Extended Data Figure 6: Accounting for within-class differences in learning.
a, Relation between amount of learning and initial impairment in performance for monkey J (top) and monkey L (bottom). Each point corresponds to one session. Lines are linear regressions for the within-manifold perturbations and outside-manifold perturbations. *Slope significantly different than 0 (F-test for linear regression, P < 0.05). b, Relation between amount of learning and mean principal angles between control spaces for perturbed and intuitive mappings. c, Relation between amount of learning and mean required preferred direction (PD) change. Same number of sessions as in Extended Data Fig. 2. Figure 3 showed that the properties of the perturbed mappings (other than whether their control spaces were within or outside the intrinsic manifold) could not account for differences in learning between the two types of perturbation. However, as is evident in Fig. 2d, within each type of perturbation, there was a range in the amount of learning, including some outside-manifold perturbations that were learnable5,7. In this figure, we examined whether learning within each perturbation type could be accounted for by considering other properties of the perturbed mapping. We regressed the amount of learning within each perturbation type against the various properties we considered in Fig. 3. Panel a shows the initial performance impairment could explain a portion of the variability of learning within both classes of perturbation for monkey J. That monkey showed more learning on sessions when the initial performance impairment was larger. For monkey L, the initial performance impairment could account for a portion of the within-class variation in learning only for outside-manifold perturbations; this monkey showed less learning when the initial performance impairment was larger. We speculate that monkey J was motivated by more difficult perturbations while monkey L could be frustrated by more difficult perturbations. Panel b shows that the mean principal angles between control planes were related to learning within each class of perturbation for monkey L only. Larger mean principal angles between the control planes led to less learning. Panel c shows that the required PD changes were not related to learning for either type of perturbation for both monkeys. This makes the important point that we were unable to account for the amount of learning by studying each neural unit individually.
