Schizophrenic patients are impaired in memory reinstatement underlying mismatch negativity system

Abstract

Objective We modified the paradigm used in the report of Cowan et al. [J Exp Psychol Learn Mem Cogn 19 (1993) 909] to investigate how the silent intervals influence the memory trace underlying mismatch negativity (MMN) generation in schizophrenic patients. Methods Experiment 1 was designed to explore how long an inter-train interval would be needed for the memory to become dormant. Experiment 2 was designed to elucidate how many standard stimuli would be needed to reinstate the memory. Results In Experiment 1, schizophrenic patients showed a significant reduction in MMN amplitude after the longer inter-train intervals compared to the shorter ones, although little difference was observed in controls. Specifically, the memory trace underlying the MMN system in the schizophrenic patients easily became dormant after the extended silent intervals. In Experiment 2, we could not conclude that schizophrenic patients needed more reminders than did controls in order to reinstate the memory once the memory trace became dormant. The patients might be little impaired with respect to forming the memory trace. Conclusions In schizophrenic patients, the memory trace in MMN generation might easily become out of context after silent intervals. Patients could not effectively reinstate the memory that was put out of context by the extended silent interval. Significance This article provides some suggestions in terms of patients' difficulty encoding episodes and retrieving them within distinct contexts in preconscious processes.