Subjects’ disturbed hand trajectories and extraction of intended trajectories from them reveal that both variance and invariance of the motor plan can occur even in response to very large disturbances.

<p>The hand path, in black, deviates from the blue baseline, as a force pulse, gray arrows, is applied. Three of the eight subjects’ intent trajectories (orange) did not significantly deviate from undisturbed movement (panel A) as observed by the intent region not departing the undisturbed movement (blue) region. Five of the eight subjects’ intent trajectories did significantly deviate from undisturbed movement (panel B). The summary plots display whole-subject statistics as shaded regions (mean ± 95% confidence interval on the mean). The time at which the hand region (black) first departed from undisturbed movement (blue) is marked with a green dot for each subject. If the intent region (orange) departed from undisturbed movement, the onset of departure is marked with a red dot for each subject. Panel A subjects’ intent did not depart while panel B subjects’ intents did depart.