Pupillary Responses in Healthy Aging: Investigating the Role of Automatic and Controlled Processing

The locus coeruleus-noradrenergic (LC-NA) system plays a crucial role in optimizing performance in different information processing domains, and its dysfunction plays an important role in age-related pathological cognitive decline. In our study, we investigated whether age-related differences are a function of the extent to which a particular task is reliant on cognitive control processes. To this end, we measured pupil responses during two tasks assessing different aspects of attention and memory processing: an n-back task and an auditory detection task. We found decreased pupil dilation in elderly participants during the n-back task. Furthermore, in the auditory detection task, elderly subjects showed a diminished pupil response to those changes in auditory stimulation which were characterized by a decrease in uncertainty. In contrast, no difference was found in pupil responses which were triggered by an increase in uncertainty. The pattern of our results suggests that no general age-related differences can be shown for pupil responses accompanying cognitive processing. In contrast, age-related differences are determined by the exact nature of the involved tasks, and the emerging pattern of selective deficits can be informative regarding the underlying neural mechanisms.Keywords: pupil dilation, aging, cognitive control, n-back task, uncertainty, LC-NA system