Reduction of Vowel Space in Alzheimer's Disease - Q&A with Arian Shamei

May 5, 2023

Reduced vowel space area (VSA) is a known effect of neurodegenerative diseases such as Parkinson's disease (PD). In the study, 'Reduction of Vowel Space in Alzheimer's Disease' by Arian Shamei, Yadong Liu and Dr. Bryan Gick, using large publicly available corpuses, two experiments were conducted comparing the vowel space of speakers with and without Alzheimer's disease (AD) during spontaneous and read speech. First, a comparison of vowel distance found reduced distance in AD for English spontaneous speech, but not Spanish read speech. Findings were then verified using an unsupervised learning approach to quantify VSA through cluster center detection. 

In this Q&A with Language Sciences, Arian Shamei, PhD Candidate in Linguistics at UBC, explains how reduced vowel space area (VSA) is a manifestation of reduced fine motor skills, why natural speech may be more susceptible to VSA reduction than read speech in those Alzheimer's Disease, and what's next for this research!

1. Can you explain how reduced vowel space area (VSA) is a manifestation of reduced fine motor skills in neurodegenerative diseases such as Alzheimer's Disease?

Great question. Believe it or not, speech is movement. In fact, speech movements are some of the most rapid and precise fine motor skills that humans employ. This makes speech a great medium for assessing fine motor skills. People make vowels by moving their tongue into specific positions. The range and precision of these movements is a good reflection of fine motor skills. People with Alzheimer’s Disease (AD) display impairments in fine motor skills throughout the body, so it’s no surprise we can see it in their speech. Specifically, we see that they produce a smaller range of movement when compared to healthy control patients. This reflects observations for other neurodegenerative diseases such as Parkinson’s Disease or ALS where we see fine motor skill deterioration throughout the body mirrored in reduced vowel space. 

2. Why might natural speech be more susceptible to VSA reduction than read speech in those with Alzheimer's Disease?

Natural speech generally involves a faster speech rate and greater variability in all domains compared to read speech. This makes it a tougher motor task than read speech, which typically follows a more monotone cadence at a more consistent speech rate. We see the same pattern for other neurodegenerative diseases too, such as Parkinson’s Disease; reductions to VSA are much greater in natural speech. So the choice of speech task has a big impact on whether changes can be detected in speech. A lot of researchers use read speech because it's easier to collect and more consistent, and this seems to result in false negatives when looking for changes to speech. 

3. How do the vowel systems of English and Spanish differ, and why is it important that these differences are recognized in this research?

In general, the vowel space of English is a lot larger and more varied than Spanish. English also employs prosodic stress on vowels, which changes the duration and articulatory emphasis of a vowel. Spanish vowels on the other hand are fairly consistent. However, regardless of whether a person with AD speaks English or Spanish, they will have the same impairment to fine motor skills, but it's possible that different languages have different motor demands. There is a lot of research around the world examining how speech is changed by neurodegenerative disease, and the general pattern is that we see changes regardless of the language being spoken because fine motor skills are always affected. Rather, the bigger influence driving variability in findings around the world is the choice of speech task. So it’s important that researchers recognize that looking at read speech may not paint the whole picture. 

4. What's next for this research?

Because speech is a great way to assess fine motor skills, it’s also a fantastic diagnostic tool. There is a lot of research on leveraging speech for the automated detection of neurodegenerative disease. We hope to identify commonalities in changes to speech across languages to improve the efficacy of automated methods for the detection of AD. Artificial intelligence has demonstrated strong potential in distinguishing AD speech from healthy controls, but there is little understanding of what those changes are, when we should expect them, and whether they are specific to individual languages. We have been doing a lot of experiments at the ISRL to get to the bottom of this.

To learn more and read the full study, click here.

Written by Kelsea Franzke

First Nations land acknowledegement

We acknowledge that UBC’s campuses are situated within the traditional territories of the Musqueam, Squamish and Tsleil-Waututh, and in the traditional, ancestral, unceded territory of the Syilx Okanagan Nation and their peoples.

UBC Crest The official logo of the University of British Columbia. Urgent Message An exclamation mark in a speech bubble. Caret An arrowhead indicating direction. Arrow An arrow indicating direction. Arrow in Circle An arrow indicating direction. Arrow in Circle An arrow indicating direction. Chats Two speech clouds. Facebook The logo for the Facebook social media service. Information The letter 'i' in a circle. Instagram The logo for the Instagram social media service. External Link An arrow entering a square. Linkedin The logo for the LinkedIn social media service. Location Pin A map location pin. Mail An envelope. Menu Three horizontal lines indicating a menu. Minus A minus sign. Telephone An antique telephone. Plus A plus symbol indicating more or the ability to add. Search A magnifying glass. Twitter The logo for the Twitter social media service. Youtube The logo for the YouTube video sharing service.