Compartmental organization and integration of inputs in the cerebellar nuclei

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The cerebellum is concerned with the control of various kinds of movements, suggesting precise functional compartmentalization in it. Our previous studies revealed that the aldolase C expression pattern in the cerebellar cortex is tightly related with its functional compartmentalization. Purkinje cell axons, which are the output of the cerebellar cortex, project to the cerebellar nuclei. Compared to the cerebellar cortex, the cerebellar nuclei have not been much studied in terms of the input and output neuronal circuits and the functional compartmentalization.In the cerebellar nuclei, aldolase C is expressed in the terminals of Purkinje cell axons. Therefore, I first reconstructed aldolase C-positive and negative areas in the cerebellar nuclei in the three-dimensional space in the rat. This revealed that the aldolase C-negative and positive areas are each collected in the rostrodorsal, and caudoventral and lateral parts of the cerebellar nuclei.To relate these areas to the olivary projection, I mapped the nuclear collateral terminations of olivocerebellar axons in three-dimensional space in the rat. This revealed very precise topography in the nuclear projection olivary axons. Based on the topography, the functional compartmentalization in the cerebellar cortex is preserved nearly exactly in the cerebellar nuclei. This supported our hypothesis about the functional significance of aldolase C compartmentalization, and suggests that the rostrodorsal part of the cerebellar nuclei (aldolase C-negative) may be concerned with somatosensory-related functions and the caudoventral and lateral part of the cerebellar nuclei (aldolase C-positive) are concerned with other functions.Furthermore, labeled Purkinje cells projections indicated that the closed-loop circuit between the inferior olive and cerebellar cortex and nuclei was generally formed. Thus, precise compartmentalization and integration of neuronal inputs in the cerebellar nuclei were revealed.