Figure 5. Common L5 and GrC Task Representations Emerge Concurrently during Learning.
(A and B) Example mean fluorescence images of the same L5 cells (A) and GrCs (B) acquired over learning. Arrowheads point to example cells that were tracked across days.
(C–F) Trial-averaged activity of example L5 cells (C and E) and GrCs (D and F) shown on days corresponding to early, mid, and late learning. Cells develop direction-preferring activity time-locked to movement (C and D) or reward (E and F) (mean±SEM; left/right turn trial numbers for C, D, E, F: Early: n=40/18, 24/68, 29/18, 29/18; Mid: 34/27, 57/33, 48/36, 17/45; Late: 109/74, 24/37, 72/71, 72/71).
(G) All cells were scored on each day for direction preference and task-locking using regression analysis as in Figure 2E. For the set of all L5 cells (left) and GrCs (right) that had direction preference on the final day of imaging, activity was primarily either modulated at the same time but without direction preference (dark gray) or was not modulated at that time (light gray) on earlier days (n=183/206 L5 cells and 172/202 GrCs from early/mid-learning, respectively). Direction-preferring activity was only infrequently maintained (white).
(H and I) Based on regression analysis (as in Figure 2E), more cells had direction-preference late in learning (H, p=6×10−6 and 5×10−6 for early vs. late for L5 and GrCs; Wilcoxon rank sum test; n=11 early, 19 mid, and 21 late imaging sessions from 7 mice), and regressions more accurately reproduced each cell’s activity (I; p< 10−6 Wilcoxon rank sum test for early vs late in L5 and GrCs; n=1,265/1,397, 2,113/2,324, 1,666/1,647 L5/GrC observations early, mid, and late, respectively).
(J and K) The entire ensemble of GrCs or L5 cells was scored for its fidelity of behavioral encoding. The accuracy of reproducing behavioral signals shown in Figure S6A via single-trial linear regression rose over learning (J, mean±SEM; late vs early, p=0.0009 and p=9×10−5 for L5 and GrC respectively; n=11 early, 19 mid, and 21 late learning imaging sessions from 7 mice). In addition, regression accuracy for GrC populations (x-axis) and L5 populations (y axis) in each imaging session (colored dots) covaried over learning (K, 51 imaging sessions from 7 mice).
(L and M) L5 and GrC ensembles both became lower-dimensional over learning, as the top 10 principal components (as computed in Figure 2I) explained greater fractions of single-trial variance (L, p=5×10−6 and 3×10−5 for GrCs and L5 cells, respectively), and fewer components were required to explain 50% of variance (M, p=4×10−5 and p=0.007 for GrCs and L5 cells respectively, Wilcoxon rank sum test, 11 early, 21 late sessions).
See Figure S6 for further analyses and related data.