC as a response to attachment scenes representing loneness at baseline might be relevant influencing factors for DBT-intervention outcomes.

Altered functional brain network patterns in patients with migraine without aura after transcutaneous auricular vagus nerve stimulation

Transcutaneous auricular vagus nerve stimulation (taVNS) shows excellent effects on relieving clinical symptoms in migraine patients. Nevertheless, the neurological mechanisms of taVNS for migraineurs remain unclear. In recent years, voxel-wise degree centrality (DC) and functional connectivity (FC) methods were extensively utilized for exploring alterations in patterns of FC in the resting-state brain. In the present study, thirty-five migraine patients without aura and thirty-eight healthy controls (HCs) were recruited for magnetic resonance imaging scans. Firstly, this study used voxel-wise DC analysis to explore brain regions where abnormalities were present in migraine patients. Secondly, for elucidating neurological mechanisms underlying taVNS in migraine, seed-based resting-state functional connectivity analysis was employed to the taVNS treatment group. Finally, correlation analysis was performed to explore the relationship between alterations in neurological mechanisms and clinical symptoms. Our findings indicated that migraineurs have lower DC values in the inferior temporal gyrus (ITG) and paracentral lobule than in healthy controls (HCs). In addition, migraineurs have higher DC values in the cerebellar lobule VIII and the fusiform gyrus than HCs. Moreover, after taVNS treatment (post-taVNS), patients displayed increased FC between the ITG with the inferior parietal lobule (IPL), orbitofrontal gyrus, angular gyrus, and posterior cingulate gyrus than before taVNS treatment (pre-taVNS). Besides, the post-taVNS patients showed decreased FC between the cerebellar lobule VIII with the supplementary motor area and postcentral gyrus compared with the pre-taVNS patients. The changed FC of ITG-IPL was significantly related to changes in headache intensity. Our study suggested that migraine patients without aura have altered brain connectivity patterns in several hub regions involving multisensory integration, pain perception, and cognitive function. More importantly, taVNS modulated the default mode network and the vestibular cortical network related to the dysfunctions in migraineurs. This paper provides a new perspective on the potential neurological mechanisms and therapeutic targets of taVNS for treating migraine.

Imaging the neural substrate of trigeminal neuralgia pain using deep learning

Trigeminal neuralgia (TN) is a severe and disabling facial pain condition and is characterized by intermittent, severe, electric shock-like pain in one (or more) trigeminal subdivisions. This pain can be triggered by an innocuous stimulus or can be spontaneous. Presently available therapies for TN include both surgical and pharmacological management; however, the lack of a known etiology for TN contributes to the unpredictable response to treatment and the variability in long-term clinical outcomes. Given this, a range of peripheral and central mechanisms underlying TN pain remain to be understood. We acquired functional magnetic resonance imaging (fMRI) data from TN patients who (1) rested comfortably in the scanner during a resting state session and (2) rated their pain levels in real time using a calibrated tracking ball-controlled scale in a pain tracking session. Following data acquisition, the data was analyzed using the conventional correlation analysis and two artificial intelligence (AI)-inspired deep learning methods: convolutional neural network (CNN) and graph convolutional neural network (GCNN). Each of the three methods yielded a set of brain regions related to the generation and perception of pain in TN. There were 6 regions that were identified by all three methods, including the superior temporal cortex, the insula, the fusiform, the precentral gyrus, the superior frontal gyrus, and the supramarginal gyrus. Additionally, 17 regions, including dorsal anterior cingulate cortex (dACC) and the thalamus, were identified by at least two of the three methods. Collectively, these 23 regions are taken to represent signature centers of TN pain and provide target areas for future studies seeking to understand the central mechanisms of TN.

Peripheral neuropathies associated with DNA repair disorders

Repair of genomic DNA is a fundamental housekeeping process that quietly maintains the health of our genomes. The consequences of a genetic defect affecting a component of this delicate mechanism are quite harmful, characterized by a cascade of premature aging that injures a variety of organs, including the nervous system. One part of the nervous system that is impaired in certain DNA repair disorders is the peripheral nerve. Chronic motor, sensory, and sensorimotor polyneuropathies have all been observed in affected individuals, with specific physiologies associated with different categories of DNA repair disorders. Cockayne syndrome has classically been linked to demyelinating polyneuropathies, whereas xeroderma pigmentosum has long been associated with axonal polyneuropathies. Three additional recessive DNA repair disorders are associated with neuropathies, including trichothiodystrophy, Werner syndrome, and ataxia-telangiectasia. Although plausible biological explanations exist for why the peripheral nerves are specifically vulnerable to impairments of DNA repair, specific mechanisms such as oxidative stress remain largely unexplored in this context, and bear further study. It is also unclear why different DNA repair disorders manifest with different types of neuropathy, and why neuropathy is not universally present in those diseases. Longitudinal physiological monitoring of these neuropathies with serial electrodiagnostic studies may provide valuable noninvasive outcome data in the context of future natural history studies, and thus the responses of these neuropathies may become sentinel outcome measures for future clinical trials of treatments currently in development such as adeno-associated virus gene replacement therapies.

Neuropathic pain, cognitive fusion, and alexithymia in patients with multiple sclerosis: Cross-sectional evidence for an explanatory model of anxiety symptoms

Multiple sclerosis (MS) presents a high prevalence, a marked increase worldwide, and a relevant impact on patients, public health, and society. Anxiety often cooccurs with MS and can contribute to the worsening of MS symptoms. However, knowledge about predictors of anxiety in Patients with MS (PwMS) is scarce.

OBJECTIVE

This preliminary study explored a novel model for anxiety symptoms in PwMS, including neuropathic pain (NeP), cognitive fusion (CF), experiential avoidance (EA), and alexithymia as explanatory factors.

METHOD

This cross-sectional study integrated two independent convenience samples: 107 PwMS recruited from the Portuguese Society for Multiple Sclerosis and 97 age- and gender-matched participants without the MS diagnosis (no-MS sample) recruited from the Portuguese general population. Self-report questionnaires that measured the constructs included in the model were administered to both groups.

RESULTS

PwMS showed significantly higher values regarding anxiety symptoms and their explanatory variables (NeP, CF, EA, alexithymia) in comparison to non-MS participants. In the MS sample, no correlations were found between anxiety symptoms and sociodemographic and clinical characteristics. NeP, CF, and alexithymia showed significant correlations with anxiety symptoms and significantly explained this symptomatology in simple linear regression models. Thus, these variables were retained in the multiple linear regression model and emerged as significant regressors that together explained 38% of the variance in anxious symptomatology in PwMS.

