LEFT LATERALIZED P300 AMPLITUDE DEFICIT IN SCHIZOPHRENIC-PATIENTS DEPENDS ON PITCH DISPARITY

The general reduction of P300 amplitude in response to auditory oddbal l stimuli is one of the most consistently replicated biological observ ations in schizophrenic patients. Several groups have reported a P300 asymmetry in schizophrenic patients, others have not been able to repl icate this finding. In order to clarify this issue, we examined the ef fect of stimulus discriminability on P300 amplitude distribution in sc hizophrenic patients and in age-matched normal control subjects, using two different auditory oddball paradigms, The detection of the target tone was either simple or difficult, due to manipulation of pitch dis parity. The P300 amplitude was comparatively smaller in the schizophre nic patient group compared to the healthy controls and in the difficul t task compared to the simple. The schizophrenic patients showed a spe cific P300 amplitude reduction over left temporal electrode sites when the simple paradigm was used. The difficult paradigm did not elicit a symmetrical P300 amplitudes in schizophrenic patients. (C) 1997 Societ y of Biological Psychiatry.