Panmodal processing imprecision as a basis for dysfunction of transient memory storage systems in schizophrenia

Schizophrenia is a severe mental disorder associated with cognitive disturbances that may reflect underlying deficits in the functioning of brain transient memory storage systems. This study investigates performance in three distinct tasks that require transient memory storage: (1) tone discrimination, (2) object weight discrimination, and (3) "AX"-type visual continuous performance task. The tests used were chosen to investigate the degree to which a similar pattern of performance deficit could be observed across multiple sensory and cognitive domains in schizophrenia. In each of the paradigms, a similar pattern emerged: subjects with schizophrenia showed severe performance deficits whenever performance depended on functioning of transient memory systems. The deficits were apparent at both short and long interstimulus intervals (ISI), however, and schizophrenia subjects were no more affected by increasing ISI than were controls. Moreover, when short ISI performance was matched across groups by manipulating task difficulty, subsequent decay in performance was equivalent across groups. Thus, although schizophrenia subjects show severe performance deficits in memory-dependent tasks, the deficits do not appear to reflect impaired transient memory per se. Rather, they appear to reflect impaired precision of operation of such systems, irrespective of the duration over which representations must be maintained. The severe deficits in processing precision, despite the relatively preserved maintenance of representation, may be relevant to pathophysiological models of schizophrenia.