Speech production is arguably the most complex motor skill that is routinely performed by humans, and among the most skilled motor acts performed by any species. During typical conversational interactions, neurologically normal speakers can produce up to six to nine syllables per second, which relies on the precise orchestration of approximately 100 different muscles throughout the respiratory, laryngeal, and supralaryngeal vocal tract. To further complicate matters, each muscle contains approximately 100 different motor units that consist of a motor neuron and associated muscle fibers. A fundamental issue in the field of speech production is the manner in which the motor system controls the large number of degrees of freedom for controlling vocal tract movement. Recent research in our laboratory (Masapollo & Nittrouer, under review) has uncovered “simplifying strategies” that the motor system uses to facilitate the coordination of vocal tract structures during speaking. Analyses of the relative timing of the jaw and tongue suggest that pairs of vocal tract structures are interdependently modulated such that timing variation in one structure (e.g., jaw) is accompanied by proportional changes in the timing of another active structure (e.g., tongue). To date, the most direct evidence for such constrained speech movement timing has come from analyses of speech actions involving oral constrictions for /t/ and /d/, involving coordination among the jaw and tongue. It is unclear how general such coordinative interactions are among different vocal tract structures. To address this gap in knowledge, this student-led research project will test whether jaw movements are coupled in their timing to those of the lips and larynx, as well as the tongue, during the production of speech. Jaw, tongue, lip, and larynx movements will be simultaneously recorded using electromagnetic articulography (or EMA) and electroglottography (or EGG). EMA is a state-of-the-art technology that allows researchers to track lip, tongue, and jaw motion on a millisecond-by-millisecond basis (Perkell et al., 1992; Rebernik et al., 2020). The tracking is performed by using a series of weak and diffuse magnetic fields to localize the 3D positions of sensors temporarily affixed to the jaw, tongue, and lips during speaking. Laryngeal movements will be concurrently recorded by EGG, which is a noninvasive method that measures changes in electrical impedance across the larynx during speaking using electrodes held against the larynx. Our lab recently developed optimal methods for combining EMA and EGG to reliably assess laryngeal and supralaryngeal motor coordination in speech (Masapollo et al., 2022; Goel et al., in progress). The planned experiments will apply these novel methods to quantify the extent to which jaw-tongue coordination predicts jaw-lip and jaw-larynx coordination in twenty neuro-typical subjects as they produce disyllabic speech sequences. If a general motor planning operation exists, then we would expect to observe high intraclass correlations between patterns of motor coordination across different sets of vocal tract structures (tongue-jaw, lip-jaw, and larynx-jaw). Outcomes of this student-led project will set the stage for future studies with clinical populations exhibiting motor timing deficits in speech production, such as stuttering and apraxia of speech.
Goel, J., Masapollo, M., Lee, Y., & Wayland, R. (in preparation). Concurrent visualization and analysis of
acoustic, flesh-point motion, and electroglottography signals during speech production. Journal of the Acoustical Society of America, Express Letters.
Masapollo, M., Wayland, R., Goel, J.,Sengupta, R., Shamsi, A., & Hegland, K.W. (2022). An investigation of
interference between electromagnetic articulography and electroglottography. Journal of the Acoustical Society of America, Express Letters. DOI: 10.1121/10.0014033
Masapollo, M., & Nittrouer, S. (under review). Inter-articulator speech coordination: timing is of the essence. Journal of Speech, Language, and Hearing Research.
Perkell, J. S., Cohen, M. H., Svirksy, M. A., Matthies, M. L., Garabieta, I., and Jackson, M. T. T. (1992).
Electromagnetic midsagittal articulometer systems for transducing speech articulatory movements. Journal of the Acoustical Society of America, 92(6), 3078–3096.
Rebernik, T., Jacobi, J., Jonkers, R., Noiray, A., and Wieling, M. (2020). A review of data collection practices using electromagnetic articulography. Laboratory Phonology, 12, 6.