Paraflocculus, cerebellum

Fig. 19. Schematic illustration of the zonal distribution of somatostatin immunoreactive Purkinje cells at different levels of the cerebellum of a 21 day old rat. Drawings have been made from frontal, cresyl-violet stained sections. Each dot represents 2-5 cells. Abbreviations 5-9, cerebellar lobules V-IX 4V, 4th ventricle COP, copula pyramis CR2, crus 2, ansiform lobule FL, flocculus PFL, paraflocculus PM, primary fissure SF, secondary fissure. Villar et al. (1989).

Nerve growth factor-like immunoreactivity was present in Purkinje cell somata and dendrites, with dense labelling in the paraflocculus, and in neurons of the cerebellar nuclei and the lateral vestibular nucleus of rat cerebellum (Nishio et ah, 1994). All but a few of the Purkinje cells of the adult rat cerebellum stain with an antiserum against basic fibroblast growth factor. Staining was observed in all cellular compartments (Matsuda et ah, 1992). 

Fig. 38. A. Nerve growth factor-R (NGF-R) transcripts are localized within Purkinje cells in the paraflocculus of rat cerebellum. B. NGF-R immunocytochemistry shows the perikarya of the Purkinje cells as well as the dense staining of the molecular layer, where the dendritic trees of the Purkinje cells arborize. Arrows in C and D point to parasagittal zones of intense labelling interdigitated with weaker labelling. Bar = 90 fim. Koh et al. (1989).

Fig. 84. Illustrations of choline-acetyltransferase (ChAT)-like immunoreactivity in the rabbit cerebellum. A. Sagittal view of the rabbit cerebellum delineating the lobules according to Larsell (Larsell, 1970). Mean measurements of ChAT activity are indicated by numbers in parentheses. B. Magnified view of the ventral vermis. The vermis contains areas of ChAT-positive mossy fiber terminals (indicated by dots). These areas in lobules 1 and 9d are illustrated in C and D, respectively. E. View of the right paraflocculus of the rabbit. ChAT-like immunoreactivity and ChAT activity was highest in the ventral paraflocculus, particularly lobule 2. The numbers in parentheses are mean measurements of ChAT activity, expressed as mmol of Ach synthe-sized/hr. g tissue at 37°C, for each cerebellar lobule in six rabbits. Barmack et al. (1992a).

Fig. 98. Cerebellum of the cat. The continuity in the folial chains of vermis and hemisphere is indicated by lines in the diagrams. CRI = crus I of the ansiform lobule CRII = crus II of the ansiform lobule FLO = flocculus LOB ANT/POST = anterior/posterior lobe PFLD = dorsal paraflocculus PFLV = ventral parafloc-culus PMD = paramedian lobule SI = simple lobule VII-X = lobules of the caudal vermis. Bigare (1980).

Fig. 99. Cerebellum of Macaca fascicularis. a. Anterior aspect, b. Ventral aspect, c. Caudal aspect, d. Dorsal aspect. Regions without cortex, where the white matter comes to the surface, are indicated with light hatching. Heavy hatching indicates cross section of the cerebellar peduncles, solid black indicates roof of the fourth ventricle in b. CrI = Crus I of the ansiform lobule CrII = crus II of the ansiform lobule FLO = flocculus fpl = posterolateral fissure PFLD = dorsal parafloculus PFLV = ventral paraflocculus PMD(cop) = paramedian lobule (copula pyramidis) SI = lobulus simplex.

Fig. 120. Compartments in the white matter of the cerebellum of the cat. Drawings and reconstructions from Haggqvist and AChE-stained sections. Compartments are indicated with different symbols. A-D. Graphical reconstructions of the rostral aspect of the anterior lobe (A) and the posterior lobe (B), the dorsal aspect (C) and the caudal aspect (D) of the cerebellum. Compare Fig. 98. E-G. Transverse sections. A = A compartment ANS = ansiform lobule ANT = anterior lobe B = B compartment Cl-3 = Cl-3 compartments cr = restiform body D(l,2) = D(l,2) compartments F = fastigial lateral cerebellar nucleus PFL = paraflocculus PMD = paramedian lobule SI = simple lobule vest = vestibular nuclei X = X compartment III-IX = lobules IIl-IX.

Only few observations in primates are available on the corticonuclear projection of the posterior lobe. Haines and Whitworth (1978) and Haines and Patrick (1981) studied the projection of the paramedian lobule and the paraflocculus in the tree shrew Tupaia glis). They concluded that , 3 and a D zone, with a similar topography and corticonuclear projection as in the cat, were present in the paramedian lobule of the tree shrew. The C2 and the D zone continued into the paraflocculus, where the D zone could be subdivided into D, and Dj zones on the basis of its differential projection to the lateral cerebellar nucleus. The organization of the posterior vermis in primates (Haines, 1975a,b) will be dealt with in the Sections on the vestibular cerebellum (6.1.5.) and the olivocerebellar projection (6.3.3.3.). 

