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Updated: Aug 2, 2026
12:43
A Protocol for Comprehensive Assessment of Bulbar Dysfunction in Amyotrophic Lateral Sclerosis (ALS)
Published on: February 21, 2011
Acoustic differences between content and function words in amyotrophic lateral sclerosis
1Department of Communication Disorders, Central Missouri State University, Warrensburg, USA.
Summary
Speech acoustics in amyotrophic lateral sclerosis (ALS) show subtle vowel differences between content and function words. Temporal speech properties, not spectral, better predict impairment, suggesting therapy targets.
Area of Science:
- Speech Science
- Neurology
- Linguistics
Background:
- Dysarthria in amyotrophic lateral sclerosis (ALS) impacts speech intelligibility.
- Acoustic analysis of speech can elucidate these intelligibility deficits.
Purpose of the Study:
- To investigate acoustic vowel distinctions in content vs. function words for speakers with ALS.
- To correlate speech impairment in ALS with acoustic vowel differences.
Main Methods:
- Nine speakers with mild-to-moderate ALS and nine controls produced vowels /i/, /ae/, /u/, /a/ in content and function words.
- Measured F1/F2 frequencies, vowel space area, and vowel durations.
- Analyzed differences between word types and their relation to speech impairment.
Main Results:
- No significant differences in spectral or duration vowel variations between ALS speakers and controls.
- ALS speakers showed a trend towards smaller vowel space area differences between word types.
- Temporal differences in vowel production were stronger predictors of speech impairment than spectral differences.
Conclusions:
- Individuals with ALS may not acoustically distinguish vowels in content vs. function words as much as controls.
- Therapeutic interventions for ALS speech should prioritize temporal acoustic features.
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