Morphological and latency abnormalities of the mid-latency auditory evoked responses in schizophrenia: a preliminary report.

INTRODUCTION: Evoked potential (EP) amplitude and latency abnormalities have been extensively examined in schizophrenia. Morphological abnormalities of the mid-latency auditory evoked responses (MLAERs; P50, N100, P200), on the other hand, received very little attention.
METHODS: Based on a priori defined set of morphological criteria, the morphology and latency of the MLAERs were blindly compared between stable outpatients with schizophrenia (N=27) and age- and gender-matched healthy control subjects (N=22). The morphology of the MLAERs was considered abnormal if one or more of the components fell outside the expected latency range, if one or more of the components were missing, or if a later occurring component was smaller in amplitude than an earlier occurring one.
RESULTS: Of the 27 schizophrenia subjects, 20 had waveforms that were deemed atypical, while only 8 from the control group were classified as atypical (chi(2)=5.52, p<0.02). The latencies of the P50 and N100 components, identified based on morphology, were significantly prolonged in schizophrenia patients.
CONCLUSIONS: These preliminary data suggest that morphological abnormalities of the MLAERs in schizophrenia patients are significant and should be taken into consideration when examining the MLAERs of this patient population.