Brain and language

Researchers create a 3D map of the brain to visualize how we understand language

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Every day we exchange thousands of words. With family, at the office, with friends. How is the brain able to reconstruct the meaning of words... What mechanisms are at work so that we can understand this endless stream? A group of scientists is mapping how the brain represents the meaning of spoken language, word by word. This is a first, published on April 27 in the journal Nature.
 
Cette research is not only a first by the feat it represents of constructing a real-time map of our brain, deciphering words, but above all it shows that language is not limited as we thought to certain specific areas of the brain, located rather in the left hemisphere. No, in order to understand language, we use an impressive number of regions of the brain, spread out in areas that are very far apart from each other. Our brain seems to "turn on" areas based on the words we hear.
 
Jack Gallant, a neuroscientist at the University of Berkeley, and his colleagues, including lead author Alex Huth, wanted to know how our brains react when we are told a story. Gallant describes the ambitions of his research at the Guardian : " Our goal was to build a giant atlas that shows how a specific aspect of language is represented in the brain, in this case semantics, or the meaning of words. ".
To do so, they asked seven participants to listen to a famous storytelling programme broadcast on the radio: The Moth Radio Hour. They connected each participant to a functional MRI, a machine that measures blood flow and neuron activity in the brain. With this equipment, it was possible to see participants' brains in action, and to map the activity in their brains.
They then matched the verbatim transcripts of the stories heard by the participants to the cards produced by the MRI. This allowed the researchers to detect how each word triggered specific areas of the brain.
 
By collecting information from all participants in a statistical model, the researchers were able to create a brain atlas, a 3D model that shows which areas are turned on by all participants in response to words. They published an interactive version online of this atlas.
 
 
Berkeley researchers found that words trigger more than 100 different areas in the brain. Some areas were even systematically activated by all participants by certain words. So, for example, words connoting places activate some areas while words connoting numbers or quantities activate others.
This research shows that each word triggers several areas of the brain, as a kind of network that would represent the meaning of each word we use. The authors state that the left side of the brain, above the ear, is one of the small regions that represents the word "victim". The same region responds to "kill," "convicted," "murdered," and "confessed. To the right, near the top of the head, is one of the areas of the brain activated by the terms in the family universe: "wife," "husband," "children," "parents. Each word is represented by more than one spot because words tend to have multiple meanings.
What is striking about this study is that the brain atlases were similar for all participants, suggesting that their brains organized the meaning of words in the same way.
 
This study is considered a tour de force. It shows how modern imaging can transform our knowledge of how the brain performs some of its most important tasks.
The Berkeley study opens up new territories but it deserves to be continued and expanded. The panel of participants is too small for the moment, and is limited to the English language. Nonetheless, this mapping opens up interesting perspectives not only for deciphering the mystery of language, but also the even greater mystery of meaning, and for understanding certain language disorders such as dyslexia or autism. According to Alexander Huth, the first author of the study, "[t]his is the first time that we've been able to understand language and its meaning. this approach could also be used to decode information about how words are understood, about the process of reading, or perhaps even of thinking ». One potential use would be a language decoder that could allow people silenced by illness to speak through a computer.
 
 
Admittedly, this study is for the moment limited to showing the anatomy of the brain in action. We do not yet distinguish physiologically between the functional aspects. Jack Gallant thus tells our colleagues of Popular Science : " In neuroscience we know a lot about brain anatomy, about individual synapses, but what we really want to know is function. The combination, he says, is the key to truly understanding the brain... ".
 
Nonetheless, this study has been praised by the neuroscience community. Uri Hasson of Princeton University says that, unlike other studies that have looked at brain activity, when an isolated word or phrase was said, Gallant's team shed light on how the brain worked in a real-world scenario. The next step, he predicts, will be to create a more complete and accurate semantic brain atlas. Ultimately, Hasson believes it will be possible to reconstruct the words a person thinks about simply by observing brain activity. The ethical implications are enormous. Imagine using such technology in the political arena to sharpen speech so that words go to the right brain areas of citizens. « There are so many consequences, and we can barely see the surface... "he added.
 
 
 

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