Oculomotor behaviors during visual short-term memorybinding in healthy aging

Abstract

The Visual Short-Term Memory Binding Task (VSTMBT) assesses the cognitive ability responsible for integrating and retaining objects' features on a temporary basis. The VSTMBT, combined with eye-tracking (ET), identified impairments in older adults with Mild Cognitive Impairment (MCI) who developed AD dementia 3 years after their baseline assessment. This study investigated whether age impacts oculomotor behaviors linked to the VSTMBT. We assessed a group of healthy young adults (18-25 years old) and a group of healthy older adults (60-83 years old) with the VSTMBT synchronized with ET. The VSTMBT required participants to detect changes across two consecutive arrays of either two or three bicolored objects. They were asked to remember the object's colors either separately (Unbound Colors Condition, UC) or combined (Bound Colors Condition, BC). We collected behavioral responses, fixation duration, saccade amplitude, and pupil dilation. Older adults remembered fewer objects but that was similar in the UC and BC conditions. Both age groups showed decreased saccade amplitudes and longer fixation duration in the BC condition, with no differential impact of age. Pupil dilation was lower in older adults, but such a behavior was equivalent across the UC and BC conditions. These null findings were confirmed by Bayesian analysis. These results suggest that binding functions and their associated oculomotor behaviors are resilient to age-related cognitive decline, highlighting the relevance of evaluating oculomotor measurements during the VSTMBT to detect the transition from normal to abnormal variants of aging earlier and more accurately.