Fig. 2: Distinct input–output organizations of the excitatory FN^E–IO and inhibitory FN^I–IO modules.

a, Experimental schematic of cell-type-specific retrograde transneuronal tracing of PC inputs to FN^E–IO neurons. b, Example images of retrogradely labeled PCs in the cerebellar cortex (1 of 4 mice displayed). Inset scale bar = 10 µm. c,d, Same as a and b, but for monosynaptic rabies tracing of the PC inputs to FN^I–IO neurons (1 of 4 mice displayed). e,f, Comparison of the distribution of PC inputs to FN^E–IO and FN^I–IO neurons. e, Three-dimensional rendering of all labeled PC projections to FN^E–IO neurons (turquoise, n = 4 mice) and FN^I–IO neurons (magenta, n = 4 mice). f, Distribution of labeled PCs across cerebellar lobules. Density is normalized to the total labeled PCs of each animal. Lighter curves represent individual mice, darker dots and bars represent mean ± s.e.m. g, Experimental schematic of tracing the climbing fibers originating from FN^E-recipient neurons in the mcMAO. h, Example images of labeled climbing fibers in the cerebellar cortex (1 of 3 mice displayed). i,j, Same as g and h, but for tracing the climbing fibers from FN^I-recipient IO neurons (1 of 3 mice displayed). k,l, Same as e and f, but for comparison of climbing fiber distribution from FN^E-recipient IO neurons (red, n = 3 mice) and FN^I-recipient IO neurons (green, n = 3 mice). Lighter curves represent individual mice, darker dots and bars represent mean ± s.e.m. m, Overlay of PCs (inputs) and climbing fibers (outputs) reveals discrete excitatory nucleo-olivo-cortical modules for the FN^E–IO pathway.

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