Perceptual hyperreactivity to auditory stimuli in patients with irritable bowel syndrome

Background: Patients with irritable bowel syndrome (IBS) have abnormal perc eption of visceral stimuli; however, no study has so far investigated the p erception of non-visceral stimuli in IBS. In the present study we used even t-related potentials (ERP) to study whether IBS patients differed from heal thy controls in processing of auditory stimuli and, if so, how this was inf luenced by emotions. Methods: We compared ERPs to auditory stimuli in 40 fe male diarrhoea-predominant IBS patients without current psychiatric illness with those in 20 healthy controls. Tones were used as standard and target stimuli, and words with emotional content as distracters. Characteristics o f the first negative wave (N100) and mean amplitudes in 50-msec rime interv als between 150 and 600 msec were assessed. Results: At the frontal midline electrode IBS patients had significantly enhanced N100 amplitude to all st imuli, persisting after adjustment for age, current emotions, and personali ty traits. They additionally had enhanced waves 200-300 msec and 400-500 ms ec after stimulus. The latter differences disappeared after adjustment for emotions and personality traits. Conclusions: In the frontal brain region, IBS patients seem to have a hyperreactivity to auditory stimuli compared wi th controls. Later elements (P300, N400) of stimulus processing were influe nced by emotions and personality traits. These may possibly contribute to c hanges in intestinal motility caused by stress. The study indicates that ab errant brain functioning may be an element of the irritable bowel syndrome. It may elucidate a mechanism for brain-gut interaction by which psychosoci al stress may influence visceral pain perception in non-psychiatric subject s with an intestinal motility disorder and also the efficacy of psychiatric treatment on IBS symptoms.