Objective Emotions are assumed to influence visceral pain perception, but experimental evidence supporting this is limited and especially the underlying mechanisms are poorly understood. We investigated emotional modulation of subjective and parasympathetic responses to visceral pain as well as potential psychobiological sources of inter-individual variability. Methods Ninety-six healthy subjects participated in a mechanistic study during which negative, positive and neutral emotions were induced in 3 experimental runs, in counterbalanced order. Esophageal balloon distensions at pain tolerance were pseudo-randomly applied in each run to evoke visceral pain. Subjective emotional state was assessed at set time points, perceptual pain responses after each distension, and cardiac vagal tone (CVT) continuously. Affective traits were assessed using questionnaires, and participants were genotyped for selected serotonergic gene polymorphisms. Results Subjective pain ratings were higher and lower during negative and positive emotion, respectively, versus neutral (all p<0.0001), and habituated upon repeated stimulation during positive (p<0.0007) and neutral (p<0.0058), but not negative (p>0.66), emotion. Fear of pain scores and polymorphisms in the serotonin receptor type 3B and serotonin transporter were associated with inter-individual differences in such emotional pain modulation (all p<0.05). Finally, CVT responses to pain were higher during negative (p=0.059) and lower during positive emotion (p=0.031), respectively, versus neutral. Conclusions We show that positive and negative emotions modulate subjective and parasympathetic responses to esophageal pain, and identify fear of pain and serotonergic gene polymorphisms as drivers of inter-individual variability in such pain modulation. These findings may help to identify subjects at risk for developing chronic visceral pain.

The autonomic nervous system (ANS) is a brain body interface which serves to maintain homeostasis by influencing a plethora of physiological processes, including metabolism, cardiorespiratory regulation and nociception. Accumulating evidence suggests that ANS function is disturbed in numerous prevalent clinical disorders, including irritable bowel syndrome and fibromyalgia. While the brain is a central hub for regulating autonomic function, the association between resting autonomic activity and subcortical morphology has not been comprehensively studied and thus was our aim. In 27 healthy subjects [14 male and 13 female; mean age 30 years (range 22–53 years)], we quantified resting ANS function using validated indices of cardiac sympathetic index (CSI) and parasympathetic cardiac vagal tone (CVT). High resolution structural magnetic resonance imaging scans were acquired, and differences in subcortical nuclei shape, that is, ‘deformation’, contingent on resting ANS activity were investigated. CSI positively correlated with outward deformation of the brainstem, right nucleus accumbens, right amygdala and bilateral pallidum (all thresholded to corrected P < 0.05). In contrast, parasympathetic CVT negatively correlated with inward deformation of the right amygdala and pallidum (all thresholded to corrected P < 0.05). Left and right putamen volume positively correlated with CVT (r = 0.62, P = 0.0047 and r = 0.59, P = 0.008, respectively), as did the brainstem (r = 0.46, P = 0.049). These data provide novel evidence that resting autonomic state is associated with differences in the shape and volume of subcortical nuclei. Thus, subcortical morphological brain differences in various disorders may partly be attributable to perturbation in autonomic function. Further work is warranted to investigate these findings in clinical populations. Hum Brain Mapp 39:381–392, 2018. © 2017 Wiley Periodicals, Inc.

The mechanisms that underpin the anti-nociceptive effect of the parasympathetic nervous system (PNS) on visceral pain remain incompletely understood. We sought to describe the effect of resting parasympathetic tone on functional brain networks during the anticipation and experience of oesophageal pain. 21 healthy participants had their resting cardiac vagal tone (CVT), a validated measure of the PNS, quantified, and underwent functional magnetic resonance imaging during the anticipation and experience of painful oesophageal distention. The relationship between resting CVT and functional brain networks was examined using 11 hypothesis-driven nodes and network-based statistics. A network comprising all nodes was apparent in individuals with high resting CVT, compared to those with low CVT, during oesophageal pain (family wise error rate (FWER)-corrected p < 0.048). Functional connections included the thalamus-amygdala, thalamus-hypothalamus, hypothalamus-nucleus accumbens, amygdala-pallidum, pallidum-nucleus accumbens and insula-pallidum. A smaller network was seen during pain anticipation, comprising the amygdala, pallidum and anterior insula (FWER-corrected p < 0.049). These findings suggest that PNS tone is associated with functional brain networks during the anticipation and experience of visceral pain. Given the role of these subcortical regions in the descending inhibitory modulation of pain, these networks may represent a potential neurobiological explanation for the anti-nociceptive effect of the PNS.

