Su1983 Mild Visceral Stimuli Interfere With Attentional Processes in IBS but Not Healthy Control Subjects

Abstract

Background: IBS patients are known to attribute high relevance to interoceptive signals from the gut and show selective attention to perceived threat from such signals. Based on these clinical observations, one would expect that IBS patients show stronger interference of mild rectal distention with attention tasks. It is unclear, however, if such interference is independent of the difficulty (load) of the attention task, with high, but not low attentional loads overriding the visceral perception. In this case focusing away from the symptoms might be sufficient to control them, otherwise a direct and relevant impact of the symptoms on every day life would supported without the option just to focus away. We therefore studied the influence of visceral stimuli on a letter search task. Methods: 19 IBS patients and 20 healthy controls (HCs) completed a validated high and low load attention letter search task during randomly ordered 20s blocks of mild rectal distention (20mmHg) or baseline (5mmHg). Subjects were instructed to focus exclusively on the attention task and to ignore the balloon, while functional brain images were acquired on a 3T MRI scanner. Image preprocessing included realignment, normalization to MNI space using a high-dimensional DARTEL-warp, and smoothing. Effects of interest were attention processing irrespective of distracting balloon inflations, as well as the interaction between attention processing and those distensions. All results were thresholded at p≤0.05 (FWE cluster level corrected). Results: Performing the high-load attention task itself was associated with stronger activations in HCs versus IBS in dorsal and ventral visual stream as well as parietal and frontal regions. These differences were much less pronounced during low load. Rectal distention during low load tasks was associated with significantly less activation of ventral and dorsal visual stream activity as well as sensorimotor areas, without group differences. However, during high attentional load, rectal distention had no significant effect in HC, while IBS showed significantly reduced activation in the dorsal and ventral visual stream, and right sensorimotor areas. Conclusions: Differences between IBS and HC were observed particularly during high attention load tasks, providing evidence for a direct impact of mild visceral stimuli on attentional processes in IBS. This may be interpreted as a deficit in suppressing distracting information from the viscera, preventing the full utilization of attention switching resources to efficiently solve the demanding attention task. This interpretation is further supported by the observation that brain areas associated with the localization and recognition of target letters (including ventral and dorsal visual stream) were affected. Supported by NIH grants DK048351, DK064539, AT002681 (EAM); DK071626, DK084169 (JSL)