Drexel PhD students discover science behind speech impairments | The Triangle

Drexel PhD students discover science behind speech impairments

John Medaglia, an assistant professor of psychology at Drexel University, was the primary author on a study, along with researchers at the University of Pennsylvania, describing how networks in the brain connect to drive language performance.

Fluent verbal communication is reliant on a person’s ability to access and choose appropriate words to effectively convey their thoughts and ideas. However, for people who have suffered a stroke or other types of brain damage, this task can often be very complex.

While scientists have discovered that the left inferior frontal gyrus (LIFG) region of the brain is critical for fluent and efficient speech,they are still unsure how this region interacts with the brain’s complex pathways to influence controlled language performance.

Through their research, Medaglia, co-author Danielle Bassett and their colleagues, aim to map out the neurological networks of the brain, in order to identify the effect of stimulation on one region of the brain and how that stimulation may affect another. These scientists are working in the realm of the newly surfacing field of research known as network neuroscience

“Network neuroscience provides computational methods to uncover structure in brain imaging data. In turn, knowledge about this structure allows us to better understand how signals travel naturally across the brain’s highways, and also how stimulation can alter that travel in a way that supports better cognitive function,” Bassett said to DrexelNow.

With this goal in mind, the study involved 28 participants performing language tasks while the researchers stimulated their brains noninvasively. The focus was on how two network control features were affected by different language tasks the participants were asked to perform. Modal controllability — a neural region’s ability to drive network into “difficult to reach states”— and boundary controllability — the theoretical ability of a brain region to communicate with a different region through the implementation of brain networks.

“Our ability to understand neural systems is fundamentally related to our ability to control them,” and “This research provides direct evidence that how we choose the words we want to say in natural language is related to the capability of the brain to integrate and segregate activity across major networks.” Medaglia said to DrexelNow.

Making use of magnetic brain stimulation technique — transcranial magnetic stimulation, a method occasionally used to treat depressive symptoms — as well as network control theory, the researchers took an ingenious approach to determining how word-choice decisions are made through the implementation of neural networks. Further this allows the researchers to evaluate how the LIFG brain region affects different neural networks, based on varying language tasks.

The two language tasks included asking them to complete a sentence, while the second task took a more descriptive approach, asking the participants to name specific images and numerals. During these tasks the researchers observed the response times and administered brain stimulations of the group, through noninvasive devices and mathematical formulas.

Through their research, it was found that boundary controllability, was an important process to handle open-ended language tasks, while modal controllability drew parallels with closed-ended language tasks.

“I thought our results would be more muddied. There are debates about how unique these processes truly are, and now we have evidence that you can make a clear distinction between them,” Medaglia said. “It was also surprising to me that you could find this effect when studying the whole brain, whereas a lot of traditional views on language would have you focus on a much more specific area.”

With their study published in the Journal of Neuroscience, according to Roy Hamilton, study co-author and behavioral neurologist in the Perelman School of Medicine at the University of Pennsylvania, the research conducted by the group of researchers, could illuminate the way for the treatment of aphasia (acquired language loss caused by  stroke) as well as other language disorders.

“This study gives us new insight into the underlying properties of areas like the LIFG that enable the brain to process language,” Hamilton said to DrexelNow. “With further research, we can begin to uncover which areas of the brain are likely to be utilized if there’s an injury to the language system. This approach may provide exciting new targets for treatment with focal therapies, including neuromodulation.”

Following their discoveries, the research team is now making use of the same type of techniques, to pursue the science behind stimulating certain parts of the brain to improve speech in stroke patients.