Abstract

Mismatch negativity (MMN) was recorded in thirteen treatment-resistant schizophrenic patients and age- and gender-matched fourteen healthy controls. The MMN was obtained by subtracting the standard from the deviant event-related potential (ERP) brain wave. Subjects responded to infrequent visual stimulation while ignoring binaurally presented auditory input. The patient population showed a larger frequency-MMN amplitude than the normal controls. Separate analyses of the standard and deviant waveforms revealed the expected reduction in the amplitude of the MMN from frontal to central and parietal locations in the control group. In contrast, treatment-resistant patients had the largest MMN amplitudes recorded at the central-posterior electrode location. Although no cerebral lateralization was noted, the patient group displayed larger negativities at the left and right temporal sites, and at the left frontal scalp location than the normal subjects. Behavioral and ERP measures of performance to task-relevant stimuli yielded no group differences for reaction time, or P300 amplitude. The percentage of correct responses was excellent for all subjects, but controls were more accurate.