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

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PROJECT SUMMARY/ABSTRACT In the field of bilingualism there has been a recent shift towards investigating how the lifelong act of managing two languages may benefit bilingual individuals in aging1 and in the face of clinical neuropathology.2- 4 This vein of research is motivated by the idea that managing two or more languages requires engagement of various control processes5,6 potentially leading to more efficient execution of domain-general cognitive control, which in turn contributes to greater cognitive reserve. Determining the factors that contribute to a behavioral advantage for bilinguals as compared to monolinguals in the face of comparable clinical neuropathology requires careful consideration of the constructs being examined as well as the underlying neural activation associated with behavioral performance. Furthermore, a critical concern when examining executive functioning in particular surrounds the ecological validity of results. Using imaging modalities that allow for completing tasks in naturalistic environments (e.g., functional near-infrared spectroscopy (fNIRS) and electroencephalography (EEG)) as opposed to laying supine in a scanner (e.g., functional magnetic resonance imaging (fMRI)) increases the ecological validity of results and allows for more robust interpretation and generalizability of results.7 Therefore, the goal of this study is to examine behavioral (accuracy and reaction time measures) and neural (fNIRS and EEG) responses across two patient (monolingual (MPWA) and bilingual (BPWA) patients with aphasia) and two healthy control (bilingual (BHC) and monolingual (MHC)) groups on cognitive control tasks, to disambiguate which components of executive functioning (e.g., shifting, inhibiting, and/or updating)8,9 are impacted by bilingualism and how this may translate to a cognitive reserve factor in aphasia. Aim 1: examines group differences in behavioral performance on three non-verbal cognitive control tasks between bilinguals and monolinguals across patient and healthy control groups. Aim 2: examines group differences in fNIRS hemodynamic response function (HRF) during non-verbal cognitive control tasks between bilinguals and monolinguals across patient and healthy control groups. Aim 3: examines group differences in EEG frequency band power during non-verbal cognitive control tasks between bilinguals and monolinguals across patient and healthy control groups. Results of this study will provide evidence of the impact of bilingualism on behavioral and neural performance and elucidate how bilingualism serves as a cognitive reserve factor in aphasia. The design of this study can be used as a framework for an ecologically valid investigation of the behavioral and neural dynamics underlying performance on cognitive tasks across bilinguals and monolinguals in neurotypical and clinical populations.