Working Memory Span and Motor and Cognitive Speed in Schizophrenia

OBJECTIVE: The aim of this study was to investigate the verbal working memory deficit and decrease of motor and cognitive speed in patients with schizophrenia, and to clarify their associations with negative and depressive symptomatology. METHODS: Forty patients with schizophrenia and 41 healthy control individuals were administered the backward digit span to assess the working memory capacity, along with 3 tests of processing speed. RESULTS: Patients demonstrated reduced backward digit span, as well as decreased motor and cognitive speed. Regression analyses indicated that the backward digit span was associated with cognitive speed. It was not associated with either negative or depressive symptoms. Decreased processing speed was unrelated to negative symptoms, but the depression score was significantly associated with the cognitive speed measure. CONCLUSIONS: Working memory and processing speed seem to share a cognitive component. Depression, but not negative symptoms, affects processing speed, especially by decreasing cognitive speed.