Cortical Thickness in the Cognitive Control Network, Task Switching, and Bilingualism

Previous research involving patients with brain damage, children with ADHD, aging adults, Alzheimer’s patients, and normal monolingual children and adults suggests that cortical thickness in certain regions of the brain, specifically the dorsolateral prefrontal cortex, anterior cingulate cortex, inferior parietal lobule, and inferior frontal gyrus, is related to cognitive control abilities. For each of these groups, greater cortical thickness in these regions is associated with better cognitive control, and lesser cortical thickness is associated with poorer cognitive control. Surprisingly, researchers have not yet examined this relationship within the bilingual population, although bilinguals have sometimes demonstrated enhanced cognitive control abilities. Additionally, previous research by Della Rosa et al. (2013) and Mechelli et al. (2004) suggests that greater grey matter density in one of these regions, the inferior parietal lobule, is related to earlier age of second language acquisition, higher second language proficiency, and better overall language skills. Therefore, in order to fully understand the relationship between cortical thickness and cognitive control, it is important to examine the relationship between cortical thickness in the aforementioned regions and performance by bilinguals on a cognitive control task. This study measured cognitive control using a non-verbal switching task in which participants switched between sorting images by color and sorting images by shape as indicated by a symbolic cue. Results indicate that, in this bilingual sample, cortical thickness of the right and left inferior parietal lobules differentially correlate with response time costs and accuracy costs as a result of switching tasks. These findings shed light on the relationship between cognitive control and language in the brain.