Personality differences affect brainstem autonomic responses to visceral pain

Personality construct as a biomarker in fibromyalgia: A narrative review from an autonomic rehabilitation perspective

BACKGROUND

The heterogeneity of symptoms and ineffective treatment raise questions about the current diagnostic criteria of fibromyalgia (FM). Misdiagnosis of FM often leads to less than efficacious treatment and poor quality of life.

OBJECTIVE

This article reviews relevant evidence-based literature on personality traits in FM patients with an autonomic dysfunction perspective based on a hierarchical model to explain the utility of considering the personality trait in FM diagnosis.

METHODS

A narrative review of articles concerning chronic pain, FM, and personality traits with respect to autonomic dysfunction in FM was conducted after extensive relevant literature searches.

RESULTS

Reports discussing the predisposing factors, including coping styles, anger, suicide risk, a lack of physical activity and social support, in maintaining persistent pain in FM exist. Relationships between pain duration and severity and personality traits like neuroticism and extraversion have been reported. Coexisting clinical manifestations of FM like sleep disorders, anxiety, and intestinal irritability indicate autonomic dysfunction.

CONCLUSIONS

This article lays out a constructive framework for individualized and personalized medicine for the effective rehabilitation of FM patients. The quest to find a definitive diagnosis of FM should include personality biomarkers that might translate into personalized medicine. An individualistic approach may bank upon artificial intelligence algorithms for both diagnostic as well as prognostic purposes in FM.

Clinical significance and related factors of rectal hyposensitivity in patients with functional defecation disorder

Background

Rectal hyposensitivity (RH) is not uncommon in patients with functional defecation disorder (FDD). FDD patients with RH are usually unsatisfied with their treatment.

Aims

The aim of this study was to find the significance of RH in patients with FDD and the related factors of RH.

Methods

Patients with FDD first completed clinical questionnaires regarding constipation symptoms, mental state, and quality of life. Then anorectal physiologic tests (anorectal manometry and balloon expulsion test) were performed. Rectal sensory testing (assessing rectal response to balloon distension using anorectal manometry) was applied to obtain three sensory thresholds. Patients were separated into three groups (non-RH, borderline RH, and RH) based on the London Classification. The associations between RH and clinical symptoms, mental state, quality of life, and rectal/anal motility were investigated.

Results

Of 331 included patients with FDD, 87 patients (26.3%) had at least one abnormally elevated rectal sensory threshold and 50 patients (15.1%) were diagnosed with RH. Patients with RH were older and mostly men. Defecation symptoms were more severe (p = 0.013), and hard stool (p < 0.001) and manual maneuver (p = 0.003) were more frequently seen in the RH group. No difference in rectal/anal pressure was found among the three groups. Elevated defecatory desire volume (DDV) existed in all patients with RH. With the number of elevated sensory thresholds increasing, defecation symptoms got more severe (r = 0.35, p = 0.001). Gender (male) (6.78 [3.07-15.00], p < 0.001) and hard stool (5.92 [2.28-15.33], p < 0.001) were main related factors of RH.

Conclusion

Rectal hyposensitivity plays an important role in the occurrence of FDD and is associated with defecation symptom severity. Older male FDD patients with hard stool are prone to suffer from RH and need more care.

Psychological Profile in Women with Chronic Pelvic Pain

(1) Background: Chronic Pelvic Pain (CPP) is a prevalent medical condition with a complex treatment due to different variables that influence its clinical course. (2) Methods: Psychological variables such as depression, anxiety, catastrophizing or neuroticism have been described as influencing CPP. This is a cross-sectional study of 63 patients with CPP sent for a psychological evaluation due to participation in group therapy for CPP. The main purpose of this study was to characterize the baseline psychological characteristics of women with CPP. The NEO Five Factor Inventory (NEO-FFI), State and Trait Anxiety Inventory (STAI), Beck Depression Inventory-Fast Screen (BDI-FS), Pain Catastrophizing Scale (PCS) and Chronic Pain Acceptance Questionnaire (CPAQ) were performed. (3) Results: The personality profile of patients (NEO FFI) shows high neuroticism, low extraversion and low conscientiousness. The 25.4% of patients had moderate or severe depression according to BDI-FS results, almost half of the patients had high levels of anxiety trait (>P75, 49.2%) and more than half the patients had high levels of anxiety state (>P75, 59.5%). Punctuations of PCS and CPAQ are similar to patients with fibromyalgia. (4) Conclusions: CPP is associated with high levels of depression, anxiety, neuroticism, catastrophizing and low pain acceptance. It is important to develop interventions that can modify these psychological factors in order to improve the clinical course of CPP.

