Investigation of Embodied Language Processing on Command-Swallow Performance in Healthy Participants

Abstract

Purpose During videofluoroscopic examination of swallowing, patients commonly are instructed to hold a bolus in their mouth until they hear a verbal instruction to swallow, which usually consists of the word swallow and is commonly referred to as the command swallow condition. The language-induced motor facilitation theory suggests that linguistic processes associated with the verbal command to swallow should facilitate the voluntary component of swallowing. As such, the purpose of the study was to examine the linguistic influences of the verbal command on swallowing. Method Twenty healthy young adult participants held a 5-ml liquid bolus in their mouth and swallowed the bolus after hearing one of five acoustic stimuli presented randomly: congruent action word (swallow), incongruent action word (cough), congruent pseudoword (spallow), incongruent pseudoword (pough), and nonverbal stimulus (1000-Hz pure tone). Suprahyoid muscle activity during swallowing was measured via surface electromyography (sEMG). Results The onset and peak sEMG latencies following the congruent action word swallow were shorter than latencies following the pure tone and pseudowords but were not different from the incongruent action word. The lack of difference between swallow and cough did not negate the positive impact of real words on timing. In contrast to expectations, sEMG activity duration and rise time were longer following the word swallow than the pure tone and pseudowords but were not different from cough. No differences were observed for peak suprahyoid muscle activity amplitude and fall times. Conclusions Language facilitation was observed in swallowing. The clinical utility of the information obtained in the study may depend on the purposes for using the command swallow and the type of patient being assessed. However, linguistic processing under the command swallow condition may alter swallow behaviors and suggests that linguistic inducement could be useful as a compensatory technique for patients with difficulty initiating oropharyngeal swallows.

Figure 1.

An example of the surface electromyography (sEMG) and nasal airflow measurements. a = sEMG latency; b = sEMG duration; c = sEMG peak amplitude; d = sEMG peak latency; e = rise time; f = fall time; g = swallow–respiratory pattern at stimulus onset.

Figure 2.

Predictive marginal mean and standard error on surface electromyography (sEMG) latency, sEMG duration, sEMG peak latency, and sEMG peak amplitude for each acoustic command cue. * = significant at p < .05; ** = significant at p < .01.

Figure 3.

Predictive marginal mean and standard error on rise and fall time durations for each acoustic command cue. * = significant at p < .05; ** = significant at p < .01.

Figure 4.

Schematic summary of the findings. sEMG = surface electromyography.

Figure 5.

Self-report stimuli preference results.

Figure 6.

Scatter plot of surface electromyography (sEMG) latency results for swallow cue and cough cue within each block.