Duration and frequency mismatch negativity in schizophrenia

Objectives: The aim of the present study was to elucidate the reasons for a pparent inconsistencies in the schizophrenia literature with respect to the mismatch negativity (MMN) waveform of the event-related potential (ERP). W hile most previous research has shown that MMN is reduced in schizophrenia, there are a small number of studies reporting that frequency MMN is not re duced. Methods: We recorded ERPs to auditory stimuli with different frequencies an d durations from patients with schizophrenia (N = 14) and control subjects (N = 17) of similar age and sex. MMNs to small but discriminable frequency deviants were contrasted with large frequency deviants and duration deviant s. Results: Only the MMN to duration deviants was significantly reduced in pat ients, although there was evidence of a similar trend for large frequency d eviants. Conclusions: The results together with a review of the frequency MMN litera ture suggest that there are 3 variables which are important in determining whether patients exhibit a reduced MMN to frequency deviants: deviant proba bility, degree of deviance and interstimulus interval. The results also ind icated that patients with schizophrenia may have particular deficits in pro cessing the temporal properties of auditory stimuli. This finding has impli cations for the pathophysiology of the disorder as time-dependent processin g is reliant on the integrity of an extensive network of brain areas consis ting of auditory cortex, areas of pre-frontal cortex, the basal ganglia and cerebellum. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.