Title: Effects of learning and experience on multisensory integration in primary somatosensory cortex
Description: Merging the senses is key to perception, yet how we achieve this remains unclear. New research finds multimodality even in primary sensory areas, but its role is not understood. We address this question by using in vivo 2-photon calcium imaging in awake mice to test several hypotheses about the possible functions primary somatosensory cortex (S1) may subserve in integrating auditory and tactile sensory input. We first test whether S1 encodes pure auditory stimulus identity by training a linear classifier to decode different sounds from S1 activity. We find that decoder accuracy is slightly-but-significantly above chance, suggesting that S1 weakly encodes sounds. We then ask whether S1 encodes specific audio-tactile feature conjunctions by testing decoder performance for distinct combinations of simultaneously-presented auditory and tactile stimuli. We find that accuracy was within chance levels, indicating that sound-evoked suppression of whisker responses is auditory-stimulus non-specific.

Subsequently, we test whether passive experience is sufficient to induce either a) Hebbian-like reactivation of tactile stimulus representations by correlated auditory stimuli or b) enhanced mixed selectivity. We find that passive experience results in neither effect. We also find S1’s auditory and audio-tactile encoding properties to be stable in the face of reinforcement conditioning. As part of a separate project, we also present results that reinforcement conditioning enhances encoding of time and temporal surprise in primary somatosensory cortex.