Findings That Would Help Treat Speech Problems

A new study showed that a region called the "dorsal precentral gyrus" the part of the brain that crosses the folded surface and it plays a very important role in controlling how people use the sounds of their voices. Researchers say that the ability to take cues from one’s own voice while talking has long been recognized as essential to fluent speech. Also recognized is each person’s ability to make possible near-immediate adaptations based on these cues, such as slowing down speech to better articulate multisyllable words, or raising the voice to overcome loud background noise. The results were published in the journal PLOS Biology.

The researchers at NYU Grossman School of Medicine lead the way to the new study focused on the half-dozen subregions of the brain’s surface layer, or cerebral cortex, because they are known to control how people move their mouth, lips, and tongue to form words, and to have a role in processing what they hear themselves saying.

But the precise role of each subregion in real-time speech feedback has until now remained unclear, in part, because of the difficulties in directly accessing the brain for study while people are alive and talking.

The results of the new investigation were increased and show that three cortical regions are primarily involved in correcting speech errors, including the superior temporal gyrus and the super-marginal gyrus, the only one of which is the dorsal precentral gyrus, which refers to feedback errors when speech is delayed. These brief feedback delays ranged from 0 milliseconds to over 200 milliseconds and were designed to mimic real-life slurring of speech.

“Our study confirms for the first time the critical role of the dorsal precentral gyrus in maintaining control over speech as we are talking and to ensure that we are pronouncing our words as we want to,” says Study Senior Investigator and Neuroscientist Adeen Flinker, PhD.

Flinker says that the team plans further studies into the brain’s feedback mechanisms for controlling speech. In particular, the team seeks to explain whether the dorsal precentral gyrus is responsible for developing the brain's initial memory of how spoken words sound, and if there are any errors in how those words are actually spoken after the "base signal" is returned. Within the muscle movements needed to form words.

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“Now that we believe we know the precise role of the dorsal precentral gyrus in controlling for errors in speech, it may be possible to focus treatments on this region of the brain for such conditions as stuttering and Parkinson’s disease, which both involve problems with delayed speech processing in the brain,” says Flinker, an assistant professor in the department of neurology at NYU Langone Health.

For the study, researchers analyzed thousands of recordings from upwards of 200 electrodes placed in each of the brains of 15 people with epilepsy already scheduled to undergo routine surgery to pinpoint the source of their seizures. All patients were mostly men and women in their 30s and 40s and were recorded in 2020 at NYU Langone.

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Patients volunteered to perform standardized reading tests during the scheduled interval of their surgery, uttering loud words and short statements. Everyone was wearing headphones so that what they said could be recorded and played back to them as they spoke.

Researchers then recorded electrical activity inside most subregions of the patients’ brains as the patients heard themselves talking and as this feedback was increasingly delayed by milliseconds.

Such audiofeedback tests have been developed to safely study how the human brain learns and processes speech. By introducing errors in normal speech, researchers say they can then compare and contrast the electrical signals to determine how various parts of the brain function and control speech.

This research was funded by NYU Langone.

Source-Medindia