Brain Responses to Visceral Stimuli Reflect Visceral Sensitivity Thresholds in Patients With Irritable Bowel Syndrome

Abstract

Background & aims Only a fraction of IBS patients show increased perceptual sensitivity to rectal distension, suggesting possible differences in processing and/or modulation of visceral afferent signals within this group. The aim was to identify brain mechanisms which may underlie these perceptual differences. Methods 44 women with IBS and 20 female healthy control subjects (HCs) were included. Symptom severity in IBS was determined by Severity Scoring System (IBS-SSS). Anxiety and depression symptoms were assessed using the Hospital anxiety & depression score (HAD). Blood oxygen level dependent (BOLD) signals were measured by functional Magnetic Resonance Imaging (fMRI) during expectation and delivery of high (45mmHg) and low (15mmHg) intensity rectal distensions. Perception thresholds to rectal distension were determined in the scanner. Brain imaging data from 18 normosensitive, 15 hypersensitive IBS patients and 18 HCs were compared. Results were reported significant if peak p-value ≤ 0.05 with family wise error correction in regions of interest. Results The two IBS subgroups were similar in age, symptom duration, psychological symptoms and IBS symptom severity. While brain responses to distension were similar in normosensitive patients and HCs, hypersensitive IBS demonstrated greater activation of insula and reduced deactivation in pregenual anterior cingulate cortex during noxious rectal distensions, compared to both HCs and normosensitive IBS. During expectation of rectal distension, normosensitive IBS had more activation in right hippocampus than HCs. Conclusions Despite similarities in symptoms, hyper- and normosensitive IBS patients differed substantially in cerebral response to standardized rectal distensions and their expectation, consistent with differences in ascending visceral afferent input.

Mapping of Brain Activations to Rectal Balloon Distension Stimuli in Male Patients with Irritable Bowel Syndrome Using Functional Magnetic Resonance Imaging

“…[12][13][14][15]18 Furthermore, resting state fMRI study performed on IBS patients demonstrated increased spontaneous neuronal activity in visceral afferent processing regions, while decreased regional brain activity in cognitive and pain regulatory regions. 21 To date, most neuro-imaging studies performed in response to visceral pain among IBS patients have been carried out in Western countries and female patients [10][11][12][18][19][20][22][23][24][25][26][27][28][29] (Table 1). However, in some Asian countries including India, a large proportion of patients with IBS are males.…”

Neural correlates of electrointestinography: Insular activity modulated by signals recorded from the abdominal surface

“…We defined the right dorsal anterior (coordinates: [34, 19, 2]), ventral anterior (coordinates: [35, 17, À10]), and middle insula (coordinates: [39, 2, 3]) as the regions of interest for cortical EIG processing according to the previous study (Larsson et al, 2012) examining brain responses to visceral stimulation. These three functional subdivisions of the insula have been reported (Chang et al, 2013), and the right anterior insula is critical for conscious visceral sensation (Craig, 2009;Critchley and Harrison, 2013).…”

“…Finally, at the group level, one-sample t-tests using individual correlation coefficients with covariates of state-anxiety scores were performed using SPM8. The left anterior insula (coordinates: [À32, 20, 1]) and anterior cingulate cortex (ACC) (coordinates: [7, 29, 27]) were defined as regions of interest for networks modulated by anxiety according to a previous study (Larsson et al, 2012) examining brain responses to visceral stimulation and anxiety. For the region of interest analysis, activations that surpassed the peak-level significance at a threshold of p < 0.05 (FWE corrected) with small-volume correction (with a sphere of 8-mm radius) were reported.…”

“…Additionally, since a previous study has suggested a link between intestinal activity and anxiety (Foster and McVey Neufeld, 2013), correlations between EIG activity and anxiety scores were examined. We hypothesized that the insula and cingulate cortices would be involved in visceral processing and anxiety (Paulus and Stein, 2006;Coen et al, 2009;Berman et al, 2012;Larsson et al, 2012).…”

Low-FODMAP Diet for Irritable Bowel Syndrome: Is It Ready for Prime Time?

“…While these physiological effects similarly affect healthy controls and IBS patients, altered sensory processing or health-related concerns may trigger different responses in these groups. This conceptual model is certainly backed by studies on visceral sensory mechanisms in IBS [38,39], but still lack empirical support.…”