Fig. 5.

Learning of the force-field adaptation task. a Scheme of the task apparatus. In this task, the handling pole was replaced with the spout pole and the marmoset manipulated it to move the cursor on the monitor. A fixed pole was put in front of the marmoset’s right arm to keep the right arm relaxed. b The target rectangle was placed below the fixation square. The width of the target rectangle was twice its height. During the FF block, a velocity- (in Y-axis direction) dependent force field was applied to the pole in the X-axis direction (representing the left direction in the hand workspace). c Example of the reaching trajectories in the first baseline, first force-field, and first washout blocks in session 2 from marmoset A. Gray and green crosses indicate the centers of the fixation square and target rectangle, respectively. d Success rate averaged over ten trials (top) and X-axis displacement of each trial (bottom) in consecutive baseline, force-field, and washout blocks (n = 117 from three marmosets). The early and late trials were the first ten and final ten reaching trials in each block. Success rate was the percentage of successful trials out of the ten trials. In the inset, the X-axis displacement in the washout block is magnified. Error bars indicate SEM