Article Figures & Data
Figures
- Figure 1.
Experimental design and learning. A–D, Hand orientations and associated force fields, as force vectors experienced by the hand (zero velocity represented by the black circle) for the four groups of subjects. Note that the three vector fields are displayed separately, for clarity, but act over the same workspace. Similarly, the actual end point location of the hand for the three hand orientations is matched across the three conditions, but is separated here for clarity. Start location, targets, and cursor were displayed as a circle, showing position with a line indicating the orientation (inset).
- Figure 2.
Force field conditions and movements across the experimental design. The wrist configuration (flexed, neutral, and extended) is shown for the three columns at the bottom of the figure. A, The control group always performed movements in six directions with the neutral wrist configuration. B, The Cartesian group performed reaching six reaching movements with the same Cartesian direction and forces for all three wrist orientations. C, The object group. The six reaching directions were rotated for each wrist orientation such that the forces experienced were identical to the Cartesian condition (but rotated by 30°). D, For the anti-object group, the force field and the reaching directions rotated in the opposite direction to the wrist. However, the forces experienced still matched those of the other groups. Importantly, the force fields and reaching directions on the middle wrist configuration were identical across all four groups.
- Figure 3.
Adaptation to the force fields. A–D, Maximum perpendicular error. E–H, Force compensation percentage for the four groups (mean and SE across subjects) with exponential fits. Blocks of 10 nonchannel trials were used for the MPE, while blocks of four channel trials were used for the force compensation. The gray shaded region indicates the exposure period. The dashed curves are the exponential fit to the control group for comparison.
- Figure 4.
Learning and kinematics as a function of hand orientation. A–C, Learning curves separated by hand orientation for three groups. D, Hand orientation (mean ± SE averaged as in Fig. 1) for the four groups as a function of time (colors are as in Fig. 1).
- Figure 5.
Learning and force compensation for the neutral wrist orientation where the force field is identical across all four groups. A–C, The maximum perpendicular error (mean ± SE across subjects). The dotted line shows the exponential fit for the control group for comparison. D, E, Force compensation.
- Figure 6.
Time constants and asymptotes of learning across conditions. A, Left, The mean (±95% CI) of the exponential fits to the group-averaged MPE for the exposure phase. Right, The asymptote and time constant (±95% CI) of the exponential fits (all comparisons were significant at the p < 0.0083 level, except for those shown with the flat bar and label n.s. indicating that the comparison was not significant after Bonferroni correction). B, Fits and parameters for the force compensation data as in A.
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