Dynamic properties, interactions and adaptive modifications of vestibulo-ocular reflex and optokinetic response in mice

Dynamic properties of horizontal vestibulo-ocular reflex (VOR) and optokinetic response (OKR) were studied in mice. The VOR was examined in the dark (VORD), in the light (VORL) and in the condition in which most of the visual field moves synchronously with the head motion (VORF). A mouse and/or a surrounding screen with vertical stripes was rotated sinusoidally, and the gain and phase of eye movements were measured in wide dynamic stimulation ranges. The working conditions of VOR and OKR were supplementary; OKR worked at low speeds of head turn and VOR at high speeds. Examination of VORL and VORF revealed non-linear interaction of VOR and OKR. The continuous sinusoidal head oscillation coupled with the in-phase or the out-of-phase oscillation of the surrounding screen, decreased or increased the VORD gain, and increased or decreased the VORD phase lead, respectively. Continuous oscillation of the surrounding screen increased the OKR gain and decreased the phase delay. These changes of VOR and OKR work to reduce the retinal slip. The present study provides fundamental information concerning the dynamic properties of VOR and OKR and the nature of their adaptive modifications in mice, which have been extensively used in genetic manipulation recently.