Understanding the Bilingual Advantage: Dual Mechanisms of Cognitive Control

Abstract

Event Abstract Back to Event Understanding the Bilingual Advantage: Dual Mechanisms of Cognitive Control Tanya Dash1*, Pierre Berroir1, Ladan Ghazi-Saidi2, Daniel Adrover-Roig3 and Ana Inès Ansaldo1 1 Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal (CRIUGM), Canada 2 University of Nebraska at Kearney, United States 3 University of the Balearic Islands, Spain Bilingualism has been associated with an age-related cognitive advantage (1,2). In comparison to monolinguals, bilingual speakers show an added advantage in managing interference (1,3,5,8). An interesting way to study cognitive control is by performing analysis of the response time distribution. Based on the temporal dynamics of the cognitive control mechanism, Braver (4) proposed a “dual mechanism of control (DMC),” which consists of two modes of cognitive control: proactive and reactive. Within a response time distribution, the slow responses reflected reactive control mechanisms and the fast responses proactive control mechanisms (4). The current study provides a methodological innovation to highlight strategy differences between bilingual and monolingual elderly populations. The goal of this research was to gain an in-depth understanding of the behavioral implications of the cognitive control mechanism by breaking performance on an executive control task down into its constituents, and thus to examine the DMC framework (4) and to dissociate the reactive and proactive modes of control by directly comparing their behavioral and neural signatures. Native-French monolinguals (n = 10; mean age = 74.5 years) and French-English bilinguals (n = 10; mean age = 74.2 years) participated in the study. They completed the experimental protocol, which consisted of an interview schedule (LEAP-Q), the experimental task (Simon task inside the MRI scanner) and a linguistic and neuropsychological assessment battery. In line with previous studies (6,7), we examined Response Time (RT) distribution, by studying the fast (Fast RTs) and slow response times (slow RTs) across conditions for each participant (9). A mixed ANOVA with Language group (Monolinguals and Bilinguals) as the between-subject factor and Trial (Slow RTs and Fast RTs) and Condition (Congruent, Neutral and Incongruent) as the within-subject factors was done. For the fMRI analysis, image preprocessing was performed using SPM12 following standard procedures. The design matrix consists of two groups (Monolinguals, Bilinguals), three conditions (Congruent, Incongruent and Neutral), and two trial types (Fast RTs, Slow RTs). A t-test (K ≥ 20, p ≤0.001) was conducted on the contrast images of interest. In addition, functional connectivity analysis was done using a small-world approach (2). Behavioral data indicated differences between the groups only on the slow RTs, indicating a group difference for the congruent (monolinguals > bilinguals; p = .00) and incongruent conditions (monolinguals > bilinguals; p = .00). The fMRI results show that the bilinguals performed efficiently in a proactive mode, as less activation and degree of node distribution were observed for the bilinguals, whereas monolinguals showed less activation of the brain areas in reactive mode, which they use more often because of aging. There is evidence that with age, individuals depend more on the reactive control strategy for performance and the proactive control strategy is more vulnerable to cognitive aging (6). Thus, the lifelong use of two languages protects the proactive control strategy. The study adds to the debate regarding the existence and possible mechanism of the effect of bilingual language experience on cognitive function with aging. Acknowledgements We thank the Canadian Institutes of Health Research (CIHR) for funding, along with the Fonds de recherche du Québec – Santé, Government of Quebec for post-doctoral fellowship (to T.D.).