How Adults Learn a Second Language: A Neurolinguistic Analysis of Brain Localization

Özet

The current study aims to investigate brain localization in the process of adult second language learning from an interdisciplinary point of view. It is believed that the knowledge of how the second language learning process works in the brain will contribute to lecturers studying second language teaching. This research was carried out on a sample of ten English-native speakers who underwent a six-month intensive Turkish as a second language program from initial exposure to high proficiency. A word task, a word/sentence-picture matching task, and a grammar violation task were used to evaluate the progress of language proficiency. In accordance with this purpose, the fMRI technique was used. Brain activity was observed in regions linked to the processing of the first language, including Broadmann Area (BA) 45/47. Additionally, activation was reported in the parietal cortex for lexical and semantic processing, and in BA44 and 6 for grammatical processing. These findings indicate that mature second language learners are able to utilize sections of the brain related to their first language. Additional areas were activated, indicating that first language mechanisms are insufficient for second language learning and processing. For both vocabulary and grammar, hippocampal activation was observed during the early phases of learning. Grammar-related basal ganglia activation was observed in the caudate nucleus during later phases. The findings suggest that the acquisition of vocabulary and grammar in the early stages is dependent on declarative memory, whereas the mastery of grammar in later stages is dependent on procedural memory. These results highlight the importance of integrating neural and behavioral methods in second language research.