THE RESPONSES OF SINGLE NEURON OF THE VESTIBULAR NUCLEI TO CALORIC STIMULATION IN THE CAT

摘要

References(39) Cited-By(6) Numerous studies on electrophysiological aspects of the single neuron in the vestibular nuclei have been presented since the investigation by Adrian (1). The vestibular nuclei consist of four groups: Schwalbe's, Bechterew's, Deiters' and Roller's nuclei. Among them the Deiters' nucleus is located in the most lateral region and its nerve cells are the largest in size. The pattern of the afferent and efferent fiber connections of the central vestibular system is extremely complex. The vestibular nuclei project the ascending fibers to the flocculonodular lobe and fastigial nucleus of cerebellum and to the reticular formation and motor nuclei in the brain stem. The descending fibers terminate near the spinal motor cells passing through the lateral vestibulo-spinal tract (2-7). There are several technical difficulties for recording the unitary discharges from the vestibular nuclei. Orientation of the structure is somewhat uncertain due to covering by the cerebellum. Vertical insertion of the microelectrode is obstructed by the tentorium cerebelli, and respiratory movement evokes the fluctuation of the recording areas. Many efforts to eliminate the difficulties, such as deep anesthesia, application of muscle relaxants and resection of the cerebellum have hitherto been devised. However, these procedures may affect the vestibular activity. Relative long-term recordings of the unitary discharges from the same single neuron in the vestibular nuclei have been developed by improvement of the microelectrode technique and the stable immobilization technique of the recording sites (8-11), but most of these experiments have been carried out in the anesthetized animals. In order to investigate the function of the vestibular nuclei in the experimental animals, following stimuli have been employed: afferent electrical stimulation of the vestibular nerve (12-20), postural rotation (14, 15, 21-24), tilting (21, 25-27), acoustic stimuli (28, 29), proprioceptive stimulation of the extremities (2, 30) and caloric stimulation (24, 31-34). Recently, direct and nongravidity stimulation in space attitude is also introduced (35). It is well-known that caloric stimulation is originally a clinical test of the vestibular function as the reliable diagnosis method for lesions of the vestibular system, but the responses of the vestibular nuclei to caloric stimulation in the unanesthetized animals still remain to be settled. In the present experiments, an attempt has been made to know the responses of the unitary discharges in the vestibular nuclei, mainly in the Deiters' nucleus, to caloric stimulation of the middle ear cavity in the pentobarbital-anesthetized cats and in the encéphale isolé preparations of unanesthetized cats.