THE NEUROPSYCHOLOGICAL SIGNATURE OF SCHIZOPHRENIA - GENERALIZED OR DIFFERENTIAL DEFICIT

Objective: The aim of this study was to provide a comprehensive assess ment of neuropsychological functioning in schizophrenia so as to evalu ate hypothesis of lateralized or differential cognitive impairment in this disorder. Furthermore, the study sought to address the potentiall y confounding factors of medication side effects and relevant demograp hic variables such as age, education, gender, and handedness. Method: The neuropsychological functioning of 28 schizophrenic patients whose medication had been withdrawn for research purposes and 15 demographic ally matched normal subjects was evaluated. A comprehensive battery of tasks was used to determine whether performance patterns of schizophr enic patients were consistent with models of lateralized or localized neuropsychological impairment in schizophrenia. To facilitate comparis on with results of other studies, several analytic strategies were use d, including comparisons of group performance on individual tests, com posite function scores, and evaluation of performance based on ''clini cal'' criteria of impairment. Results: In contrast to the normal subje cts, the schizophrenic patients displayed impairment across measures o f motor, sensory, and perceptual functioning, verbal and nonverbal mem ory, and indexes of frontal lobe functioning. This pattern of generali zed dysfunction was evident regardless of the method of analysis used to assess performance. Conclusions: These findings fail to support con jectures regarding differential neurocognitive deficits in schizophren ia. However, the psychometric limitations of currently available neuro psychological measures may obscure the finding of differential impairm ent and must be considered in interpreting the results of this study a s well as those of any investigation using such instruments.