Neurons coordinate group activities for language processing

Language processing is one of the most complex and captivating abilities of the human brain, enabling us to communicate, comprehend, and connect with one another.

Language allows us to share our thoughts, express our emotions, and convey information, forming the foundation of human relationships and society itself.

Mysteries of language processing

Despite its central role in human interaction, the intricacies of how the brain processes language remain a mystery.

Understanding the neural mechanisms behind language processing is crucial, as it can shed light on how we learn, how we develop our communication skills, and how various neurological disorders impact speech and comprehension.

Now, a team of neuroscientists from the Massachusetts Institute of Technology (MIT) has made a significant breakthrough in our understanding of language processing.

“Despite long knowing what brain areas support language comprehension, our knowledge of the neural computations that these frontal and temporal regions implement remains limited,” noted the study authors.

“One important unresolved question concerns functional differences among the neural populations that comprise the language network.”

Unraveling the role of neurons

The experts identified distinct clusters of neurons that handle language at various “temporal windows,” responding to linguistic context over different timeframes, ranging from a single word to about six words.

The discovery of these temporal windows was made using a sophisticated technique that involves recording electrical activity in the brain.

With this method, the team was able to identify the specific functions performed by different populations of neurons. The research challenges former beliefs that all neurons involved in language processing perform the same functions.

“This is the first time we see clear heterogeneity within the language network. Across dozens of fMRI experiments, these brain areas all seem to do the same thing, but it’s a large, distributed network, so there’s got to be some structure there,” said study senior author Professor Evelina Fedorenko.

The limitations of fMRI

Previously, functional magnetic resonance imaging (fMRI), a method that measures changes in blood flow, has been instrumental in identifying brain areas responsible for language processing.

However, Professor Fedorenko pointed out that the resolution of fMRI is not high enough to understand what small populations of neurons are doing. The team overcame this limitation by recording electrical activity using electrodes implanted in the brain.

While the data were hard to obtain, as the procedure is only done in patients undergoing surgery for neurological conditions like severe epilepsy, they provided extensive and precise insights.

“These data, of course, are the best kind of data we can get from human brains: You know exactly where you are spatially and you have very fine-grained temporal information,” said Professor Fedorenko.

Language processing clusters in the brain

With the in-depth analysis, the experts discovered that neurons seemed to process language in groups, or clusters, based on temporal windows of one word, four words, or six words.

According to study lead author Tamar Regev, it appears that these neural populations integrate information across different timescales along the sentence.

Another significant finding from the study reveals the anatomical locations of these different clusters. Those with the shortest temporal window were found predominantly in the posterior temporal lobe, while those with longer windows were spread more evenly throughout the temporal and frontal lobes.

Future research directions

Now that this differentiation has been established, the next step for the team is to determine if the timescales correspond with specific functions.

“The longest timescale is sensitive to things like syntax or relationships between words, and maybe the shortest timescale is more sensitive to features of single words or parts of them,” said Regev.

The study has paved the way for a more comprehensive and detailed understanding of the brain’s language processing abilities. Future studies could employ similar methodologies to investigate other cognitive functions in the brain.

The research was made possible with the support of numerous organizations, including the U.S. National Institutes of Health, the Poitras Center for Psychiatric Disorders Research, and MIT’s Department of Brain and Cognitive Sciences.

The study is published in the journal Nature Human Behavior.

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