Movement-related brain macropotentials of persons with Down syndrome during skilled performance.

Motor performances and movement-related brain macropotentials of nine 23-year-old males with Down syndrome whose mean MA was 10.2 years were compared to those of two control groups whose members were matched to the experimental subjects on CA or MA. A self-paced, voluntary, goal-directed task, which consisted of calculating a time interval of 40 to 60 msec by pressing two buttons, was employed. Subjects with Down syndrome had great difficulty in organizing and timing a correct temporal sequence of ballistic movements. They were much slower, less accurate, and achieved a smaller number of target performances. These behavioral patterns were associated with movement-related brain macropotentials altered in amplitude and latency. The potentials related to programming movements and processing reafferent sensory information were absent, and those involved in the evaluation of the outcome of the performance were reduced.