Arousal response with aging: pupillographic study

The performance of cognitive behaviors requires an activated, aroused cerebral cortex. Although studies have shown that there are decrements of cognitive functions in the elderly, changes in arousal with aging have not been fully studied. Our objective was to learn if there are attention-arousal changes associated with aging. Visual stimuli were presented to induce orienting responses or arousal reactions. Because changes in pupil size reflect changes in arousal, we recorded and compared pupillary responses of young and older normal participants using infared pupillography. During the 1 s that we recorded pupillary changes, we found major phases: a brief initial constriction (C1), then a maximal dilation (D1)--an arousal response, followed by constriction (C2), a habituation response. Although amplitude of these 3 phases was not different between the 2 groups, the interval between the D1 and C2 response was prolonged in the older group. Although the arousal response is not dramatically altered with aging, habituation appears to be delayed.