Behavioural and neuronal correlates of visual saliency in mouse

While early parts of the brain’s sensory pathways convey signals about the entire environment, animal behaviour is usually devoted to one or just a few potential objects of interest at any given time. Objects that are more salient (more distinct) are usually prioritised, particularly if they are potential threats, but how and where salience is represented in the brain is not known. Here I examine how salience may be constructed in the visual pathways of mice. To highlight the importance of vision in mice I first show that vision can guide the selection of distinct defence behaviours in response to potential threats - freeze and flight. I then characterise potential neural mechanisms for salience, by making recordings from neurons in the superficial layers of the mouse superior colliculus, an area important in orienting behaviour towards- or away from objects and likely to be part of the salience circuit. I show that many of these neurons are sensitive to visual discontinuities in both the spatial and the temporal domain, and that this sensitivity is more pronounced in awake animals than in anesthetized animals. These results suggest that neurons in the mouse superior colliculus can highlight parts of the environment that are distinct from the spatial and temporal context that they are embedded in, and thus may help in directing animal behaviour with respect to salient objects