Oral Electromyography Activation Patterns for Speech Are Similar in Preschoolers Who Do and Do Not Stutter

Abstract

Purpose We determined whether basic patterns of muscle activation for speech were similar in preschool children who stutter and their fluent peers. Method We recorded right and left lower lip muscle activity during conversational speech and sentence repetition in 64 preschool children (CWS) diagnosed as stuttering and in 40 children who do not stutter (CWNS). Measures of EMG amplitude, right/left asymmetry, and bilateral coordination were computed for fluent speech. The potential presence of tremor-like oscillations during disfluencies of CWS was assessed, and EMG amplitudes of fluent and disfluent speech were compared in CWS. Results Across both speaking tasks lip muscle activation was similar in CWS and CWNS in overall amplitude, bilateral synchrony, and degree of right/left asymmetry. EMG amplitude was reduced during disfluent compared to fluent conversational speech of CWS, and there was no evidence of tremor in the disfluencies of CWS. Conclusion These results support the assertion that stuttering in young children arises not from basic features of muscle contraction, but rather from the command signals that control the timing and amplitude of muscle activity. Our results indicate that no frank abnormality is present in muscle activation patterns in preschoolers who stutter.

How Stuttering Develops: The Multifactorial Dynamic Pathways Theory

“…We found no evidence of any differences in CWS and CWNS in perioral electromyographic amplitude during conversational speech or sentence production, no differences in the bilateral synchrony of activation, and no group differences in left/right amplitude ratios (Walsh & Smith, 2013). These data, considered with the kinematic data reviewed above, point to a deficit in speech motor processes in early childhood stuttering-that is, a speech motor programming and execution deficit and not a hyperactivation or overactivation of the speech production system.…”

Anticipatory coarticulation and stability of speech in typically fluent speakers and people who stutter

“…Little is known about how lingual speech articulation varies between people who stutter in comparison to typically fluent speakers. Previous research has primarily examined lingual articulation indirectly using formant transitions (Chang, Ohde, & Conture, 2002; Robb & Blomgren, 1997; Sussman, Byrd, & Guitar, 2011), or has examined lip movement (Smith, Sadagopan, Walsh, & Weber-Fox, 2010; Walsh & Smith, 2013). Studies of speech production with children and young adults using ultrasound imaging have found that direct articulatory measures provide insight into lingual articulation and coarticulation that are not revealed through acoustic measures (Zharkova, Hewlett, & Hardcastle, 2012)…”

“…Much of the recent articulatory research in people who stutter has examined lip and jaw kinematics in adults and children with and without stuttering (Smith et al, 2010; Walsh & Smith, 2013). These studies have used word, sentence, and nonword repetition and investigated effects of complexity on articulatory performance.…”

A Lag in Speech Motor Coordination During Sentence Production Is Associated With Stuttering Persistence in Young Children

“…To the contrary, maturation of speech motor coordination to a degree similar to that of typical children appears to be a characteristic of recovery from stuttering by 5-7 years of age. The mechanism underlying the group differences in LAVar is likely the atypical temporal and spatial coding of the neural commands to muscles necessary for fluent speech production (Smith, 1989) and not orofacial characteristics such as bone mass or muscle physiology (Walsh & Smith, 2013). Possible sources for the higher movement variability of CWS-Per include variability in motor planning (Churchland, Afshar, & Shenoy, 2006) and execution (Smith, 1989), aberrant neural synchrony and deficits in the use of sensory feedback (Kurz, Heinrichs-Graham, Arpin, Becker, & Wilson, 2013), and the amount of neuromotor noise during movement execution (Harris & Wolpert, 1998).…”

“…tuttering is a multifactorial neurodevelopmental disorder characterized by the presence of involuntary stuttering-like disfluencies (SLDs) during speech production, which are the overt result of disruptions in coordination patterns of neural commands to the muscle systems involved in speech (Ludlow & Loucks, 2003;Smith, 1989;Walsh & Smith, 2013). Stuttering has long been described as a disorder of speech motor discoordination and instability, with intervals of fluency and disfluency not observed as dichotomous phenomena, but instead as events along a continuum of speech motor coordination (Adams & Runyan, 1981;Van Riper, 1982;Zimmermann, Smith, & Hanley, 1981).…”