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Mindreading: Neurons can somehow "predict" human speech before we say a word

In a fascinating study, researchers have unlocked remarkable insights into how neurons in the human brain orchestrates the complex process of speech production.

Using sophisticated brain recording techniques, they have mapped out the intricate pathways that allow us to formulate and articulate words.

This research, spearheaded by Massachusetts General Hospital (MGH) and detailed in the prestigious journal Nature, sheds light on the previously enigmatic process of language production.

It marks a significant leap in our understanding of how speech sounds, like consonants and vowels, are pre-formed in the brain before being voiced.

Unraveling the mystery of language production

Dr. Ziv Williams, MD, an associate professor in Neurosurgery at MGH and Harvard Medical School and the study’s senior author, explains the complexity and efficiency of this process.

“Although speaking usually seems easy, our brains perform many complex cognitive steps in the production of natural speech — including coming up with the words we want to say, planning the articulatory movements and producing our intended vocalizations,” Williams explains.

“Our brains perform these feats surprisingly fast — about three words per second in natural speech — with remarkably few errors. Yet how we precisely achieve this feat has remained a mystery.”

Neuropixels: A technological marvel

One of the study’s pivotal breakthroughs came from utilizing Neuropixels probes. These probes, thinner than a human hair, can record activities from numerous neurons simultaneously.

The researchers discovered that specific neurons in the prefrontal cortex become active before we even speak, playing a crucial role in language production.

Williams says, “The use of Neuropixels probes in humans was first pioneered at MGH. These probes are remarkable — they are smaller than the width of a human hair, yet they also have hundreds of channels that are capable of simultaneously recording the activity of dozens or even hundreds of individual neurons.”

Decoding speech: From neurons to words

Dr. Williams had worked to develop these recording techniques with Sydney Cash, MD, PhD, a professor in Neurology at MGH and Harvard Medical School, who also helped lead the study.

“Use of these probes can therefore offer unprecedented new insights into how neurons in humans collectively act and how they work together to produce complex human behaviors such as language,” Williams clarified.

This finding demystifies how we assemble basic speech elements like phonemes into more complex structures such as syllables.

For instance, the study showed that certain neurons activate before articulating the phoneme “da,” a building block of the word “dog.”

Neurons, speech synthesis and prosthetics

Using neurons as a “decoding” device, this technology offers the potential to predict speech sounds before they are spoken, opening doors to developing advanced prosthetics or brain-machine interfaces for synthetic speech production.

This could revolutionize the lives of those with speech and language impairments due to neurological conditions such as stroke, brain injury, and neurodegenerative disorders.

“Disruptions in the speech and language networks are observed in a wide variety of neurological disorders — including stroke, traumatic brain injury, tumors, neurodegenerative disorders, neurodevelopmental disorders, and more,” says Arjun Khanna who is a co-author on the study.

“Our hope is that a better understanding of the basic neural circuitry that enables speech and language will pave the way for the development of treatments for these disorders.”

The future of decoding speech with neurons

The team at MGH is not resting on their laurels. They plan to delve deeper into complex language processes, exploring how the brain selects words and assembles them into meaningful sentences.

This work promises to further unravel the mysteries of how we express our thoughts and emotions through language, potentially transforming the landscape of neurological treatment and rehabilitation.

In summary, this study represents a major stride in understanding the brain’s role in language production. By harnessing cutting-edge Neuropixels technology, this brilliant team of scientists has illuminated the neural pathways that underpin speech, from the activation of individual neurons to the construction of complex words and sentences.

This research deepens our understanding of the human brain’s remarkable capabilities and holds the promise of transformative applications in treating speech and language disorders.

As the team looks toward exploring more intricate aspects of language processing, their work stands as a beacon of innovation, paving the way for future advancements in neuroscience and medical technology.

The full study, funding by the NSF, was published in the journal Nature.


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