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Abstract:
Individuals with severe psychopathology show deficits on a
variety of tasks, although the diagnostic and cognitive specificity
of the deficits is largely undetermined. Schizophrenics have
inconsistently shown auditory sensory memory deficits, measured via
mismatch negativity (MMN) in the event-related potential (ERP), but
have consistently shown working memory deficits, measured
behaviorally and with ERPs. Questions can be raised about the
appropriateness of the MMN paradigms used to date in
schizophrenics. Depressives' memory deficits have been
conceptualized more abstractly, in terms of controlled processing
involved in working memory. Sensory memory has not been examined in
depressives, although theories predict that it is intact. An ERP
study of sensory and working memory was designed to avoid
confounding MMN with other components. Schizophrenics, depressives,
and controls performed a tone discrimination task, in which
subjects counted or ignored tones. Evidence of memory abnormalities
emerged as a function of diagnosis and stimulus sequence. All three
groups showed intact auditory sensory memory, with comparable
amplitudes and sequence effects. Depressives showed dysfunctional
working memory, as indexed by exaggerated N2b. Schizophrenics did
not differ from controls overall, but, in analyses as a function of
diagnostic subtype, N2b for target stimuli was exaggerated in
negative-symptom schizophrenics, who most resemble depressives.
Results suggest abnormal voluntary, strategy-sensitive processing
in psychopathology, particularly in patients showing negative
symptoms.
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