Effects of schizophrenia and aging on pupillographic measures of working memory

The amount of cognitive resources used to perform a task can be indexed as changes in pupil size. In a previous study, we examined pupillary response measures of slave store and central executive cognitive resources during a working memory task and found abnormally reduced utilization of these resources in schizophrenia. In the present study, multiple regression analyses were performed to examine the independent and combined effects of aging and schizophrenia on pupillary response and recall measures in a larger sample of community-dwelling schizophrenia patients. Schizophrenia was associated with a significant decline in working memory capacity, and an additional moderate decline was associated with aging, but these two factors did not interact. Baseline pupil size was significantly correlated with symptom severity, independent of medication. However, pupillary responses evoked by the working memory task and recall scores were not related to symptom severity. Results were consistent with an additive, rather than a synergistic, relationship between aging and schizophrenia, and suggested that working memory impairment in noninstitutionalized outpatients with schizophrenia may remain stable across symptom status and across the life span.