Material and Method: Right handed idiopathic PDs (Hoehn and Yahr stage 2-3) (n = 20) and age-matched controls (n = 10) without dementia and psychological impairment were recruited. They were asked to perform RTG “as soon as you see the light and as fast as you can” with their right hands under barrier condition. The RTG performance were assessed in three domains, planning, execution (or kinematics), and coordination. The planning was measured by reaction time. The kinematics variables were movement time, maximum velocity, time to maximum velocity, deceleration time, maximum aperture, time to maximum aperture, aperture closure time, and aperture closure distance. The coordination was assessed using a cross correlation analysis between transport velocity and aperture size, which consisted of maximal correlation oefficient (rmax ) and associated time lag (Tmax ).

Results: Compared to the controls, the PD group had delayed planning. In execution domain, they showed decreased maximum velocity, smaller amplitude of maximum aperture, and prolonged all raw times comparing to controls. When considering the coordination, they had only prolonged Tmax than controls.

Conclusion: PD participants with mild to moderate impairment showed poorer RTG planning, execution, and coordination during barrier avoidance when compared to age-matched controls.

Keywords: Reach to grasp, Parkinson’s disease, Barrier task, Manual coordination