PROJECTIONS OF INDIVIDUAL PURKINJE-CELLS OF IDENTIFIED ZONES IN THE VENTRAL NODULUS TO THE VESTIBULAR AND CEREBELLAR NUCLEI IN THE RABBIT

The projections of Purkinje cells from zones in the ventral nodulus of pigmented rabbits were studied with the use of extracellularly inject ed biocytin as an anterograde tracer. The zones were physiologically i dentified according to the complex spike modulation of Purkinje cells in response to optokinetic stimulation. Purkinje cells in the most med ial zone do not respond to optokinetic stimulation; they project to th e fastigial nucleus, the perifastigial white matter, the periinterpose d white matter, and the medial vestibular nucleus. In the adjacent zon e, Purkinje cells respond best to optokinetic stimulation about the ve rtical axis; they project to the periinterposed white matter and the m edial vestibular nucleus. Purkinje cells in the next zone respond best to optokinetic stimulation about an axis approximately perpendicular to the ipsilateral anterior canal; they project to the periinterposed white matter, dorsal group y, the superior vestibular nucleus, and the medial vestibular nucleus. In the most lateral zone, Purkinje cells r espond best to optokinetic stimulation about the vertical axis; they p roject to the periinterposed white matter, dorsal group y, and the med ial vestibular nucleus. The majority of axons gave off collaterals and innervated more than one nucleus. Often, three or four different area s received terminals from a single Purkinje cell axon. The zonal proje ction pattern of the ventral nodulus is compared to that of the floccu lus, which, with respect to the visual climbing fiber afferents, has s imilar zones. (C) 1994 Wiley-Liss, Inc.