SUPERIOR COLLICULUS NEURONS ENCODE BODY STATE DURING FREELY MOVING TACTILE EXPLORATION

Recent methodological advances enable the investigation of sensory processing in naturally moving animals, free of restraint. This research has revealed that the sensory cortices, including whisker S1 (wS1), depend not only on their afferent sensory drive but also on body state (the spatial configuration of body parts and their velocities). The aim of this study was to investigate the function of the Superior Colliculus (SC) during tactile exploration in freely moving mice. The SC is a midbrain structure involved in sensory processing and orienting behaviours. To determine how SC neurons depend on somatosensory and body-state signals during natural behaviour, the body and whiskers of freely moving mice were tracked in 3D in mice chronically implanted with Neuropixels probes in the SC. We found that body-state (encompassing postural, locomotive and head angle variables) exerted substantial influence on neuronal activity in the SC. Similar to wS1, locomotion speed and pitch angle were the most strongly encoded body-state variables. This effect persisted following deafferentation of the afferent whisker input by the section of the infraorbital nerves. However, compared to wS1, whisker touch (estimated using a snout-surface distance proxy) exerted a weaker effect in SC. Overall, our findings suggest a striking commonality between neocortical and midbrain sensory areas, with body-state modulation as a basic and widespread principle of sensorimotor function.