CONCLUSIONS

This preliminary study provides novel evidence on NeP and some maladaptive emotion regulation strategies related to EA/psychological inflexibility, as vulnerability to anxiety in PwMS can be considerably increased by CF and alexithymia. Clinical implications were discussed.

Feeling the music: The feel and sound of songs attenuate pain

BACKGROUND

Extensive research has demonstrated that music and touch can separately attenuate perceived pain intensity. However, little research has investigated how auditory and tactile stimulation can synergistically enhance pain attenuation by music. In the current study, we investigated whether tactile stimulation can enhance music-induced analgesia for noxious force stimulation on the fingertip.

METHODS

We systematically applied force to 34 listeners' fingertips to induce pain. We then compared the force measurement (in Newton) that gave rise to the same perceived moderate pain intensity when listeners were presented their self-selected liked or disliked song with auditory-only, tactile-only and auditory-tactile stimulation. Higher force indicated less perceived pain. The tactile stimulation were low-frequency modulations extracted from the songs and presented as vibrations on the wrist.

RESULTS

The results showed a significant interaction between song preference and stimulation condition. Listeners had higher force measurements at the same moderate pain for their liked compared to disliked song only in the auditory-tactile condition. They also had higher force measurements for their liked song with auditory-tactile stimulation compared to the other remaining conditions except for the liked song with auditory-only stimulation.

CONCLUSIONS

The addition of tactile stimulation enhanced music-induced analgesia which reduced subjective pain intensity. The findings suggest that combined auditory and tactile stimulation may increase the affective content of self-selected preferred music, which may stimulate affective and motivation mechanisms which inhibit pain transmission.

From nociception to pain perception, possible implications of astrocytes

Astrocytes are determinants for the functioning of the CNS. They respond to neuronal activity with calcium increases and can in turn modulate synaptic transmission, brain plasticity as well as cognitive processes. Astrocytes display sensory-evoked calcium responses in different brain structures related to the discriminative system of most sensory modalities. In particular, noxious stimulation evoked calcium responses in astrocytes in the spinal cord, the hippocampus, and the somatosensory cortex. However, it is not clear if astrocytes are involved in pain. Pain is a private, personal, and complex experience that warns us about potential tissue damage. It is a perception that is not linearly associated with the amount of tissue damage or nociception; instead, it is constructed with sensory, cognitive, and affective components and depends on our previous experiences. However, it is not fully understood how pain is created from nociception. In this perspective article, we provide an overview of the mechanisms and neuronal networks that underlie the perception of pain. Then we proposed that coherent activity of astrocytes in the spinal cord and pain-related brain areas could be important in binding sensory, affective, and cognitive information on a slower time scale.

Pain management after third molar extractions in adolescents: a qualitative study

Background

Understanding how adolescent patients make decisions about pain management after complex dental procedures could help reduce the use of opioid medications and the potential for future opioid misuse in this population. This qualitative study explores how adolescents manage pain, including how decision making with parents and providers affect their experience with opioid and non-opioid analgesics after third molar dental extractions.

Methods

We used a qualitative approach for the analysis of 30 telephone-based semi-structured interviews completed by 15 dyads between May and August 2019, which included 15 adolescents (15–17 years) who underwent a dental extraction, and a parent or guardian for each adolescent. The total sample included 30 participants. Interviews were conducted separately for patients and parents. De-identified interview transcripts were analyzed using qualitative analysis software using a directed content analysis approach.

Results

A total of 15 patient/parent dyads were interviewed. Key themes associated with pain management included sources of information, pain management behaviors engaged in by the adolescents and their caregivers, and the use of medication. In addition to conversations with their dental provider, most patients and their parents discussed pain management plans that included non-medication options, over-the-counter medications, and opioid medications to be taken as needed, which guided their post-extraction behaviors. All participants reported that the adolescent received an opioid prescription for post-extraction pain management, to be taken on an “as needed” basis, but most only took it the day of the extraction and up to 2 days following, usually based on the patient’s reported pain levels and perceptions of over-the-counter medication adequacy. Participants said they did not receive guidance from their provider concerning disposal of unused opioid medications.

Conclusions

Involving adolescents in the pain management decision making process and allowing them to carry out the plan with some caregiver support was acceptable and well executed following third molar extractions. Providers may have an opportunity to reduce the number of opioids prescribed, since respondents reported little to no use of opioids that they were prescribed. Providers should educate patients and their parents about safe disposal of opioids to mitigate the potential for diversion.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-022-03261-x.

Neural Correlates of Attachment Representation in Patients With Borderline Personality Disorder Using a Personalized Functional Magnet Resonance Imaging Task

Background

Fear of abandonment and aloneness play a key role in the clinical understanding interpersonal and attachment-specific problems in patients with borderline personality disorder (BPD) and has been investigated in previous functional Magnet Resonance Imaging (fMRI) studies. The aim of the present study was to examine how different aspects of attachment representations are processed in BPD, by using for the first time an fMRI attachment paradigm including personalized core sentences from the participants’ own attachment stories. We hypothesized that BPD patients would show increased functional involvement of limbic brain regions associated with fear and pain (e.g., the amygdala and the anterior cingulate cortex) when presented personalized attachment relevant stimuli representing loneliness compared to healthy controls (HC).

Methods

We examined the attachment classifications of 26 female BPD patients and 26 female HC using the Adult Attachment Projective Picture System (AAP). We used an fMRI-adapted attachment paradigm to investigate the neural correlates of attachment. All participants were presented three personalized (vs. neutral) sentences extracted from their AAP attachment narrative, combined with standardized AAP pictures representing being alone (monadic) or in interactive (dyadic) attachment situations.

Results

As expected, the classification of unresolved attachment was significantly greater in BPD compared to HC. BPD patients showed increased fMRI-activation in brain areas associated with fear, pain, and hyperarousal than HC when presented with personalized attachment-relevant alone stimuli. In particular, pictures with monadic attachment situations induced greater anterior medial cingulate cortex, anterior insula, amygdala, thalamus and superior temporal gyrus activation in the patient group.

Conclusion

The results point to increased fMRI-activation in areas processing emotional distress and painful experiences in BPD patients. In particular, the emotional cascade reflecting attachment distress was evoked by combining monadic pictures, representing abandonment and aloneness, with the patients’ personalized narrative material. Our results confirmed and replicated previous results that illustrate once again the high relevance of aloneness and feelings of abandonment for BPD in the context of attachment trauma. Moreover, our results support the hypothesis of hypermentalization in response to attachment distress as a core feature of social-cognitive impairment in BPD associated with common treatment implications across different therapeutic orientations.