Heart Rate Variability and Pain: A Systematic Review

Background and Objective: Heart rate variability (HRV) as an index of the autonomic nervous system appears to be related to reactivity to experimental pain stimuli. HRV could better explain the contributions of sympathetic and parasympathetic activity response to nociceptive stimulation. The aim of this study was to systematically review and synthesize the current evidence on HRV in relation to the experience of pain in experimental tasks. Databases and Data Treatment: Studies indexed in the PubMed, PsycINFO, MEDLINE, WebOfScience, and Scopus databases were reviewed for eligibility. Studies on the autonomic response (i.e., HRV) to experimentally induced pain in healthy adults were included. Different methods of pain induction were considered (e.g., thermal, pressure, and electrical). Data were synthesized considering the association between HRV and both pain induction and subjective measures of pain. Results: Seventy-one studies were included. The results underline significant change in both the sympathetic and parasympathetic autonomic nervous systems during the painful stimulation independent of the pain induction method. The autonomic reaction to pain could be affected by several factors, such as sex, age, body mass index, breathing patterns, the intensity of the stimulation, and the affective state. Moreover, an association between the autonomic nervous system and the subjective experience of pain was found. Higher parasympathetic activity was associated with better self-regulation capacities and, accordingly, a higher pain inhibition capacity. Conclusions: HRV appears to be a helpful marker to evaluate nociceptive response in experimentally induced pain. Future studies are also needed in clinical samples to understand better the interindividual changes of autonomic response due to pain stimuli.

A comparison using standardized measures for patients with irritable bowel syndrome: Trust in the gastroenterologist and reliance on the internet

BACKGROUND

Irritable bowel syndrome (IBS) patients' use of the Internet for health information interacts with the way they trust their gastroenterologist. No standardized measure has targeted IBS patients and gastroenterologists specifically, nor their use of the Internet. The aims of this paper were as follows: the development of a scale that measures an IBS patient's trust in their gastroenterologist, the development of a scale measuring an IBS patient's reliance on Internet health information, and testing the hypothesis that IBS patients, who use the Internet for IBS-related information, trust their gastroenterologist less than those who do not.

METHOD

A total of 82 patients (mean age 49, SD = 14.62) diagnosed with IBS completed two questionnaires: one about trust in their gastroenterologist and the other about the reliance on Internet health information regarding IBS. The two questionnaires were built using current literature as well as our previous qualitative research. The statistical computations were performed using the SPSS 20 program.

KEY RESULTS

Both questionnaires proved to be reliable in measuring gastroenterologist-IBS patient trust (alpha = 0.87) and Internet information reliance (alpha = 0.88), respectively. The IBS patients who did not look for information about IBS over the Internet had significantly higher trust in their gastroenterologist compared with those who did (U = 535.5; z = -2.26; P < 0.05).

CONCLUSIONS

We developed two ready-to-use scales to measure both the gastroenterologist-IBS patient's trust and the IBS patient's reliance on the Internet. Further studies will be able to explore the interaction among all variables in IBS patients' trust.

Preliminary report: parasympathetic tone links to functional brain networks during the anticipation and experience of visceral pain

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.

New evidence for a pain personality? A critical review of the last 120 years of pain and personality

BACKGROUND

Personality traits may influence development and adjustment to ongoing pain. Over the past 120 years, there has been considerable research into the relationship between pain and personality. This paper presents new evidence for common personality traits found amongst chronic pain sufferers. In particular, it evaluates evidence for Cloninger's biopsychosocial model of personality in distinguishing typical personality features of chronic pain sufferers. It evaluates this evidence in the context of the past 120 years of research including psychodynamic formulations, MMPI studies, personality disorder investigations, and the influence of neuroticism on chronic pain.

