title: Effects of a moving target versus a temporal constraint on reach and grasp in patients with Parkinson's disease.
abstract: The reaction times and kinematics of reach and grasp were analyzed for eight subjects with Parkinson's disease (PD) and eight healthy subjects during three variations of a maximal speed prehension task: (a) grasping a stationary ball as fast as possible, (b) grasping a stationary ball within specific time constraints (520 ms and 450 ms), and (c) grasping a moving ball within the same time constraints. Subjects with PD exhibited bradykinesia when reaching for a stationary ball. When reaching for a moving or stationary ball with temporal constraints, subjects with PD moved as fast as healthy subjects. The reaction times of both groups were shorter when reaching to a moving ball than to a stationary ball, regardless of the time constraint. Subjects with PD had a slower velocity of hand opening and closing, a smaller maximal aperture, and a longer time to maximal aperture than healthy subjects in all task conditions. Thus, visual motion cues and external temporal constraints had a greater effect on reach than on grasp. The results suggest that the bradykinesia observed in individuals with PD during self-determined maximal speed prehension may reflect a strategy used to compensate for deficiencies in the grasp component of the task.
authors.affiliation: Department of Physical Therapy, School of Public Health, New York Medical College, Valhalla, New York, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Majsak
authors.forename: Terry
authors.initials: T
authors.lastname: Kaminski
authors.forename: Antoinette M
authors.initials: AM
authors.lastname: Gentile
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Gordon
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D005260:Female; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D009048:Motor Skills / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D010300:Parkinson Disease / Q000503:physiopathology*; D011930:Reaction Time / Q000502:physiology; D013997:Time Factors