The proposed project is designed to investigate the effects of age and a gene associated with striatal dopamine play on a set of cognitive and language control tasks in a group of Spanish-English bilinguals. To achieve this, the proposed project will use functional Magnetic Resonance Imaging (fMRI), which measures neural activity indirectly via changes in deoxyhemoglobin which is correlated with blood flow and energy metabolism. Work in many laboratories including our own has identified the brain areas involved in cognitive and language control in bilinguals. However, recent work on a putative advantage in bilinguals has led for calls to abandon any further study of cognitive control in this population. Furthermore, recent studies suggest that differences in the ability to perform nonverbal cognitive control tasks also exist within the bilingual population. Finally, this difference may also be involved in language control. One factor that has not received much consideration in this literature is the nature of genetic differences that might moderate this effect. Independent studies with single language speakers have found an advantage on nonverbal switching tasks for carriers of the A1 allele of the ANKK1 taq1A polymorphism. These individuals have reduced dopamine D2 receptors, show a decrease in switching costs, and have decreased activity in neural areas devoted to cognitive control. A group of old and young adult bilinguals will be screened for their genetic makeup. Comparisons between young and older adult bilinguals will be performed to investigate whether age interacts with carrier status of the ANNK1 gene influences neural activity during tasks involving cognitive and language control. The results from the proposed studies will serve to extend studies conducted in my laboratory using the DRD2 to an aging population. By doing so we hope to elucidate the extent to which aging and striatal dopamine may play a role in bilinguals? ability to flexibly adapt between languages. The results of these studies should serve as the springboard for future studies with older adults that can investigate the extent to which bilingualism may serve as a protective factor against changes in cognitive control due to genetic differences. They may also help to further elucidate the role of individual genetic and language experience differences in the neural activity associated with cognitive control.
The proposed project is designed to investigate how aging and genetic status (carriers or noncarriers of the DRD2 gene) affect the neural activity observed when performing cognitive and language control tasks. The results from these studies should help to break new ground by informing researchers, educators and clinicians about the ways in which individual genotypic differences differentially affect the ability to flexibly adapt between languages and/or tasks when comparing young and older adult bilinguals.