METHODS

A literature search was conducted using PubMed, Medline, PsycINFO, SCOPUS and Cochrane library. Search terms included chronic pain, pain, personality, neuroticism, harm avoidance, self-directedness, attachment, Temperament and Character Inventory (TCI-R), MMPI, MMPI-2, NEO-PI, EPI, Millon Clinical Multiaxial Inventory, Millon Behavioral Health Inventory, Millon Behavioral Medicine Diagnostic, the Personality Assessment Inventory, the Locus of Control Construct and different combinations of these terms.

CONCLUSIONS

Recent descriptive studies using Cloninger's Temperament and Character Inventory (TCI-R) suggest that higher harm avoidance and lower self-directedness may be the most distinguishing personality features of chronic pain sufferers. High harm avoidance refers to a tendency to be fearful, pessimistic, sensitive to criticism, and requiring high levels of re-assurance. Low self-directedness often manifests as difficulty with defining and setting meaningful goals, low motivation, and problems with adaptive coping. Evidence for this personality profile is found across a wide variety of chronic pain conditions including fibromyalgia, headache and migraine, temporomandibular disorder, trigeminal neuropathy, musculo-skeletal disorders and heterogeneous pain groups. Limitations are also discussed. For example, high harm avoidance is also found in those suffering anxiety and depression. While many studies control for such factors, some do not and thus future research should address such confounds carefully. The evidence is also evaluated within the context of past research into the existence of 'a pain personality'. Psychodynamic formulations are found to be deficient in objective scientific methods. MMPI studies lack sufficient evidence to support 'a pain personality' and may be confounded by somatic items in the instrument. More recent neuroticism studies suggest a relationship between neuroticism and pain, particularly for adjustment to chronic pain. Personality disorders are more prevalent in chronic pain populations than non-pain samples.

CLINICAL IMPLICATIONS

Because harm avoidance reflects a tendency to developed conditioned fear responses, we suggest that higher harm avoidance may create more vulnerability to developing a fear-avoidance response to chronic pain. Furthermore, lower self-directedness may contribute to keeping a sufferer within this vicious cycle of fear, avoidance and suffering. Moreover, we suggest that harm avoidance and self-directedness are broader and more complex constructs than current clinical targets of CBT such as fear-avoidance and self-efficacy. Thus, assessing such personality traits may help to address the complexity of chronic pain presentations. For example, it may help to identify and treat sufferers more resistant to treatment, more prone to comorbidity and more vulnerable to entering the vicious cycle of chronic pain, suffering and disability.

Abnormal regional homogeneity and its correlations with personality in first-episode, treatment-naive somatization disorder

BACKGROUND

Structural and functional abnormalities of the default mode network (DMN) and their correlations with personality have been found in somatization disorder (SD). However, no study is conducted to identify regional neural activity and its correlations with personality in SD. In this study, regional homogeneity (ReHo) was applied to explore whether abnormal regional neural activity is present in patients with SD and its correlations with personality measured by Eysenck Personality Questionnaire (EPQ).

METHODS

Twenty-five first-episode, treatment-naive patients with SD and 28 sex-, age-, and education-matched healthy controls participated in the whole study. During the scanning, all subjects were instructed to lie still with their eyes closed and remain awake. A ReHo approach was employed to analyze the data.

RESULTS

The SD group had a significantly increased ReHo in the left angular gyrus (AG) compared to healthy controls. The increased ReHo positively correlated to the neuroticism scores of EPQ (EPQ-N). No other correlations were detected between the ReHo values and other related factors, such as symptom severity and education level.

CONCLUSIONS

Our results suggest that abnormal regional neural activity of the DMN may play a key role in SD with clinical implications and emphasize the importance of the DMN in the pathophysiological process of SD.

Visually induced nausea causes characteristic changes in cerebral, autonomic and endocrine function in humans

An 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.

