Altered oculomotor signatures of emotional conflict and valence processing in late-life depression

Late-life depression (LLD) is a heterogeneous neuropsychiatric condition characterized by affective, cognitive, and autonomic disturbances, underscoring the need for objective markers that index dysfunction in specific neural control systems. Microsaccades, small fixational eye movements generated through oculomotor circuitry that includes the superior colliculus, provide a temporally precise behavioral measure sensitive to arousal and cognitive control signals, yet their clinical relevance in LLD remains largely unexplored. In this study, we examined whether task-evoked microsaccade dynamics are altered in LLD during emotional conflict and valence processing using an emotional face-word Stroop task. Microsaccade rate and kinematic metrics were analyzed in 26 individuals with LLD and 27 healthy older adults (CTRL). Across groups, microsaccade rates were higher during emotionally incongruent compared with congruent trials, indicating sensitivity to emotional conflict, with a trend toward lower overall rates in LLD. During valence processing, microsaccade rates were higher for fearful than happy faces and were significantly lower in LLD than in CTRL participants. In contrast, microsaccade kinematics were largely preserved across groups. Exploratory inter-individual analyses identified nominal associations with somatic symptom burden and cognitive status, but none survived correction for multiple comparisons. An exploratory multivariate classification analysis combining microsaccade, pupil, eye-blink, and reaction time indices yielded chance-level differentiation between groups. Together, these findings indicate that microsaccade rate and kinematics are sensitive to emotional conflict and valence processing, with selective alterations in these dynamics in LLD, highlighting microsaccades as a potentially informative behavioral index of affective interference control in clinical aging.