Figure 2.

Granular layer stimulation by NMDA evokes beam-like response. A, Cerebellar activation evoked by NMDA/glycine microinjection. Left, Background fluorescence of Crus II followed by a series of grayscale images to the right showing typical Ca²⁺ responses to NMDA/glycine microinjections at 50, 200, and 400 μm below the cerebellar surface. Peak beam-like activity is evoked when NMDA/glycine is microinjected at 200–350 μm below the cortical surface, depths corresponding to the granular layer. B, To verify that the responses were NMDA receptor-mediated, NMDA injections were performed at a depth evoking a maximal response in the 0 mm Mg²⁺ Ringer's solution and repeated upon reintroduction of 2 mm Mg²⁺ into the optical chamber bath. C, Fluorescence responses (ΔF/F on left axis) are summarized for the center and beam components (Fig. 1A, ROI example) as well as the ML/RC ratios (right axis) for NMDA/glycine injection within three depth ranges below the cerebellar surface (n = 9 mice). The *, □, ◊ values are significantly different from all other values in the same group (i.e., control, beam, ML/RC). The ◊ indicates the ML/RC ratio for injection at 400–500 μm is significantly different from the ML/RC ratio for injections at either 50–150 or 200–130 μm. D, Summary fluorescence responses and ML/RC ratios for NMDA/glycine injections with and without Mg²⁺. The *, □, ◊ values are significantly different from all other values in the same group (i.e., control, beam, ML/RC). The ◊ indicates the ML/RC ratio for injection at 400–500 μm is significantly different from the ML/RC ratio for injections at either 50–150 or 200–130 μm.