Pupil and Eye Blink Response Abnormalities During Emotional Conflict Processing in Late-Life Depression

Introduction This study aims to investigate the locus coeruleus-norepinephrine system (LC-NE) function in late-life depression (LLD) patients by examining task-evoked pupil dilation in the emotional face-word Stroop task, given the recently established coupling between task-evoked pupil dilation and LC-NE activation. Materials and Methods Using video-based eye-tracking and principal component analysis, we explored task-evoked pupil responses and eye blinks in LLD patients (N = 25) and older healthy controls (CTRL) (N = 29) to determine whether there were alterations in pupil responses and eye blinks in LLD compared to CTRL. Results LLD patients exhibited significantly different pupil and eye-blink behavior compared to CTRL, with dampened task-evoked pupil dilation associated with emotional congruency and valence processing mediated by the sympathetic system compared to CTRL. Eye-blink rates associated with emotional valence were also altered in LLD compared to CTRL Moreover, Geriatric Depression Scale-15 scores in LLD correlated with emotional congruency effects revealed by task-evoked pupil dilation. Conclusion The findings demonstrate that LLD patients display altered pupil behavior compared to CTRL. These altered responses correlated with the severity of depressive symptoms, indicating their potential as objective biomarkers for use in large at-risk populations for LLD.