Psychophysiological responses to visceral and somatic pain in functional chest pain identify clinically relevant pain clusters

BACKGROUND

Despite chronic pain being a feature of functional chest pain (FCP) its experience is variable. The factors responsible for this variability remain unresolved. We aimed to address these knowledge gaps, hypothesizing that the psychophysiological profiles of FCP patients will be distinct from healthy subjects.

METHODS

20 Rome III defined FCP patients (nine males, mean age 38.7 years, range 28-59 years) and 20 healthy age-, sex-, and ethnicity-matched controls (nine males, mean 38.2 years, range 24-49) had anxiety, depression, and personality traits measured. Subjects had sympathetic and parasympathetic nervous system parameters measured at baseline and continuously thereafter. Subjects received standardized somatic (nail bed pressure) and visceral (esophageal balloon distension) stimuli to pain tolerance. Venous blood was sampled for cortisol at baseline, post somatic pain and post visceral pain.

KEY RESULTS

Patients had higher neuroticism, state and trait anxiety, and depression scores but lower extroversion scores vs controls (all p < 0.005). Patients tolerated less somatic (p < 0.0001) and visceral stimulus (p = 0.009) and had a higher cortisol at baseline, and following pain (all p < 0.001). At baseline, patients had a higher sympathetic tone (p = 0.04), whereas in response to pain they increased their parasympathetic tone (p ≤ 0.008). The amalgamating the data, we identified two psychophysiologically distinct 'pain clusters'. Patients were overrepresented in the cluster characterized by high neuroticism, trait anxiety, baseline cortisol, pain hypersensitivity, and parasympathetic response to pain (all p < 0.03).

CONCLUSIONS & INFERENCES

In future, such delineations in FCP populations may facilitate individualization of treatment based on psychophysiological profiling.

Psychological traits influence autonomic nervous system recovery following esophageal intubation in health and functional chest pain

BACKGROUND

Esophageal intubation is a widely utilized technique for a diverse array of physiological studies, activating a complex physiological response mediated, in part, by the autonomic nervous system (ANS). In order to determine the optimal time period after intubation when physiological observations should be recorded, it is important to know the duration of, and factors that influence, this ANS response, in both health and disease.

METHODS

Fifty healthy subjects (27 males, median age 31.9 years, range 20-53 years) and 20 patients with Rome III defined functional chest pain (nine male, median age of 38.7 years, range 28-59 years) had personality traits and anxiety measured. Subjects had heart rate (HR), blood pressure (BP), sympathetic (cardiac sympathetic index, CSI), and parasympathetic nervous system (cardiac vagal tone, CVT) parameters measured at baseline and in response to per nasum intubation with an esophageal catheter. CSI/CVT recovery was measured following esophageal intubation.

KEY RESULTS

In all subjects, esophageal intubation caused an elevation in HR, BP, CSI, and skin conductance response (SCR; all p < 0.0001) but concomitant CVT and cardiac sensitivity to the baroreflex (CSB) withdrawal (all p < 0.04). Multiple linear regression analysis demonstrated that longer CVT recovery times were independently associated with higher neuroticism (p < 0.001). Patients had prolonged CSI and CVT recovery times in comparison to healthy subjects (112.5 s vs 46.5 s, p = 0.0001 and 549 s vs 223.5 s, p = 0.0001, respectively).

CONCLUSIONS & INFERENCES

Esophageal intubation activates a flight/flight ANS response. Future studies should allow for at least 10 min of recovery time. Consideration should be given to psychological traits and disease status as these can influence recovery.

Gender, variation in opioid receptor genes and sensitivity to experimental pain

Background

Pain tolerance is subject to considerable inter-individual variation, which may be influenced by a number of genetic and non-genetic factors. The mu, delta and kappa opioid receptors play a role in pain perception and are thought to mediate different pain modalities. The aim of this study was to explore associations between pain thresholds and gender and genetic variants in the three opioid receptor genes (OPRM, OPRD and OPRK). Experimental multi-modal pain data from previously published studies carried out in healthy Caucasian volunteers were used in order to limit the number of confounders to the study outcome. Data on thermal skin pain (n=36), muscle pressure pain (n=31) and mechanical visceral pain (n=50)) tolerance thresholds were included.

