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Poster F in Poster Session F: Thursday, August 6, 1:45 – 3:30 pm, Kimmel Center, Shorin & Rosenthal Rooms

Shared neural geometries for bilingual semantic and grammatical representations in human hippocampal neurons

Xinyuan Yan¹, Ana G. Chavez¹, Mellisa Franch¹, Vigi Katlowitz¹, James L.Belanger¹, Taha Ismail¹, Assia Chericoni¹, Elizabeth Mickiewicz², Hanlin Zhu¹, Eleonora Bartoli¹, Nicole Provenza¹, Benjamin Y Hayden¹, Sameer A. Sheth¹; ¹Baylor College of Medicine, ²Pennsylvania State University

Presenter: Xinyuan Yan

The human brain has the remarkable ability to comprehend and express similar concepts in multiple languages. To understand how it does so, we examined responses of hippocampal neurons during passive listening, directed speaking, and spontaneous conversation, in both English and Spanish, in a small group of balanced bilinguals. We find a small number of putative cross-language neurons, whose responses to equivalent words (e.g., “tierra” and “earth”) are correlated. However, neurons’ semantic tunings differed substantially by language, suggesting language-specific neural implementations. Instead, the crucial driver of translation was a preserved geometric organization of neural responses between the two languages, one that did not depend on neuron level functional overlap. Indeed, that geometry was implemented by a common set of neurons along distinct readout axes; this difference in readout may help prevent cross-language interference. Beyond word-level semantics, shared neural geometry also extended to grammatical categories, with parts of speech encoded in a language-invariant geometric structure. Together, these results suggest that hippocampus encodes a language-independent internal model for meaning and grammatical structure.

Topic Area: Memory, Learning & Knowledge Structures