The decay of motor adaptation to novel movement dynamics reveals an asymmetry in the stability of motion state-dependent learning
Fig 3
Gain-space representation of adaptation and decay for training in position- and velocity-dependent force-fields.
(A) Evolution of position- and velocity-dependent gains during adaptation and decay for pFF training. Gain-space trajectories during adaptation and decay periods are shown in blue and gray, respectively, and are averaged across all subjects. The adaptation goal is shown as a blue filled square. Each point in the trajectory has a contribution that is goal-aligned and goal-misaligned, as shown by the two vectors. Three points were selected to compare the gains of the goal-aligned and misaligned components, labeled by the filled ellipses and the numbers 1, 2, and 3. Points 1 and 2 were early and late in the adaptation period, and were the same for both force-field types (training trials 1–15 and 150–160). Point 3 represents the average over a two trial window during the decay period at which the adaptation coefficient for the goal-aligned component was not significantly different from the early learning value (trials 12–14 and 16–18 of the decay period for pFF and vFF, respectively). Ellipses show standard error. (B) Evolution of position- and velocity-dependent gains during adaptation and decay for vFF training. Gain-space trajectories during adaptation and decay are shown in red and gray, respectively. The goal of adaptation is represented as a red filled square. Direction of the goal-aligned and goal-misaligned components are shown as red and cyan vectors, respectively. (C and D) The evolution of the goal-aligned and goal-misaligned components during training and decay are shown for each force-field perturbation. Each point during the adaptation period is the average across subjects for windows of 10 or 15 trials. Shaded regions show the standard error. Bar graphs show the amplitude of the goal-misaligned component during the periods that are highlighted in panels A and B as 1, 2, and 3. The asterisk above the bar graph represents the result of the ANOVA across the goal-misaligned components at points 1, 2, and 3. Error bars show standard error of gains for each point.