Accelerated age-related decline in processing resources in schizophrenia: evidence from pupillary responses recorded during the span of apprehension task

Abstract

Cognitive impairment in schizophrenia may be related to reduced availability of information-processing resources (resource limitations hypothesis). An abnormally accelerated age-related decline in processing resource availability may also occur in older patients with schizophrenia (neurodegeneration hypothesis). To test these hypotheses, pupillary responses were recorded as an index of processing resource availability during performance of the span of apprehension (SOA) task in 33 middle-aged and older patients with schizophrenia and 37 age-comparable nonpsychiatric participants. Consistent with the resource-limitations hypothesis, the patients with schizophrenia showed impaired detection accuracy and abnormally small pupillary responses (reduced resource allocation) only in the higher processing load SOA conditions. This pattern of results suggests that the patients depleted their available processing resources at lower processing loads than the nonpsychiatric participants. Consistent with the neurodegeneration hypothesis, cross-sectional analyses showed abnormally accelerated rates of age-related decline in SOA performance and pupillary responses in the patients with schizophrenia relative to age-comparable normal participants.