Headaches and the use of personal protective equipment in the general population during the COVID-19 pandemic

INTRODUCTION

Headaches associated with personal protective equipment were reported in health-care workers in previous epidemiological studies.

METHODS

National web-based survey advertised by the Portuguese Headache Society and National Headache and Migraine patient´s organization between September-December 2020 screening for personal protective equipment usage pattern, pre-existing and de novo headaches after the onset of the COVID-19 pandemic, and its relation to personal protective equipment use.

RESULTS

Of 5064 participants, 90.6% (4562/5034) were women, mean age was 37.2 ± 11 years. Most questions had a completion rate above 87% (non-completion rate ranging from 0-12.7%). Twenty percent were health-care professionals (993/5046). Surgical and cloth masks were the most common personal protective equipment type, whereas protective eyewear and FFP2/FFP3 masks were mostly used by health-care professionals. About 97% (1814/1870) of migraine and headache participants reported aggravation of pre-existing headaches with personal protective equipment use, and 56% (2476/4420) had de novo headaches. Participants with de novo headaches had a higher frequency of pre-existing migraine (1118/1226, 91.2% vs 1408/1600, 88%, P = .042), and wore personal protective equipment for longer periods of time (7 ± 2 h 42 vs 6 ± 2 h 54 min per day, P < .001). In multivariate analysis longer mean duration of personal protective equipment use (OR of 1.1, 95% CI 1-1.2) and previous migraine (OR of 1.2, 95% CI 1-1.4) were predictors of developing de novo headaches.

CONCLUSIONS

Almost all participants with pre-existing headache reported worsening of their headaches, and more than half of the study population developed de novo headaches following personal protective equipment use. Duration of personal protective equipment usage and pre-existing migraine were the strongest predictors of de novo headaches.

Multiple Functional Brain Networks Related to Pain Perception Revealed by fMRI

The rise of functional magnetic resonance imaging (fMRI) has led to a deeper understanding of cortical processing of pain. Central to these advances has been the identification and analysis of "functional networks", often derived from groups of pre-selected pain regions. In this study our main objective was to identify functional brain networks related to pain perception by examining whole-brain activation, avoiding the need for a priori selection of regions. We applied a data-driven technique-Constrained Principal Component Analysis for fMRI (fMRI-CPCA)-that identifies networks without assuming their anatomical or temporal properties. Open-source fMRI data collected during a thermal pain task (33 healthy participants) were subjected to fMRI-CPCA for network extraction, and networks were associated with pain perception by modelling subjective pain ratings as a function of network activation intensities. Three functional networks emerged: a sensorimotor response network, a salience-mediated attention network, and the default-mode network. Together, these networks constituted a brain state that explained variability in pain perception, both within and between individuals, demonstrating the potential of data-driven, whole-brain functional network techniques for the analysis of pain imaging data.

Inter-individual differences in pain anticipation and pain perception in migraine: Neural correlates of migraine frequency and cortisol-to-dehydroepiandrosterone sulfate (DHEA-S) ratio

Previous studies targeting inter-individual differences in pain processing in migraine mainly focused on the perception of pain. Our main aim was to disentangle pain anticipation and perception using a classical fear conditioning task, and investigate how migraine frequency and pre-scan cortisol-to-dehydroepiandrosterone sulfate (DHEA-S) ratio as an index of neurobiological stress response would relate to neural activation in these two phases. Functional Magnetic Resonance Imaging (fMRI) data of 23 participants (18 females; mean age: 27.61± 5.36) with episodic migraine without aura were analysed. We found that migraine frequency was significantly associated with pain anticipation in brain regions comprising the midcingulate and caudate, whereas pre-scan cortisol-to DHEA-S ratio was related to pain perception in the pre-supplementary motor area (pre-SMA). Both results suggest exaggerated preparatory responses to pain or more general to stressors, which may contribute to the allostatic load caused by stressors and migraine attacks on the brain.

Event-based control of autonomic and emotional states by the anterior cingulate cortex

Despite being an intensive area of research, the function of the anterior cingulate cortex (ACC) remains somewhat of a mystery. Human imaging studies implicate the ACC in various cognitive functions, yet surgical ACC lesions used to treat emotional disorders have minimal lasting effects on cognition. An alternative view is that ACC regulates autonomic states, consistent with its interconnectivity with autonomic control regions and that stimulation evokes changes in autonomic/emotional states. At the cellular level, ACC neurons are highly multi-modal and promiscuous, and can represent a staggering array of task events. These neurons nevertheless combine to produce highly event-specific ensemble patterns that likely alter activity in downstream regions controlling emotional and autonomic tone. Since neuromodulators regulate the strength of the ensemble activity patterns, they would regulate the impact these patterns have on downstream targets. Through these mechanisms, the ACC may determine how strongly to react to the very events its ensembles represent. Pathologies arise when specific event-related representations gain excessive control over autonomic/emotional states.

Differences in resting cerebellar and prefrontal cortical blood flow in spinal cord injury-related neuropathic pain: A brief report

Context: Little is understood about differences in resting neural activity among those with spinal cord injury (SCI)-related neuropathic pain. The purpose of this pilot study was to determine resting cerebral blood flow differences in persons with SCI-related neuropathic pain compared to healthy, pain-free able-bodied controls.Methods: Five persons with paraplegia and ten able-bodied participants were included in this study. Resting blood flow, as measured by a continuous arterial spin labeling (ASL) method of fMRI, was analyzed via statistical parametric mapping.Results: Persons with SCI-related neuropathic pain had significantly lower resting blood flow in the cerebellum (Crus I/II), rostral ventromedial medulla and left insular cortex. In contrast, greater resting blood flow occurred in the medial orbitofrontal cortex among those with SCI-related neuropathic pain compared to controls.Conclusion: Differences in resting blood flow were observed among those with SCI-related pain, particularly in regions that may be involved in affective-motivational and cognitive-evaluative aspects of pain. Larger ASL studies in addition to functional connectivity studies using fMRI are needed to clarify unique neural patterns in this complex and often intractable form of pain.

Comparing Patient-Controlled Analgesia Versus Non-PCA Hydromorphone Titration for Severe Cancer Pain: A Randomized Phase III Trial

BACKGROUND

Opioid titration is necessary to achieve rapid, safe pain relief. Medication can be administered via patient-controlled analgesia (PCA) or by a healthcare provider (non-PCA). We evaluated the efficacy of intravenous PCA versus non-PCA hydromorphone titration for severe cancer pain (≥7 at rest on the 11-point numeric rating scale [NRS]).

