MOUSE SACCADES IN A VIRTUAL-REALITY FORAGING TASK ARE GOAL DIRECTED AND TASK- AND STATE- DEPENDENT

Eye movements in mice have been thought to largely provide reflexive eye-head coupling, rather than actively select visual input, due to the absence of a retinal fovea in mice, and their reliance on non-visual senses. Here, we explored whether in a context that rewarded visual tracking of target cues, mice would exhibit goal-directed saccades, and how those saccades might correlate with task performance.
To study mouse eye movements in a naturalistic context featuring self-initiated visual flow and visual target tracking, we designed a virtual-reality foraging task, projected onto an immersive environment covering 210 degrees of visual angle. Mice were required to run towards one of two leaf-shaped objects presented in the left and right visual field, only one of which was rewarded. Eye movements were recorded using two infra-red cameras at 60Hz, and saccades were identified using Lightning Pose and a custom saccade detection algorithm.
Mice exhibited saccades that respond to task-relevant visual stimuli and are modulated by cognitive state. Specifically, saccades disappear around stimulus onset, suggesting periods of informative fixation, and increase as animals make visually driven behavioural choices. Moreover, off-target saccades increase in non task- adherent trials, and become more target-selective as the mice become adept at the task.
These findings demonstrate that under conditions of naturalistic self-motion eye movement in mice reflect both stimulus and task processing, as well as internally driven fluctuations of cognitive state. This suggests that, contrary to prior beliefs, mice can use goal-directed saccades to actively gather behaviourally relevant visual information.