An electromyographic study of velopharyngeal function in speech

Area of Science:

• Speech motor control
• Biomechanics of articulation
• Phonetics

Background:

• Understanding muscle activation patterns is crucial for speech production.
• Previous research has identified key muscles involved in velopharyngeal closure, but detailed electromyographic data across various speech sounds is limited.

Purpose of the Study:

• To investigate the electromyographic activity of specific pharyngeal and palatal muscles during American English speech.
• To identify the primary muscles responsible for velopharyngeal closure and their modulation by speech context (vowels, consonants).

Main Methods:

• Electromyography (EMG) using bipolar hooked-wire electrodes was performed on three American English speakers.
• Subjects produced nonsense words with various stop-nasal and nasal-stop consonant contrasts and three vowels (/i, a, u/).
• EMG signals were recorded and computer-processed to analyze muscle activation patterns.

Main Results:

• The levator palatini muscle was identified as the primary muscle for velopharyngeal closure in all subjects.
• Palatopharyngeus muscle activity was consistently observed during oralization but varied with vowel environment.
• Pharyngeal constrictor activity showed differential patterns related to oral articulation or vowel quality depending on the subject.
• Nasal articulation was achieved through the suppression of oral articulation.
• Vowel quality, particularly /a/, influenced the strength of EMG signals in lateral and posterior pharyngeal wall muscles.

Conclusions:

• The levator palatini plays a critical role in achieving velopharyngeal closure for speech.
• Speech sound context, including vowels and consonant types, significantly modulates the activity of muscles involved in articulation.
• Individual differences in muscle activation patterns may exist, particularly for pharyngeal constrictors.