PATIENTS AND METHODS

Patients with severe cancer pain were randomized 1:1 to PCA or non-PCA titration, stratified by opioid-tolerant or opioid-naïve status. The PCA pump was set to no continuous dose, with a hydromorphone bolus dose 10% to 20% of the total previous 24-hour equianalgesic (for opioid-tolerant patients) or 0.5 mg (for opioid-naïve patients). For the non-PCA group, the initial hydromorphone bolus dose was identical to that in the PCA group, with the subsequent dose increased by 50% to 100% (for NRS unchanged or increased) or repeated at the current dose (for NRS 4-6). Hydromorphone delivery was initiated every 15 minutes (for NRS ≥4) or as needed (for NRS ≤3). The primary endpoint was time to successful titration (TST; time from first hydromorphone dose to first occurrence of NRS ≤3 in 2 consecutive 15-minute intervals).

RESULTS

Among 214 patients (PCA, n=106; non-PCA, n=108), median TSTs (95% CI) were 0.50 hours (0.25-0.50) and 0.79 hours (0.50-1.42) for the PCA and non-PCA groups, respectively (hazard ratio [HR], 1.64; 95% CI, 1.23-2.17; P=.001). TSTs in opioid-tolerant patients were 0.50 hours (0.25-0.75) and 1.00 hours (0.50-2.00) for the PCA and non-PCA groups, respectively (HR, 1.92; 95% CI, 1.32-2.78; P=.003); in opioid-naive patients, TST was not significantly different for the PCA versus non-PCA groups (HR, 1.35; 95% CI, 0.88-2.04; P=.162). Pain score (median NRS; interquartile range) over 24 hours was significantly lower in the PCA group (2.80; 2.15-3.22) than in the non-PCA group (3.00; 2.47-3.53; P=.020). PCA administration produces significantly higher patient satisfaction with pain control than non-PCA administration (P<.001).

CONCLUSIONS

Intravenous hydromorphone titration for severe cancer pain was achieved more effectively with PCA than with non-PCA administration.

Episodic future thinking reduces chronic pain severity: A proof of concept study

BACKGROUND

Chronic pain is a major public health challenge in the United States and around the world. Current treatments including opioid analgesics and cognitive behavioral therapy possess harmful side effects or limited efficacy, respectively. Chronic pain is associated with a variety of unhealthy behaviors including opioid misuse. Moreover, individuals who suffer from chronic pain exhibit excessive discounting of delayed rewards, suggesting a constricted temporal window of valuation. Reductions in the excessive discounting of delayed rewards has been achieved with Episodic Future Thinking (EFT; vividly imagining realistic future events). EFT has also been associated with reductions in a variety of unhealthy behaviors. In this study, the effects of EFT on delay discounting and levels of pain were investigated in individuals reporting chronic pain.

METHODS

Individuals reporting chronic pain (N = 250; 42.4 % female) were recruited through the Amazon Mechanical Turk platform. Measures of delay discounting and pain were collected at baseline and again after randomization to EFT (N = 128) or Control Episodic Thinking (CET) (N = 122).

RESULTS

EFT significantly reduced delay discounting relative to baseline (p < 0.001) and EFT reduced pain scores in a baseline dependent manner (p = 0.001) when compared to CET; that is, those with the greatest reports of pain experienced the greatest reduction. Furthermore the reduction in delay discounting fully mediated the reduction in pain.

CONCLUSIONS

These findings suggest that Episodic Future Thinking, by widening the temporal window, may reduce pain in those reporting chronic pain and therefore represents a potential novel therapeutic.

Ultra-high-field imaging reveals increased whole brain connectivity underpins cognitive strategies that attenuate pain

We investigated how the attenuation of pain with cognitive interventions affects brain connectivity using neuroimaging and a whole brain novel analysis approach. While receiving tonic cold pain, 20 healthy participants performed three different pain attenuation strategies during simultaneous collection of functional imaging data at seven tesla. Participants were asked to rate their pain after each trial. We related the trial-by-trial variability of the attenuation performance to the trial-by-trial functional connectivity strength change of brain data. Across all conditions, we found that a higher performance of pain attenuation was predominantly associated with higher functional connectivity. Of note, we observed an association between low pain and high connectivity for regions that belong to brain regions long associated with pain processing, the insular and cingulate cortices. For one of the cognitive strategies (safe place), the performance of pain attenuation was explained by diffusion tensor imaging metrics of increased white matter integrity.

Sustained perturbation in functional connectivity induced by cold pain

BACKGROUND

Functional connectivity (FC) perturbations have been reported in multiple chronic pain phenotypes, but the nature of reported changes varies between cohorts and may relate to the consequences of living with chronic-pain related comorbidities, such as anxiety and depression. Healthy volunteer studies provide opportunities to study the effects of tonic noxious stimulation independently of these sequelae. Connectivity changes in task negative and positive networks, for example, the default mode and salience networks (DMN/SN), respectively, have been described, but how these and other connectivity networks, for example, those governing descending pain control are affected by the presence of tonic, noxious stimulation in healthy, pain-free individuals, remains unknown.

METHOD

In 20 healthy volunteers, we assessed FC prior to, during, and following tonic cold painful stimulation in the ventromedial prefrontal cortex (vmPFC), rostral anterior insula (rAI), subgenual anterior cingulate cortex (ACC) and periaqueductal grey (PAG). We also recorded subjectively reported pain using a computerised visual analogue scale.

RESULTS

We saw DMN FC changes during painful stimulation and that inter-network connectivity between the rAI with the vmPFC increased during pain, whereas PAG-precuneus FC decreased. Pain-induced FC alterations persisted following noxious stimulation. FC changes related to the magnitude of individuals' subjectively reported pain.

CONCLUSIONS

We demonstrate FC changes during and following tonic cold-pain in healthy participants. Similarities between our findings and reports of patients with chronic pain suggest that some FC changes observed in these patients may relate to the presence of an ongoing afferent nociceptive drive.

SIGNIFICANCE

How pain-related resting state networks are affected by tonic cold-pain remains unknown. We investigated functional connectivity alterations during and following tonic cold pain in healthy volunteers. Cold pain perturbed the functional connectivity of the ventro-medial prefrontal cortex, anterior insula, and the periacquaductal grey area. These connectivity changes were associated with the magnitude of individuals' reported pain. We suggest that some connectivity changes described in chronic pain patients may be due to an ongoing afferent peripheral drive.

Neural and molecular correlates of psychological pain during major depression, and its link with suicidal ideas

OBJECTIVES

Psychological pain increases the risk of suicidal ideas and acts, and represents a potential therapeutic target. However, the mechanisms of mental pain remain unclear. Here, we assessed the peripheral transcriptomic and central neural correlates of mental pain during a depressive episode.

