Unraveling Visuomotor Control in Parkinson Disease With and Without Freezing of Gait

Visuomotor processing is the ability to integrate visual information into motor plans and movement correction, which is highly required in daily activities such as writing and walking. As visual impairments have been reported in people with Parkinson's disease (PD), it is likely that those impairments may affect visuomotor processing ability and subsequently impair motor performance. Furthermore, people with PD and freezing of gait (FOG) have exhibited poorer visual perception than those without FOG, yet the differences of visuomotor control have not been well investigated. Additionally, little did the studies apply neurophysiological assessment to investigate the associated neural mechanisms. This study aims to investigate behavioral and neurophysiological differences in visuomotor control among people with PD and FOG (freezers), without FOG (non-freezers), and age-matched healthy controls. Sixty-three participants, 21 freezers, 21 non-freezers, and 21 age-matched healthy controls, will be enrolled in this study. Behavioral assessments, including a manual control task and visual perception tests will be used to evaluate visuomotor and visual perceptual abilities. Neurophysiological correlates, including corticomotor excitability and corticocortical connectivity between V1-M1 and PPC-M1, will be examined using transcranial magnetic stimulation. It is hypothesized that freezers will demonstrate the greatest visuomotor impairments and disrupted corticocortical connectivity compared to non-freezers and controls. By integrating behavioral and neurophysiological outcomes, this study seeks to unravel the mechanisms linking visual and motor impairments to FOG, ultimately providing insights into targeted interventions to improve visuomotor processing and motor performance in PD.