Demonstration of zonal projections from the cerebellar flocculus to vestibular nuclei in monkeys (Macaca fuscata).

Purkinje cells in the flocculus of macaque monkeys were labeled by retrograde axonal transport of horseradish peroxidase from the vestibular nuclei. These neurons are organized in three adjacent, narrow bands which span all folia of the ipsilateral flocculus. The central band, 500-750 micrometer wide, projects to the medial vestibular nucleus, while the two adjacent bands, each 300-500 micrometer wide, innervate the superior vestibular nucleus. These three bands cover about one-half of the total area of the Purkinje cell layer of flocculus. Thus, the pattern of zonal projections in monkeys is the same as reported in rabbits and cats.