Quantitative analysis of spontaneous saccade-like rapid eye movements in C57BL/6 mice

Saccadic eye movement is a rapid shift of eye position to capture an object in the environment. In this study, we will describe the fundamental properties of spontaneously evoked saccade-like rapid eye movement (SLREM) in mice in order to establish the mouse experimental model for studying saccades. Spontaneous SLREM were recorded and analyzed in C57BL/6 mice in a quantitative manner, using high-speed video-oculography at a high temporal resolution (240 frames/s) under head-fixed conditions. Mice made spontaneous SLREMs in the dark with median amplitude of 14.3 ± 2.1°, mainly in the horizontal direction. The peak velocity of SLREM increased almost linearly against its amplitude with slope of 43.6 ± 6.1 (°/s)/° in the upward, 63.3 ± 18.0 (°/s)/° in the downward, 51.3 ± 3.9 (°/s)/° in the nasal, and 31.7 ± 3.2 (°/s)/° in the temporal direction. The duration of SLREM was 56.6 ± 23.3 ms in the upward, 57.3 ± 18.0 ms in the downward, 52.0 ± 5.0 ms in the nasal, and 69.3 ± 5.5 ms in the temporal direction. This study provides the basis for analyzing the neural and molecular mechanisms engaged in the control of saccadic eye movements in genetically-engineered mice.