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Find Your Voice: Unlocking the Mysteries of Stuttering

The views expressed are those of the author and are not necessarily those of Scientific American.


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Terrence Murgallis, a 20 year-old undergraduate student in the Department of Speech-Language Pathology at Misericordia University has stuttered all his life and approached us recently about conducting brain research on stuttering. His timing was perfect because our research group, in collaboration with a team led by Dr. Arjun Yodh in the Department of Physics and Astronomy at the University of Pennsylvania, had recently deployed two novel optical methods to compare blood flow and hemoglobin concentration differences in the brains of those who stutter with those who are fluent.

These noninvasive methods employ diffusing near-infrared light and have been dubbed near-infrared spectroscopy (NIRS) for concentration dynamics, and diffuse correlation spectroscopy (DCS) for flow dynamics. The near-infrared light readily penetrates through intact skull to probe cortical regions of the brain. The low power light has no known side-effects and has been successfully utilized for a variety of clinical studies in infants, children, and adults.

DCS measures fluctuations of scattered light due to moving targets in the tissue (mostly red blood cells). The technique measures relative changes in cerebral blood flow. NIRS uses the relative transmission of different colors of light to detect hemoglobin concentration changes in the interrogated tissues. Though there are numerous diagnostic tools available to study brain activity, including positron emission tomography (PET), magnetic resonance imaging (MRI), and magnetoencephalography (MEG), these methods are often invasive and/or expensive to administer. In the particular case of electroencephalography (EEG), its low spatial resolution is a significant limitation for investigations of verbal fluency.

Our initial results (Tellis et al., 2011), in persons who stutter and in normally fluent speakers (figure 1), suggest that speech tasks induce hemodynamic changes in parts of the brain that control speech, including Broca’s area and pre-frontal regions. We observed a greater amount of blood flow in Broca’s area when compared to the pre-frontal region in all subjects; however, in normally fluent speakers, a greater increase in blood flow to Broca’s area was observed compared to persons who stutter.

This trend suggests a possible speech-related difference for comparing the two populations during speaking tasks. Like flow, total hemoglobin concentration increased in Broca’s area and in the pre-frontal cortex during most speech tasks we studied, but unlike flow, these changes were similar for both persons who stutter and normally fluent speakers. Interestingly, for two tasks, i.e., free speech and choral speech, a decrease in total hemoglobin concentration was exhibited by persons who stutter.

Figure 1. (a) Schematic showing the probe on the participant’s head, as well as the blood flow probe with its sources and detectors. (b) A representative time-course of blood flow changes (i.e., cerebral blood flow changes) in the pre-frontal lobe (averaged over all the channels in this region) during the monologue task for both participant types -Normally Fluent Speakers (NFS) and Persons who Stutter (PWS). The task lasted 60 seconds starting at time t = 0.

Figure 1. (a) Schematic showing the probe on the participant’s head, as well as the blood flow probe with its sources and detectors. (b) A representative time-course of blood flow changes (i.e., cerebral blood flow changes) in the pre-frontal lobe (averaged over all the channels in this region) during the monologue task for both participant types -Normally Fluent Speakers (NFS) and Persons who Stutter (PWS). The task lasted 60 seconds starting at time t = 0.

Now, Terrence has an even greater cause to be excited about brain studies. President Obama, in his 2013 State of the Union address, announced that his administration aims to fund scientists to map the human brain and thereby unlock the mysteries of memory, learning, and thinking. Our research, as well as research by others, indicates that the diffuse optical methodologies are attractive for determining differences in cerebral blood flow and blood oxygenation levels during speech tasks.

Ultimately, progress along these lines could lead to improved diagnostic and treatment techniques for persons with speech and language disorders, including stuttering. Our strategy going forward is to obtain a large amount of baseline data for typical speech and language patterns. Then, we plan to then apply these same technical paradigms to test those with disorders of speech and language including stuttering, voice, articulation, language, autism, aphasia, apraxia, dysarthria, and other conditions. These technologies are thus expanding our knowledge of the brain and could even improve upon the care we provide to clients.

Reference:

Tellis, G. M., Mesquita, R., & Yodh, A. (2011). Using diffuse correlation spectroscopy to measure brain blood flow differences during speaking and nonspeaking tasks for fluent speakers and persons who stutter. Perspectives on Fluency and Fluency Disorders, 21(3), 96-106.

Glen Tellis, Rickson C. Mesquita, and Arjun G. Yodh About the Author: Glen Tellis is Professor and Chair of the Speech-Language Pathology Department at Misericordia University in Dallas, Pennsylvania. He is a Board-Recognized Fluency Specialist and is the Director of the Fluency Laboratory.

Rickson C. Mesquita is an Assistant Professor in the Institute of Physics at the University of Campinas, Brazil and a Visiting Researcher in the Department of Physics and Astronomy at the University of Pennsylvania. His research focuses on diffuse optical and correlation spectroscopies to the brain.

Arjun G. Yodh is the James M. Skinner Professor of Science and the Director of The Laboratory for Research on the Structure of Matter (LRSM) at the University of Pennsylvania. Physics & Astronomy is his home department and he has a secondary appointment in the Department of Radiation Oncology in the Medical School. Follow on Twitter @MisericordiaU.

The views expressed are those of the author and are not necessarily those of Scientific American.






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  1. 1. Horace P. Bogardis 4:16 pm 07/30/2013

    Great article! This type of scientific research is imperative. Such research resulted in the February 2010 discovery of the very first “stuttering genes”, which account for 9% of all cases of stuttering. The near future will no doubt bring more identification of stuttering genes.

    The genetic link in stuttering has been talked about for ages. The website of the Stuttering Foundation (www.stutteringhelp.org) has “Celebrity Corner” profile articles of famous people and one is on Lewis Carroll; for over 100 years biographers of the great author have speculated on his genetic link to stuttering on account of the fact that his parents were two first cousins who married and nine of their eleven children stuttered past childhood. Also, an in-depth profiles on B.B. King, Gareth Gates, Dominick Dunne & John Gregory Dunne, and Sophie Gustafson give credence to the genetic link as stuttering runs in the families of these famous people. Also, some of the people on the site’s list of “Famous People Who Stutter” convey the genetic link through stuttering running in the family. Rubin Hurricane Carter, Charles Darwin, and others come to mind. The website of the Stuttering Foundation offers many free resources for adults, children, parents and teachers

    Link to this

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