P50 SUPPRESSION AMONG SCHIZOPHRENIA AND NORMAL COMPARISON SUBJECTS - A METHODOLOGICAL ANALYSIS

The present report investigated the relationship between P50 suppressi on and habituation among 20 schizophrenia and 20 normal comparison sub jects, Subjects were presented with clicks delivered over headphones i n a S-1-S-2 paradigm (clicks were separated by 500 msec; average inter trial interval was 8 sec), There were 60 total trials; the data were a nalyzed separately for the first and second 30 trials, The grolrps did not differ either on the number of usable trials or on the morphology of their P50 responses, Consistent with previous reports, schizophren ia patients demonstrated deficient P50 suppression, The overall suppre ssion effect was not due to a group difference on S-1 P50 amplitudes, but was associated with schizophrenia patients having smaller S-1 - S- 2 P50 amplitude difference scores than normal comparison subjects, Fur thermore, the suppression effect appears to be more pronounced during the first than during the second block of trials, Thus, it may be impo rtant to evaluate changes in P50 responses over time among schizophren ia and normal comparison subjects. (C) 1997 Society of Biological Psyc hiatry.