Pterygoid muscle activity in speech: A preliminary investigation

Abstract

Background: Speaking depends on refined control of jaw opening and closing movements. The medial pterygoid muscle (MPT), involved in jaw closing, and the lateral pterygoid muscle (LPT), involved in jaw opening, are two key mandibular muscles in mastication and are likely to be recruited for controlled movements in speech.Objectives: Three hypotheses were investigated, that during speech the MPT and LPT: (1) were both active, (2) but exhibited different patterns of activity, (3) which fluctuated with the vowels and consonants in speech. Methods: Intramuscular EMG recordings were made from the right inferior head of the LPT and/or the right MPT in five participants during production of 40 target nonsense words (NWs) consisting of three syllables in the form /V 1 C 1 V 2 C 2 ə/ (V = vowel; C = consonant; ə = unstressed, reduced vowel), spoken by each participant 10 times per NW; analysis focussed on the target syllable, C 1 V 2 .Results: Both MPT and LPT exhibited robust increases in EMG activity during utterance of most NWs, relative to rest. Peak LPT activation was time-locked to the final part of the target consonant (C 1 ) interval when the jaw begins opening for the target vowel (V 2 ), whereas peak MPT activation occurred around the temporal midpoint of V 2 , when the jaw begins closing for C 2 . EMG amplitude peaks differed in magnitude between "high" vowels, i.e., for which the tongue/jaw are high (e.g., in SEEK), and "low" vowels, i.e., for which the tongue/jaw are low (e.g., in SOCK).Conclusions: These novel findings suggest a key role for the LPT and MPT in the fine control of speech production. They imply that speech may impose major synergistic demands on the activities of the MPT and the LPT, and thereby provide insights into the possible interactions between speech activities and orofacial activities (e.g. mastication) and conditions (e.g. Temporomandibular Disorders) that involve the masticatory muscles.

Association between tooth loss‐related speech and psychosocial impairment with cognitive function: A pilot study in Hong Kong's older population

“…41 The act of speech production is a highly intricate and exact process involving the coordinated movement of various oral structures, including the tongue, lips, jaw and masticatory muscles. 42,43 Throughout the various stages of speech production, several brain regions, including the primary motor cortex, the prefrontal cortex, the supplementary motor area and the cerebellum, are activated, which are essential in the execution of speech-related movements. 44,45 Thus, reduced occluding units may not only impair proprioception from the oral cavity, but also disrupt the coordination among various oral structures, further compounding the negative impact on cognitive function.…”