Different trait markers for schizophrenia and bipolar disorder: a neurocognitive approach

Background. The aim of this study was to assess visual information processi ng and cognitive functions in unaffected siblings of patients with schizoph renia, bipolar disorder and control subjects with a negative family history . Methods. The siblings of patients with schizophrenia (N = 25), bipolar diso rder (N = 20) and the controls subjects (N = 20) were matched for age, educ ation, IQ, and psychosocial functioning, as indexed by the Global Assessmen t of Functioning scale. Visual information processing was measured using tw o visual backward masking (VBM) tests (target location and target identific ation). The evaluation of higher cognitive functions included spatial and v erbal working memory, Wisconsin Card Sorting Test, letter fluency, short/lo ng delay verbal recall and recognition. Results. The relatives of schizophrenia patients were impaired in the VBM p rocedure, more pronouncedly at short interstimulus intervals( 14, 28, 42 ms ) and in the target location task. Marked dysfunctions were also found in t he spatial working memory task and in the long delay verbal recall test. In contrast, the siblings of patients with bipolar disorder exhibited spared performances with the exception of a deficit in the long delay recall task. Conclusions. Dysfunctions of sensory-perceptual analysis (VBM) and working memory for spatial information distinguished the siblings of schizophrenia patients from the siblings of individuals with bipolar disorder. Verbal rec all deficit was present in both groups, suggesting a common impairment of t he fronto-hippocampal system.