Pitch control and pharynx with in Twi: an electromyographic study

Area of Science:

• Linguistics
• Phonetics
• Biomechanics

Background:

• Understanding the physiological underpinnings of speech production is crucial for phonological analysis.
• Electromyography (EMG) provides direct insight into muscle activation patterns during speech.
• Twi phonology involves complex features such as tone, vowel quality, and consonant context.

Purpose of the Study:

• To investigate the electromyographic activity of specific laryngeal and tongue muscles during Twi syllable production.
• To correlate muscle activation patterns with phonetic and phonological features of Twi vowels and preceding consonants.
• To evaluate the role of muscles like genioglossus (GG) and digastric (D) in pitch control and tongue root positioning.

Main Methods:

• Electromyographic (EMG) tracings were recorded from four muscles: genioglossus (GG), anterior belly of the digastric (D), sternothyroid (ST), and thyrohyoid (TH).
• Analysis focused on 210 Twi syllables designed to elicit specific phonetic contrasts.
• Seven parameters were examined: tense/lax vowels, long/short vowels, close/open vowels, front/back vowels, high-tone/low-tone vowels, and preceding fricative/plosive and voiced/voiceless consonants.

Main Results:

• Genioglossus (GG) and digastric (D) muscles were identified as functioning in pitch control, though the mechanism of laryngeal elevation for pitch increase remains unclear.
• GG did not appear to be the primary muscle for tongue root fronting, suggesting it may comprise multiple functional units.
• Muscle activity patterns indicated a ranking of features, with 'high-tone', 'fricative', and 'voiced' features showing dominance for GG, D, and ST respectively.

Conclusions:

• The study provides physiological evidence for the role of GG and D in pitch control in Twi.
• Findings challenge the expected role of GG in tongue root fronting and suggest a more complex functional organization.
• Limited evidence supports a prosodic view of vowel harmony in Twi, with feature dominance observed in muscle activity.