Results

Nineteen genetic polymorphisms were included in linear regression modeling. Males were found to tolerate higher thermal and muscle pressure pain than females (p=0.003 and 0.02). Thirty four percent of variability in thermal skin pain was accounted for by a model consisting of OPRK rs6473799 and gender. This finding was just outside significance when correction for multiple testing was applied. Variability in muscle pressure pain tolerance was associated with OPRK rs7016778 and rs7824175. These SNPs accounted for 43% of variability in muscle pressure pain sensitivity and these findings remained significant after adjustment for multiple testing. No association was found with mechanical visceral pain.

Conclusion

This is a preliminary and hypothesis generating study due to the relatively small study size. However, significant association between the opioid receptor genes and experimental pain sensitivity supports the influence of genetic variability in pain perception. These findings may be used to generate hypotheses for testing in larger clinical trials of patients with painful conditions.

Secular changes in personality: study on 75-year-olds examined in 1976-1977 and 2005-2006

OBJECTIVE

In order to study secular changes in personality factors neuroticism and extroversion, representative population samples of non-demented 75-year-olds underwent psychiatric examinations in 1976-1977 (total n = 223, 138 women, 85 men) and 2005-2006 (total n = 556, 322 women and 234 men).

METHODS

Eysenck Personality Inventory was used at both occasions. Demographic factors (educational level, marital status, having children) were registered.

RESULTS

Seventy-five-year-olds examined in 2005-2006 had higher values on extroversion and lower values on the Lie scale compared with those examined in 1976-1977. Neuroticism did not differ between the two birth cohorts. Neuroticism scores were higher in women than in men both in 1976-1977 and 2005-2006, and Lie score was higher in women than in men in 2005-2006.

CONCLUSIONS

Our findings suggest that present cohorts of 75-year-olds are more extroverted and less prone to respond in a socially desirable manner than those born three decades earlier. Neuroticism levels remained unchanged, suggesting this trait may be less influenced by environmental factors than the other traits studied.

Assessment of rectal afferent neuronal function and brain activity in patients with constipation and rectal hyposensitivity

BACKGROUND

Blunted rectal sensation (rectal hyposensitivity: RH) is present in almost one-quarter of patients with chronic constipation. The mechanisms of its development are not fully understood, but in a proportion, afferent dysfunction is likely. To determine if, in patients with RH, alteration of rectal sensory pathways exists, rectal evoked potentials (EPs) and inverse modeling of cortical dipoles were examined.

METHODS

Rectal EPs (64 channels) were recorded in 13 patients with constipation and RH (elevated thresholds to balloon distension) and 11 healthy controls, in response to electrical stimulation of the rectum at 10 cm from the anal verge using a bipolar stimulating electrode. Stimuli were delivered at pain threshold. Evoked potential peak latencies and amplitudes were analyzed, and inverse modeling was performed on traces obtained to determine the location of cortical generators.

KEY RESULTS

Pain threshold was higher in patients than controls [median 59 (range 23-80) mA vs 24 (10-55) mA; P = 0.007]. Median latency to the first negative peak was 142 (±24) ms in subjects compared with 116 (±15) ms in controls (P = 0.004). There was no difference in topographic analysis of EPs or location of cortical activity demonstrated by inverse modeling between groups.

CONCLUSIONS & INFERENCES

This study is the first showing objective evidence of alteration in the rectal afferent pathway of individuals with RH and constipation. Prolonged latencies suggest a primary defect in sensory neuronal function, while cerebral processing of visceral sensory information appears normal.

Rectal hyposensitivity

Impaired or blunted rectal sensation, termed rectal hyposensitivity (RH), which is defined clinically as elevated sensory thresholds to rectal balloon distension, is associated with disorders of hindgut function, characterised primarily by symptoms of constipation and fecal incontinence. However, its role in symptom generation and the pathogenetic mechanisms underlying the sensory dysfunction remain incompletely understood, although there is evidence that RH may be due to 'primary' disruption of the afferent pathway, 'secondary' to abnormal rectal biomechanics, or to both. Nevertheless, correction of RH by various interventions (behavioural, neuromodulation, surgical) is associated with, and may be responsible for, symptomatic improvement. This review provides a contemporary overview of RH, focusing on diagnosis, clinical associations, pathophysiology, and treatment paradigms.