Fig. 129. Schematic drawing of the distribution of motilin-immunoreactive (M-i) Purkinje cells (open triangles) and glutamic acid decarboxylase-immunoreactive (GAD-i) Purkinje cells (filled circles) in a coronal section of rat cerebellum. M-i cells and GAD-i cells are both more concentrated in the flocculus and the paraflocculus than elsewhere. Both cell types occur in the vermis and participate in the formation of the sagittal microzones (arrows). M-i terminal axon projections in the deep cerebellar nuclei are heaviest in the dentate (D left side) and GAD-i projections are heaviest in the lateral vestibular nucleus (LV right side). 1 = interposed nucleus F = fastigial nucleus. Chan-Palay et al. (1981).

Fig. 130. Schematic summary of cysteine sulfinic acid decarboxylase (CSADCase)-positive sagittal microzones or bands in mouse cerebellum. The bands are clearest in the anterior lobe and the vermis, less sharply defined in the hemispheres (dense stipple), and most difficult to discern in the paraflocculus and flocculus (light stipple), because of intense CSADCase reactivity in most Purkinje cells. The dentate (D), interpositus (I), fastigial (F), and lateral vestibular nuclei (LVN) contain numerous CSADCase-positive cells. Chan-Palay et al. (1982b).

Fig. 131. Reconstructions of the zonal distribution of 5 -nucleotidase (5 -N) in the molecular layer of the cerebellum of the mouse. Numbers without prefix indicate the nomenclature for the 5 -N-positive bands of Marani (1982) P-numbers on the left side refer to the nomenclature for corresponding Zebrin I-positive bands of Hawkes and Leclerc (1987). ANT = anterior lobe FLO = flocculus PFL = paraflocculus II-X = lobules...

Fig. 139. Drawings of three surface views of the mouse cerebellum, anterior, dorsal and posterior, showing the locations of the Zebrin+ bands of Purkinje cells. The Purkinje cell bands PI +-P7 + are labelled in the dorsal view (for clarity, only the numerals have been used). Note that in the vermis of the posterior lobe the immunoreactive Purkinje cells form five to seven bands (posterior and dorsal views), whereas in lobules VII and VI all vermal Purkinje cells are immunoreactive (posterior and dorsal view). This pattern gradually changes in the anterior lobe to result in three to five very narrow immunoreactive bands (anterior view). In the hemispheres there are three major immunoreactive bands of Purkinje cells on either side (P5b+, P6+, P7+) plus two sub-bands in the para vermal area of the paramedian and ansiform lobules (P4b-t, P5a+). Note too that the Purkinje cells are all Zebrin+ in the nodulus (lobule X, illustrated as indicated by arrows reflected out from the ventral surface of the cerebellum), the paraflocculus, and the flocculus. From Eisenman and Hawkes (1993).

Fig. 140. Computer drawing of the reconstruction of the Zebrin Purkinje cells bands in the unfolded adult C57/B6 mouse cerebellum. The drawing was from immunostained 40 fim thick coronal frozen sections. The continuity of the bands has been determined as best as possible. On the left and bottom are the scales in millimeters. The two axes have different magnifications. On the right are marked the approximate boundaries of the vermal lobules. The flocculus and paraflocculus are not illustrated. One place where the data are ambiguous is within lobule V-VI, where a large number of short bands more caudally are dramatically reduced to just three at the rostral limit. It is not clear whether the P2 + or P3 + bands extend through the anterior lobe vermis (see also Fig. 139). The reconstruction data from coronal sections were not suitable to resolve the issue, so the cerebellum has also been reconstructed from horizontal sections. The upper inset panel shows the data from such a reconstruction, equivalent to the region indicated by a rectangle on the main drawing (scale in millimeters). The preferred interpretation is that the P2+ compartment does not extend far into the anterior lobe vermis, and that the first lateral Zebrin + band in lobules I-IV is continuous with P3+ (as indicated by continuous lines in the upper inset panel and as shown in the main drawing). The alternative hypothesis, that the first lateral Zebrin + band in lobules I-IV is continuous with P2+, is shown schematically in the lower inset panel. Eisenman and Hawkes (1993).

Fig. 190. Distribution of CRF and CGRP-immunoreactive climbing fibers in P7 mouse cerebellum (A-C) and in neurons of the inferior olive (D-F). CRF-immunoreactive climbing fibers and neurons are indicated by dots, CGRP-immunoreactive climbing fibers and neurons by open circles, a, b and c = subnuclei a, b and c of the medial accessory olive beta -i- group beta Cl, C2 = Crus I and II DAO = dorsal accessory olive dc = dorsal cap EGL.ML = external granular layer and molecular layer F = flocculus IGL = internal granular layer PF = paraflocculus MAO = medial accessory olive PO = principal olive PL = Purkinje cell layer. Redrawn from Yamano and Tohyama (1993).

