Eye movement evidence for locus coeruleus-noradrenaline system contributions to age differences in attention

Neuroimaging studies have shown that aging alters the brain mechanisms underlying attentional control, even when behavioral performance is equivalent between younger and older adults. Instead of attributing these changes to compensatory mechanisms, we investigated whether age-related neuromodulatory changes in the locus coeruleus-noradrenaline (LC-NA) system are underlying these effects. To test whether aging leads to LC-NA system hyperactivity, we combined two methodological approaches: an oculomotor visual search task to assess eye movements and the threat of unpredictable electric shock paradigm to induce sustained arousal. Using pupillometry, we found that arousal reduced evoked pupil responses in both age groups, demonstrating the expected pattern of lower phasic noradrenergic activity under arousal. Young adults made significantly more first fixations to the physically salient distractor under threat of shock compared to baseline conditions, unlike in older adults with no effect. This modulation of attentional priority was only observable immediately following shock delivery and dissipated over time. Additionally, we found moderate evidence supporting the null hypothesis that arousal does not modulate the speed of attention processing in either age group. These results suggest that arousal selectively modulates attentional priority maps in the early visual cortex but does not influence broader interactions across higher order attentional networks. While first fixation measures revealed age-related differences consistent with the hypothesis of LC-NA system hyperactivity in aging, pupillometry and processing speed measures showed age-equivalent effects. Together, these findings highlight the potential for age-related changes in the LC-NA system to modulate mechanisms of attentional control and demonstrate the utility of eye movement measures as a promising tool to track changes across the adult lifespan. (PsycInfo Database Record (c) 2025 APA, all rights reserved).