Anatomical and functional relationships between deep cerebellar nuclei and cerebellar cortical Crus II in vivo in mice.

We previously reported that an air-puff stimulation on the ipsilateral whisker pad evoked responses in molecular layer (ML) and Purkinje cell (PC) layer in cerebellar cortex folium Crus II. We used anterograde tracing and electrophysiological methods to investigate the anatomical and functional relationships between the trigeminal tactile response area in the cerebellar cortex Crus II and deep cerebellar nuclei (DCN) in living mice. We found that the axons of tactile activated PCs projected in anterior part (IntA) and posterior part (IntP), and dorsolateral hump (IntDL) of ipsilateral interposed cerebellar nucleus (ICN). In ICN, the tactile stimulus evoked-field potential expressed a sequence of two negative components N1 and N2, while extracellular recordings from ICN neurons revealed that an increase in spike frequency in response to tactile stimulus. When the duration of facial air-puff stimulus were ≥ 30 ms, stimulation off response (Roff) were observed in the ICN, but an increase in the duration of facial air-puff stimulation did not significantly affect the amplitude of Ron (N1 and N2) and Roff. The latency and time to peak of N1 in ICN were significantly shorter than that of N1 in the ML, but the latency and time to peak of N2 in ICN were significantly later than that of P1 in the ML. The present results suggest that the facial sensory information, at least in part, is transferred to ICN by PC axons from Crus II, which evokes excitation in ICN neurons.