IMPAIRED SENSORY-MOTOR RECONFIGURATION AND PUPIL-LINKED AROUSAL IN AGING

Mounting evidence indicates impairments of decision-making and brainstem arousal systems in aging. To shed light on the relationship between these phenomena, we modeled behavior and pupil diameter of older and younger adults performing tasks structured in a compositional manner to probe different processes underlying flexible decision-making.
The “full” task required continuous online inference about hidden context changes, which determined the stimulus-response mappings required for reporting a perceptual (face versus house) categorization judgment mapped to button presses with the left or right index fingers. In different “component” tasks, people performed (i) only the online inference or (ii) only the perceptual categorization task under explicitly instructed switches in stimulus-response mappings. We monitored participants’ pupil diameter throughout task performance. All participants underwent a neuropsychological test battery assessing working memory, executive control and processing speed.
Accuracy in the full task was reduced in older compared to younger adults. Comparison with the component tasks showed that this age-related impairment was due to the objective and perceived difficulty in switching between stimulus-response mappings rather than in performing the online inference. Further, the impairment was specifically related to impairments in executive control assessed with neuropsychological testing. Participants’ pupils dilated during moments of high probability of switches in stimulus-response mappings as well as during intervals of high uncertainty about the required mapping. The amplitude and time course of these cognitively-driven pupil dilations differed between age groups.
We conclude that aging impairs the ongoing reconfiguration of sensory-motor association, potentially through impaired cognitive engagement of pupil-linked arousal systems.