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A brand new examine from UC San Francisco challenges the standard view of how the mind strings sounds collectively to kind phrases and orchestrates the actions to pronounce them.
Talking is likely one of the most intricate issues a human can do. Earlier than you even say a phrase, your mind has to translate what you need to say into a wonderfully sequenced set of directions to the handfuls of muscle groups you employ to talk.
For greater than a century, scientists thought all this planning and coordination—known as speech-motor sequencing—occurred in part of the frontal lobe known as Broca’s space.
Now, a brand new examine from UC San Francisco reveals that it depends on a a lot wider community of neurons throughout many mind areas. This community is centered in an space known as the center precentral gyrus, or mPrCG, which scientists thought would possibly solely management the larynx, part of the vocal tract that helps us make high- or low-pitched sounds.
“It turns out that this part of the brain has a much more interesting and important role,” stated Edward Chang, MD, Chair of Neurosurgery, and senior writer of the examine. “It strings together the sounds of speech to form words, which is crucial to being able to pronounce them.”
The examine, which seems in Nature Human Behaviour, may encourage new methods of taking a look at speech problems, help within the growth of units that permit paralyzed individuals to speak, and assist protect a affected person’s potential to talk after mind surgical procedure.
Past Broca’s space
Broca’s space, named for physiologist Pierre Paul Broca, who found it in 1860, has been believed to deal with most of our language processing. That encompasses each how we make sense of the language we hear or learn, and the way we produce the phrases we intend to say.
However a number of years in the past, Chang, who’s a member of the UCSF Weill Institute for Neurosciences and has spent over a decade exploring the query of how the mind produces speech, started to suspect that it entails areas past Broca’s.
In a uncommon case examine, he’d seen that when a affected person had a tumor faraway from their mPrCG, they developed apraxia of speech, a situation wherein individuals know what they need to say however wrestle to coordinate the actions wanted to say it clearly. The identical situation did not end result from comparable surgical procedures in Broca’s space.
Chang and then-graduate pupil Jessie Liu, Ph.D. additionally seen exercise related to speech planning within the mPrCG whereas growing a tool to permit individuals with paralysis to speak.
To research what was occurring, Chang, Liu, and postdoctoral scholar Lingyun Zhao, Ph.D., labored with 14 volunteers present process mind surgical procedure as a part of their therapy for epilepsy. Every affected person had a skinny mesh of electrodes positioned on the floor of their mind, which may file mind indicators occurring simply earlier than they spoke their phrases.
Neurosurgeons like Chang routinely use these electrodes to assist them map the place within the affected person’s mind the seizures are occurring. If there are speech areas close by, the surgeon will map these as effectively, to keep away from damaging them throughout surgical procedure.
Liu and Zhou had been in a position to piggyback on the expertise to see what was occurring within the mPrCG when sufferers had been speaking.
They confirmed the volunteers units of syllables and phrases on a display after which requested them to make the sounds out loud. Some units had been easy repeated syllables, like “ba-ba-ba,” whereas others included extra complicated sequences, like “ba-da-ga,” that comprise a wide range of sounds.
The researchers noticed that once they gave individuals extra complicated sequences, the mPrCG was extra lively than when individuals got easy ones. The group additionally discovered that the rise in exercise in that area predicted how rapidly the individuals would start talking after they learn the phrases.
“Seeing this combination—working harder to plan more complex sequences and then signaling muscles to put the plan into action—tells us that even though the mPrCG is outside of Broca’s area, it’s critical to orchestrating how we speak,” Liu stated.
Connecting intention to motion
The group additionally used the electrodes to stimulate the mPrCG in 5 of the examine individuals whereas they had been uttering set sequences of syllables.
If the sequences had been pretty easy, the individuals had no drawback. However once they got extra complicated sequences, the stimulation brought on individuals to make errors resembling the apraxia of speech Chang noticed in his case examine.
That provides extra proof that the mPrCG is central to coordinating a number of totally different speech sounds and acts as a bridge connecting what an individual needs to say with the actions which might be required to say it.
“It’s playing this vital role that had been thought to belong to Broca’s area but didn’t quite fit there,” Liu stated. “This points us in a new research direction, where learning how the mPrCG does this will lead us to a new understanding of how we speak.”
Extra data:
Jessie R. Liu et al, Speech sequencing within the human precentral gyrus, Nature Human Behaviour (2025). DOI: 10.1038/s41562-025-02250-1
Offered by
College of California, San Francisco
Quotation:
How the mind turns our supposed phrases into the sounds of speech (2025, July 16)
retrieved 16 July 2025
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