METHODS

172 adult un-medicated depressed patients were recruited. Leucocytes were extracted for RNA quantification at baseline (T0) and after 8 weeks (T8) of an antidepressant treatment. Ninety-nine genes of the cortisol, immune, opioid, serotonergic, and kynurenine systems were a priori selected, and 41 were sufficiently expressed to be analyzed. At both T0 and T8, mean level of mental pain over the last 15 days was measured with a visual analog scale. A subset of 38 patients was additionally scanned with Magnetic Resonance Imaging at T0. Resting-state sequences of 4 networks (default-mode, basal ganglia, central executive, salience) were examined.

RESULTS

Mean psychological pain scores significantly decreased between T0 and T8. At conservative p-corrected levels, T0 mental pain was significantly correlated with 11 brain clusters encompassing the prefrontal, parietal, and temporal cortices, the striatum, and the cerebellum. There was no direct association between peripheral gene expression and mean mental pain at any time points or in terms of temporal changes. However, expressions of 5HTR2B at p-corrected levels, and 5HTR3A, TPH1, and OPRL1 were correlated with the activity of several identified brain clusters at T0. Finally, while suicidal ideas and mental pain were correlated, the neural and molecular correlates of suicidal ideas were not the same.

CONCLUSION

Our study suggests that the serotonergic and nociceptin systems are associated with the activity of a cortico-subcortical brain network underlying the perception of mental pain during depression. Mental pain may be a necessary but insufficient condition for the emergence of suicidal ideation during depression.

Translation and Validation of the Farsi Version of the Pain Management Self-Efficacy Questionnaire

Introduction

Pain management is a complex process that is managed through a multi-disciplinary team in which nurses have a significant role. The present study aimed at translating and examining the psychometric properties of the Pain Management Self-Efficacy Questionnaire (PMSEQ) among Iranian nurses.

Methods

This was a cross-sectional, methodological study conducted in 2019 among nurses working in two teaching hospitals in Sanandaj (Tohid and Kosar). The participants were selected using a convenience sampling method. Responsiveness; interpretability; and face, content, and construct validities were examined using exploratory and confirmatory factor analyses. In addition, internal consistency and stability were examined using the Cronbach’s alpha and test-retest, respectively.

Results

Overall, 410 nurses (210 for the EFA and 200 for the CFA) were included in the sample. In the exploratory factor analysis, two factors of comprehensive pain assessment and pain management with eigenvalues of 6.36 and 1.91, respectively, were extracted. The two factors together explained 56.64% of the variance of nurses’ pain management self-efficacy. The confirmatory factor analysis indicated that the model had a moderate fit to the data (RMSEA: 0.12; NFI: 0.84; NNFI: 0.86; CFI: 0.88; IFI: 0.88; RFI: 0.81; GFI: 0.76; AGFI: 0.69; PGFI: 0.59; RMR: 0.09; standardized RMR: 0.09). Total questionnaire and the two factors (i.e. comprehensive pain assessment and pain management) had internal consistency coefficients of 0.891, 0.876, and 0.803, respectively.

Conclusion

The Farsi version of PMSEQ had good internal consistency and reliability, as well as content and construct validity, and can be used in future studies.

An exploratory proton MRS examination of gamma-aminobutyric acid, glutamate, and glutamine and their relationship to affective aspects of chronic pain

Veterans experience chronic pain more frequently than civilians. Identification of neurobiological mechanisms underlying the pathophysiology of chronic pain in a veteran population may aid in the development of novel treatment targets. In this pilot proof-of-concept study, veterans with chronic pain (N = 61) and no chronic pain (N = 19) completed clinical interviews, self-report questionnaires inquiring about pain history, interference of pain with daily life, and pain catastrophizing, as well as measures of depressive and anxious symptoms. Veterans also underwent single-voxel proton (¹H) magnetic resonance spectroscopy (MRS) at 3 T in the anterior cingulate cortex (ACC) using a two-dimensional (2D) J-resolved point spectroscopy sequence. We found no group difference in neurometabolites between veterans with and without chronic pain; however, pain intensity, negative thinking about pain, and description of pain in affective terms were associated with lower GABA/Cre in the ACC. In addition, the Glu/GABA ratio in the ACC was positively associated with anxiety and depressive symptoms in veterans with chronic pain. Reductions in GABA in the ACC may contribute to increased pain intensity and greater pain catastrophizing in veterans with chronic pain. Furthermore, a disturbance in the excitatory-inhibitory balance may contribute to the anxious and depressive symptoms related to chronic pain. Given the pilot nature of the study, these findings must be considered preliminary.

Linking Pain Sensation to the Autonomic Nervous System: The Role of the Anterior Cingulate and Periaqueductal Gray Resting-State Networks

There are bi-directional interactions between the autonomic nervous system (ANS) and pain. This is likely underpinned by a substantial overlap between brain areas of the central autonomic network and areas involved in pain processing and modulation. To date, however, relatively little is known about the neuronal substrates of the ANS-pain association. Here, we acquired resting state fMRI scans in 21 healthy subjects at rest and during tonic noxious cold stimulation. As indicators of autonomic function, we examined how heart rate variability (HRV) frequency measures were influenced by tonic noxious stimulation and how these variables related to participants’ pain perception and to brain functional connectivity in regions known to play a role in both ANS regulation and pain perception, namely the right dorsal anterior cingulate cortex (dACC) and periaqueductal gray (PAG). Our findings support a role of the cardiac ANS in brain connectivity during pain, linking functional connections of the dACC and PAG with measurements of low frequency (LF)-HRV. In particular, we identified a three-way relationship between the ANS, cortical brain networks known to underpin pain processing, and participants’ subjectively reported pain experiences. LF-HRV both at rest and during pain correlated with functional connectivity between the seed regions and other cortical areas including the right dorsolateral prefrontal cortex (dlPFC), left anterior insula (AI), and the precuneus. Our findings link cardiovascular autonomic parameters to brain activity changes involved in the elaboration of nociceptive information, thus beginning to elucidate underlying brain mechanisms associated with the reciprocal relationship between autonomic and pain-related systems.

Dispute cases related to pain management in Korea: analysis of Korea Medical Dispute Mediation and Arbitration Agency data

Background

Various developments in imaging techniques, interventional procedures, and medications for pain management have beneficial consequences. However, the nature of pain management often results in physicians becoming involved in medico-legal disputes with patients who purposely or accidentally bring litigation.

Methods

Data on medical disputes cases related to pain management were collected and analyzed through the Korea Medical Dispute Mediation and Arbitration Agency from 2012 to 2016.

