It's a lesson that many language learners have learned the hard way: while words in a familiar language are distinguishable, words in an unfamiliar language are often difficult to separate because they blur together into a single sound. But why is it so easy for the brain to distinguish between words in one language and so difficult to distinguish between them in another? Does it have to do with your brain or with the language itself?
According to two parallel studies published in Nature And Neuronthe difference is all due to experience. Focusing on an area of the brain's temporal lobe called the superior temporal gyrus (STG), two studies show that specialized STG neurons learn to recognize the beginning and end of words over time, after years of exposure to a given language.
“This shows that the STG doesn't just hear sounds, it uses experience to identify words as they are spoken,” said Edward Chang, co-author of two studies and a neuroscientist at the University of California, San Francisco, according to the study. statement. “This work gives us a neural blueprint for how the brain converts continuous sound into meaningful units.”
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Familiar and unfamiliar languages
When we listen to a familiar language, we easily distinguish the beginning and ending of words, even if there are almost no words. It has long been theorized that the STG was not involved in this discrimination. In fact, this area was once thought to be involved in only basic sound processing, including the isolation of consonant and vowel sounds.
Testing this theory, Chang and a team of researchers recorded the brains of several participants as they heard excerpts from both. familiar and unfamiliar languages. The results showed that the brain actually learns language patterns in unexpected places over time, and STG neurons gradually become more experienced at distinguishing words.
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Neurons listen and learn
We are gathering a group of 34 participants for Nature In the study, the researchers worked with both monolingual and bilingual people, 26 of whom spoke English, Spanish, or Chinese, and eight of whom spoke English and Spanish.
By recording their brain activity as they listened to snippets of speech in all three languages, and analyzing the recordings using machine learning models, the researchers determined that specialized neurons in the STG behaved differently. depending on the language the participants heard – became active when listening to a familiar language, and remained inactive when listening to an unfamiliar one.
“This explains a little bit about the magic that allows us to understand what someone is saying,” said Ilina Bhaya-Grossman, co-author of the two studies and a Ph.D. According to the statement, a student at the University of California, San Francisco.
We begin and end with words
IN Neuron Meanwhile, the researchers recruited a total of 16 participants and turned to brain recordings to demonstrate that these specialized neurons in the STG are activated and deactivated in time with the beginning and end of words, turning on and off as a way of breaking up speech into smaller components.
“It's a kind of reset where the brain has processed a word it recognizes and then resets to move on to the next word,” said Matthew Leonard, co-author of the two studies and a neuroscientist at the University of California, San Francisco, according to the statement.
By providing insight into the importance of language learning and clarity on the distinctive issues that differentiate the language learning process in early and late life, the study also contextualizes why STG injuries can cause such significant damage to an individual's language processing abilities.
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