Thus, Pars magnocellularis of medialis dorsalis (MD) assumes a critical role in any thalamic mediated cerebellar-orbital gyri linkage. Evidence to support this actual anatomical linkage is sparse; however, the study of Nimi, et al. (1962) demonstrated terminal degeneration in medialis dorsalis subsequent to unilateral lesions of the cerebellar nuclei which is supportive of these speculations. The finding of Fox (1949) that pars magnocellularis of DM receives pathways from the amygdala and of Guillery (1959), who traced fibers to it from the midbrain tegmentum and septal region, give greater interpretative significance to Heath's (1969/1975) findings of septal and cerebellar spiking activity in the somatosensory deprived rhesus. It is appropriate to mention the observations of Dow (1970) that the extraordinary development of the neocerebellum in the higher primate corresponds specifically to the development of the frontal and temporal association areas and not to the cerebral cortex as a whole, and that projections from association areas of the frontal and temporal lobes to the pons in man constitute 1/5 of the whole of the internal capsule (as the fronto and tempero-pontine fibers). Thus, sufficient neuroanatomical, neurophysiological and behavioral evidence appears to exist to encourage speculation of a cerebellar--orbital frontal--limbic--reticular circuit in the mediation of abnormal emotional behaviors (pp10-11). It is for the above reasons that special attention must be given to Areas 8,9,13 and 14 within the frontal granular cortex in the enhanced MR Imaging analyses of these brain structures.
There is substantial evidence that the cerebellum plays a major role in the regulation of autonomic nervous system activity and emotional-social behaviors (Prescott, 1976). It is beyond the scope of this proposal to review this evidence as background for the study of cerebellar structures in this proposed research. A few studies should suffice.
Anand, et. al (1959), utilizing evoked potential techniques, demonstrated strong functional relationships between the paleocerebellum and limbic system structures. They report:
(i) Projections from posterior paleocerebellum. Stimulation of the posterior paleocerebellar structures, including the flocculonodular lobe, evoked potentials in all the limbic regions from which recordings were obtained. The results indicated quite heavy projections from the flocculonodular and adjoining posterior regions.
(ii) Projections from anterior paleocerebellum. Stimulation of anterior paleocerebellum evoked potentials mainly to orbital cortex and hippocampus. There was evidence also of connections with the hypothalamus (p.452). Specifically, stimulation of the lingula, centralis, and culmen of cerebellar cortex resulted in evoked potentials in the limbic region; and stimulation of the pyramis, uvula, nodulus, paraflocculus and flocculus resulted in evoked potentials in the orbital surface of the cerebral cortex. These authors conclude:
The present observations point to the existence of extensive projections from the posterior part of the paleocerebellum (including the flocculonodular lobe) to most of the limbic structures of frontal and temporal lobes as well as to the hypothalamic regions. These projections appear to be especially strong to orbitomesial cortex, and amygdaloid-hippocampal complex"(p.456). Additionally, MacLean, Denniston and Dua (1963) reported positive loci for penile erection in the substantia nigra, pons and the brachium pontis, thus, suggesting the involvement of a "nigro-ponto-cerebellar" pathway in penile erection.
Heath (1972ab, 1975) has provided substantial electrophysiological evidence for extensive connections between the cerebellum and limbic system structures through stimulating and recording from the deep cerebellar nuclei.
In addition to the above specific areas of the cerebellum that have been identified for enhanced MR Imaging there is merit to also examining the corticopontine projection areas on the cerebellar cortex which involves primarily Lobules H1-H IX of the intermediate-lateral cerebellar hemispheres.