Results

In total, we identified 210 public-disclosed cases; of these, we identified 36 cases related to pain management. The department of orthopedics (n = 9, 25%) was the most related to these pain management cases. Pain management was most commonly offered for pain in the lumbar region (n = 13, 37%), lower extremities (n = 12, 34%), and for infection (n = 7, 19%). The time spent resolving disputes ranged from 8.0 to 17.5 months and the final settlement amount ranged from 1,800,000 to 15,000,000 Korean won. Causal relationships and medical malpractice were the most common controversial subjects of legal debate.

Conclusions

Various characteristics of medical disputes related to pain management in Korea were identified. Information regarding medical disputes in pain management should be available to help prevent further disputes and litigation, which is also useful to both patients and pain physicians. Guidelines and recommendations for pain management are needed, especially those focused on medico-legal cases.

Effects of social exclusion and physical pain in chronic opioid maintenance treatment: fMRI correlates

Opioids interact with systems processing pain and social stimuli. Both systems are crucial for responding to strains of everyday life and both are linked to relapse risk in opioid-dependent patients. The investigation of those systems seems essential to better understand opioid addiction as a whole. 17 patients on opioid maintenance treatment (OMT) and 21 healthy individuals underwent a functional magnetic resonance imaging (fMRI) social ball-tossing (Cyberball) paradigm simulating social inclusion and exclusion. In addition, painful and non-painful temperature stimuli were applied, in order to test pain sensitivity. Patients on OMT showed reduced pain sensitivity. Subjective pain was higher after social exclusion compared to social inclusion trials. In comparison to healthy controls, OMT patients felt less included and more excluded during inclusion and control conditions, and equally excluded during the social exclusion condition. Feelings of exclusion during the inclusion trials were associated with higher scores on the childhood trauma questionnaire. Across all conditions, OMT patients demonstrated decreased fMRI activation in the bilateral superior and middle occipital and bilateral cunei, the lingual gyri, as well as in the left fusiform gyrus (whole brain FWE-corrected). Comparing social exclusion and inclusion conditions, healthy individuals showed significant activation in brain areas related to social feedback and emotion processing, such as the anterior cingulate cortex, the insula and fusiform gyrus, whereas OMT patients showed no difference across conditions. As negative social affect is a potential trigger for relapse, patients might benefit from therapeutic strategies that enhance social integration.

Analgesic Effects Evoked by Real and Imagined Acupuncture: A Neuroimaging Study

Acupuncture can provide therapeutic analgesic benefits but is limited by its cost and scheduling difficulties. Guided imagery is a commonly used method for treating many disorders, such as chronic pain. The present study examined a novel intervention for pain relief that integrates acupuncture with imagery called video-guided acupuncture imagery treatment (VGAIT). A total of 27 healthy subjects were recruited for a crossover-design study that included 5 sessions administered in a randomized order (i.e., baseline and 4 different interventions). We investigated changes in pain threshold and fMRI signals modulated by: 1) VGAIT, watching a video of acupuncture previously administered on the participant's own body at baseline while imagining it being concurrently applied; 2) a VGAIT control condition, watching a video of a cotton swab touching the skin; 3) real acupuncture; and 4) sham acupuncture. Results demonstrated that real acupuncture and VGAIT significantly increased pain threshold compared with respective control groups. Imaging showed that real acupuncture produced greater activation of the insula compared with VGAIT. VGAIT produced greater deactivation at the rostral anterior cingulate cortex. Our findings demonstrate that VGAIT holds potential clinical value for pain management.

Physical Fitness and the Level of Pain Intensity in Adolescents: A School-based Study

Background: The main aim of the study was to explore the association between objectively measured physical fitness and the level of pain intensity. Methods: In this cross-sectional study, we included 1036 adolescents (m_age ± SD = 16.3 ± 1.1 years; m_height ± SD = 1.74 ± 0.1 m; m_weight ± SD = 64.7 ± 12.4 kg; m_{body-mass index} ± SD = 21.3 ± 3.0 kg/m²) from 11 secondary schools located in the city of Zagreb (Croatia). Physical fitness was determined by using waist circumference, sit-ups in 1 min, standing long jump and sit-and-reach tests. Overall physical fitness index was calculated by summing the z-score values of each physical fitness test. The level of pain intensity was assessed with the Numeric Pain Rating Scale, a one-dimensional measure of pain intensity. Associations were calculated with correlation analyses. Results: In boys, pain intensity was associated with sit-ups in 1 min (r = -0.16, p < 0.001), standing long jump (r = -0.14, p = 0.003) and overall physical fitness index (r = -0.13, p = 0.004), while no significant associations with waist circumference (r = 0.04, p = 0.438) and sit-and-reach test (r = -0.01, p = 0.822) were observed. In girls, pain intensity was associated with standing long jump (r = -0.17, p < 0.001) and overall physical fitness index (r = -0.10, p = 0.018), while no significant associations with waist circumference (r = 0.01, p = 0.735), sit-ups in 1 min (r = -0.06, p = 0.126) and sit-and-reach test (r = -0.05, p = 0.232) were observed. When we adjusted for self-rated health, sleep duration, smoking status, alcohol consumption, screen-time and psychological distress, similar associations remained. Conclusions: Our study shows a weak association between physical fitness and pain intensity in a large sample of adolescents. Although a cross-sectional design, health-professionals should use physical fitness as a screening tool to assess the level of pain intensity.

Are Functional Brain Alterations Present in Low Back Pain? A Systematic Review of EEG Studies

This systematic review analyzed available literature on functional brain alterations in low back pain (LBP) measured with electroencephalography (EEG), as until now evidence thereof was unclear. Four electronic databases were systematically searched the 10th of March 2018, resulting in 12 included studies. Studies showed a risk of bias of 37.5 to 75% using the Newcastle-Ottawa Scale for case-control studies. Limited evidence reported higher amplitudes of balance-related potentials and early components of somatosensory evoked potentials (SEP) to noxious stimuli, and altered feedback-related negativity and P300 potentials during decision-making in chronic LBP (CLBP). These findings suggest postural strategies requiring a higher cortical attention-demand, increased sensory-discriminative processing of noxious input, and altered decision-making in CLBP. However, further research is warranted as these inferences were based on single studies. Moderate evidence for unaltered amplitude of late-phase SEPs to noxious stimuli and auditory evoked potentials in LBP implies that the affective-emotional processing of stimuli might be unaffected in LBP. Furthermore, moderate evidence indicated disturbed habituation of somatosensory stimuli in LBP. Most studies examined nonspecific or mixed CLBP populations, hence EEG-quantified brain activity in (sub)acute or recurrent LBP still needs to be explored. PERSPECTIVE: This review presents an overview of the current understanding of the functional LBP brain measured with EEG. The limited evidence in current research suggests altered cortical function regarding balance control, somatosensory processing, and decision making in LBP, and highlights opportunities for future EEG-research.

