OBJECTIVE: The multiple disorders of selective attention found in
schizophrenia could be secondary to disturbances in sensory processing. The
authors investigated this possibility by using an event-related potential
index of auditory sensory memory, called "mismatch negativity." METHOD:
Medicated (N = 11) and neuroleptic-free (N = 11) patients with
schizophrenia and patients with bipolar affective disorder (N = 11) were
compared with age- and sex-matched healthy comparison subjects. Auditory
stimuli were presented while the subjects were distracted with an
attention-demanding visual task. Event-related potentials were elicited by
infrequently occurring auditory stimuli (deviants) and by regularly
presented auditory stimuli (standards), which differed slightly in
duration. The difference in amplitude between the event-related potentials
elicited by the deviant and standard stimuli was the mismatch negativity.
RESULTS: The amplitude of the mismatch negativity was significantly lower
in both groups of schizophrenic patients than in the healthy comparison
subjects. Mismatch negativity amplitude was significantly correlated with
ratings of negative schizophrenic symptoms but not with positive symptoms.
Compared with the matched comparison subjects, the bipolar affective
disorder patients did not show lower amplitude of mismatch negativity.
There was a significant negative correlation between age and mismatch
negativity amplitude. CONCLUSIONS: The abnormal auditory sensory memory
processing indicated by low mismatch negativity amplitude in the
schizophrenic patients cannot be accounted for by neuroleptic medication
status. Because this abnormality was significantly related to measures of
negative symptoms only, it may be a chronicity marker or reflect a
predisposition to the development to schizophrenia. These findings
implicate the auditory cortex in the pathophysiology of schizophrenia.