Gating of auditory evoked responses in normal college students

Several neurophysiological indicators of abnormal sensory processing found in psychosis are also found in lower incidence in normal populations, particularly those at the age of risk for illness. One such parameter, gating of the auditory evoked potential, was evaluated in college students. Auditory stimuli were presented in pairs to 21 normal subjects, who generally showed gating or suppression of the vertex P50 wave to the second stimulus. Since suppression in this conditioning-testing paradigm is often absent in psychotic patients, we attempted to see if particular parameters, perhaps related to the psychotic state, that would interfere with suppression could be identified in these normal subjects. Increase in motor activity by either active or passive movement did not alter suppression. Distraction of attention by a serial subtraction test also did not interfere. Suppression was not related to mood in most subjects. Extreme self-ratings of tension-anxiety and anger-hostility were closely associated with absence of suppression, however. The results suggest that changes in concentration or motor activity do not affect suppression, but absence of suppression is associated with significant disturbance of mood in a fraction of a normal population of college students.