Background:The Ca 2+ -activated Cl - channel, Ano1, is expressed on interstitial cells of Cajal (ICC) in the gastrointestinal tunica muscularis.It is required for normal ICC function and proliferation.We previously reported that the glioma-associated oncogene transcription factors, Gli1 and Gli2 bind to, and inhibit activity of the human ANO1 promoter.However the impact of Gli-Ano1 interaction on ICC function has not been determined.Aim: To determine how inhibition of Ano1 promoter activity by Gli in ICC affects electrical slow waves in the mouse small intestine.Methods: The mouse Ano1 promoter was identified by examining the sequence upstream of the first exon for the presence of core promoter elements, binding sites for transcription factors of interest and activating histone marks.The Ano1 promoter was studied by chromatin immunoprecipitation (ChIP).Promoter activity was determined by luciferase reporter assay.Mice genetically engineered to conditionally overexpress Gli2 in ICC in response to tamoxifen treatment, were generated by breeding Kit CreERT2/ + and Gt(ROSA)26Sor tm2(Gli2)Jmao mice.Electrical slow wave activity in jejunal smooth muscle was recorded by sharp electrode electrophysiology.Results: The 2 kb region upstream of the mouse Ano1 gene was found to contain core promoter elements, binding sites for Stat6, SMAD and CEBP and sequences for potential Gli binding sites.These same sites were in similar locations to the recently characterized human ANO1 promoter.Luciferase assays confirmed that the cloned mouse Ano1 promoter was functional, could be activated by IL-4 and repressed by Gli1 and Gli2 by 60 and 70%, respectively.Tamoxifen treatment increased Gli2 expression in the small intestine of Kit CreERT2/+ , Gt(ROSA)26Sor tm2(Gli2)Jmao mice and suppressed expression of Ano1 mRNA, when compared to vehicle-treated mice.ChIP using anti-FLAG antibodies pulled down the genomic DNA corresponding to the putative Gli binding sites in the mouse Ano1 promoter.Electrical slow waves had shorter duration (607.5±33.5 ms) consistent with partial Ano1 knockdown in tamoxifen-treated mice when compared to vehicle-treated controls (897.9±110.7 ms, P<0.05, n=11-18 cells).Summary and Conclusions: The mouse Ano1 promoter showed it contains functional Gli binding sites that inhibit transcription of Ano1 gene.Increased Gli2 expression in ICC reduces Ano1 expression and alters slow wave activity.These data indicate a physiological role in regulation of Ano1 transcription by Gli in ICC.

Part 1 is a literature review exploring the functional neuroanatomy of pain and psychological modulation of the pain experience. The focus of the review is a description and evaluation of peer reviewed research on functional brain imaging of hypnosis induced pain relief. The findings are summarised and discussed in the context of generalizability. Future research and clinical implications are then outlined. Part 2 is a research study exploring the processes, application, clinical benefits and potential mechanisms of hypnosis for chronic pelvic pain. A mixture of quantitative and qualitative methods were employed to assess a number of psychological and sensory (i.e. pain) changes from baseline to end of treatment. All participants completed the study. Overall, the results suggest that participants benefited from hypnosis treatment but that such benefits varied between individuals in terms of sensory, psychological and behavioural effects such as pain relief, acceptance of pain and engaging in more activity. Several of these benefits were clinically significant and reliable, notably in terms of pain reduction and less catastrophizing. Part 3 is a critical appraisal. Here reflections on the research process, from conducting the study for the empirical paper are discussed.

Eysenck proposed a 'trait theory' of personality, the dimensions of which encompass numerous individual qualities. Whilst the influence of neuroticism on the brain processing of pain is well described, the role of extraversion, to date, has not been systematically investigated. Our aim was to address this knowledge gap using functional magnetic resonance imaging (fMRI).Extraversion was measured in 33 healthy volunteers (17 males, mean age 29 years [range 20-53]) using the Eysenck Personality Questionnaire. fMRI data were acquired using a 3T MRI scanner during rest, pain anticipation, and painful oesophageal balloon distention. The effect of extraversion on flVIRI responses was determined.Extraversion scores varied (range 6-22) and did not influence pain threshold or rating. High extraversion was associated with significantly greater activity in the left cuneus during rest (p <= 0.001), and the right insula during both anticipation (p <= 0.0002) and pain (p <= 0.0008). Low extraversion was associated with significantly greater brain activity in the bilateral precuneus, bilateral lingual gyrus, right inferior temporal gyrus, left fusiform gyrus and left superior parietal lobule during pain anticipation (all p <= 0.0001).These results suggest that extraversion is associated with differences in the brain processing of visceral pain. Future studies of visceral pain, using fMRI, should control for extraversion. (C) 2014 Elsevier Ltd. All rights reserved.

