Abstract
<p>The locus coeruleus-noradrenerg (LC-NA) system plays a crucial role in optimizing performance in different information processing domains and changes in its function plays an important role in age-related cognitive decline. Because pupil responses are linked to LC-NA activity, we investigated whether the expression of age-related differences in pupil responses depends on the interplay between age-related LC-NA decline and compensatory cognitive effort. To this aim, we measured pupil responses during two tasks differing substantially in their demands on compensatory cognitive effort: an n-back task and an auditory detection task. We found decreased pupil dilation of elderly participants during the high-demand n-back task, whereas no age differences were evident in the lower-demand auditory detection task. These findings are consistent with the idea that age-related differences in pupil responses emerge primarily under high cognitive demands, whereas under more modest task demands compensatory cognitive effort may partially offset the effects of age-related LC-NA decline. The pattern of our results also 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 background. Keywords: pupil dilation, aging, cognitive control, n-back task, uncertainty, LC-NA system</p>