The autonomic response to human esophageal acidification and the development of hyperalgesia

BACKGROUND

Distal esophageal acidification induces variable hyperalgesia in the non-acid exposed proximal esophagus. As the autonomic nervous system (ANS) modulates nociception, the aim was to determine whether autonomic reactivity to acid infusion predicted inter-individual differences in hyperalgesia.

METHODS

In 25 healthy volunteers (18 women, age range 22-58, mean 36.5 years), using a double-blind, placebo-controlled crossover design, pain thresholds to electrical stimulation were determined in the proximal esophagus and foot (control) pre and post a 30-min distal esophageal infusion of 0.15 mol L(-1) HCl or saline with autonomic monitoring. Sympathetic Cardiac Sympathetic Index and Skin Conductance Response and parasympathetic Cardiac Vagal Tone and Cardiac Sensitivity to Baroreflex measures were derived. Plasma cortisol was measured pre and post infusion as were anxiety and unpleasantness.

KEY RESULTS

Acid infusion reduced group pain threshold in the proximal esophagus (adjusted mean change -5.0 mA vs saline +3.4 mA, P < 0.001), and raised sympathetic measures (Cardiac Sympathetic Index, Skin Conduction Response) and cortisol levels, but reduced parasympathetic measures (cardiac vagal tone and cardiac sensitivity to Baroreflex) (all P < 0.05). Acid infusion also increased anxiety and unpleasantness scores (both P < 0.05). In 16 acid-sensitizers, the degree of hyperalgesia correlated with increasing heart rate (r = -0.66, P = 0.005), and fall in cardiac vagal tone (r = 0.54, P = 0.03) and Cardiac Sensitivity to Baroreflex (r = 0.54, P = 0.03).

CONCLUSIONS & INFERENCES

Acid-induced esophageal hyperalgesia correlated with reduced parasympathetic tone, suggesting that the parasympathetic nervous system may have anti hyperalgesic properties. Additional studies on the autonomic modulation of esophageal hyperalgesia are required.

Neuroticism influences brain activity during the experience of visceral pain

BACKGROUND & AIMS

One particularly important individual dynamic known to influence the experience of pain is neuroticism, of which little is known about in visceral pain research. Our aim was to study the relationship between neuroticism, psychophysiologic response, and brain processing of visceral pain.

METHODS

Thirty-one healthy volunteers (15 male; age range, 22-38 years) participated in the study. The Eysenck Personality Questionnaire was used to assess neuroticism. Skin conductance level, pain ratings, and functional magnetic resonance imaging data were acquired during anticipation of pain and painful esophageal distention. The effect of neuroticism was assessed using correlation analysis.

RESULTS

There was a wide spread of neuroticism scores (range, 0-22) but no influence of neuroticism on skin conductance level and pain tolerance or pain ratings. However, a positive correlation between brain activity and neuroticism during anticipation was found in regions associated with emotional and cognitive pain processing, including the parahippocampus, insula, thalamus, and anterior cingulate cortex. These regions showed a negative correlation with neuroticism during pain (P < .001).

CONCLUSIONS

This study provides novel data suggesting higher neuroticism is associated with engagement of brain regions responsible for emotional and cognitive appraisal during anticipation of pain but reduced activity in these regions during pain. This may reflect a maladaptive mechanism in those with higher neuroticism that promotes overarousal during anticipation and avoidance coping during pain.

Understanding gut-brain interactions in gastrointestinal pain by neuroimaging: lessons from somatic pain studies

BACKGROUND

Neuroimaging research on gut-brain interactions has greatly improved our understanding of the brain mechanisms involved in processing and perceiving visceral pain in health and functional gastrointestinal disorders (FGID). However, discrepancies in the results of these studies continue to exist, which is at least partially due to the fact that important factors contributing to the intrinsic heterogeneity of symptom-based FGID, including psychological processes and psychiatric comorbidity, are insufficiently integrated in visceral pain neuroimaging research.