This study aimed to investigate affective modulation of eye blink startle by aversive visceral stimulation. Startle blink EMG responses were measured in 31 healthy participants receiving painful, intermittent balloon distentions in the distal esophagus during 4 blocks (positive, negative, neutral or no pictures), and compared with startles during 3 ‘safe’ blocks without esophageal stimulations (positive, negative or neutral emotional pictures). Women showed enhanced startle during blocks with distentions (as compared with ‘safe’ blocks), both when the balloon was in inflated and deflated states, suggesting that fear and/or expectations may have played a role. Men's startle did not differ between distention and non-distention blocks. In this particular study context affective picture viewing did not further impose any effect on startle eye blink responses. The current results may contribute to a better understanding of emotional reactions to aversive interoceptive stimulation.

Key points Nausea is a highly individual and variable experience. The reasons for this variability are incompletely understood although psychophysiological factors have been proposed. Herein we describe objective psychophysiological changes induced by the subjective sensation of motion sickness. In comparison to subjects who did not develop nausea, nausea‐sensitive subjects demonstrated electrogastrographic and autonomic changes, which included an increase in sympathetic nervous system activity with a concomitant reduction in parasympathetic activity. Furthermore, differences were also evident in plasma ghrelin, and subcortical and cortical activity. These data have a number of important implications for future research examining the physiological mechanisms that underlie nausea: The physiological, hormonal and cortical patterns identified herein represent potential biomarkers of the physiological mechanisms of nausea. Reverse translation of the physiological factors identified may facilitate refinement of animal models used to investigate novel anti‐emetic agents and emetic liability of candidate drugs, increasing their validity and translation of finding to humans. AbstractAn integrated understanding of the physiological mechanisms involved in the genesis of nausea remains lacking. We aimed to describe the psychophysiological changes accompanying visually induced motion sickness, using a motion video, hypothesizing that differences would be evident between subjects who developed nausea in comparison to those who did not. A motion, or a control, stimulus was presented to 98 healthy subjects in a randomized crossover design. Validated questionnaires and a visual analogue scale (VAS) were used for the assessment of anxiety and nausea. Autonomic and electrogastrographic activity were measured at baseline and continuously thereafter. Plasma vasopressin and ghrelin were measured in response to the motion video. Subjects were stratified into quartiles based on VAS nausea scores, with the upper and lower quartiles considered to be nausea sensitive and resistant, respectively. Twenty‐eight subjects were exposed to the motion video during functional neuroimaging. During the motion video, nausea‐sensitive subjects had lower normogastria/tachygastria ratio and cardiac vagal tone but higher cardiac sympathetic index in comparison to the control video. Furthermore, nausea‐sensitive subjects had decreased plasma ghrelin and demonstrated increased activity of the left anterior cingulate cortex. Nausea VAS scores correlated positively with plasma vasopressin and left inferior frontal and middle occipital gyri activity and correlated negatively with plasma ghrelin and brain activity in the right cerebellar tonsil, declive, culmen, lingual gyrus and cuneus. This study demonstrates that the subjective sensation of nausea is associated with objective changes in autonomic, endocrine and brain networks, and thus identifies potential objective biomarkers and targets for therapeutic interventions.

was significantly correlated with the tachyarrhythmia and vomiting; also, the decrease of antral contraction was significantly associated with bradygastria and emetic symptoms (such as licking tongue or salivation) but not vomiting.4) Gastric emptying of liquids was substantially delayed during vasopressin infusion (P<0.01,vs the corresponding period in saline control).Conclusion: Vasopressin induces both vomiting and nausea and each symptom has a specific motility pattern.This animal model for nausea and vomiting represents a good target for future pharmaceutical and device intervention.

