Fig. 1

Distribution of Scaled activity difference. All SAD values ranged from − 1 to 1; values of 1 indicate left arm use only, values of − 1 indicate right arm use only, values of 0 indicate equal left and right arm use, values between 0 and 1 indicate left arm use is dominant, and values between 0 and − 1 indicate right arm use is dominant. A Typically-developing participant: Note the high degree of rotational symmetry in all graphs, indicating nearly equal use of left and right arms. B Participant with stroke: Movement is markedly asymmetric with a low degree of rotational symmetry, indicating that left arm use is much greater than right arm use