Investigating Speech Intelligibility Loss and Recovery Researcher Antje Mefferd investigates ways to increase speech intelligibility in people with dysarthria. Foundational Questions
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Foundational Questions  |   December 01, 2017
Investigating Speech Intelligibility Loss and Recovery
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Speech, Voice & Prosodic Disorders / Dysarthria / Foundational Questions
Foundational Questions   |   December 01, 2017
Investigating Speech Intelligibility Loss and Recovery
The ASHA Leader, December 2017, Vol. 22, online only. doi:10.1044/leader.FQ.22122017.np
The ASHA Leader, December 2017, Vol. 22, online only. doi:10.1044/leader.FQ.22122017.np
Name: Antje Mefferd, PhD, CCC-SLP, assistant professor, Department of Hearing and Speech Sciences, and director, Speech Kinematics and Acoustics Lab, Vanderbilt University Medical Center
ASHFoundation Awards:
  • 2013 Research Conference Travel Grant

  • 2012 New Investigators Research Grant

What is the focus of your research?
I study the articulatory mechanisms that underlie speech intelligibility loss and recovery in speakers with dysarthria. That is, I investigate how neurological conditions (for example, degenerative neuromuscular diseases) affect speech motor performance and how these disease-related speech performance deficits affect speech acoustics. Based on this information we can infer articulatory factors of speech intelligibility loss.
I also investigate speech performance changes in response to specific instructions (for example, speak slower, speak louder, speak as clear as possible) and link these articulatory changes to speech acoustic measures to better understand the mechanisms of speech intelligibility recovery.
How did your award from the ASHFoundation lead to your current work?
My dissertation focused on motor performance in people with amyotrophic lateral sclerosis (ALS). However, in the long term I wanted to study dysarthria in various clinical groups. The New Investigators grant allowed me to collect my first pilot data on a different group of speakers with dysarthria, those with Parkinson’s disease (PD). I proposed a study that compared the effect of various speech modifications commonly used in speech treatments (slow, loud, clear speech) on tongue motor control in talkers with ALS and PD. I also wanted to know if and how changes in tongue motor control are reflected in the speech acoustic signal.
My lab’s current work builds on the findings of the ASHF New Investigators grant. Specifically, we are now studying in addition to tongue movements the role of the jaw in speech intelligibility loss and recovery in people with ALS and PD.
What do you hope to demonstrate through your research or what has it already demonstrated?
Ultimately, I want to know if and how specific treatment approaches can be used to target specific speech motor deficits. This knowledge can help clinicians select the most effective speech treatments for each individual speaker with dysarthria.
The New Investigators grant was a first step in this direction. I focused specifically on tongue motor performance and how tongue movements relate to speech acoustics in speakers with dysarthria. I was able to provide preliminary empirical evidence that tongue motor performance changes (in response to instructions to modify speech behavior) are tightly linked in a linear fashion to speech acoustic changes in talkers with PD.
However, in talkers with ALS, such tongue articulatory-to-acoustic relations were much more complex. The finding suggested that increases in the range of motion of the tongue can make speech acoustics more distinct in talkers with PD, whereas in talkers with ALS such acoustic changes may be less predictable. I speculated that the difference in these articulatory-to-acoustic mappings may be due to the different articulatory impairment profiles of speakers with PD and speakers with ALS. This observation led me to think about the role of the jaw, in addition to the role of the tongue in speech production.
Why did you choose this particular research focus?
Honestly, I never thought that I would become a speech scientist and study speech movements and acoustics in dysarthria. When I was an undergraduate, my guru was the Dutch psycholinguist Willem Levelt—I had enthusiastically read his books “Speaking” and “Lexical Access in Speech Production.”
After graduation, I worked in acute care and enjoyed assessing and treating patients with neurogenic communication disorders and dysphagia. But I felt uncomfortable treating dysarthria, because I couldn’t find solid scientific support for the speech treatments I was taught to use. I struggled “selling” these approaches to my patients and questioned their effectiveness. The more I searched, the more I realized that we have serious knowledge gaps when it comes to speech physiology in general, not just a lack of empirical evidence for dysarthria treatment effectiveness. Because I like to get to the bottom of things, I knew basic research was for me.
However, I am a clinician as much as a researcher, so my work had to deal with basic science questions that would also have clinical implications. When I started to look into PhD programs, optical and electromagnetic motion-capture systems for the study of speech movements became more available. Studying speech production directly at the movement level seemed intriguing and exciting.
How has ASHFoundation funding affected your professional life?
As a new assistant professor, my goal was to apply for an NIH grant to fund the work in my lab; however, writing an NIH grant for the first time can be daunting. A mentor suggested applying for an ASHFoundation grant to fund my pilot data for the NIH R03 application. By submitting the New Investigators grant, I could apply to Lessons for Success, a workshop that teaches NIH grant-writing skills and provides opportunities to discuss specific aspects of the NIH application with NIH-funded researchers. Lessons for Success really helped me improve my grant-writing skills and I received valuable feedback on my ASHF grant application. Securing funding from the ASHFoundation also assured me that my research ideas are important to the speech science field. I submitted my first R03 application to NIDCD two years after Lessons for Success and received funding in 2016.
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December 2017
Volume 22, Issue 12