PMC

Group average results for experiment 3. A. Learning curves for initial training and test sessions for SAME-SOLN_hand. Shading indicates s.e.m. B. Learning curves for initial training and test sessions for SAME-SOLN_visual. C. Estimated learning rates for training and test (means of the time constant of a single exponential fit to individual subject data). Error bars indicate s.e.m.

Adp⁺Rep⁻,Adp⁺Rep⁺,Adp⁻Rep⁺ and Adp⁻Rep⁻ protocols for Experiment 2, illustrated in the same format as . The Adp⁺ groups initially trained with counter-clockwise rotations drawn from a uniform distribution ranged from 0° to +40°. The Adp⁻ groups initially trained without rotation. The test block is shown with a gray box background: in all four groups, every subject was tested at the 95° target with a counter-clockwise 25° rotation.

Protocol for Experiment 3. A. SAME-SOLN_hand and SAME-SOLN_visual were first trained on a +30° rotation then tested on a -30° rotation. B. Illustrations of ideal solution in hand space and in visual (cursor) space for SAME-SOLN_hand. The adapted movement in hand space was the same for both the +30° and -30° rotations. Black labels indicate the imposed rotation, the displayed target, and the adapted hand movement direction for initial training with the +30° rotation. Gray labels indicate the imposed rotation, the displayed target, and the ideal hand movement direction for the -30° rotation. C. Illustrations of ideal solution in hand space and in visual (cursor) space for SAME-SOLN_visual. The adapted movement in visual (cursor) space was the same for both the +30° and -30° rotations.

Group average results for Experiment 2. A. Test block learning curves for Adp⁺Rep⁻, Adp⁺Rep⁺, and, Adp⁻Rep⁻. Square and circular markers show the average errors for the first test trial. Errors were computed as the angular separation between cursor and target direction. B. Test block learning curves for Adp⁻Rep⁺ and Adp⁻Rep⁻. Square markers show the average errors for the first test trial. Errors were computed as the angular separation between cursor and target direction. S.e.m. was omitted for clarity. C. Estimated error reduction rates for all four groups during the test block (means of the time constant of a single exponential fit to individual subject data). Error bars indicate s.e.m.

Protocols for Experiment 1. A. Adapted movement directions in hand space are represented by solid “pointing hand” arrows, corresponding cursor movement directions in visual space are represented by dotted arrows in the same color. For Adp⁺Rep⁻ training, cursor feedback was rotated by random, counter-clockwise angles sampled from a uniform distribution ranging from 0° to +40°. For Adp⁺Rep⁺ training, cursor feedback was rotated by a target-specific angle, sampled from the same uniform distribution as Adp⁺Rep⁻, such that the hand always had to move in the 70° direction for the cursor to hit the target (repeated direction in hand space). In probe trials subjects had to move to targets shown clockwise from the training targets without cursor feedback. Numbers and locations of targets are schematic and not to scale. B. In Adp⁺Rep⁻, the imposed rotation was randomly selected every time the subject visited each target. In Adp⁺Rep⁺, the rotations were structured so that the adapted hand movement was always toward the 70° direction in hand space.

Group average results for Experiment 1. Left column: Adp⁺Rep⁻; right column: Adp⁺Rep⁺. A, B. Time courses for empirical trial-to-trial data (dots) and adaptation (state-space) model simulations (lines). Errors were computed as the angular separation between cursor and target direction (shadings indicate s.e.m). C, D. Hand-movement direction versus displayed target direction for the initial, middle and asymptotic phases of training: both data and simulation at asymptote shown. For comparison, baseline data from all subjects are also plotted (green line). Shading indicates s.e.m. The two “peaks” in initial training line show that the performance of the first two trials in training was close to naïve performance. E, F. Hand-movement direction versus target direction for generalization probes: both data and simulation shown. Panels from C and D are re-plotted in faded colors. Baseline performance to the probe target directions for a separate group of subjects is plotted (green) for comparison. Shading indicates s.e.m.