Neural correlates of cognitive processing in monolinguals and bilinguals

Abstract

Here, we review the neural correlates of cognitive control associated with bilingualism. We demonstrate that lifelong practice managing two languages orchestrates global changes to both the structure and function of the brain. Compared with monolinguals, bilinguals generally show greater gray matter volume, especially in perceptual/motor regions, greater white matter integrity, and greater functional connectivity between gray matter regions. These changes complement electroencephalography findings showing that bilinguals devote neural resources earlier than monolinguals. Parallel functional findings emerge from the functional magnetic resonance imaging literature: bilinguals show reduced frontal activity, suggesting that they do not need to rely on top-down mechanisms to the same extent as monolinguals. This shift for bilinguals to rely more on subcortical/posterior regions, which we term the bilingual anterior-to-posterior and subcortical shift (BAPSS), fits with results from cognitive aging studies and helps to explain why bilinguals experience cognitive decline at later stages of development than monolinguals.

Keywords: EEG; bilingualism; brain function; brain structure; fMRI.

Figure 1

The bilingual anterior-to-posterior and subcortical shift (BAPSS). (A) Regions showing expansion of gray and white matter with L2 acquisition. (B) Hypothetical functional recruitment of frontal regions in response to task demand by language group and age. (C) Shift of functional recruitment from frontal to posterior and subcortical regions with L2 learning. Early frontal recruitment (red) gives way to posterior and subcortical regions at later stages of L2 acquisition (blue). (D) Hypothetical shift from controlled (late) to automatic (early) processes with L2 learning. This shift is indicated by the red lines. CC, corpus callosum; ACC, anterior cingulate cortex; DLPFC, dorsolateral prefrontal cortex; BG, basal ganglia; OL, occipital lobe; OA, older adult; YA, younger adult; ERN, error-related negativity.