The effect of 12-week physical exercise intervention to the sleep-dependent motor sequence memory consolidation in schizophrenia

Abstract

Among the many cognitive deficits that have been found in schizophrenia, procedural memory is one of the few spared cognitive constructs. However, recent studies have demonstrated that the memory consolidation in procedural learning is impaired, and the impairment is sleep-dependent. Concurrently, the sleep quality has been frequently reported to be disrupted, and it further strengthens the association with the impaired memory consolidation in schizophrenia. To restore the sleep-dependent memory consolidation, here we explore the effectiveness of physical exercise in enhancing the consolidation performance via improving the subjective sleep quality. Four studies have been carried out to demonstrate the interaction between exercise, sleep and memory consolidation. The first study was designed to explore and compare the subjective sleep quality between schizophrenia and healthy control. A few specific subjective sleep abnormalities have been found among the patients with schizophrenia. The second study was designed to compare the practice-dependent procedural learning, time-dependent procedural memory consolidation and sleep-dependent procedural memory consolidation by using the finger-tapping Motor Sequence Task (MST). The results were in line with the literature that the practice-dependent learning and time-dependent consolidation were performed similarly with the healthy control. However, patients with schizophrenia have failed to demonstrate sleep-dependent consolidation. To restore this impairment, two exercise RCTs have been conducted to test the exercise effects towards time-dependent and sleep-dependent memory consolidation. Our results have indicated that exercise does not facilitate the time-dependent consolidation, but it successfully enhances the sleepdependent consolidation after 12 weeks of physical exercise. The results have implicated that physical exercise may not have a direct interaction with the memory consolidation construct, but the interaction occurred through the underlying sleep component which could not be demonstrated through subjective sleep quality.