Shared and Separate Neuromuscular Underpinnings of Swallowing and Motor Speech Development in the School-Age Years

Abstract

Purpose: Despite co-occurrence of swallowing and speech disorders in childhood, there is limited research on shared and separate neuromuscular underpinnings of these functions. The purpose of this study was to (a) compare neuromuscular control of swallowing and speech between younger and older children and (b) determine similarities and differences in neuromuscular control of swallowing and speech.

Method: Twenty-six typically developing children (thirteen 7- to 8-year-olds and thirteen 11- to 12-year-olds) completed this cross-sectional study. Neuromuscular control was evaluated using surface electromyography of submental muscles and superior and inferior orbicularis oris muscles during parallel tasks of swallowing and speech. Outcome measures included normalized mean amplitude, burst duration, time to peak amplitude, and bilateral synchrony, which were examined using mixed-effects models.

Results: For normalized mean amplitude, burst duration, and time to peak amplitude, there were significant two- and three-way interactions between muscle group, task, and age group, indicating that older and younger children demonstrated different muscle activation patterns, and these patterns varied by muscle and task. No differences were noted between groups for bilateral synchrony. For parallel tasks, children demonstrated different magnitudes of normalized mean amplitude and time to peak amplitude of speech and swallowing. However, they demonstrated a similar pattern: increases in magnitude as task complexity increased.

Conclusions: Children continue to demonstrate refinement of their neuromuscular control of swallowing and speech between 7-8 and 11-12 years of age, and there are both shared and separate elements of neuromuscular control between these two vital functions. To improve generalizability of findings, future research should include longitudinal analysis of swallowing and speech development, as well as measures of central neurophysiology.

Supplemental material: https://doi.org/10.23641/asha.23796258.

Figure 1.

Interaction plots showing burst duration of the smoothed surface electromyography (sEMG) signal during swallow tasks for the younger and older children.

Figure 2.

Interaction plots showing normalized mean amplitude (%MVC) of the smoothed sEMG signal during swallow tasks for the younger and older children. MVC = maximum voluntary contraction; sEMG = surface electromyography.

Figure 3.

Interaction plots showing time to peak surface electromyography (sEMG) amplitude during swallow tasks for the younger and older children.

Figure 4.

Interaction plots showing burst duration of the smoothed surface electromyography (sEMG) signal during speech tasks for the younger and older children.

Figure 5.

Interaction plots showing normalized mean amplitude (%MVC) of the smoothed sEMG signal during speech tasks for the younger and older children. MVC = maximum voluntary contraction; sEMG = surface electromyography.

Figure 6.

Interaction plots showing time to reach peak surface electromyography (sEMG) amplitude during speech tasks for the younger and older children.

Figure 7.

Interaction plots depicting normalized mean surface electromyography (sEMG) amplitude, time to reach peak sEMG amplitude, and bilateral synchrony, for parallel swallowing and speech tasks at three levels of complexity, with standard error (see Table 1 for reminder of levels).