Feature-independent Encoding of Visual Salience in the Mouse Superior Colliculus

Detecting conspicuous stimuli in a visual scene is crucial for animal survival, yet it remains debated how the brain encodes visual salience. Here we investigate how visual salience is represented in the superficial superior collicular (sSC) of awake mice using two-photon calcium imaging. We report on a feature-independent salience map in the sSC. Specifically, conspicuous stimuli evoke stronger responses in both excitatory and inhibitory neurons compared to uniform stimuli, with similar encoding patterns observed in both neuron types. The largest response occurs when a salient stimulus is positioned at the receptive field center, with contextual effects extending ∼40° away from the center. The response amplitude correlates well with the salience strength of stimuli and is not influenced by the orientation or motion direction preferences of neurons. Furthermore, visual salience is encoded in a feature-independent manner, and neurons involved in salience encoding are less likely to exhibit orientation or direction selectivity.