The diencephalo-olivary projection in the cat as studied with retrograde transport of horseradish peroxidase

Summary The projection from certain diencephalic regions (zona incerta, Forel's fields, the parafascicular and subparafascicular nuclei, the periventricular grey and the hypothalamus) to the inferior olive in the cat was studied by means of retrograde protein tracing. Small injections of horseradish peroxidase were made into various parts of the inferior olive from a ventral approach. The number of retrogradely labelled neural cells in the diencephalic nuclei of all cats is presented in Table 2. The majority of the labelled cells was found in the parafascicular and subparafascicular nuclei, especially within the medial part of the former. The connection is ipsilateral, and the caudal as well as the rostral part of the olivary complex appears to receive the descending afferents. The findings are discussed and related to recent observations concerning descending afferents to the olivary complex.