Figure 4. Emergence of reward expectation responses during forelimb movement task learning.

a, Example in vivo two-photon mean fluorescence images of the same granule cells acquired on different days, registered to the final day (magnified in Extended Data Fig. 9). Arrows indicate example corresponding neurons across days. b, Average responses of all detected granule cells on rewarded trials on Day 1 and Day 6 of imaging, sorted separately for each day by time of peak response (97 neurons from an example mouse). c, Average response of all granule cells on rewarded trials on all six days, sorted by their Day 6 activity, for the mouse in b. d, Average response to omitted reward on Day 2 and Day 6, ordered by time of peak response on rewarded trials on the same days. e–g, Top, For each day, average fluorescence of the top 10% of cells across mice (24 neurons) ranked by their Day 6: (e) anticipatory rise in fluorescence (mean fluorescence difference between −0.25 to −0.05 s and −1.3 to −1 s), (f) response preference for omitted reward over reward (mean difference over 0.1 to 1 s), or (g) forelimb movement response (fluorescence rise during movement, −1.3 to −1 s, compared to pre-movement, −1.8 to −1.3 s). Bottom, summary across all neurons of changes in anticipatory responsiveness (e), omitted reward preference (f), or forelimb movement responsiveness (g). (***p < 10⁻⁶; n.s. p = 0.76; n = 233 neurons from 3 mice, Wilcoxon signed-rank test).