Abstract of Aging Effects on Task-Evoked Pupillary Reponses, by Mingjian He, Degree ScM., Brown University, May 2018. Previous studies have found decreased cell counts and increased neurofibrillary pathology in locus-coeruleus (LC) nuclei in the aging population, and impairments of the noradrenergic (NA) neuromodulatory system have been hypothesized to mediate age-related cognitive decline. This study utilized task-evoked pupil dilation to investigate age-related changes in the functional integrity of the LC-NA system during active task performance. To capture the broad influence of NA neuromodulation on cognitive processes, three cognitive tasks were administered incorporating eye-tracking measurements to examine the roles of LC-NA signaling in: 1) arousal response using a phasic alerting task; 2) memory retrieval using a recognition memory task; and 3) conflict resolution using a flanker task. Using a novel multiple regression approach to pupillary data, phasic pupillary responses to task manipulations were characterized as continuous response curves across the test trial duration. Results from healthy young adults replicated the patterns of increased pupil dilation previously reported in pupillometry studies of the three cognitive tasks. Despite general slowing and reduced memory performance, the healthy elderly participants nonetheless showed task-evoked pupillary responses comparable to young adults in the phasic alerting and recognition memory tasks. However, associations between pupil dilation and behavioral performance were found to be attenuated with aging in these two tasks. In the flanker task, a pupillary response to congruency conditions was observed only in the young adults but not in the elderly participants, possibly due to a strategic shift in coping with potential response conflicts in the elderly group. Overall, the patterns of pupillary responses characterized in this study suggest: 1) preserved functional properties of the LC-NA system during cognitive task performance in aging; and 2) reduced neuromodulatory efficacy of NA projections on downstream sensory-motor processes. Taken together, results from this study demonstrated an improved analytical approach to pupillometry data for assessing functional LC-NA activity, and identified intact phasic responses of the LC-NA system in healthy aging that, unlike young adults, were decoupled from observed behavioral performance.
He, Mingjian,
"Aging Effects on Task-Evoked Pupillary Responses"
(2018).
Cognitive, Linguistic, and Psychological Sciences Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.26300/mt8s-f124
