Generalization of Stochastic Visuomotor Rotations

Abstract

Generalization studies examine the influence of perturbations imposed on one movement onto other movements. The strength of generalization is traditionally interpreted as a reflection of the similarity of the underlying neural representations. Uncertainty fundamentally affects both sensory integration and learning and is at the heart of many theories of neural representation. However, little is known about how uncertainty, resulting from variability in the environment, affects generalization curves. Here we extend standard movement generalization experiments to ask how uncertainty affects the generalization of visuomotor rotations. We find that although uncertainty affects how fast subjects learn, the perturbation generalizes independently of uncertainty.

An implicit memory of errors limits human sensorimotor adaptation

“…In Fig. 1B, we reference earlier work from a study by Fernandes and colleagues 8 . The experiment 650 methodology is fully described in their original manuscript.…”

“…82 1H, Fernandes, median residual error on last 10 trials; repeated measures ANOVA: F(2,14)=17. 8,83 p<0.001, 2 =0.54). 84 Here we designed a set of experiments to answer two questions: (1) why does adaptation suffer 85 from residual errors and (2) why does the size of the residual errors depend on perturbation variance?…”

“…An examination of the data in Figs. 1 and 2 illustrates a frequently observed characteristic of motor 190 adaptation: even at the late stages of training, performance continues to suffer from small, persistent 191 errors 3,4,8,15,31,[35][36][37] . Such persistent, steady-state errors are one of the fundamental predictions of 192 mathematical models of adaptation [11][12][13][14][15] in which performance is driven by an interaction between two 193 opposing forces, error-based learning, and trial-to-trial forgetting: 194…”

“…To quantify the relationship between mean residual error and perturbation variance, we started by re-76 analyzing data collected in an earlier study 8 in which the authors perturbed reaching movements in 77 three groups of participants using visuomotor rotations ( Fig. 1A, Rotation).…”

“…Perturbation variance limits sensorimotor adaptation 88 We began by repeating the experiment performed by Fernandes and colleagues 8 , but with an important 89 adjustment. In the earlier work, all three perturbation conditions were experienced by the same set of 90 subjects, raising the possibility that prior exposure to the visuomotor rotation could have altered 91 subsequent learning in the other environments [26][27][28] .…”