Background Typically, conventional functional imaging methods involve repeated exposures to sensory stimulation. In rectal distension (RD) studies that involve multiple distensions, however, it is difficult to disambiguate the central response to RD from pathological alterations in peripheral neural responses associated with relaxation and accommodation of the rectum.
Methods This study addressed potential confounders found in previous imaging studies by collecting functional magnetic resonance imaging studies (fMRI) data during a single slow ramp-tonic distension paradigm and analysing fMRI signal changes using independent component analysis.
Key Results Compared with controls, IBS participants showed increased activation of the anterior cingulate cortices, insula and ventral medial prefrontal regions suggesting heightened affective responses to painful visceral stimuli. In addition, the failure by IBS patients to down-regulate activity within ventral medial prefrontal and the posterior cingulate/precuneus regions was suggestive of reduced sensitivity to somatic changes and delayed shifts away from rest in `default network' activity patterns. Controls showed heightened activation of the thalamus, striatal regions and dorsolateral prefrontal cortex suggesting greater arousal and salience-driven sustained attention reactions and greater modulation of affective responses to discomfort and pain.
Conclusion&Inferences This work points to alterations in the central response to visceral pain and discomfort in IBS, highlighting diminished modulation and heightened internalization of affective reactions.