Auditory and visual working memory performance in patients with frontal lobe damage and in schizophrenic patients with low scores on the Wisconsin Card Sorting Test.

Impaired performance in the Wisconsin Card Sorting Test (WCST) has frequently been postulated to be one typical feature indicating frontal dysfunction in patients with schizophrenia. From a functional point of view, impairments were attributed to a dysfunction of working memory. The present study compares the performance of groups of schizophrenic patients, groups of patients with acquired brain damage as well as normal controls on tasks involving visual and auditory working memory. Modified versions of Sternberg tasks were used varying the physical attributes of the material to be rehearsed in order to force a different involvement of both the 'visuo-spatial sketch-pad' and the 'phonological loop'. Within a group of frontal-lobe-damaged patients (n=6), processing was markedly prolonged for both kinds of material, an observation attributed to a dysfunction of the central executive component of the working memory model. On the other hand, results for schizophrenic patients with poor WCST performance (n=6) suggest a more discrete dysfunction of the phonological loop, but not the visuo-spatial sketch-pad. There were no significant differences between normal controls (n=6) and clinical control groups [patients with non-frontal lesions (n=6) and schizophrenic patients with normal scores on the WCST (n=6)]. Comparisons of the various group data rule out an unspecified frontal dysfunction of schizophrenic patients with low scores on the WCST.