Gaps in Understanding Mechanism and Lack of Treatments: Potential Use of a Nonhuman Primate Model of Oxaliplatin-Induced Neuropathic Pain

The antineoplastic agent oxaliplatin induces an acute hypersensitivity evoked by cold that has been suggested to be due to sensitized central and peripheral neurons. Rodent-based preclinical studies have suggested numerous treatments for the alleviation of oxaliplatin-induced neuropathic pain, but few have demonstrated robust clinical efficacy. One issue is that current understanding of the pathophysiology of oxaliplatin-induced neuropathic pain is primarily based on rodent models, which might not entirely recapitulate the clinical pathophysiology. In addition, there is currently no objective physiological marker for pain that could be utilized to objectively indicate treatment efficacy. Nonhuman primates are phylogenetically and neuroanatomically similar to humans; thus, disease mechanism in nonhuman primates could reflect that of clinical oxaliplatin-induced neuropathy. Cold-activated pain-related brain areas in oxaliplatin-treated macaques were attenuated with duloxetine, the only drug that has demonstrated clinical efficacy for chemotherapy-induced neuropathic pain. By contrast, drugs that have not demonstrated clinical efficacy in oxaliplatin-induced neuropathic pain did not reduce brain activation. Thus, a nonhuman primate model could greatly enhance understanding of clinical pathophysiology beyond what has been obtained with rodent models and, furthermore, brain activation could serve as an objective marker of pain and therapeutic efficacy.

A Collaborator's Reputation Can Bias Decisions and Anxiety under Uncertainty

Informational social influence theory posits that under conditions of uncertainty, we are inclined to look to others for advice. This leaves us remarkably vulnerable to being influenced by others' opinions or advice. Rational agents, however, do not blindly seek and act on arbitrary information, but often consider the quality of its source before committing to a course of action. Here, we ask the question of whether a collaborator's reputation can increase their social influence and, in turn, bias perception and anxiety under changing levels of uncertainty. Human male and female participants were asked to provide estimations of dot direction using the random dot motion (RDM) perceptual discrimination task and were paired with transient collaborators of high or low reputation whom provided their own estimations. The RDM varied in degrees of uncertainty and joint performance accuracy was linked to risk of an electric shock. Despite providing identical information, we show that collaborating with a high reputation compared with a low reputation partner, led to significantly more conformity during the RDM task for uncertain perceptual decisions. Consequently, high reputation partners decreased the subjects' anxiety during the anticipatory shock periods. fMRI data showed that parametric changes in conformity resulted in increased activity in the ventromedial PFC, whereas dissent was associated with increased in activity in the dorsal anterior cingulate cortex (dACC). Furthermore, the dACC and insula, regions involved in anticipatory pain, were significantly more active when collaborating with a low reputation partner. These results suggest that information about reputation can influence both cognitive and affective processes and in turn alter the neural circuits that underlie decision-making and emotion.SIGNIFICANCE STATEMENT Humans look to others for advice when making decisions under uncertainty. Rational agents, however, do not blindly seek information, but often consider the quality of its source before committing to a course of action. Here, we ask the question of whether a collaborators' reputation can increase social influence and in turn bias perception and anxiety in the context of perceptual uncertainty. We show that when subjects are partnered with collaborators with a high reputation, this leads to increased conformity during uncertain perceptual decision-making and reduces anxiety when joint performance accuracy leads to an electric shock. Furthermore, our results show that information about reputation alters the neural circuits that underlie decision-making and emotion.

Comparison of gray matter volume between migraine and "strict-criteria" tension-type headache

BACKGROUND

Despite evidently distinct symptoms, tension-type headache (TTH) and migraine are highly comorbid and exhibit many similarities in clinical practice. The purpose of this study was to investigate whether both types of headaches are similar in brain morphology.

METHODS

Consecutive patients with TTH and age- and sex-matched patients with migraine and healthy controls were enrolled for brain magnetic resonance imaging examination. Patients with TTH were excluded if they reported any headache features or associated symptoms of migraine. Changes in gray matter (GM) volume associated with headache diagnosis (TTH vs. migraine) and frequency (episodic vs. chronic) were examined using voxel-based morphometry. The correlation with headache profile and the discriminative ability between TTH and migraine were also investigated for these GM changes.

RESULTS

In comparison with controls (n = 43), the patients with TTH (25 episodic and 24 chronic) exhibited a GM volume increase in the anterior cingulate cortex, supramarginal gyrus, temporal pole, lateral occipital cortex, and caudate. The patients with migraine (31 episodic and 25 chronic) conversely exhibited a GM volume decrease in the orbitofrontal cortex. These GM changes did not correlate with any headache profile. A voxel-wise 2 × 2 factorial analysis further revealed the substantial effects of headache types and frequency in the comparison of GM volume between TTH and migraine. Specifically, the migraine group (vs. TTH) had a GM decrease in the superior and middle frontal gyri, cerebellum, dorsal striatum, and precuneus. The chronic group (vs. episodic group) otherwise demonstrated a GM decrease in the bilateral insula and anterior cingulate cortex. In receiver operating characteristic analysis, the GM volumes of the left superior frontal gyrus and right cerebellum V combined had good discriminative ability for distinguishing TTH and migraine (area under the curve = 0.806).

CONCLUSIONS

TTH and migraine are separate headache disorders with different characteristics in relation to GM changes. The major morphological difference between the two types of headaches is the relative GM decrease of the prefrontal and cerebellar regions in migraine, which may reflect a higher allostatic load associated with this disabling headache.

Additive effect of tDCS combined with Peripheral Electrical Stimulation to an exercise program in pain control in knee osteoarthritis: study protocol for a randomized controlled trial

BACKGROUND

Knee osteoarthritis (OA) has been linked to maladaptive plasticity in the brain, which may contribute to chronic pain. Neuromodulatory approaches, such as Transcranial Direct Current Stimulation (tDCS) and Peripheral Electrical Stimulation (PES), have been used therapeutically to counteract brain maladaptive plasticity. However, it is currently unclear whether these neuromodulatory techniques enhance the benefits of exercise when administered together. Therefore, this protocol aims to investigate whether the addition of tDCS combined or not with PES enhances the effects of a land-based strengthening exercise program in patients with knee OA.

