[Study on the nature of tonic ocular movement produced during pendular vestibular stimulation (author's transl)].

During vestibular function tests using the pendulum chair, electronystagmography has repeatedly shown that a tonic ocular deviation precedes the change in nystagmus. This tonic movement may be anticipated in respect to the change in the sinusoidal movement of the chair. Greiner, Conraux, Collard and more recently J.B. Causse, have proposed a hypothesis based on the own periodicity of the vestibular system. J. Max explained this phenomenon in terms of a difference in phase with the electronic system. Our investigation suggests another explanation of this phenomenon. Each half-period consists of a acceleration phase and a decelaration phase. Thus within half-period alone there are two successive forms of nystagmus induced. The succession of half-periods gives the usual systagmus response. We consider that the tonic response of the eyes is not an anticipated one in respect to the change in sinusoidal movement of the chair, but rather a delayed one in respect to the reversal in the direction of acceleration.