Impairment of inhibition of unattended stimuli in schizophrenic patients: event-related potential correlates during selective attention.

Auditory event-related potentials (ERPs) were recorded during a dichotic listening task in 18 remitted schizophrenic patients and in 18 age-matched controls. The subjects were instructed to press a button in response to the target tones applied to one designated ear. In schizophrenic patients, P300 amplitude for attended target was significantly smaller than in controls. Schizophrenic patients also exhibited reduced positive potentials between 200 and 400 ms in ERPs for unattended nontarget. These results suggested that schizophrenic patients lack the ability to inhibit unattended or irrelevant stimuli, in addition to impairment of 'context closure' in the information processing.