Figure 3. Sensorimotor experiment results.

A. A healthy control subject in the Sensorimotor experiment (reaching with endpoint visual feedback), age 65. i. VP endpoints (purple dashed line) followed the V component of VP targets (solid grey line), reflecting that the subject succeeded in hitting or nearly hitting the target. P endpoints (red dotted line) shifted substantially (ΔP = 42.1 mm), reflecting motor adaptation and/or proprioceptive realignment (Block & Bastian 2011).

ii. This subject relied heavily on vision, such that the weight of vision (W_v) at the end of the adaptation block was 0.69. iii. Early in the adaptation block, VP endpoints (purple circle) fell closer to V endpoints (blue circle) than P endpoints (red circle), reflecting a high weight of vision. P targets were at the origin.

iv. VP endpoints continue to be closer to V endpoints in late adaptation. The shift of P endpoints (red circle) in the positive y direction reflects proprioceptive realignment or motor adaptation.

B. Patient CB7 in the Sensorimotor experiment.

i. VP endpoints (purple dashed line) followed the V component of VP targets (solid grey line), reflecting that the subject succeeded in hitting or nearly hitting the target. P endpoints changed less than the control example from early to late adaptation (ΔP = 11.1 mm).

ii. The subject relied heavily on vision, with W_v = 0.76 late in the adaptation block; VP endpoints (purple circle) fell closer to V endpoints (blue circle) than to P endpoints (red circle), both early (iii.) and late (iv.) in adaptation.

C. Significant realignment occurred in controls (ΔP = 28.0 mm, t = 7.1, p < 0.0001, N = 10), probably reflecting both sensory realignment of the proprioceptive estimate of target hand position and motor adaptation of the reaching hand (Block & Bastian, 2011).

D. Significant realignment occurred in cerebellar patients as well (ΔP = 16.1 mm, t = 4.8, p = 0.001, N = 10), but it was significantly less than controls (t = −2.3, p = 0.035). We speculated that the realignment exhibited by patients represents sensory realignment of proprioception and not motor adaptation of the reaching hand, since cerebellar patients are impaired at motor adaptation (Motor experiment). *significantly different from zero.

E. Weight of vision in late adaptation (W_v) versus realignment of P endpoints (ΔP) for cerebellar patients (grey circles) and age-matched controls (black circles). Cerebellar patients tend to have a smaller ΔP, but (F) mean Wv in early and late adaptation is similar for patients and controls. Two-way ANOVA showed no difference across groups (p=0.36) or time (p=0.13). This suggests weighting of vision vs. proprioception may not be a cerebellum-dependent process.