Vertical Purkinje Cells of the Monkey Floccular Lobe: Simple-Spike Activity During Pursuit and Passive Whole Body Rotation

Department of Physiology, Hokkaido University School of Medicine, Sapporo 060-8638, Japan; and Department of Physiology and Biophysics and Regional Primate Research Center, University of Washington, Seattle, Washington 98195 Fukushima, Kikuro, Junko Fukushima, Chris R. S. Kaneko, and Albert F. Fuchs. Vertical Purkinje Cells of the Monkey Floccular Lobe: Simple-Spike Activity During Pursuit and Passive Whole Body Rotation. J. Neurophysiol. 82: 787-803, 1999. To understand how the simian floccular lobe is involved in vertical smooth pursuit eye movements and the vertical vestibuloocular reflex (VOR), we examined simple-spike activity of 70 Purkinje (P) cells during pursuit eye movements and passive whole body rotation. Fifty-eight cells responded during vertical and 12 during horizontal pursuit. We classified P cells as vertical gaze velocity (V ) if their modulation occurred for movements of both the eye (during vertical pursuit) and head (during pitch VOR suppression) with the modulation during one less than twice that of the other and was less during the target-fixed-in-space condition (pitch VOR X1) than during pitch VOR suppression. V P cells constituted only a minority of vertical P cells (19%). Other vertical P cells that responded during pitch VOR suppression were classified as vertical eye and head velocity (V / ) P cells (48%), regardless of the synergy of their response direction during smooth pursuit and VOR suppression. Vertical P cells that did not respond during pitch VOR suppression but did respond during rotation in vertical planes other than pitch were classified as off-pitch V / P cells (33%). The mean eye-velocity and eye-position sensitivities of the three types of vertical P cells were similar. One-third (2/7 V , 2/11 V / , 6/13 off-pitch V / ), in addition, showed eye position sensitivity during saccade-free fixations. Maximal vestibular activation directions (MADs) were examined during VOR suppression by applying vertical whole body rotation with the monkeys oriented in different vertical planes. The MADs for V P cells and V / P cells with eye and vestibular sensitivity in the same direction were distributed near the pitch plane, suggesting convergence of bilateral anterior canal inputs. In contrast, MADs of off-pitch V / P cells and V / P cells with oppositely directed eye and vestibular sensitivity were shifted toward the roll plane, suggesting convergence of anterior and posterior canal inputs of the same side. Unlike horizontal P