Experience-dependent neuroplasticity in the hippocampus of bilingual young adults

Abstract

Models of experience-dependent neuroplasticity predict that the acquisition and extensive use of a new skill trigger a nonlinear trajectory of neurostructural modifications, where initial expansion of relevant brain areas subsequently (once the skill is acquired) gives way to volumetric re-normalization. Such predictions also apply in the domain of language during learning and/or simultaneous management of two (or more) linguistic systems. In a sample of 69 young adult Russian-English bilinguals, we tested the hypothesis that individual differences in bilingual engagement non-linearly correlate with normalized volume of the hippocampus – a key learning-related brain region particularly amenable to experience-dependent plasticity. Results revealed an inverted-U shape association between second language engagement and left hippocampal gray matter volume. The present results replicate and expand the findings from aging populations, showing a non-linear pattern of structural hippocampal plasticity in healthy young adults. These findings support the role of bilingualism as a promoter of experience-dependent neuroplasticity.