The broad goal of the project is to advance our understanding of the relationship between aging, cognitive impairment and pathophysiology in schizophrenia. Some, but not all, studies support the neurodegenerative hypothesis that the extent of age- related cognitive decline in schizophrenia is greater than the decline found in normal aging. Discrepant findings may be due to differences in the sensitivity of cognitive tasks used (traditional neuropsychological v. information processing or IP). Specific IP tasks are very sensitive to schizophrenia in younger patients, but aging effects on these tasks have not been studied in older schizophrenia patients. In addition, the findings from IP, brain imaging and psychophysiology studies suggest that the IP resources of patients with schizophrenia are easily overloaded, possibly due to abnormalities in thalamocortical- reticular brain circuits. Despite current interest in this resource-limitations hypothesis, few schizophrenia studies have attempted to directly measure processing resource overload. Pupillary responses recorded during cognitive tasks can be used to index the extent of resource allocation to the task, which is thought to be mediated by the thalamocortical-reticular circuits that may be involved in the pathophysiology of information overload in schizophrenia. METHODS: In cross-sectional and longitudinal studies, a novel, innovative application of pupillography methods will be used to examine the relationship between aging and processing resource limitations indexed on well-studied IP tasks in 100 middle-age and older outpatients with schizophrenia and 100 age-comparable normal comparison participants.
AIMS : To determine whether older patients with schizophrenia show the characteristic patterns of impairments found on well-studied IP tasks in younger patients, whether older patients with schizophrenia show abnormal resource limitations on pupillary response measures, and whether the extent of age- related decline on these measures is greater in older patients with schizophrenia than in nonpsychiatric participants. Abnormal age-related decline on these measures would suggest an abnormally accelerated depletion of processing resources with aging in schizophrenia in late life and would support the neurodegeneration hypothesis.
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