Background: Patients with irritable bowel syndrome (IBS) have abnormal perception of visceral stimuli; however, no study has so far investigated the perception of non-visceral stimuli in IBS. In the present study we used event-related potentials (ERP) to study whether IBS patients differed from healthy controls in processing of auditory stimuli and, if so, how this was influenced by emotions.
Methods: We compared ERPs to auditory stimuli in 40 female 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 distractors. Characteristics of the first negative wave (N100) and mean amplitudes in 50-msec time intervals between 150 and 600 msec were assessed.
Results: At the frontal midline electrode IBS patients had significantly enhanced N100 amplitude to all stimuli, persisting after adjustment for age, current emotions, and personality traits. They additionally had enhanced waves 200-300 msec and 400-500 msec 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 with controls. Later elements (P300, N400) of stimulus processing were influenced by emotions and personality traits. These may possibly contribute to changes in intestinal motility caused by stress. The study indicates that aberrant brain functioning may be an element of the irritable bowel syndrome. It may elucidate a mechanism for brain-gut interaction by which psychosocial stress may influence visceral pain perception in non-psychiatric subjects with an intestinal motility disorder and also the efficacy of psychiatric treatment on IBS symptoms.