直立姿勢の視性制御の研究 逆転プリズムを用いて

Abstract

The purpose of this study is to clarify the role of visual information in the regulation of the upright standing posture.The subject was requested to stand on a stabilometer with the feet close together. The sway of the body's center of gravity was recorded for 60 seconds with an X-Y recorder and stored in the disk of a microcomputer. The examination was performed with eyes open and closed, and with the wearing of horizontal and vertical vision reversing prisms.The stored data were processed by a program designed for stabilometry.The body sway was evaluated by the following items : left-right diameter (X), forward-backward diameter (Y), Y/X ratio, area, displacement and velocity of the left-right (LR) and forward-backward (FB) sways, and power spectrum.The subjects were 14 normal persons and 5 patients with labyrinthine disturbances.1. Normal subjects1) The body sway when wearing horizontal vision reversing prisms (HRP) or vertical vision reversing prisms (VRP) was larger than when the eyes were open without prisms. Furthermore, the body sway when wearing HRP tended to be larger than when the eyes were closed.2) The power spectrum of the LR sway when wearing HRP was high at 0.2-0.4 Hz.3) In maintaining the upright standing posture, confused visual information induced by wearing HRP provoked a marked body sway.2. Patients with labyrinthine disturbances1) The body sways of the patients when wearing HRP or VRP, in contrast to normal subjects, were smaller than when the eyes were closed.2) The FB sways of the patients with eyes closed were markedly larger than those of normal subjects.The increased FB sway was decreased when wearing HRP or VRP.3) The power spectra of the LR and FB sways of patients with eyes closed showed an increase of power at frequency range from 0.6 to 1 Hz above that when eyes were open. The increase of the power was lowered by the wearing of HRP or VRP.4) The finding that body sways are better stabilized when wearing HRP and VRP than when the eyes are closed indicates the usefulness of reversed visual information and of the action of proprioceptive reflexes.