Stephen Wilson, an assistant professor of speech, language and hearing sciences, and a team of researchers are making breakthroughs in how the brain processes speech.
While scientists have known for more than 100 years which areas of the brain actually process speech, Wilson and his colleagues are interested in developing an understanding of how grammar syntax is formed.
The group’s research expands on the findings of 19th-century neurologists Pierre Paul Broca and Carl Wernicke. While Broca found that a portion of the left frontal lobe of the brain actually produced language, Wernicke determined that a part of the brain’s posterior involved language comprehension. These two regions are now known as Broca’s area and Wernicke’s area. Wilson’s work focuses on analyzing the two white matter pathways — dorsal and ventral — and which of the two is responsible for forming sentences.
“We’ve got a new imaging technology called Diffusion Tensor Imaging, where it can track the neurons and look at how they’re sending information from one region to another,” Wilson said. “What we’ve realized is that there are two different pathways that lead between these regions. We wanted to figure out which one, or if both of these, is important for processing syntactic information.”
The new imaging technology, Diffusion Tensor Imaging, was developed in the early 1990s, and has only been used in the study of human cognition for the past five to 10 years, according to Wilson. The technology allows scientists to see the directionality of the fiber tracks within the brain, which are color-coded according to area of the brain and direction of the movements. Without this imaging technology, the brain images are a homogenous white, giving scientists little information regarding the activity happening inside.
As Wilson started his work at the UA quite recently, his research was compiled from a study he conducted during his time as a post-doctoral fellow at the University of California, San Francisco. There, Wilson studied 27 patients who all had primary-progressive aphasia, an incurable language deficit. His research is now being analyzed here at the UA.
“It turns out that some of them have damage to the dorsal pathway, and some of them have damage to the ventral pathway,” he added. “Then we test their syntax, see how well they produce sentences normally and see how well they comprehend sentences. Then we can look at correlations between how they do on those tasks and whether those pathways are damaged or not. What we’ve found is that people who have damage to the dorsal pathway are really impaired in grammatical syntax, while people who have damage to the ventral pathway don’t know the meanings of words.”
Wilson said the uniqueness and significance in his research is found of the fact that the patients for his study are quite rare, and fewer than six institutions in the world have a significant number of aphasia patients to study.
“A million Americans have aphasia,” Wilson said. “There is a variable path of recovery, so by really understanding the neuroanatomy of language, it opens up the possibility of designing treatments and maybe find alternate pathways in their brain that patients can use.”
