Studies on physiology of the vestibulo-ocular system in humans--with reference to transfer function (author's transl)

Abstract

In order to explain physiological function of the vestibulo-ocular system, transfer function (TF)of the oculomotor system was studied in 5 healthy male subjects. For this purpose, the following three tests were pezformed, that is, eye tracking test(ETT) and pendular rotation tests(PRT)in the dark and light were respectively performed in order to examine the opto-oculomotor, vestibulo-oculomotor and optovestibulo-oculomotor system.The target movement and eye movement in the ETT, or the skull's angular displacement and acceleration and the eye movement in the PRT were simultaneously recorded with a polygraph and a data-recorder. From the recordings of the data-recorder, the TF was calculated using a specially designed program with PDP-12 computer, namely, the TF of the oculooculomotor system was calculated with regard to the target movement as input and the eye movement as output. From the record obtained by the PRT in the dark and light, the TF of the vestibulo-oculomotor system and the optovestibulo-oculomotor system were respectively calculated for the skull's angular displacement as input and the eye movement as output. The reason for using the skull's angular displacement as input is that the interrelationship between the head displacement and the eye movement directly indicates the vestibulo-oculomotor function which is to stabilize the retinal image during head movement. The results computed were displayed as a Bode plots(gain and phase diagram)on a cathode ray tube of the PDP-12. The results obtained were as follows.(1) The opto-oculomotor system performs a proportional control in eye tracking to visual object with pendular motion from 0.4 to 1.0 Hz.(2) The vestibulo-oculomotor system performs a derivative control in inducing the eye movement to the skull's displacement This results indicate that the eye movement produced by the vestibulo-oculomotor system is a predictive and supplemental movement which does not coincide with displacement of visual objects. And, it plays an important role in visual fixation during short, rapid head movement.(3) The optovestibulo-oculomotor system performs a proportional control by making the eye movement correspond to the skull's displacement during head movement from o.3 to 1.5Hz.The result indicates the capability of maintaining visual fixation to external objects through the collaboration of the eye and labyrinth. Furthermore, the result shows that the vestibulo-oculomotor system plays an active part in visual fixation during head movement with periodic motion exceeding 1.0Hz.