The drinking action of Parkinson's disease subjects.

Using the ELITE system, a kinematic analysis was performed of the upper limb drinking action of nine Parkinson's disease patients and nine control subjects. The aim was to use a natural task to investigate the reported Parkinson's disease dysfunction in the performance of simultaneous and sequential movements. Subjects were required to reach 28 cm, grasp a half-filled glass and then take a sip of water. Dysfunction for simultaneous movements was supported by the finding that, in both absolute and relative terms, Parkinson's disease subjects often began to open the hand later than control subjects. Dysfunction for sequential movements was supported by the finding that Parkinson's disease subjects often showed a pause between the first ('reach-grasp') and second ('take-to-lips') parts of the drinking action. Despite these delays and pauses, the proportional organization of the action was similar for both groups. This suggested that Parkinson's disease subjects were able to compensate for the problem in activating the different components of the drinking action. The results are discussed in relation to the influence of the abnormal basal ganglia input to cortical motor regions.