Figure 7. Coherent L5-GrC Dynamics Reflect a Learned Circuit State.
(A) Behavioral learning. Pure turns as a fraction of trials increased (left, p=0.003, n=7 mice). Total movement duration decreased (middle, p<10−6), reflecting briefer transitions between the forward and lateral motions (right, p<10−6; n=460/2,062 Day-1/late learning trials; 19.3±1.1 days between day 1 and last day). Statistics compare all Day 1 to all late-learning days, using trials from all mice (2.8±0.5 expert days per mouse; Wilcoxon rank sum test).
(B, C) Behavioral encoding via linear regression in L5 (B) and GrC (C) ensembles covaried with behavioral performance over learning.
(D) The fraction of GrC variance explained by L5 ensembles via linear regression also covaried with behavioral performance.
(E) Within each imaging session, each successful trial was ranked by its kinematic similarity to the average pure turn trajectory of the same direction. From an example mouse, 10 trajectories in each direction are shown from three sets of trials: from a late-learning day, the subsets of trials most and least consistent with the average trajectory (left two columns), and from a mid-learning day, the subset of trials most consistent with the average trajectory (right column). Top row shows trajectories in x-y space, and middle and bottom rows show forward and lateral motion over time.
(F) For each late- and mid-learning imaging session, best-match L5-GrC correlations were computed using only trials from either the most consistent or least consistent subset (20 top- and bottom-ranked trials in each direction). L5-GrC correlations were not significantly different between most and least consistent trials on the late learning day (distributions shown for mouse in E; black versus grey, p=0.35, Kolmogorov-Smirnov test, n=149/152 GrCs, and 143/134 L5 cells, from the mid-/late-learning days, respectively). By contrast, even the most consistent trials on the mid-learning day exhibited substantially smaller L5-GrC correlations than did the least consistent late learning trials (p=0.0001).
(G) Schematic of evolution of L5 and GrC ensemble dynamics over learning. From an initially less coherent, higher-dimensional, less task-related set of activity patterns, L5 and GrC ensembles converge onto a more shared, low-dimensional, task-encoding set of activity patterns.
See Figure S7 for further analyses and related data.