Figure 3. Proprioceptive shift and variability correlate with the upper bound of adaptation.

(A) Experimental setup for proprioceptive probe trials in Tsay et al., 2021a. The experimenter sat opposite the participant and moved the participant’s hand from the start position to a location specified in the corner of the monitor (e.g. 110°) that was only visible to the experimenter. After the participant’s hand was passively moved to the probe location, a cursor appeared at a random position on the screen (right panel). The participant used their left hand to move the cursor to the perceived hand position. A similar method was used in Ruttle et al., 2021, but instead of the experimenter, a robot manipulandum was programmed to passively move the participant’s arm. (B) Abrupt visuomotor rotation design from Ruttle et al., 2021 (Exp 1; adapted from Figure 2a in Ruttle et al., 2021). After a baseline veridical feedback block, participants were exposed to a –30° rotated cursor feedback block, a 30° rotated feedback block, and a 0° clamped feedback block. Vertical dotted lines indicate block breaks. Green dots denote hand angle. Orange dots denote proprioceptive probe trials. Shaded error bars denote SEM. (C) Gradual visuomotor rotation design from Tsay et al., 2021b (Exp 1; adapted from Figure 3a in Tsay et al., 2021c). After baseline trials without feedback (dark grey) and veridical feedback (light grey), participants were exposed to a perturbation that gradually increased to –30° and then held constant. There were periodic proprioceptive probe blocks (orange dots) and no feedback motor aftereffect blocks (dark grey). (D) Clamped rotation design from Tsay et al., 2021b (Exp 2; adapted from Figure 5a in Tsay et al., 2021c). After a period of baseline trials, participants were exposed to clamped visual feedback that moves 15° away from the target. (E – G) Correlation between proprioceptive shift and the extent of implicit adaptation. Note that the correlations are negative because a leftward shift in proprioception (toward the cursor) will push adaptation further to the right (away from the target and in the opposite direction of the cursor). Black dots represent individual participants. (H – J) Correlation between variability on the proprioceptive probe trials during baseline and the extent of implicit adaptation in the three experiments depicted in (B-D).