Bilingualism as a cognitive reserve factor: The behavioral and neural underpinnings of cognitive control in bilingual aphasia

The primary goal of this project is to investigate if the lifelong act of being bilingual provides greater reserve against brain damage in post-stroke aphasia. Broadly, the concept of reserve refers to the discrepancy between brain pathology–such as age-related atrophy, tau or β-amyloid accumulation, or stroke lesions–and behavioral symptoms, where people with greater reserve are able to sustain greater amounts pathology while maintaining higher cognitive functioning. Research from the past few decades has provided clear evidence that individual differences in reserve can be explained by various factors including genetics, environment, lifestyle habits, and personal experiences, with recent findings pointing to bilingualism as another life experience that contributes to greater reserve in aging in dementia. It remains unclear, however, whether bilingualism also contributes to better outcomes in post-stroke aphasia. To investigate this outstanding question, 15 bilinguals with aphasia (BWA), 15 monolinguals with aphasia (MWA), 15 age-matched bilingual healthy controls (BHC), and 15 age-matched monolingual healthy controls (MHC) will complete two non-linguistic cognitive control tasks while undergoing functional brain imaging. The cognitive control tasks will examine monitoring performance through an N-Back task and shifting abilities via a task-switching paradigm. The functional brain imaging will collect task-based hemodynamic responses using functional near-infrared spectroscopy (fNIRS) and task-based electrophysiological responses using electroencephalography (EEG). It is anticipated that bilingual participants will display higher behavioral performance (i.e., accuracy and reaction times) on cognitive control tasks than monolinguals and the difference in performance will be more pronounced in patient groups when controlling for lesion size. Furthermore, we expect that bilingual participants will demonstrate greater neural efficiency during cognitive control tasks, indexed by smaller increases in fNIRS and EEG signals, when progressing from easy to hard conditions. This work will shed light on how life experiences may contribute to better outcomes in post-stroke aphasia and may provide insight into how people can maintain better overall brain health and improve neuroplastic potential during aging. It also has the potential to enhance therapeutic interventions that help to prevent the onset and severity of symptoms for people who are at risk for neurological disorders and optimize behavioral recovery or maintenance of function for people with neurological disorders.