Analysis of temporal saccade prediction in Parkinson’s Disease using video-based eye tracking

In Parkinson’s Disease, key brain regions involved in generating saccades and producing adaptive anticipatory behaviour are impacted, however the intersection of these deficits is not well characterized. Effective Parkinson’s Disease biomarkers are lacking, and video-based eye tracking provides a low-cost, non-invasive means to quantify eye-movement behaviour and address this knowledge gap. In a preliminary study, we analyzed predictive saccade behaviour in eight Parkinson’s patients (ON and OFF medication) and twenty controls aged 51-80 years. Participants performed a visual metronome task, moving their eyes in synchrony with a visual target jumping at a fixed rate on a computer screen. This was contrasted with a random task where the timing of target jumps was not predictable. Saccades made in anticipation of target appearance were classified as predictive, while those made significantly after were classified as reactive. There were no significant differences in saccadic metrics (i.e., reaction time, peak velocity, and amplitude) between groups. Parkinson’s Disease’s impact on saccade reaction time and predictive saccade generation was subtle, however these patients generated multi-stepping, hypometric saccades with reduced velocity compared to controls. The effects of dopaminergic medication on saccade metrics were inconsistent, with some improvement of saccade amplitude. Weak to moderate correlations were obtained between saccade metrics and disease severity and duration. This pilot study contributes to the understanding of saccade performance in evaluating the neural underpinnings of motor impairments in Parkinson’s Disease. Further investigation with more participant recruitment will be necessary to identify which saccade features are sensitive and specific to Parkinson’s Disease.