Demonstration of hypothalamo-cerebellar and cerebello-hypothalamic fibres in a prosimian primate (Galago crassicaudatus).

Hypothalamo-cerebellar and cerebello-hypothalamic fibres in the greater bushbaby (Galago crassicaudatus) have been demonstrated by means of retrograde and anterograde transport of the wheat germ agglutinin--horseradish peroxidase complex. The hypothalamo-cerebellar projection is bilateral and has its main origin in the lateral hypothalamic area. The posterior and dorsal hypothalamic areas and the lateral mammillary, tuberomammillary and periventricular nuclei also project to cerebellum. Cerebello-hypothalamic fibres are crossed and terminate in the dorsal, posterior and lateral hypothalamic areas. The hypothalamo-cerebellar and cerebello-hypothalamic projections appear to be in part reciprocal. The results are discussed with reference to our findings in other species, and some comments are made concerning the possible circuits involved in cerebellar regulation of non-somatic responses.