Freezing of gait is associated with increased saccade latency and variability in Parkinson's disease

Objective: Freezing of gait (FOG) is a locomotor disturbance in Parkinson disease (PD) related to impaired motor automaticity. In this study, we investigated the impact of freezing on automaticity in the oculomotor system using an anti-saccade paradigm. Methods: Subjects with PD with (PD-FOG, n = 13) and without (PD-NON, n = 13) FOG, and healthy age-matched controls (CTRL, n = 12) completed automatic pro-saccades and non-automatic anti-saccades. Primary outcomes were saccade latency, velocity, and gain. Results: PD-FOG (pro-saccade latency = 271 ms, anti-saccade latency = 412 ms) were slower to execute both types of saccades compared to PD-NON (253 ms, 330 ms) and CTRL (246 ms, 327 ms). Saccade velocity and gain variability was also increased in PD-FOG. Conclusions: Saccade performance was affected in PD-FOG for both types of saccades, indicating differences in automaticity and control in the oculomotor system related to freezing. Significance: These results and others show that FOG impacts non-gait motor functions, suggesting global motor impairment in PD-FOG.