Mechanism of memory impairment in patients with schizophrenia.

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The first purpose of this study was to develop and examine the scoring system of memory organization for patients with schizophrenia. Second, we administered neuropsychological tests battery including memory function, and investigated the relationship between memory function and other neuropsychological functions. Third, we examined the relationship between memory performance and brain morphological feature by the Magnetic Resonance Imaging(MRI) in order to study neural basis of impairment of memory organization and semantic memory. The patients with schizophrenia and healthy normal subjects were administered a neuropsychological battery including the Wechsler Memory Scale-Revised, the Wechsler Adult Intelligence Scale-Revised, the verbal learning test, the verbal fluency test, and the card sorting test. MRI scans were obtained in the possible subjects. The organization structure of memory was evaluated with the Logical Memory stories of the Wechsler Memory Scale-Revised or the verbal learning test. As a result of story memory, schizophrenic patients showed lower scores of memory organization, particularly, semantic sequence than normal controls. In the verbal leaning test, patients with schizophrenia showed less semantic clustering than normal people irrespective of the number of recall, but not serial clustering. Factor analysis of neuropsychological functions indicated the logical memory was related to the verbal fluency in normal subjects. On the other hand, the verbal fluency was not related to the logical memory and the verbal learning index in patient with schizophrenia. These results suggest memory structure is different between patients with schizophrenia and normal people. Moreover, there was a significant relationship between frontal lobe volume and score of memory organization in patients with schizophrenia. This indicates that memory organization deficits in schizophrenia may be related to dysfunction in the frontal region.