THE RELATIONSHIP AMONG GRAY MATTER CORTICAL THICKNESS, ACTIVITY, AND BILINGUAL BACKGROUND VARIABLES

A bilingual person’s brain has to manage two languages. According to psycholinguistic models, lexical representations of the two languages are always active and to select the correct language, the other has to be inhibited (Green, 1998). This includes cognitive control processes (e.g. language planning, response inhibition, maintenance of representation) that might require additional brain networks beyond those classically involved in language processing. Regions such as prefrontal, anterior cingulate cortices, inferior parietal lobule, and caudate have been found to be involved in cognitive control processes (Abutalebi & Green, 2007). The present study examined whether or not bilingual experience shapes the structure and function of the brain by examining relationships among language proficiency, second language age of acquisition, and structural and functional correlates. Participants were 49 Spanish-English bilinguals who learned English between the ages of 0 and 17 years. Cortical thickness measures as well as functional activity during a picture-naming task requiring switching between the two languages on a trial-by-trial basis were acquired using a functional Magnetic Resonance Imaging scanner. The results indicate that age of acquisition of the second language but not proficiency is related to gray matter structure in the right dorsolateral prefrontal cortex, a cognitive control region and that gray matter cortical thickness is related to functional activity during a condition that requires switching in naming pictures between two languages. These results carry implications for the understanding of how language experience shapes the functional and neural correlates of the bilingual brain.