Article Figures & Data
Figures
- Figure 1.
Illustration of the workspace, events during the task, and force field. A, 3D view of the experimental setup and participant’s position. B, Participants were instructed to perform forward reaching movements toward a visual target that was presented in front of either the left or the right arm, with each arm having its own home and goal target. C, The force field for experiment 1 had a clockwise direction for the right arm (orange line) and was mirrored for the left arm, hence directing the arm toward the exterior direction. D, Events happening during a trial for the left and the right arm. An open goal target was presented for a random period, uniformly distributed between 2 and 4 s, before it was filled in. The cue to reach the target was provided by filling the goal target in red. If the participant reached the target in a time comprised between 0.6 and 0.8 s, the goal target was filled in a green color to indicate a good trial and red if the target was reached too slowly.
- Figure 2.
First and last trajectories for the force field perturbed trials, the evolution of parameters across all trials, and histograms of the learning rate of path length and maximal deviation. A, First and last force field trials for the left arm (green line) and the right arm (orange line) of participants. B, Mean and Standard Error of the Mean (SEM) of Path length (PL), maximal deviation (MD), maximum speed (MS), and maximum force (MF) across perturbed trials of experiment 1 for the right arm (orange line) and the left arm (green line). C, Bootstrapping results of the learning rate (parameter
- Figure 3.
Correlation between the force exerted by participants on the handle of the robotic arm and the force exerted by the robot on the participants’ arms. A, The mean and SEM of the normalized x force applied by the participant on the handle (blue line) and the normalized y velocity of the reaching movement (black line) for the first and last perturbed trials. The force and velocity were normalized to their peak value and averaged across all participants. B, Mean and SEM of the correlation between force and velocity across all perturbed trials for the left arm (green) and the right arm (orange). C, Correlation average for the final 20 trials for the left and the right arm of each participant (black dots), horizontal and vertical error bars represent the standard deviations of the correlation of the left arm and the right arm, respectively.
- Figure 4.
Trajectories of first and last catch trials of experiment 1 for all participants and mean maximal deviation, path length, and maximum speed of participants across all catch trials of experiment 1. The left arm is presented using a green color across all panels and the right arm is presented using orange color. In panels B–D, the global average for each arm is presented as a black dot. A, Trajectories of the first and last catch trials for all participants. B, Maximal deviation across all catch trials. C, Path length across all catch trials. D, Maximum speed across all catch trials.
- Figure 5.
Evolution of extracted parameters in the null field trials in experiment 2. A, Mean and SEM of the path length, maximal deviation, and maximal speed of the reaching trajectories for the left arm (green line) and the right arm (orange line) across all trials. The gray zone indicates baseline trials without force field trials. B, Mean MS and MD for baseline trials and trials following force field trials for each participant. The x-axis shows the index of the trials after a force field trial.
- Figure 6.
Outputs of the force field trials of experiment 2. A, Representative traces for outward force field trials for the left arm (green line) and the right arm (orange line). The hand paths shown in the figure are for demonstration purposes and do not represent real data. B, Representative traces for inward force field trials for the left arm (green line) and the right arm (orange line). C, The mean and SEM of the normalized x force applied by the participant on the handle (blue line) and the normalized y velocity (black line) of the outward force field trials reaching movements for the first and last perturbed trials. The force and velocity were normalized to their peak value and averaged across all participants. D, The mean and SEM of the normalized x force applied by the participant on the handle (blue line) and the normalized y velocity (black line) of the inward force field trials reaching movements for the first and last perturbed trials. E, Mean and SEM of the correlation between force and velocity across all perturbed trials for the left arm (green) and the right arm (orange) for outward force field trials. F, Mean and SEM of the correlation between force and velocity across all perturbed trials for the left arm (green) and the right arm (orange) for inward force field trials.
- Figure 7.
Mean and SEM of normalized EMG of the posterior deltoid and the pectoralis major averaged across all participants for the right arm (orange line) and the left arm (green line). The mean EMG for both muscle groups was computed in a 100-ms window before movement onset (the gray region in the plot). A, Mean and SEM of the normalized EMG of the 10 first and 10 last force field trials in experiment 1. B, Mean and SEM of the normalized EMG of the 10 first baseline trials and 10 last null field trials after the introduction of force field trials in experiment 2.
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