Sit, Pak Hang Timothy; (2024) Audiovisual integration in mice: representation, learning, and decision making. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Audiovisual integration is important in humans and other animals. In humans, one of the ways audiovisual integration is used is to aid communication, and in animals, audiovisual localisation is used for both predator avoidance and prey capture. Here, we studied how and where audio and visual signals are represented and used to make decisions in the mouse cortex, and how they interact with other non-sensory signals. We first investigated the neural correlates of sensory and choice behaviour during an audiovisual decision-making task in mice, and found that the secondary motor cortex (MOs) contains signals sufficient to perform the task. By modelling this neural activity, we found that MOs additively encodes auditory and visual signals, which allows it to perform the task in an additive manner akin to the observed behaviour of mice. We next asked whether multisensory signals are already present in primary sensory areas by studying the activity of the primary visual cortex during presentation of nat- ural sounds and videos. We found that auditory-evoked activity in the primary visual cortex is highly correlated with sound-evoked movement. Finally, we asked whether there are differences in the representation of movement and visual signals within the different layers of the primary visual cortex. We recorded from layer 2/3 and layer 5 units, and found that layer 5 neurons respond more strongly to movement, whilst layer 2/3 neurons respond more strongly to visual stimuli.

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