Fig. 191. Schematic line drawings of the unfolded opossum cerebellum modified after Larsell and Jansen (1972). The broken lines indicate the boundaries of the corticonuclear zones A-D after Klinkhachorn et al. (1984a). The distribution of the three types of enkephalinergic axons is indicated by the frequency and size of the symbols the beaded axons by asterisks (C), the mossy fibers by dots (A), and the climbing fibers by triangles (B). I-X indicate vermal lobules CR I, II, crura I and II, F, flocculus LS, lobulus simplex PFL, paraflocculus PML, paramedian lobule. D. Distribution of enkephalinergic axons in a horizontal section through the cerebellar nuclei. D, dentate nucleus, F, fastigial nucleus IPA, anterior interposed nucleus IPP, posterior interposed nucleus. From King et al. (1987).

Fig. 194. Three transverse sections through the cerebellum of the cat showing corticotrophin releasing factor (CRF)-like immunoreactivity in climbing fibers in the molecular layer (radial lines) and mossy fibers (dots) in the granular layer. Note corresponding positions (arrows) of strongly labelled climbing fibers and mossy fibers (arrows). Abbreviations CR I, II, Crus I and II FL, flocculus LS, simple lobule NIP, posterior interposed nucleus NL, lateral cerebellar nucleus NM, medial nucleus PFL, paraflocculus PML, paramedian lobule I-X, lobules I-X of Larsell. Cummings (1989).

The paramedian pontine reticular formation of the cat projects bilaterally to lobule VII and the caudal part of lobule VI and to the ansiform lobule, i.e. to the visual areas of the cerebellum involved in control of saccades (Gerrits and Voogd, 1986 Yamada and Noda, 1987). Fibers of the reticular nucleus of the pons distribute bilaterally, with ipsilateral predominance, to all lobules of the cerebellum, with the exception of the lobules I and X and the dorsal paraflocculus (Kawamura and Hashikawa, 1981 Gerrits and Voogd, 1986). This projection includes the flocculus and the adjacent part of the ventral paraflocculus (Fig. 203) (Gerrits and Voogd, 1989) and collateral projections to the cerebellar nuclei (see Section 5.6.). 

Fig. 202. Cuneocerebellar projection to ipsilateral cerebellum in the cat. Left side diagrams from antegrade axonal transport of [ Hjleucine in transverse sections. Borders of compartments in adjacent Haggqvist-stained sections are indicated on the right. Abbreviations A(l-3) = A( 1-3) compartment A = concentration of mossy fibers in A compartment B = B compartment bp = brachium pontis Cl -tC2 = concentration of mossy fibers in Cl and C2 compartments Cl-3 = Cl-3 compartment C3 = concentration of mossy fibers in C3 compartment cr = restiform body D = Dcompartment D = concentration of mossy fibers in D compartment F = fastigial nucleus FL = flocculus HVI = hemisphere of lobule VI (simple lobule) lA = anterior interposed nucleus L = dentate nucleus PAR = paramedian lobule PFLD = dorsal paraflocculus PFLV = ventral paraflocculus X = X compartment X/B = concentration of mossy fibers in border region of X and B compartments. Gerrits et al. (1985b).

Fig. 208. Diagram of the fractured somatotopy of the mossy fiber projections in the cerebellum of the rat. Patches with similar receptive fields are indicated with abbreviations for the stimulation sites on the head and the extremities. Redrawn from Welker (1987). Cr = crown El = eyelids Fbp = furry buccal pad FL = forelimb and hand G = gingiva HL = hindlimb I, II = crus I and II Li = lower incisor LI = lower lip Lob.ant. = anterior lobe lob.sim = lobulus simplex N = nose Nk = neck P = pinna PFL = paraflocculus PML = paramedian lobule PY = pyramis Rh = rhinarium Ui = upper incisor U1 = upper lip UV = uvula.

The distribution of CRF-immunoreactive mossy fibers in the cerebellum of the cat is very similar to the opossum, with concentrations of mossy fibers underlying the stained bands of immunoreactive climbing fibers in vermis and pars intermedia, and heavy labelling in the flocculonodular lobe (Cummings, 1989) (Fig. 194). The localization of CGRP-immunoreactive mossy fibers over the cerebellum of the cat differs substantially from that of the other peptides. They are present in the paraflocculus, the paramedian and ansiform lobules and in the pars intermedia of the simple lobule and the anterior lobe. In the anterior vermis they are located in the apices of the lobules. 

Does the Zebrin pattern result from the interdigitation of two sets of Purkinje cells that differ in their biochemical properties and in their afferent and efferent connections The truth, probably, is less simple. Purkinje cells of the A and B zones of rat cerebellum, that project to the lateral vestibular nucleus, are uniformly Zebrin-negative and are delimited by Zebrin-positive bands and satellite bands (Fig. 143). Other zones, that can be defined by their corticonuclear and olivocerebellar connections, such as the lateral extension of the A zone of Buisseret-Delmas (1988a), include both Zebrin-positive and Zebrin-negative regions (Fig. 144). Morever, uniformly Zebrin-positive lobules, like lobule VII, the nodulus, the flocculus and the paraflocculus, contain a complex zonal substructure (Sections 6.1.4., 6.1.5. and 6.3.3.3.). 

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