Abstract/Summary

Current research suggests that bilingualism affects both the structure of the brain and several cognitive processes. However, few studies have specifically examined effects of individual differences in bilingual language use on domain-general control processes and their neural correlates. This thesis project assesses the hypothesis that specific language use factors within the bilingual experience will alter neural activity and plasticity in regions implicated in language/executive control. Three studies are run. The first study is longitudinal, examining effects of long-term linguistic immersion on neural plasticity in highly proficient non-native (L2) speakers of English. Data from this study shows adaptations in brain structure related to increased efficiency of language processing and control and modulated by the length of L2 use prior to the study. The second and third studies are cross-sectional, examining effects of specific language use factors on 1) neural structure and intrinsic functional connectivity and 2) performance and neural activation patterns on executive function tasks. Factors related to duration of L2 use correlate to neurocognitive adaptations suggesting increased efficiency in language control. Factors related to extent of L2 use correlate to neurocognitive adaptations suggesting increased language control demands. Considered together, the data suggest that the brain constantly strives to be maximally effective and efficient in language processing control, which in turn affects domain-general cognitive processes. Crucially, the data highlight the necessity of considering specific, individual language experiences in assessing neurocognitive effects of bilingualism.