| Bilingualism can serve both as a means for studying general cognitive and linguistic processing and as an end in itself for understanding how the human brain accommodates more than one language at the same time. The present research integrates behavioral and neuroimaging data to examine how bilingual speakers process linguistic input. The population of interest consists of fluent, balanced Russian-English bilinguals who acquired their second language post-puberty. The first part of the dissertation reports four experiments in which spoken language processing was studied at the lexical and sub-lexical levels using bilinguals' eye movements. Results suggest that, during spoken language processing, bilinguals may activate both languages in parallel, experiencing between-language competition even when linguistic input is in one language only. In addition, similar to monolinguals, bilinguals showed within-language competition from items in the same language. In instances of simultaneous competition from both languages, within-language competition was stronger than between-language competition. The second part of the dissertation reports four comparisons in which cortical activation during bilingual language processing was examined throughout the processing stream: at the semantic level, at the lexical level, and at the orthographic and phonetic levels. Results of the functional magnetic resonance imaging study suggest that language processing is not limited to the left hemisphere, but also involves the right hemisphere. The areas active during first and second language processing included the Inferior Frontal Gyrus, the Superior Temporal Gyrus, the Middle Temporal Gyrus, the Precentral Gyrus, the Angular Gyrus, the Supramarginal Gyrus, and the Extrastriate cortex. Although both languages activated the same cortical areas, different centers of activation were observed in the left Inferior Frontal Gyrus for first versus second language processing. In addition, the second language activated a larger cortical surface than the first language in all four comparisons. By complementing behavioral evidence from eye tracking with cortical evidence from functional neuroimaging, this work provides a more complete understanding of bilingual language processing. It argues for parallel processing of the two languages and shows important differences and similarities between the processing of the two languages at the cortical level. |
