BRAIN POTENTIAL EVIDENCE FOR AN AUDITORY SENSORY MEMORY DEFICIT IN SCHIZOPHRENIA

Objective: The multiple disorders of selective attention found in schi zophrenia could be secondary to disturbances in sensory processing. Th e authors investigated this possibility by using an event-related pote ntial index of auditory sensory memory, called ''mismatch negativity.' ' Method: Medicated (N=11) and neuroleptic-free (N=11) patients with s chizophrenia and patients with bipolar affective disorder (N=11) were compared with age- and sex-matched healthy comparison subjects. Audito ry stimuli were presented while the subjects were distracted with an a ttention-demanding visual task. Event-related potentials were elicited by infrequently occurring auditory stimuli (deviants) and by regularl y presented auditory stimuli (standards), which differed slightly in d uration. The difference in amplitude between the event-related potenti als elicited by the deviant and standard stimuli was the mismatch nega tivity. Results: The amplitude of the mismatch negativity was signific antly lower in both groups of schizophrenic patients than in the healt hy comparison subjects. Mismatch negativity amplitude was significantl y correlated with ratings of negative schizophrenic symptoms but not w ith positive symptoms. Compared with the matched comparison subjects, the bipolar affective disorder patients did not show lower amplitude o f mismatch negativity. There was a significant negative correlation be tween age and mismatch negativity amplitude. Conclusions: The abnormal auditory sensory memory processing indicated by low mismatch negativi ty amplitude in the schizophrenic patients cannot be accounted for by neuroleptic medication status. Because this abnormality was significan tly related to measures of negative symptoms only, it may be a chronic ity marker or reflect a predisposition to the development to schizophr enia. These findings implicate the auditory cortex in the pathophysiol ogy of schizophrenia.