Three-dimensional optokinetic eye movements in the C57BL/6J mouse
PURPOSE. To study three-dimensional optokinetic eye movements of wild-type C57BL/6J mice, the most commonly used mouse in oculomotor physiology. Optokinetic eye movements are reflexive eye movements that use visual feedback to minimize image motion across the retina. These gaze-stabilizing reflexes are a prominent model system for studying motor control and learning. They are three dimensional and consist of a horizontal, vertical, and torsional component. METHODS. Eye movements were evoked by sinusoidally rotating a virtual sphere of equally spaced dots at six frequencies (0.1-1 Hz), with a fixed amplitude of 5°. Markers were applied to the mouse eye and video oculography was used to record its movements in three dimensions. In addition, marker tracking was compared with conventional pupil tracking of horizontal optokinetic eye movements. RESULTS. Gains recorded with marker and pupil tracking are not significantly different. Optokinetic eye movements in mice are equally well developed in all directions and have a uniform input- output relation for all stimuli, including stimuli that evoke purely torsional eye movements, with gains close to unity and minimal phase differences. CONCLUSIONS. Optokinetic eye movements of C57Bl6 mice largely compensate for image motion over the retina, regardless of stimulus orientation. All responses are frequency-velocity dependent: gains decrease and phase lags increase with increasing stimulus frequency. Mice show strong torsional responses, with high gains at low stimulus frequency.