ACC for both groups by thresholding stimulus-induced activation in the liminal state.Compared with controls, IBS patients' salience network demonstrated significant overlapping with the DMN and ECN in the prefrontal and posterior cingulate cortices (Fig. 1B).An excessive coupling of the salience network with other intrinsic networks can invokes more extensive attentional and cognitive processing of incoming sensory stimuli across brain networks.Therefore, our results suggest a link between the observed excessive coupling of the salience network with the DMN and ECN and the neural expression of visceral hypersensitivity in IBS patients.In a more general theoretical context, the findings support the theory that aberrant functional connectivity of the salience network may underline various attentional and cognitive disorders in human subjects.

Background The parasympathetic nervous system has been implicated in the pathogenesis of a number of gastrointestinal disorders including irritable bowel syndrome. Within the field, cardiometric parameters of parasympathetic/vagal tone are most commonly derived from time, or frequency, domain analysis of heart rate variability (HRV), yet it has limited temporal resolution. Cardiac vagal tone (CVT) is a non-invasive beat-to-beat measure of brainstem efferent vagal activity that overcomes many of the temporal limitations of HRV parameters. However, its normal values and reproducibility in healthy subjects are not fully described. The aim of this study was to address these knowledge gaps. Methods 200 healthy subjects (106 males, median age 28 years, range 18-59 years) were evaluated across three study centers. After attachment of CVT recording equipment, 20 min of data (resting/no stimulation) was acquired. 30 subjects, selected at random, were restudied after 1 year. Results The mean CVT was 9.5±4.16 linear vagal scale (LVS). Thus, the normal range (mean±2 standard deviations) for CVT based on this data was 1.9-17.8 LVS. CVT correlated negatively with heart rate (r=-0.6, P=0.001). CVT reproducibility over 1 year, as indexed by an intra-class correlational coefficient of 0.81 (95% confidence interval 0.64-0.91), was good. Conclusions In healthy subjects, the normal range for CVT should be considered to be 1.9-17.8 LVS and is reproducible over 1 year. Future research utilizing CVT should refer to these values although further study is warranted in patient groups.

Background: The mechanism(s) mediating the higher prevalence of chronic abdominal pain and IBS in women remain incompletely understood.Although the importance of central mechanisms is increasingly acknowledged, sex differences in associative learning and memory processes have thus far not been studied in the context of visceral pain.Fear conditioning is an established experimental model to investigate learning and memory processes relevant for the pathophysiology and/or treatment of conditions including anxiety disorders, chronic back pain and fibromyalgia.Fear conditioning appears particularly well-suited also in the context of visceral hyperalgesia and IBS given the well-documented overlap between IBS (and other somatization disorders) with pre-clinical as well as clinical anxiety.We recently implemented the first fear conditioning study with painful rectal distensions as US in healthy subjects (Kattoor et al., PLOS ONE, in press).Herein, we present results from an extension of this study testing sex differences in the behavioral and neural processes mediating aversive visceral learning, extinction and the recovery of fear, i.e., reinstatement.Methods: In BMImatched healthy males and females (N = 15 males, 15 females), visual conditioned stimuli (CS+) were paired with painful rectal distensions as unconditioned stimuli (US), while different visual stimuli (CS-) were presented without US (differential delay conditioning).During extinction, all CSs were presented without US, whereas during reinstatement, a single, unpaired US was presented.In region-of-interest analyses, males and females were compared with respect to conditioned anticipatory neural activation (CS+ .CS-) along with perceived CS-US contingency, CS unpleasantness and salivary cortisol.Results: Pain ratings and distension-induced neural activation were comparable between males and females.Similarly, no sex differences were observed in perceived CS-US contingency, CS+ valence ratings or cortisol.However, in the late acquisition phase, presentation of the CS+ led to significantly greater anticipatory activation of the insular cortex in women.During extinction, women demonstrated reduced anticipatory activation of the posterior cingulate cortex compared to males.During reinstatement, the CS+ led to significantly greater activation of the hippocampus, thalamus and cerebellum in women.Conclusions: This is the first study to support differences between males and females in the neural processes of aversive visceral learning and memory.Our finding of enhanced neural responses in key brain areas for memory, especially in hippocampus, suggest enhanced reactivation of the old fear memory trace in women.This could play a role in the female preponderance of chronic abdominal pain and irritable bowel syndrome.

