Floccular peduncle

Fig. 103. The cerebellar nuclei of the cat. The transitional U-shaped region of the fastigial and posterior interposed nuclei is indicated by double hatching, be = brachium conjunctivum cr = restiform body DV = descending vestibular nucleus F = fastigial nucleus flo = floccular peduncle Ftail = tail of the fastigial nucleus lA = anterior interposed nucleus IP = posterior interposed nucleus L = lateral cerebellar nucleus LV = lateral vestibular nucleus MV = medial vestibular nucleus SV = superior vestibular nucleus u = uncinate tract Y = group y of Brodal and Pompeiano (1957).

Fig. 104. Two transverse, AChE-incubated sections through the cerebellar nuclei of the cat, A. Rostral section. B. Caudal section. Note medium-sized cells of dorsal group y in floccular peduncle and strongly AChE positive ventral group y along dorsal border of restiform body in (A) U-shaped nucleus between IP and F in (B). cr = restiform body F = fastigial nucleus flo-i-y = floccular peduncle with group y lA = anterior interposed nucleus IP = posterior interposed nucleus IP/F = U-shaped nucleus between F and IP L = lateral cerebellar nucleus sad = stria acoustica dorsalis.

McCrea, 1988). A more realistic approach would be to consider the cells of the y group as the bed-nucleus of the floccular peduncle, and to realize that a distinction between the group y and the superior vestibular nucleus, that receives a major part of the fibers of the floccular peduncle, remains arbitrary (Tan et al., 1995a). 

Gacek (1977, 1979) used the term infracerebellar nucleus for the cells embedded in the fasciculus angularis (i.e. the floccular peduncle) as it arches over the restiform body and applied the term y group to the cells of the group 1 of Brodal and Pompeiano (1957). 

The white matter compartments of the flocculus do not simply continue as components of the floccular peduncle, but a reorganization takes place, that directs Purkinje cell axons from the compartments 2 and 4 to the medial vestibular nucleus and of the compartments 1 and 3 to the superior vestibular nucleus. The C2 compartment does not contribute to the floccular peduncle, but leads its fibers towards the posterior interposed nucleus. In monkeys the equivalent of compartment 1 of the rabbit extends in the roof of the fourth ventricle, along the basal interstitial nucleus of the cerebellum (Fig. 148). 

Fig. 147. Photographs and diagrams of AChE-stained sections from rabbit flocculus. The compartments Cj and 1-4 of the flocculus white matter are indicated in the diagrams with different symbols, a-d. Rostralmost section, c-f. Caudalmost section. Arrows indicate the AChE-postive borders between the compartments, bp = brachium pontis Cj = compartment CO = cochlear nuclei f (1-4, p) = folium 1-4 and folium p of the flocculus L = lateral cerebellar nucleus m = folium m of the flocculus pf = floccular peduncle PFLDA = dorsal and ventral paraflocculus. Tan et al. (1995a).

Fig. 148. Compartmentation in AChE-stained transverse sections of the flocculus, the ventral paraflocculus and the petrosal lobule and the caudal hemisphere of Saimiri sciureus. Note AChE stained borders of the compartments and the differential staining in the molecular layer AChE-positive cells of the basal interstitial nucleus of Langer are located along the borders of the compartments C2, 1 and 2 in (D) and (E). Group y is located within the floccular peduncle in (E), ANS = ansiform lobule br.p = brachium pontis c.rest = restiform body Cl-3 = C21-3 compartments D = dentate nucleus Dl,2 = Dl,2 compartments F = fastgial nucleus fis.post.lat = posterolateral fissure FLOC = flocculus lA = anterior interposed nucleus IP = posterior interposed nucleus Ib.petr = petrosal lobule PFLD = dorsal paraflocculus PFLV = ventral paraflocculus. Courtesy of Dr. D.T. Hess.

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