The Feel of Speech: Multisystem and Polymodal Somatosensation in Speech Production

Abstract

Purpose: The oral structures such as the tongue and lips have remarkable somatosensory capacities, but understanding the roles of somatosensation in speech production requires a more comprehensive knowledge of somatosensation in the speech production system in its entirety, including the respiratory, laryngeal, and supralaryngeal subsystems. This review was conducted to summarize the system-wide somatosensory information available for speech production. Method: The search was conducted with PubMed/Medline and Google Scholar for articles published until November 2023. Numerous search terms were used in conducting the review, which covered the topics of psychophysics, basic and clinical behavioral research, neuroanatomy, and neuroscience. Results and Conclusions: The current understanding of speech somatosensation rests primarily on the two pillars of psychophysics and neuroscience. The confluence of polymodal afferent streams supports the development, maintenance, and refinement of speech production. Receptors are both canonical and noncanonical, with the latter occurring especially in the muscles innervated by the facial nerve. Somatosensory representation in the cortex is disproportionately large and provides for sensory interactions. Speech somatosensory function is robust over the lifespan, with possible declines in advanced aging. The understanding of somatosensation in speech disorders is largely disconnected from research and theory on speech production. A speech somatoscape is proposed as the generalized, system-wide sensation of speech production, with implications for speech development, speech motor control, and speech disorders.

Active inference and speech motor control: a review and theory

“…Proprioception has generally received relatively little attention in speech motor control; however, a recent review by Kent (2024) highlights the importance of somatosensation for speech production, contributed to by proprioceptive, tactile and baroreceptive sensations. Together, these sources of sensory input inform an estimate of the status of the multiple sub-systems serving speech (respiratory, laryngeal and supralargyngeal), both at rest and during movement (Haggard and de Boer 2014).…”

“…While there is some debate over which speech articulators contain muscle spindles innervated by the trigeminal nerve (e.g. lips, tongue, pharynx and larynx), most appear equipped with their own special types of receptors which convey proprioceptive information via the facial nerve (Cobo 2017;Kent 2024).…”

“…Extending active inference accounts to speech motor control may therefore require consideration of these differences from proprioceptive mechanisms in other domains; overall however, active inference has the potential to provide a clear theoretical framework for understanding the role of somatosensation in speech production, as called for by Kent (2024).…”