Study finds neurons in human brain capable of predicting what we’re going to say before we say it

Using advanced brain recording techniques, a new study led by researchers at Massachusetts General Hospital (MGH) demonstrates how neurons in the human brain work together to allow people to think about the words they want to say, then say them. produce out loud through speech.

Together, these findings provide a detailed map of how speech sounds, such as consonants and vowels, are represented in the brain long before they are spoken and how they are strung together during production. of language.

The work, published in Naturereveals information about the neurons in the brain that enable language production and could lead to improvements in the understanding and treatment of speech and language disorders.

“Although speaking generally seems easy, our brains carry out many complex cognitive steps in producing natural speech, including finding the words we want to say, planning articulatory movements, and producing the vocalizations we want,” explains the author. Principal Ziv Williams, MD. , associate professor of neurosurgery at MGH and Harvard Medical School.

“Our brains accomplish these feats surprisingly quickly – about three words per second in natural speech – with remarkably few errors. Yet precisely how we achieve this feat remains a mystery.”

When they used cutting-edge technology called Neuropixel probes to record the activities of single neurons in the prefrontal cortex, a frontal region of the human brain, Williams and his colleagues identified cells involved in language production that might be responsible for the origin of the ability to speak. They also discovered that there are distinct groups of neurons in the brain dedicated to speaking and listening.

“The use of Neuropixel probes in humans was launched for the first time at MGH. These probes are remarkable: they are smaller than the width of a human hair, but they also have hundreds of channels capable of “simultaneously record the activity of dozens or even hundreds of individual neurons,” says Williams, who worked to develop these recording techniques with Sydney Cash, MD, Ph.D., professor of neurology at MGH and the Harvard Medical School, who also helped lead the study.

“Using these probes may therefore offer unprecedented new insights into how human neurons act collectively and how they work together to produce complex human behaviors such as language,” Williams continues.

The study showed how neurons in the brain represent some of the most fundamental elements involved in constructing spoken words, from simple speech sounds called phonemes to their assembly into more complex strings such as syllables.

For example, the consonant “da,” produced by touching the tongue with the hard palate behind the teeth, is necessary to produce the word dog.

By recording individual neurons, the researchers found that some neurons become active before that phoneme is spoken aloud. Other neurons reflected more complex aspects of word construction, such as the specific assembly of phonemes into syllables.

Using their technology, the investigators showed that it is possible to reliably determine the speech sounds that individuals utter before articulating them.

In other words, scientists can predict what combination of consonants and vowels will be produced before the words are actually spoken. This ability could be harnessed to build artificial prosthetics or brain-machine interfaces capable of producing synthetic speech, which could benefit a wide range of patients.

“Disruptions in speech and language networks are observed in a wide variety of neurological disorders, including stroke, head trauma, tumors, neurodegenerative disorders, neurodevelopmental disorders, etc.,” explains Arjun Khanna, co-author of the study. . “Our hope is that a better understanding of the basic neural circuits that enable speech and language will pave the way for developing treatments for these disorders.”

The researchers hope to expand their work by studying more complex linguistic processes that will allow them to study questions related to how people choose the words they intend to say and how the brain puts words together. in sentences that convey one individual’s thoughts and feelings to others. .

Other authors include William Muñoz, Young Joon Kim, Yoav Kfir, Angelique C. Paulk, Mohsen Jamali, Jing Cai, Martina L Mustroph, Irene Caprara, Richard Hardstone, Mackenna Mejdell, Domokos Meszena, Abigail Zuckerman and Jeffrey Schweitzer.