Observations on the cerebello-hypothalamic projection, with comments on non-somatic cerebellar circuits

The circuits responsible for cerebellar influences on nonsomatic responses have remained largely unknown. This report reviews some recent findings and present new data concerning pathways probably involved in this aspect of cerebellar function. A projection from the cerebellar nuclei to the hypothalamus was described several years ago, and a direct projection from hypothalamus to the cerebellum has recently been reported (6, 7, 8, 14, 15, 16). The present study gives evidence that the projections between hypothalamus and the cerebellar nuclei are at least in part reciprocal. The discovery of such reciprocal connections introduces new routes through which the cerebellum may directly interact with non-somatic centres and offers a more complete picture of the circuits which may be responsible for cerebellar modulation of visceral activity and certain aspects of affective behavior. The demonstration of such circuits indicates that the cerebellum acts as a general modulator and coordinator of a variety of activities, many of which are non-somatic in nature.