Working memory and schizophrenia: evidence for slowed encoding.

Previous studies have found impairments in working memory in individuals with schizophrenia, but have not identified the underlying information processing deficit. Because schizophrenia is associated with slowed cognitive processing, deficits on working memory tests may be due to decreased speed of encoding rather than an inability to maintain information over time. This hypothesis was examined using a Delayed Match to Sample (DMTS) Test. Task difficulty under 0-delay conditions was equated by individually establishing the stimulus presentation time needed to reach approximately 80% accuracy. Schizophrenia participants required longer presentation durations, but there were no group differences under delay conditions when performance was equated in the 0-delay condition. These results suggest that poor working memory performance in schizophrenia results from slowed encoding processes.

Wisconsin Card Sorting Test performance in schizophrenia: the role of working memory.

Schizophrenia typically results in reduced performance on the Wisconsin Card Sorting Test (WCST). In the current study, we used a variety of approaches to examine the role of working memory (WM) in this deficit. One approach was to examine patterns of perseverative and non-perseverative errors. A second approach involved the comparison of the standard WCST to a modified version that used visual cues to reduce demands on WM. A third approach was to quantify the impact of WM demands on performance on a trial by trial basis. Consistent with theories of WM, the schizophrenia group showed increases in both perseverative and non-perseverative errors and differences between individuals with schizophrenia and controls were largest when WM demands were high. The visual cues helped the schizophrenia group overcome the high WM demands of the test, although they did not reduce the impairment in terms of standard scoring procedures. All impairments disappeared, however, after controlling for group differences on a measure of the speed of encoding information in WM. The pattern of results supports the conclusion that WM impairment contributes to poor performance on the WCST in individuals with schizophrenia, with additional evidence that this impairment results from generalized slowing of information processing.

Combined Use of Thyroid Hormone and ECT.

Neurocognitive deficits, including acute confusion and memory impairment, remain important effects of electroconvulsive therapy (ECT). Laboratory and clinical research demonstrates interactions among neurocognitive functioning, the hypothalmic-pituitary-thyroid axis, depressive mood, and ECT. Preclinical studies have demonstrated that exogenous triiodothyronine (T(3)) administered to animals receiving electroconvulsive shock (ECS) protects against ECS-related amnesia and accelerates the "antidepressant effects" of ECS, possibly due to alterations in catecholamine and/or indoleamine neurotransmission. Clinical data suggest that combined treatment with T(3) and ECT results in increased clinical efficacy of ECT and diminished neurocognitive side effects.