Electrophysiological and behavioural results for participants in the Tapping Task 1 (cued and self-paced Conditions).

Relative amplitude and latency are computed based on the difference in peak values between the negative peak occurring -50 to 100ms prior to the motor response, and the positive peak 100 to 300 ms post response. Peak amplitude represents the negative peak occurring around time of response (-150 to 200 ms). Independent samples t-tests used for differences between groups,* p ** p a significantly different from controls,b significantly different from pre-HD.Amplitude and latency by at Cz, averaged across groups. Standard deviations (SD) provided in parentheses.