Working memory performance in poor outcome schizophrenia: relationship to age and executive functioning

Area of Science:

• Neuroscience
• Psychiatry
• Cognitive Psychology

Background:

• Schizophrenia patients show correlated performance on Letter-Number Sequencing (LNS) and Wisconsin Card Sorting Tests (WCST).
• This correlation is often attributed to shared working memory demands.
• An alternative hypothesis suggests sorting demands, not just working memory, may explain the association.

Purpose of the Study:

• To investigate whether sorting demands or working memory underlies the LNS-WCST performance correlation in schizophrenia.
• To determine if working memory tasks without sorting demands predict WCST performance less effectively than LNS.
• To explore the role of LNS as a measure of executive functioning in schizophrenia.

Main Methods:

• Evaluated 34 schizophrenia patients (half over 65) on Digit Span Forward, spatial working memory, LNS, and WCST.
• Analyzed correlations between working memory tasks and WCST performance.
• Examined predictors of WCST performance, focusing on LNS and other working memory measures, in a subset of patients with non-zero WCST scores.

Main Results:

• WCST performance significantly correlated with LNS performance, but not with Digit Span Forward or spatial working memory.
• Age-related performance differences were most pronounced on WCST Categories.
• In patients with valid WCST Category scores, LNS predicted performance, while Digit Span and spatial working memory did not.

Conclusions:

• The findings support the hypothesis that sorting demands, as measured by LNS, are critical for WCST performance in schizophrenia.
• LNS appears to be a more sensitive index of executive functioning relevant to the WCST than general working memory tasks.
• LNS may serve as a valuable proxy for executive function in schizophrenia patients unable to complete the WCST.