Investigating the Neurofunctional Bases of Reading in the Spanish-English Bilingual Brain

Abstract

Dual-language use from early stages in life is the experience of over half of the world’s population. This experience is becoming more prevalent worldwide, even in countries that predominantly use one language as the official method of communication. Yet, little is known about whether this lifelong experience with two languages rather than one modulates the neurofunctional foundations that support language, including written language. Of particular interest from the perspectives of neurodevelopment and learning is to better understand the functional brain bases of reading in the context of bilingualism and biliteracy. Specifically, while there has been substantial research into characterizing the brain regions involved in reading, this work has largely been limited to monolinguals. These studies have shown that word reading is predominantly supported by a functional brain system formed by the occipito-temporal, temporo-parietal, and inferior frontal cortices in the left hemisphere. Further, some studies have shown that activity in these areas is modulated by language experience, specifically bilingual versus monolingual backgrounds; and, other studies have focused on the influence of languages with different orthographic depth. Therefore, the first study examined whether bilingual experience modulates the brain system for English word reading, by comparing bilinguals to monolinguals. The second study addressed whether English versus Spanish word reading, given their differences in orthographic depth, rely on different functional systems in bilinguals. Brain activity, functional connectivity, and spatially distributed activity patterns were measured with functional magnetic resonance imaging during single-word reading in Spanish-English bilingual and English monolingual adults. In the first study, it was revealed that while bilingual experience does not have an effect on local activity during English word reading, it does modulate functional connectivity. In the second study, we found that while reading in two languages with different orthographic depth does not require different local activity and functional connectivity between regions of the brain system for reading, there were distinct patterns of neural representations for English and Spanish. Taken together, the results demonstrated the influence of lifelong bilingual experience on the neurofunctional intercommunication supporting English word reading, and the bilingual brain’s representation of two languages differing in orthographic depth.