High-density electrocorticography reveals sensorimotor cortex engagement in two distinct sites with different roles during audiovisual, audio, and visual speech perception

Recent neuroimaging studies have shown the involvement of the speech motor system in the sensorimotor cortex (SMC) in speech perception, but knowledge on the relative contributions of visual and auditory speech information on SMC engagement and the cortical representation thereof remains scarce. To further elucidate the representation of different components of perceived speech on the SMC, we recorded high-density ECoG during a passive speech perception task. We found that audiovisual, visual-only, and auditory-only speech perception increased high frequency band activity in the SMC. We discovered two distinct regions of the SMC that are differentially engaged depending on the perceptual input modality, being a dorsally located cluster of activity associated with both unimodal and bimodal perception of auditory and visual information and a ventral cluster that is involved specifically in auditory speech perception. Together, these results shine a new light on the engagement of the sensorimotor cortex during speech perception and suggest that auditory and visual information play different roles.