METHODS

Patients with knee OA (n = 80) will undertake a structured exercise program for five consecutive days. In addition, they will be randomized into four subgroups receiving either active anodal tDCS and sham PES (group 1; n = 20), sham tDCS and active PES (group 2, n = 20), sham tDCS and PES (group 3, n = 20), or active tDCS and PES (group 4, n = 20) for 20 min/day for five consecutive days just prior to commencement of the exercise program. The primary outcomes will be subjective pain intensity (VAS) and related function (WOMAC). Secondary outcomes will include quality of life (SF-36), anxiety and depression symptoms (HAD), self-perception of improvement, pressure pain thresholds over the knee, quadriceps strength, and quadriceps electromyographic activity during maximum knee extension voluntary contraction. We will also investigate cortical excitability using transcranial magnetic stimulation. Outcome measures will be assessed at baseline, 1 month after, before any intervention, after 5 days of intervention, and at 1 month post exercise intervention.

DISCUSSION

The motor cortex becomes less responsive in knee OA because of poorly adapted plastic changes, which can impede exercise therapy benefits. Adding tDCS and/or PES may help to counteract those maladaptive plastic changes and improve the benefits of exercises, and the combination of both neuromodulatory techniques must have a higher magnitude of effect.

TRIAL REGISTRATION

Brazilian Registry on Clinical Trials (ReBEC) - Effects of electrical stimulation over the skull and tight together with exercises for knee OA; protocol number RBR-9D7C7B.

TRIAL REGISTRATION

ID: RBR-9D7C7B . Registered on 29 February 2016.

Prefrontal hemodynamic mapping by functional near-infrared spectroscopy in response to thermal stimulations over three body sites

Functional near-infrared spectroscopy (fNIRS) was used to examine hemodynamic responses in the prefrontal cortex (PFC) during noxious thermal pain, induced by thermal stimulations over three different body sites over the right forearm, right temporomandibular joint, and left forearm. Functional NIRS measurements were obtained from three groups of healthy volunteers, one group for each body region. Each group was subjected to both low-pain stimulation (LPS) and high-pain stimulation (HPS) by a [Formula: see text] thermode of a temperature-controlled thermal stimulator over the respective three body sites. Our results showed that HPS given at three sites induced significant increases ([Formula: see text]) in oxy-hemoglobin concentration ([Formula: see text]) in the PFC with similar temporal patterns in relatively spread PFC areas. In contrast, LPS did not cause any significant [Formula: see text] in the PFC of any subject group. Our observed PFC activations induced by acute HPS were generally consistent with previous reports by fMRI studies. The study also found a peculiar global trend of postpain deactivation in the PFC, which is attributed to global vasoconstriction due to acute nocuous pain. Overall, these results indicate that hemodynamic activities in PFC exhibit consistent temporal and spatial patterns in response to acute thermal stimulation given across all three body sites.

Thalamic Functional Connectivity in Mild Traumatic Brain Injury: Longitudinal Associations With Patient-Reported Outcomes and Neuropsychological Tests

OBJECTIVES

(1) To examine differences in patient-reported outcomes, neuropsychological tests, and thalamic functional connectivity (FC) between patients with mild traumatic brain injury (mTBI) and individuals without mTBI and (2) to determine longitudinal associations between changes in these measures.

DESIGN

Prospective observational case-control study.

SETTING

Academic medical center.

PARTICIPANTS

A sample (N=24) of 13 patients with mTBI (mean age, 39.3±14.0y; 4 women [31%]) and 11 age- and sex-matched controls without mTBI (mean age, 37.6±13.3y; 4 women [36%]).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Resting state FC (3T magnetic resonance imaging scanner) was examined between the thalamus and the default mode network, dorsal attention network, and frontoparietal control network. Patient-reported outcomes included pain (Brief Pain Inventory), depressive symptoms (Patient Health Questionnaire-9), posttraumatic stress disorder ([PTSD] Checklist - Civilian Version), and postconcussive symptoms (Rivermead Post-Concussion Symptoms Questionnaire). Neuropsychological tests included the Delis-Kaplan Executive Function System Tower test, Trails B, and Hotel Task. Assessments occurred at 6 weeks and 4 months after hospitalization in patients with mTBI and at a single visit for controls.

RESULTS

Student t tests found increased pain, depressive symptoms, PTSD symptoms, and postconcussive symptoms; decreased performance on Trails B; increased FC between the thalamus and the default mode network; and decreased FC between the thalamus and the dorsal attention network and between the thalamus and the frontoparietal control network in patients with mTBI as compared with controls. The Spearman correlation coefficient indicated that increased FC between the thalamus and the dorsal attention network from baseline to 4 months was associated with decreased pain and postconcussive symptoms (corrected P<.05).

CONCLUSIONS

Findings suggest that alterations in thalamic FC occur after mTBI, and improvements in pain and postconcussive symptoms are correlated with normalization of thalamic FC over time.

Transcranial Direct Current Stimulation (tDCS) Targeting Left Dorsolateral Prefrontal Cortex Modulates Task-Induced Acute Pain in Healthy Volunteers

OBJECTIVE

Current chronic pain treatments target nociception rather than affective "suffering" and its associated functional and psychiatric comorbidities. The left dorsolateral prefrontal cortex (DLPFC) has been implicated in affective, cognitive, and attentional aspects of pain and is a primary target of neuromodulation for affective disorders. Transcranial direct current stimulation (tDCS) can non-invasively modulate cortical activity. The present study tests whether anodal tDCS targeting the left DLPFC will increase tolerability of acute painful stimuli vs cathodal tDCS.

METHODS

Forty tDCS-naive healthy volunteers received anodal and cathodal stimulation targeting the left DLPFC in two randomized and counterbalanced sessions. During stimulation, each participant performed cold pressor (CP) and breath holding (BH) tasks. We measured pain intensity with the Defense and Veterans Pain Rating Scale (DVPRS) before and after each task.

RESULTS

Mixed ANOVA revealed no main effect of stimulation polarity for mean CP threshold, tolerance, or endurance, or mean BH time (allP > 0.27). However, DVPRS rise associated with CP was significantly smaller with anodal vs cathodal tDCS (P = 0.024). We further observed a significant tDCS polarity × stimulation order interaction (P = 0.042) on CP threshold, suggesting task sensitization.

CONCLUSIONS

Although our results do not suggest that polarity of tDCS targeting the left DLPFC differentially modulates the tolerability of CP- and BH-related pain distress in healthy volunteers, there was a significant effect on DVPRS pain ratings. This contrasts with our previous findings that tDCS targeting the left dorsal anterior cingulate cortex showed a trend toward higher mean CP tolerance with cathodal vs anodal stimulation. The present results may suggest tDCS-related effects on nociception or DLPFC-mediated attention, or preferential modulation of the affective valence of pain as captured by the DVPRS. Sham-controlled clinical studies are needed.