PURPOSE

This review will defend the thesis that, to increase our understanding of the heterogeneous etiopathogenesis of FGID, visceral pain neuroimaging studies need to be integrated with: (i) epidemiological and behavioral evidence on the influence of psychological processes on visceral pain in health and FGID, and (ii) methodology and evidence from affective, cognitive, and psychiatric neuroimaging studies. To illustrate this point, the somatic pain neuroimaging field will be taken as an example before giving an overview of novel and integrative visceral pain studies in health and FGID. Some limitations of current pain neuroimaging studies will be outlined, before providing a summary of suggestions for moving the visceral pain neuroimaging field forward.

Differential responding of autonomic function to histamine H₁ antagonism in irritable bowel syndrome

BACKGROUND

The role of histamine in the pathophysiology of irritable bowel syndrome (IBS) is largely unknown. Dysfunction of the autonomic nervous system (ANS) in IBS patients is also not fully confirmed. We hypothesized that blockade of histamine H₁ receptors affects ANS responses differently between IBS subjects and controls.

METHODS

Subjects were 12 IBS subjects and 12 age- and sex-matched controls. Either 100 μg kg⁻¹ chlorphenamine or the same amount of saline was administered on different days. The rectum was stimulated with electrical currents of 0 mA (sham) or 30 mA. Autonomic nervous system function was measured using mean arterial pressure (MAP), heart rate (HR), high frequency (HF) component of HR variability, low frequency/high frequency ratio (LF/HF ratio) and plasma catecholamines and histamine. Subjective perceived stress during the examination was evaluated on an ordinate scale.

KEY RESULTS

Mean arterial pressure showed significant effects of diagnosis (P < 0.05) and drug × diagnosis interaction (P < 0.05). The MAP significantly increased after chlorphenamine administration in IBS subjects, but not in controls. Heart rate revealed a significant drug effect (P < 0.001), which decreased after chlorphenamine administration in controls, but not in IBS subjects. Perceived stress significantly increased by rectal stimulation (P < 0.001) and a significant stimulus × diagnosis interaction (P < 0.05) was revealed, indicating greater reduction in IBS subjects by chlorphenamine.

CONCLUSION & INFERENCES

Sympathetic vasomotor tone in IBS subjects differentially responded on administration of a histamine H₁ antagonist to that of controls. These findings suggest an increased histaminergic activity in IBS subjects.

The future of neuroscientific research in functional gastrointestinal disorders: integration towards multidimensional (visceral) pain endophenotypes?

The growing evidence for a key role of psychophysiological processes in the etiopathogenesis of functional gastrointestinal disorders (FGID) originates from various sources, including epidemiological, psychometric, physiological, and behavioural studies. Functional neuroimaging has improved our knowledge about central processing of visceral pain, a defining feature of FGID. However, results have been disappointingly inconsistent, often due to psychosocial factors not being controlled for. In this paper, we aim to show that using integrated research strategies, encompassing a number of scientific disciplines, is critical to advancing our understanding of FGID. We will illustrate this by describing recent integrative studies that may serve as good examples. More specifically, future FGID neuroimaging studies should control for psychosocial factors and incorporate methods from other branches of neuroscience outside this field, especially cognitive, affective and autonomic neuroscience. We therefore propose a framework for the development of an integrative cross-disciplinary research strategy based on advancing our understanding of visceral nociceptive physiology in health as well as vulnerability and susceptibility factors for FGID. This approach will allow the identification of factors responsible for the inter-individual differences in visceral pain perception and susceptibility to chronic visceral pain, leading to the description of multidimensional (visceral) pain "endophenotypes." These may represent the critical steps needed towards a pathophysiological, rather than symptom-based, classification of FGID, which may be more suitable for genetic association studies. This approach may ultimately culminate in individual tailoring of treatment, in addition to disease prevention, thereby improving outcomes for the patient and researcher alike.