Extended Data Fig. 2: Additional results of neural activity patterns during curl field learning and VMR learning.
From: Cortical preparatory activity indexes learned motor memories
a, Initial hand forces predicted by the 2D TDR preparatory states were correlated with real forces of the upcoming movement (the slope is 0.41 and the intercept is 0.02 with \({{\rm{R}}}^{2}\) = 0.59 and P = 6.06 x 10−9). The sign of hand force indicates its direction. Lighter dots, earlier learning trials; darker dots, later learning trials. b, Single-trial prediction MSE of initial hand forces was significantly smaller using original data than shuffled data (two-sided Wilcoxon rank-sum test: P = 0.0006 for both training and test sets of monkey U and P = 0.008 for both training and test sets of monkey V). Training set: before-learning trials. Test set: learning trials. Control results (blue) were forces predicted by models built from training sets that had neural and behavioural data shuffled. One datapoint per session. c, Changes of preparatory states in the force-predictive TDR subspace reflected generalization of learning, quantified as the rotatory angle from before-learning to error-clamp neural states. Zero degree on the x axis, the trained target. Error bars, s.e.m. across sessions (n = 5, 3). d, Normalized single-trial neural shift during learning along the uniform-shift learning axis. Solid line: linear-log regression (n = 1200, 900). e, Preparatory neural repertoires changed similarly for trained and untrained reaches. Black: no-learning control results (n =36). Blue: far targets more than 45 degrees from the trained target (n = 15). Red: near targets within 45 degrees from the trained target (n = 21). One-sided Wilcoxon rank-sum test: Pblack vs. blue = 2.33 x 10−7, Pblack vs. red = 4.74 x 10−8, Pblue vs. red = 0.059. f, g, VMR learning results. f, Preparatory neural states projected to PCs 1-3. After-learning states (diamonds) were mixed with before-learning states (circles). One example session. g, Preparatory and peri-movement neural activity patterns did not show repertoire change during VMR learning. One-sided Wilcoxon rank-sum test: P > 0.1 for all comparisons. Three learning sessions (n = 24) and three control sessions (n = 24) for both monkeys. h, i, Neural preparatory states in the 3D TDR subspace. The 3D subspace was constructed by TDR capturing the variance due to initial hand forces and a binary indicator of trial conditions (an indicator of before-learning versus after-learning). One example session. h, In the force-predictive TDR subspace, rotatory shifts of preparatory neural states were similar to Fig. 2b. i, Along the TDR 3 axis (the binary indicator axis), this 3D model revealed a uniform shift similar to what we observed along PC 3 in the PCA subspace (Fig. 2d). For all the box plots, the central line indicates the median, the bottom and top edges indicate the 25th and 75th percentiles of the data, and the whiskers extend to the 5th and 95th percentiles of the data.
