Zonal organization of the climbing fiber projection to the flocculus and nodulus of the rabbit: A combined axonal tracing and acetylcholinesterase histochemical study

Abstract

The localization and termination of olivocerebellar fibers in the flocculus and nodulus of the rabbit were studied with anterograde axonal transport methods [wheatgerm agglutinin-horseradish peroxidase (WGA-HRP) and tritiated leucine] and correlated with the compartments in the white matter of these lobules delineated with acetylcholinesterase histochemistry (Tan et al. J. Comp. Neurol., 1995, this issue). Olivocerebellar fibers originating from the caudal dorsal cap travel through floccular compartments FC2 and FC4 to terminate as climbing fibers in floccular zones FZII and FZIV. Fibers from the rostral dorsal cap and the ventrolateral outgrowth traverse compartments FC1 and FC3, which are interleaved with compartments FC2 and FC4, and terminate in zones FZI and FZIII. Fibers from the rostral pole of the medial accessory olive traverse the C2 compartment and terminate in the C2 zone. FZI-III extend into the adjoining folium (folium p) of the ventral paraflocculus. The C2 zone continues across folium p into other folia of the ventral paraflocculus and into the dorsal paraflocculus. Four compartments and five zones were distinguished in the nodulus. Medial compartment XC1 contains olivocerebellar fibers from the caudal dorsal cap and subnucleus beta that terminate in the XZI zone. Olivocerebellar fibers from the rostral dorsal cap and the ventrolateral outgrowth occupy XC2 and terminate in XZII. The XC4 compartment contains fibers from both the caudal dorsal cap and from the rostral dorsal cap and the ventrolateral outgrowth. The latter terminate in a central portion of the XZIV zone. The dorsomedial cell column projects to the XZIII zone, which is present only in the dorsal part of the nodulus. The rostral medial accessory olive projects to the XZV zone, which occupies the lateral border of the nodulus. These results confirm and extend the conclusions of Katayama and Nisimaru ([1988] Neurosci. Res. 5:424-438) on the zonal pattern in the olivo-nodular projection in the rabbit. Additional observations were made on the presence of a lateral A zone (Buisseret-Delmas [1988] Neurosci. Res. 5:475-493) in the hemisphere of lobules VI and VII. Retrograde labeling of the nucleo-olivary tract of Legendre and Courville ([1987] Neuroscience 21:877-891) was observed after WGA-HRP injections into the inferior olive including the rostral dorsal cap and the ventrolateral outgrowth. The anatomical and functional implications of these observations are discussed.

Immunoreactivity for calcium-binding proteins defines subregions of the vestibular nuclear complex of the cat

“…There is anatomical evidence that suggests that the region of the calretinin area is reciprocally connected with the cerebellum, and specifically the nodulus (Sato et al 1983;Langer et al 1985b;Shojaku et al 1987;Walberg and Dietrichs 1988;Epema et al 1990;Barmack et al 1992c;Tan and Gerrits 1992;Tan et al 1995;Xiong and Matsushita 2000). The notion that the calretinin-immunoreactive cells themselves project to the cerebellum is consistent with the finding of a cholinergic projection from the VNC to the cerebellum (Barmack et al 1992a(Barmack et al , 1992c.…”

“…That study found that the region at the border of PH and VMN, the site of our dense patch of calbindin-labeled fibers, was free of calbindin-labeled fibers in those animals. Several studies suggest the most likely source of cerebellar projections to the regions of dense calbindin fiber label is the flocculus (Sato et al 1982;Langer et al 1985a;Shojaku et al 1987;Umetani 1992;De Zeeuw et al 1994;Tan et al 1995). The calbindin-dense patches thus define input compartments.…”

Topographical organization of inferior olive cells projecting to translation and rotation zones in the vestibulocerebellum of pigeons

“…Cerebellar zones containing rVA cells receive input from the caudal dorsal cap, whereas r45 c cells receive input from the rostral dorsal cap and ventrolateral outgrowth. 2,16,23 Nonetheless, in the present study, we found no appreciable differences in the location of retrograde labeling in the IO following injections at locations containing rVA vs r45 c cells. Likewise, we found no obvious differences in the locations of retrogradely labeled cells following injections in areas of the translation zone at locations containing different response types.…”

“…2,16,23 Barmack et al 3,4,5 have shown that many neurons in this zone and the beta subnucleus respond to static head tilt, thus demonstrating an input originating in the otolith organs. Although not self-translation per se, the medial zone of the nodulus/uvula and the beta subnucleus in rabbits receive inputs related to linear acceleration during self-motion, as does the medial VbC in pigeons.…”

“…Given these findings, it is not surprising that, in rabbits, the ventral uvula, nodulus and flocculus receive input from the same areas of the IO, namely the dorsal cap and ventrolateral outgrowth. 2,16,23 In fact, Takeda and Maekawa 21,22 have shown that individual IO neurons in rabbits project to the uvula/ nodulus and the flocculus. From the present study we conclude that the dorsomedial mc of pigeons is functionally equivalent to the dorsal cap and ventrolateral outgrowth of mammals, because these structures provide input to rotation cells.…”