UC Riverside

In the past two decades, there has been a surge of attention given to the study of bilingualism. Much of this interest has centered around trying to understand whether the continual act of selecting and controlling multiple languages can provide domain-general benefits to other aspects of cognition, particularly those that involve inhibitory processes. While most of this research has focused on testing bilinguals’ abilities to suppress prepotent responses or ignore perceptual distractors, very little attention has been given to bilingual performance on tasks that involve inhibiting irrelevant memory traces in order to focus attentional resources on more relevant to-be-remembered information – otherwise known as resistance to proactive interference (PI). In addition, more recent research has suggested that being bilingual might provide cognitive preservation in the face of neural atrophy (cognitive reserve) or neural enhancement that maintains cognition (brain reserve). Therefore, the present study sought to determine whether being bilingual does in fact provide benefits and/or preservation to resistance to PI performance and brain structure in the regions important for resistance to PI abilities. Eighty-two younger and older adult participants, half of whom were English monolinguals and half were highly proficient Spanish-English bilinguals, participated in this study. They completed directed forgetting and release from PI tasks and underwent an MRI scan that captured indices of both cortical structure and white matter integrity. The results indicated that while bilinguals and monolinguals did not differ in their behavioral performance, the bilinguals displayed thinner cortex in resistance to PI-related regions (cognitive reserve) and showed significant positive relationships between white matter integrity and resistance to PI task performance (brain reserve). In addition, certain aspects of Spanish proficiency and use predicted better performance on the resistance to PI tasks among the bilinguals, indicating that knowing a second language does provide some protective effect to cognition. Importantly, this study is the first of its kind to demonstrate both cognitive reserve and brain reserve in different indices of brain structure within the same participants and shows that being bilingual supports important structural relationships between the brain regions necessary for inhibition, memory, and language.