Motor disorder in Huntington's disease begins as a dysfunction in error feedback control.

Reports that movement jerkiness, which characterizes the smoothness and efficiency of motion was a sensitive indicator of presymptomatic Huntington's disease (HD). Observation that a large fraction of asymptomatic HD gene-carriers displayed elevated jerk even when more than seven years remained until predicted disease onset; Suggestion that a dysfunction in error correction characterizes the motor control deficit in early HD.