Speaker
Description
Midbrain circuits through the superior colliculus (SC) are involved in rapid threat response to visual stimuli. However, the precise mechanisms that allow these critical visuo-motor computations to take place in uncertain, varying scenarios are still unknown. We analyse data from longitudinal recordings on free moving mice, where visual stimuli were shown via a screen, and subsequent behavioural reactions were recorded with cameras. One of the stimuli was a looming disk, which can trigger escape behaviours as it simulates an approaching predator. Neural spiking data was registered with Neuropixels 2.0 probes implanted in the midbrain, and context was controlled for two distinct levels of environmental light as well as two circadian times. We fitted a hierarchical Bayesian model to disentangle visual stimulus representations from environmental and physiological context information across different areas on the pathway. Across SC layers there was strong modulation of neural activity according to animal-centred variables, like head direction and speed of motion, which were accounted for using a regression model. We confirmed that SC responses were selectively stronger to the ethologically relevant stimulus, a result which was robust across data pooled from multiple animals. Representation of environmental setups appears to be segregated into distinct subpopulations. However, it is unclear how this relates to the triggering of the following motor response. Intersection information is a measure to decompose the mutual information between stimulus and neural activity to determine how much of it is relevant for the consequent output of the circuit. With more data being acquired, the next steps will be to include behavioural outcome decoders and use intersection information to quantify the information flow across the midbrain.
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