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Poster E63, Friday, November 10, 10:00 – 11:15 am, Harborview and Loch Raven Ballrooms

A dynamic causal modeling analysis of the role of the caudate nucleus and prefrontal cortex in bilingual language control

Roy Seo1,2, Jose M. Ceballos1,2, Brianna L. Yamasaki1,2, Chantel S. Prat1,2;1Department of Psychology, University of Washington, 2Institute for Learning and Brain Sciences, University of Washington

Bilingual language control is characterized by the information processing demands associated with dynamically selecting from co-activated languages based on the appropriate language context. Previous research suggests that this is accomplished in part using general cognitive control mechanisms including the anterior cingulate cortex (ACC: Abutalebi, et al., 2011), the left dorsolateral prefrontal cortex (DLPFC: Hernandez, Martinez, & Kohnert, 2000) and the left caudate (Crinion et al., 2006). To better understand the role of each of these regions in bilingual language control, we employed a novel, Rapid Instructed Task Learning (RITL) task, which separated the process of bilingual language control into three phases. In the first, preparation phase, a target language cue indicated which language participants were to use. In the second, rule-encoding phase, a morpho-syntactic cue indicated the relevant morpho-syntactic rule for that trial. Lastly, during the execution phase, participants were required to apply the morpho-syntactic rule provided in phase 2, in the target language provided in phase 1, to the word provided in phase 3. Twenty-three early Spanish-English bilinguals performed the RITL task in an MRI scanner. Previous research using ROI analyses of the ACC, DLPFC and left caudate revealed that the ACC activation was only significant during the preparation phase; whereas activation in the DLPFC and left caudate was observed across all three task phases. Activity in the DLPFC increased over the course of the three task phases; however, activity in the left caudate remained constant across the course of the trial. The current analysis followed up on these findings using Dynamic Causal Modeling (DCM) to examine the extent to which the processes in DLPFC and caudate were cumulative (i.e., processing in phase 1 was maintained and added to processing in phase 2) versus phase-specific (i.e., processing in each phase was unique). DCM was used because it allows for hierarchical, non-orthogonal modeling of data where general linear modeling does not. The results revealed that the best fitting model was the non-cumulative model, with exceedance probabilities of .69 compared to the exceedance probabilities of the phase-specific model, which was .31. These results extend previous research by suggesting that the ACC, DLPFC, and caudate each contribute to bilingual language control, and contribute uniquely during target-language preparation and execution phases. Hernandez, A. E., Martinez, A., & Kohnert, K. (2000). In search of the language switch: An fMRI study of picture naming in Spanish–English bilinguals. Brain and Language, 73(3), 421-431. Abutalebi, J., Della Rosa, P. A., Green, D. W., Hernandez, M., Scifo, P., Keim, R., ... & Costa, A. (2012). Bilingualism tunes the anterior cingulate cortex for conflict monitoring. Cerebral Cortex, 22 (9): 2076-2086. Crinion, J., Turner, R., Grogan, A., Hanakawa, T., Noppeney, U., Devlin, J. T., ... & Usui, K. (2006). Language control in the bilingual brain. Science, 312(5779), 1537-1540.

Topic Area: Multilingualism

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