MRPG: FMRI Studies on Language and Task Switching in Spanish-English Bilinguals

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

How do bilinguals select the appropriate language? Some have suggested that selection of the appropriate language involves some sort of functional switching mechanism. However, the question remains whether this switching mechanism is specific to switching across two languages, whether the same mechanism is used in switching within one language, or whether it is an instance of a general switching mechanism that is used across any cognitive domain. This project will address that question by investigating language switching and task switching in bilinguals. Switching is a fundamental process that is necessary when one has to disengage from one activity to engage in another. This process requires executive function, a form of focused attention that helps one to manipulate information temporarily. Although these processes are fundamental, they are also very fragile. Damage to the frontal lobes, either through dementia, normal aging, or stroke, leads to a reduction in executive function and consequently in the ability to switch between tasks and between languages. This research will use functional Magnetic Resonance Imaging (fMRI) to investigate the neural substrates responsible for switching in bilinguals across two languages, within a single language, and with a non-verbal task. Previous neuroimaging studies have documented the role of the dorsolateral prefrontal cortex and other associated areas (the supplementary motor area, and the posterior parietal lobe) in executive function. In addition, previous studies by Hernandez have found increased activity in these same areas when switching between two languages. The findings of this research are expected to parallel previous results. Specifically, switching, relative to not switching, will reveal activation in the dorsolateral prefrontal cortex, supplementary motor area, and the posterior parietal lobe. Furthermore, the results will demonstrate whether the increased activation when switching across all three tasks involves the same neural structures. In a second experiment, event-related fMRI will be used to look more closely at switching into the dominant language relative to switching into the non-dominant language. It is predicted that activation in the dorsolateral prefrontal cortex, the supplementary motor area, and the posterior parietal lobe will be larger when switching into the non-dominant language. The results from this project may confirm further the notion that executive function is necessary for switching across domains. Furthermore, it may also confirm that level of executive control depends on the fluency in the language. This approach will also help to further elucidate whether selective access involves neural structures that are general to any cognitive domain. As a Minority Research Initiation project, this research will aid Hernandez in expanding his expertise in neuroimaging. Furthermore, it will provide both graduate and undergraduate students in his laboratory with additional training in cognitive neuroscience.