Cerebellar corticonuclear and corticovestibular fibers of the flocculonodular lobe in a prosimian primate (Galago senegalensis)

Abstract

Efferent projections from the flocculonodular lobe and the ventral part of the uvula were studied in a prosimian primate (Galago senegaLensis) utilizing the Fink and Heimer ('67) method. Corticonuclear and corticovestibular fibers of the flocculonodular lobe and ventral uvula are ipsilateral. Fibers from both the flocculus and nodulus appear to terminate in cell group y (of Brodal and Pompeiano, '57) although there is little evidence of other projections beyond the vestibular complex. The cortex of the flocculus sends numerous fibers into ventral portions of the NL, central areas of the SVN, and rostra1 and ventral regions of the MVN and fewer fibers into dorsal and medial SpVN. Many fibers from the nodulus terminate in ventrocaudal NM, peripheral areas of the SVN, and dorsal and caudal MVN. Fewer fibers course into ventral areas of the ipsilateral NL and in approximately the dorsal half of the SpVN and in its ventrolateral area a t caudal levels. The LVN receives few, if any, fibers from the flocculonodular lobe. When present they appear to end almost exclusively in those areas of the LVN which border the SVN, MVN, or SpVN. The ventral uvula sends fibers mainly to the dorsomedial SVN, throughout the dorsal SpVN and in its ventrocaudal area, and to a limited region of the ventrolateral MVN at caudal levels. A few fibers from the ventral uvula distribute to dorsolateral SVN, to central areas of the caudal SpVN, and to the ventral MVN a t caudal levels.Corticonuclear and corticovestibular fibers of the flocculus, nodulus and ventral uvula are (1) topographically organized with respect to their specific nuclei of termination and (2) have terminal fields in the cerebellar nuclei and vestibular complex which are partially coextensive (with the terminal field of one or both of the other lobules) and partially exclusive (to that particular lobule). Projections are seen into ventral portions of the ipsilateral NL from both floccular (hemisphere) and nodular (vermis) cortices. It is postulated that this may represent a direct route through which the flocculonodular cortex may assist in the regulation of eye movement since the primate NL, expecially its ventral part, sends fibers to certain of the contralateral oculomotor nuclei via the crossed ascending limb of the brachium conjunctivum (Carpenter and Strominger, '64; Martin et al., '74; Chan-Palay et al., '76).Early reports on flocculonodular lobe projections were inconclusive and provided little data concerning their topographical distribution (e.g., Clark and Horsely, '05; Bender, '32; Dow, '36, '38; Jansen and Brodal, '40, '42). There was a consensus, however, that lesions of the flocculus elicited degeneration within the superior and lateral vestibular nuclei whereas destruction of the nodulus and uvula (from Dow, '36, '38) produced degeneration in "all the vestibular nuclei of the same side." A number of subsequent investigations, while describing projections from many lobules, Eager, '63, '66, '67; Marling and Eager, '67; Achenbach and Goodman, '68; Srees...

Cerebellar Corticonuclear and Corticovestibular Fibers from the Posterior Lobe of the Albino Rat, with Comments on Zones

“…The hypothesis of cortical zonal organi zation proposed by Voogd [1969] has been supported by many reports on various cer ebellar cortical areas in cats [Courville and Diakiw, 1976;Courville and Faraco-Cantin, 1976;Walberg, 1979, 1980;Voogd and Bigare, 1980;Dietrichs, 1981a, b], rabbits [ van Rossum, 1969], gal agos [Haines, 1976[Haines, , 1977Rubertone, 1977, 1979], tree shrews [Haines and Patrick, 1981;Haines and Whitworth, 1978] and opposums Klinkhachorn et al, 1984a, b]. Many studies of the topical relation of olivo cerebellar projections also provide further evidence of zonal conFiguration in the cerebellar cortex [see reviews of Brodal, 1980;Brodal and Kawamura, 1980;Wal berg, 1980].…”

“…Gener ally, corticovestibular fibers originate from the lateral part of the vermis of the anterior lobe, the caudal part of the poste rior lobe (pyramis and uvula) and the floc culonodular lobe in cats Jansen, 1961, 1964;Eager, 1963;Angaut and Brodal, 1967;Jansen, 1972;Walberg, 1972Walberg, , 1975, opossums [Sreesai, 1974;Henkel, 1975;Henkel and Martin, 1977;Klinkhachorn et al, 1984a, b], primates [Jansen andBrodal, 1940, 1942;Eager 1967;Haines, 1976Haines, . 1977Rubertone, 1977, 1979], rabbits [ van Rossum, 1969] and rats [Achenbach and Goodman, 1968].…”

The role of the flocculus of the monkey in saccadic eye movements.

“…A projection from the flocculus to ventral portions of the dentate nucleus have been shown anatomically 329 H. NODA AND D. A. SUZUKI (Angaut & Brodal, 1967;Haines, 1977). The same regions of the dentate nucleus project to the oculomotor complex (Rand, 1954;Carpenter & Strominger, 1964;Martin, King & Dom, 1974;Chan-Palay, Sweikhart, Van Itallie & Brown, 1976).…”

Cardiovascular Modules in the Cerebellum

“…Purkinje cell projections from the nodulus and uvula to the VN were well described in rabbits [64, [112][113][114][115][116], cats [58, [117][118][119][120], rats [121], and prosimian primates [122]. Those specifically from the lateral nodulus to the superior vestibular nucleus (SVN), MVN and group y were described in rabbits by using tracing methods [114,116].…”