平衡制御に占める前庭神経核の役割

抄録

The purpose of this paper is to give an account of the vestibular nuclei from the point of view of phylogeny, behaviors, and neural networks of the vestibular nuclei. In the early vertebrates, the vestibular endorgans developed by isolation of the lateral line organ from the body surface. Although vestibular control based on inertial inputs works ideally under a stationary space, it breaks down in moving spaces. To compensate for the shortcoming, discomfort (motion sickness) was utilized to avoid moving spaces. Along with progress of locomotion, the vestibular cerebellum developed as a supplementary route of the vestibular nuclei to stabilize the gaze and posture; the flocculus for visual-inertial integration, and the uvula-nodulus for gravito-inertial integration. Further, the vestibular cerebellum (vermis) and the somatically arranged lateral vestibular nucleus developed for coordination of posture and four-limb locomotion. The superior vestibular nucleus is distributed centrally by the canal fibers and flocculus fibers of visual origin, and peripherally by the uvula-nodulus fibers of otolith origin. The nucleus carries spatial rotation with gravito-inertial axis to the ocular motor nuclei. Body balance is maintained by a somatic-to-spatial transformation of the coordinates, that is, transfer of contents of the cerebellum-fastigial-and-vestibular nuclues routes to the vestibular nucleus-motor nucleus routes. Thus, gaze and posture are stable when spatial coordinates remain still in space, but they become unstable when the coordinates are moving in space.