Extended Data Fig. 1. Ca²⁺ imaging in cerebellar granule cells.

a, Parasagittal section of the cerebellum of a transgenic mouse (Math1-Cre / CAG-lox-stop-lox-tTA / TRE-lox-stop-lox-GCaMP6f) used for in vivo two-photon Ca²⁺ imaging. GCaMP6f expression (green) is widespread throughout most granule cells. GCaMP-expressing somas were not detected in the molecular layer, and only rarely coincided with Purkinje cells (red). For unknown reasons, granule cell expression is substantially reduced in lobules IX and X. A, anterior; P, posterior; D, dorsal; V, ventral. b, Mean two-photon fluorescence image for the session shown in Fig. 1c,d. c, Location of all identified active cerebellar granule cells in the field of view in b (n = 53 cells total). Numbered cells indicate the example cell traces shown in Fig. 1d, counting from the bottom to the top.