A novel method for objective quantification of apathy based on gaze and physiological reactivity to stimuli presented in a virtual reality environment

INTRODUCTION: We developed a tool for objective quantification of apathy. METHODS: Participants (n = 97; 67 with cognitive impairment, 30 cognitively normal; mean age = 74.3 ± 6.2 years, 56.7% females) were exposed to emotional and cognitive stimuli in a virtual reality environment. Gaze metrics (time to first fixation [TTFF] and total fixation duration [TFD]) and autonomic nervous system (ANS) reactivity were measured. Apathy and depression were clinically assessed using the Lille Apathy Rating Scale short version and the Geriatric Depression Scale 15-item version, respectively. Cutoffs of ≥ –7 and ≥ 5 were used to define apathy and depression, respectively. RESULTS: The sample comprised 14 participants with apathy only, 9 with depression only, 10 with both, 63 with neither, and 1 with missing data. For all emotional stimuli, participants with apathy only showed longer TTFF (P = 0.039, effect sizes [ES] = 0.798), and shorter TFD (P = 0.023, ES = 0.578) compared to those without apathy or depression. ANS reactivity was not associated with apathy. DISCUSSION: Apathy is associated with decreased gaze engagement at emotional stimuli. Highlights: Apathy measurement via questionnaires is limited by subjectivity biases. Apathy measurement via questionnaires is limited by simplistic scoring. We present a novel method for objective measurement of apathy. Gaze characteristics reflect the emotional and cognitive components of apathy.