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Reaction time and movement velocity abnormalities in Parkinson's disease under different task conditions

Department of Neurology and Neurological Surgery (Neurology), Washington University School of Medicine, St. Louis, MO.

We examined reaction times, movement velocities, and the associated agonist and antagonist muscle behaviors in nine Parkinson's disease (PD) patients and eight normal subjects before and after medications, using a wrist extension task to changing locations of a visual target. Targets changing 500 msec before an auditory "go" signal act as a preparatory cue, while targets changing at the time of the go signal provide a combined auditory and visual stimulus. Late target changes allowed examination of (1) reaction times during an ongoing movement, and (2) movement in the presence and absence of visual targets. PD prolonged the time from the onset agonist electromyographic activity and reduction of antagonist activity to movement onset. Both were shortened by preparatory cues and combined visual and auditory go signals. PD slowed movement only in a subset of trials in which there was movement to a displayed target.

Address correspondence and reprint requests to Dr. Erwin B. Montgomery, Jr., Department of Neurology, The University of Arizona, Arizona Health Sciences Center, 1501 N. Campbell Avenue, Tucson, AZ 85724.

Supported by a grant from the American Parkinson Disease Association and its Greater St. Louis Chapter and the Jane K. Pelton Fund for Movement Disorders Research.

Received August 8, 1990. Accepted for publication in final form February 14, 1991.

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