Executive disorders in patients with schizophrenia and its correlates with neurological signs

Abstract

Both neuropsychological impairments and neurological signs are often demonstrated in schizophrenia. However, very few studies have been conducted to investigate relationship between executive functions and sub-groups of neurological signs. This study was designed to address such issue. A total of 51 patients with chronic schizophrenia were recruited. The Sustained Attention Response to Task ŽSART., Six Elements Test ŽSET., and Hayling Sentence Completion Test ŽHSC. were used to assess executive functions. The Cambridge Neurological Inventory was used to assess the neurological signs. Three factors were identified within the executive function tests: Ž1. Semantic inhibition factor comprised the items in HSC, Ž2. Action rattention inhibition factor comprised the SART commission error and SET rule-breaking score, and Ž3. Output generation factor comprised the SET raw score and SART correct response. Significant and modest relationships were found between these derived factors and clinical symptoms after partial ling out the confounding effect of age, education and illness duration. However, such relationships were not so clear-cut between the derived factors and neurological signs. In conclusion, the three tests of executive function were shown to have good construct validity among a group of chronic schizophrenic patients. The derived factors seem to share common neural substrates with the general symptomatology of schizophrenia. However, there is not a simple relationship between neuropsychological impairments and neurological signs. The basis of this relationship has yet to be elucidated in future study.