Responses of Pigeon Vestibulocerebellar Neurons to Optokinetic Stimulation. I. Functional Organization of Neurons Discriminating Between Translational and Rotational Visual Flow

vestibulocerebellum ( VbC), including the flocculus (lateral VbC), nodulus ( folium X), and ventral uvula (ventral folium IXc,d), of the anesthetized pigeon, in response to an optokinetic stimulus. 2. The optokinetic stimuli consisted of two black and white random-dot patterns that were back-projected onto two large tan-gent screens. The screens were oriented parallel to each other and placed on either side of the bird’s head. The resultant stimulus covered the central 100 ” X 100 ” of each hemifield. The directional tuning characteristics of each unit were assessed by moving the largefield stimulus in 12 different directions, 30 ” apart. The direc-tional tuning curves were performed monocularly or binocularly. The binocular directional tuning curves were performed with the direction of motion the same in both eyes (in-phase; e.g., ipsi = upward, contra = upward) or with the direction of motion oppo