Muratori LM¹, Dapul, G¹, Gordon, AM^1,2; ¹Department of Biobehavioral Science, Teachers College, and ² Dept. of Rehabilitation Medicine, Columbia University, New York, NY. lmm24@columbia.edu.

PURPOSE: This experiment was designed to determine whether individuals with Parkinson’s disease (PD) have deficits in grasp coordination when performing such tasks while maintaining a stable standing posture. BACKGROUND: It has been suggested that posture and grasp are tightly coupled in human movement. Previous work on healthy adults has shown that there are increases in grip force prior to arm motion to provide object stability during grasp. In addition, anticipatory postural adjustments have been associated with minimizing the perturbing effects of arm movements on body posture. Therefore, it is hypothesized that when one or both components of this task are compromised, as in PD, deficits in this coupling will occur. SUBJECTS: Ten right-handed individuals with PD and ten age-matched, healthy right-handed individuals (control group) participated in this study. METHODS: While standing on a force plate, subjects were asked to: 1) lift an instrumented object using a precision grip to a height of 10 cm, and 2) transport the grip device a distance of 110% arm’s length at a self-selected pace. All participants were asked to perform ten trials of each testing condition with two weights (150g and 800g). Individuals with PD were tested "ON" and "OFF" medication. ANALYSIS: Signals from the grip instrument and an electromagnetic position-angle sensor were digitized and stored in a flexible computer system. Ground reaction forces were collected using a Kistler forceplate. Group and condition differences were analyzed using repeated measures analysis of variance and, when appropriate, Newman-Keuls post-hoc tests were performed. RESULTS: Based on preliminary data, individuals with PD exhibit delays during multiple phases of these tasks resulting in prolonged movements compared to control subjects. Although individuals with PD retain anticipatory scaling of fingertip forces, these forces are generated at a slower rate and never reach the magnitude exhibited by control subjects. In addition, individuals with PD display lower amplitude AP postural adjustments which occur later in the movement resulting in poor coupling of the postural adjustments with grasping. CONCLUSION: Individuals with PD show deficits in grasp control and poor coordination of grasp with postural adjustments while standing. FUNDING SOURCE: NYAPTA Research Designated Fund.

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