RESPONSES OF NEURONS OF THE CAT CENTRAL CERVICAL NUCLEUS TO NATURAL NECK AND VESTIBULAR STIMULATION

1. The central cervical nucleus (CCN) is known to receive neck and ves tibular input and to project to the contralateral cerebellum and vesti bular nuclei. To investigate the processing of neck and vestibular inp ut by cells in the CCN, we studied their responses to sinusoidal neck rotation and to whole-body tilt in vertical planes in decerebrate, par alyzed cats. CCN neurons were identified by antidromic stimulation wit h electrodes placed in or near the contralateral restiform body. 2. Fo r every neuron, we first identified the preferred direction of neck ro tation (response vector orientation), then studied the neuron's dynami cs with rotations in a plane close to this direction at 0.05-1 Hz. 3. Responses of CCN neurons to neck rotation resembled those of previousl y studied neck spindle primary afferents in terms of their dynamics an d nonlinear responses to stimuli of differing amplitudes. They also re sembled the neck responses of Deiters' neurons studied in similar prep arations. 4. The activity of two-thirds of CCN neurons also was modula ted by natural vestibular stimulation. Orientation and dynamics of ves tibular responses were characterized in the same way as neck responses . Labyrinthine input originated predominantly from the contralateral v ertical canals, and there was no evidence of otolith input. Neck and v estibular inputs were always antagonistic, but the gain of the vestibu lar response was lower than that of the neck response at all frequenci es studied. 5. The quantitative aspects of the interaction between nec k and vestibular inputs can be expected to vary with the type of prepa ration and with stimulus parameters, and its functional significance r emains to be investigated.