Cross-task Relations of Verbal Memory Performance in Schizophrenia: A Case for Cognitive Dysconnectivity

Abstract

The neural ‘dysconnectivity’ hypothesis of schizophrenia proposes that core symptoms of schizophrenia arise from abnormal connectivity between distinct brain regions. While this hypothesis is supported by a mounting number of neuroimaging studies, few have examined how dysconnectivity might manifest behaviorally through cognitive task performance. Here, we present the concept of cognitive dysconnectivity as aberrant connections between cognitive processes, as observed in the disintegration of normal correlations across cognitive abilities. We specifically examined cross-task relations within the domain of verbal memory – a core area of dysfunction in schizophrenia. Twenty patients with schizophrenia (SZ) and 20 demographically matched healthy controls (HC) completed a battery of verbal memory tasks meant to assess working memory (letter-number span), long-term memory (verbal free-recall), and semantic memory processes (category fluency and a remote associates task). As expected, performance across tasks was impaired in SZ. Cross-task correlations were also significantly different between groups. While the majority of task intercorrelations were significant in HC, none of the intercorrelations were significant in SZ. A comparison of covariances also confirmed differences between SZ and HC in the cross-task covariance matrices as a whole. Differences remained after employing robust correlation and regression analyses that accommodate deviations from standard correlation testing assumptions. These findings suggest that verbal memory deficits in SZ could result from disrupted connections between various component cognitive processes, and thus offer a behavioral interpretation of neural dysconnectivity in schizophrenia.