For many bilingual people, switching between languages feels effortless. Now, scientists have figured out how bilingual brains accomplish this feat at the single neuron level.
In a study publishing on June 24 in the Cell Press journal Cell , researchers reveal that bilingual brains store concepts in a mental map that spans both languages. Using language-specific neurons to read the multilingual map, the brain can switch languages smoothly while also keeping them distinct.
“This is the very first study to look at how bilingual brains work at the level of individual neurons, and to do so in real time,” says first author Xinyuan Yan of the Baylor College of Medicine in Houston.
Being bilingual herself, Yan has always been curious about how the brain processes different languages. “The brain must have an internal model for representing words. There are roughly 7,000 different languages in the world, so this model would form the basis for our shared understanding of the world.”
Previous studies suggest that certain brain regions respond similarly when bilingual people hear equivalent words in different languages. But those studies did not show how the brain organizes individual words within each language or how it connects equivalent meanings across languages.
The researchers had the rare opportunity to work with four English-Spanish bilinguals who have been speaking both languages from an early age and were equally comfortable using both. All participants were people with epilepsy and who have electrodes implanted in their brains as part of their treatment for the condition.
The team recorded the participants’ brain activity while they listened, read, and conversed in English and Spanish. To the researchers’ surprise, only a few neurons in the hippocampus responded equally when the participants heard or spoke the same word in different languages, such as “dog” and “perro.” This suggests that individual neurons are largely language specific, say the researchers.
The team also observed that the brain places words onto a “map,” made up of a group of these language-specific neurons, and organized them according to the word’s meaning. Within the map, words like “dog” and “wolf” that are closely related, for example, sit near each other. “Fork,” which is semantically distant from the two animals, is located much farther away. This mapping system was consistent across languages.
“This is how the brain encodes the meaning of words across languages,” Yan says. “It doesn’t rely on individual neurons translating individual words, but groups of neurons adjusting their activities to create the similar pattern for equivalent words in both languages.”
To test just how deeply the two languages shared the same semantic map, the team tried to predict the location of a Spanish word on the map using the English map. By analyzing how neighboring concepts around “dog” were organized, the researchers were able to accurately predict the location of “perro” in the Spanish neuron map.
“It’s like looking into a room from a different window. Everything inside is the same, but the perspective is different,” says senior author Sameer Sheth of the Baylor College of Medicine. By reading the semantic map from different angles, the brain can use different languages without confusion, he adds.
The researchers also compared the finding to a large language model called mBERT, which is trained to understand more than 100 languages. They found that mBERT also mapped out the relationships among words in a semantic map across languages, closely resembling the hippocampus.
“Our study shows that the brain is wired to learn multiple languages,” says senior author Benjamin Hayden of the Baylor College of Medicine. “Once it maps relationships among words, it can apply those same relationships across languages. We all have the potential to become bilingual, or even trilingual.”
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This work was supported by the McNair Foundation, the National Institutes of Health, the SNS Allan Friedman RUNN Research Grant, The National Library of Medicine, the Gordon and Mary Cain Pediatric Neurology Research Foundation, and the National Research Foundation of South Korea.
Cell , Yan et al., “Shared neural geometries for bilingual semantic representations in human hippocampal neurons” https://www.cell.com/cell/fulltext/S0092-8674(26)00579-9
Cell ( @CellCellPress ), the flagship journal of Cell Press, is a bimonthly journal that publishes findings of unusual significance in any area of experimental biology, including but not limited to cell biology, molecular biology, neuroscience, immunology, virology and microbiology, cancer, human genetics, systems biology, signaling, and disease mechanisms and therapeutics. Visit: http://www.cell.com/cell . To receive Cell Press media alerts, contact press@cell.com .
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Shared neural geometries for bilingual semantic representations in human hippocampal neurons
24-Jun-2026