Inconsistencies between species has stunted the progress of developing new analgesics. To increase the success of translating results between species, improved comparable models are required. Twelve rats received rectal balloon distensions on 2 different days separated by 24.3 (SD 24.6) days. Rectal balloon distensions were also performed in 18 humans (mean age: 34 yr; range: 21-56 yr; 12 men) on two separate occasions, separated by 9.3 (SD 5.5) days. In rats, cerebral evoked potentials (CEPs) were recorded by use of implanted skull-electrodes to distension pressure of 80 mmHg. In humans surface electrodes and individualized pressure, corresponding to pain detection threshold, were used. Comparison of morphology was assessed by wavelet analysis. Within- and between-day reproducibility was assessed in terms of latencies, amplitudes, and frequency content. In rats CEPs showed triphasic morphology. No differences in latencies, amplitudes, and power distribution were seen within or between days (all P ≥ 0.5). Peak-to-peak amplitude between the first positive and negative potential were the most reproducible characteristic within and between days (evaluated by intraclass correlation coefficients, ICC) (ICC = 0.99 and ICC = 9.98, respectively). In humans CEPs showed a triphasic morphology. No differences in latencies, amplitudes, or power distribution were seen within or between days (all P ≥ 0.2). Latency to the second negative potential (ICC = 0.98) and the second positive potential (ICC = 0.95) was the most reproducible characteristic within and between days. A unique and reliable translational platform was established assessing visceral sensitivity in rats and humans, which may improve the translational process of developing new drugs targeting visceral pain.

Women demonstrate higher pain sensitivity and prevalence of chronic visceral pain conditions such as functional gastrointestinal disorders than men. The role of sex differences in the brain processing of visceral pain is still unclear. In 16 male and 16 female healthy subjects we compared personality, anxiety levels, skin conductance response (SCR), and brain processing using functional MRI during anticipation and pain induced by esophageal distension at pain toleration level. There was no significant difference in personality scores, anxiety levels, SCR, and subjective ratings of pain between sexes. In group analysis, both men and women demonstrated a similar pattern of brain activation and deactivation during anticipation and pain consistent with previous reports. However, during anticipation women showed significantly greater activation in the cuneus, precuneus, and supplementary motor area (SMA) and stronger deactivation in the right amygdala and left parahippocampal gyrus, whereas men demonstrated greater activation in the cerebellum. During pain, women demonstrated greater activation in the midcingulate cortex, anterior insula, premotor cortex, and cerebellum and stronger deactivation in the caudate, whereas men showed increased activity in the SMA. The pattern of brain activity suggests that, during anticipation, women may demonstrate stronger limbic inhibition, which is considered to be a cognitive modulation strategy for impending painful stimulation. During pain, women significantly activate brain areas associated with the affective and motivation components of pain. These responses may underlie the sex differences that exist in pain conditions, whereby women may attribute more emotional importance to painful stimuli compared with men.

Pain is a ubiquitous yet highly variable experience. The psychophysiological and genetic factors responsible for this variability remain unresolved. We hypothesised the existence of distinct human pain clusters (PCs) composed of distinct psychophysiological and genetic profiles coupled with differences in the perception and the brain processing of pain. We studied 120 healthy subjects in whom the baseline personality and anxiety traits and the serotonin transporter-linked polymorphic region (5-HTTLPR) genotype were measured. Real-time autonomic nervous system parameters and serum cortisol were measured at baseline and after standardised visceral and somatic pain stimuli. Brain processing reactions to visceral pain were studied in 29 subjects using functional magnetic resonance imaging (fMRI). The reproducibility of the psychophysiological responses to pain was assessed at year. In group analysis, visceral and somatic pain caused an expected increase in sympathetic and cortisol responses and activated the pain matrix according to fMRI studies. However, using cluster analysis, we found 2 reproducible PCs: at baseline, PC1 had higher neuroticism/anxiety scores (P ≤ 0.01); greater sympathetic tone (P<0.05); and higher cortisol levels (P ≤ 0.001). During pain, less stimulus was tolerated (P ≤ 0.01), and there was an increase in parasympathetic tone (P ≤ 0.05). The 5-HTTLPR short allele was over-represented (P ≤ 0.005). PC2 had the converse profile at baseline and during pain. Brain activity differed (P ≤ 0.001); greater activity occurred in the left frontal cortex in PC1, whereas PC2 showed greater activity in the right medial/frontal cortex and right anterior insula. In health, 2 distinct reproducible PCs exist in humans. In the future, PC characterization may help to identify subjects at risk for developing chronic pain and may reduce variability in brain imaging studies.