Figure 4.

Design of the attribute-isolating experiments. A, The effects of movement vector adaptation can be isolated for a test movement (T4 to T3) when the MV-matched movement (C to T2) is trained with rotation while the GL-matched (C to T3) and SL-matched (C to T4) movements are trained with zero rotation. When this is the case, the difference in end points of the baseline and adapted MV-matched movements define a nontrivial ΔMV (middle column, thick solid blue arrow). ΔGL and ΔSL can be defined analogously, but are both essentially zero because the SL-matched and GL-matched movements were trained with zero rotation. If ΔGL and ΔSL are essentially zero, the adaptation vector, which indicates the difference in end points between the baseline test movements and the adapted test movements, will depend only on ΔMV, and the gain associated with it (K_MV) can be estimated by comparing the adaptation vector with the translated version of ΔMV as shown in the third column, which is a zoomed in depiction of the lower right area in the second column. B, C, Analogously, test movements with isolated GL adaptation (B) and with isolated SL adaptation (C) can be trained when visuomotor rotations are applied in isolation to the GL-matched and the SL-matched movements, respectively, to estimate K_GL and K_SL. Note that the traces shown in the second and third columns are across-subject-averaged movements based on experimental data from three of the movement configurations studied in Experiment 1. Note that the ellipses drawn on the hand path plots in this and the subsequent figures all represent 1 SEM for movement end points.