The cerebellar nucleo-olivary projection in the cat.

The crossed cerebello-olivary projection in the cat was studied by means of retrograde transport of HRP. The cerebello-olivary connection is organized according to a zonal pattern similar to that of the olivocerebellar projection. However, some labelled neurons are in addition found in cerebellar nuclear areas adjacent to a nuclear zone sending its fibres to the corresponding olivary region. This observation indicates that there is a certain degree of overlapping between the different nuclear zones. The cerebello-olivary fibres from the fastigial nucleus appear to be more widely distributed than those from the other cerebellar nuclei. Nuclear neurons of all sizes project to the inferior olive, but the majority of the cells are medium sized. The findings are discussed and related to previous studies on the cerebello-olivary connection.