Fig. 7.

Presynaptic populations of vMNs. (A) Maximum confocal projection image across all histological brain sections that comprise the Sp5O of the BS in a second-order experiment after injecting rabies virus into the C3 whisker (same experiment as shown in Fig.5B, C). Images were superimposed with the corresponding pages from the Paxinos rat brain atlas and all rabies-positive neurons were marked and assigned to the respective BS nuclei. Right panel: zoom-into the GI reveals sparse labeling of second- order neurons that are presynaptic to the first-order vMNs in the FN, e.g. the ones in Fig. 6. (B) Maximum confocal projection image across all histological brain sections that comprise the Sp5I of the BS in same experiment as shown in panel (A) Right panel: zoom-into the IRt. (C) Maximum confocal projection image across all histological brain sections that comprise the Sp5C of the BS in the same experiment as shown in panels (A, B). Right panel: zoom-into the MdD. (D) Same BS regions as shown in the zoom-ins in panel (A) for a second second-order experiment after injections into the C3 whisker muscle. Labeling in the second animal was in general sparser than in the first experiment. (E) Quantification of the number of neurons in all rabies-infected BS nuclei in the two second-order C3 injection experiments. The red marked BS nuclei represent those that are consistently labeled in both experiments. The major sources of common input to vMNs are highlighted in green.