Projections of purkinje cells in the translation and rotation zones of the vestibulocerebellum in pigeon (Columba livia).

Abstract

Previous electrophysiological studies have shown that the pigeon vestibulocerebellum (ventral uvula, nodulus, and flocculus) can be divided into two parasagittal zones based on responses to optic flow stimuli. The medial zone (ventral uvula and nodulus) responds best to optic flow resulting from self-translation, whereas the lateral zone (flocculus) responds best to optic flow resulting from self-rotation. In this study we investigated the projections of the Purkinje cells in the translation and rotation zones of the vestibulocerebellum by using the anterograde tracer biotinylated dextran amine. Extracellular recording of Purkinje cell activity (complex spikes) in response to large-field visual stimuli were used to identify the injection sites. Injections into the translation zone resulted in extremely heavy terminal labeling in the cerebellovestibular process adjacent to the medial cerebellar nucleus. A moderate amount of terminal labeling was found in the medial cerebellar nucleus, the superior vestibular nucleus (laterally, dorsally, and medially), and the descending vestibular nucleus, particularly in the lateral half. Light terminal labeling was observed in the dorsolateral vestibular nucleus, the medial vestibular nucleus, the tangential nucleus, and the lateral vestibular nucleus pars ventralis. Injections into the rotation zone resulted in heavy terminal labeling in the superior vestibular nucleus (particularly dorsally and medially), the descending vestibular nucleus (particularly medially), and the medial vestibular nucleus. A moderate amount of terminal labeling was seen in the cerebellovestibular process adjacent to the lateral cerebellar nucleus, and the dorsolateral vestibular nucleus. A small amount of terminal labeling was found in the lateral cerebellar nucleus, the tangential nucleus, the prepositus hypoglossi, and the lateral vestibular nucleus pars ventralis.