TOPOGRAPHICAL ORGANIZATION OF INFERIOR OLIVE CELLS PROJECTING TO TRANSLATION AND ROTATION ZONES IN THE VESTIBULOCEREBELLUM OF PIGEONS

Previous electrophysiological studies in pigeons have shown that the v estibulocerebellum can be divided into two parasagittal zones based on responses to optic how stimuli. The medial zone responds best to opti c flow resulting from self-translation, whereas the lateral zone respo nds best to optic flow resulting from self-rotation. This information arrives from the retina via a projection from the accessory optic syst em to the medial column of the inferior olive. In this study we invest igated inferior olive projections to translational and rotational zone s of the vestibulocerebellum using the retrograde tracer cholera toxin subunit B. Extracellular recordings of Purkinje cell activity (comple x spikes) in response to large-held visual stimuli were used to identi fy the injection sites. We found a distinct segregation of inferior ol ive cells projecting to translational and rotational zones of the vest ibulocerebellum. Translation zone injections resulted in retrogradely labeled cells in the ventrolateral area of the medial column, whereas rotation zone injections resulted in retrogradely labeled cells in the dorsomedial region of the medial column. Motion of any object through space, including self-motion of organisms, can be described with refe rence to translation and rotation in three-dimensional space. Our resu lts show that, in pigeons, the brainstem visual systems responsible fo r detecting optic flow are segregated into channels responsible for th e analysis of translational and rotational optic how in the inferior o live, which is only two synapses from the retina. (C) 1998 IBRO. Publi shed by Elsevier Science Ltd.