Background. The study attempts to recruit well known
‘cognitive’ event related potential measures as an objective
estimate
of cognitive and specific memory impairment in schizophrenia.
Methods. We examined 19 schizophrenic patients and 28 healthy controls
using
an auditory discrimination task to elicit event related potentials, and
a number
of neuropsychological tests,
including tests of general intellectual ability, putative frontal lobe
function
and verbal memory.
Results. The late positive deflection presumed to be associated
with stimulus evaluation (P300)
was of lower amplitude and had a longer latency in the patients compared
with
controls of
similar age and sex. We found correlations between P300 amplitude and latency,
and neuropsychological performance scores in patients. There were correlations
between decreased P300
amplitude and lower IQ and poorer memory performance, in particular, abnormal
semantic clustering, discriminability and intrusion errors. Increased P300
latency
was correlated with lower
pre-morbid IQ, poorer total memory scores and serial clustering, but paradoxically
less relative retrieval deficit and fewer intrusion errors.
Conclusions. These findings suggest that abnormal P300 is generally
more likely to occur in patients with memory impairment.