Towards an understanding of somatosensory perturbation on covert speech production: a functional near infrared spectroscopy study.

Introduction: Recent initiatives have sought to understand the impact of somatosensory feedback during varying speech production tasks. The supramarginal gyrus (SMG) is a multi-function region that represents the somatosensory system and plays an essential role in the DIVA model via the generation and monitoring of novel motor commands. Here, we investigate the extent to which SMG activity is modulated via somatosensory perturbations (i.e., oral anesthesia via lidocaine and oral stimulation via lollipop) during covert production tasks. Methods: Thirty adult participants completed two covert production tasks: a spelling judgment task that emphasized stored speech patterns (stored articulation; e.g., Results: The lollipop perturbation resulted in significantly higher activity, compared to the lidocaine, in the left SMG ( Conclusion: These findings provide evidence that the SMG is sensitive to alterations in oral sensory context even in the absence of overt articulation, supporting its proposed role within the DIVA model as a somatosensory state monitoring region that interacts with speech motor planning systems. Clinical trial registration: https://clinicaltrials.gov/study/NCT05854082?term=lidocaine%20speech&rank=1, Identifier, NCT05854082.