Abstracts

Rationale: When language function is lost after surgical treatment by fiber tract damage, such as corpus callosotomy and hemispherotomy, plasticity of brain allows patients to regain language function. To study the mechanisms of recovery, we assessed the language function of a Japanese bilingual patients using functional Magnetic resonance imaging (MRI) and tried to clarify the plasticity related areas through assessment of activated areas with tasks specific for the second language. Methods: There were 22 bilingual (Japanese and English) speakers, aged from 19 to 49 years, divided to three groups according to the age of learning the second language : Early group (0 to 6 years), Midterm group (6-12 years), Late group (after 12 years). MRI equipment was PHILIPS Achieva 3.0T TX. Tasks consisted of hearing a short story in Japanese (Issunboshi) and English (Peter Rabbit). Activated area was assessed by comparison of BOLD oxygenation levels dependent in hearing tasks and reverse play. Data analysis was performed using MATLAB (MathWorks) and SPM (Statistical Parametric Mapping). We focused on Broca's area, Wernicke's area and premotor cortex. Results: There were 11 bilinguals in the Early group, 6 in the Midterm group and 5 in the Late groups. Hearing the Japanese story, only Wernicke's area was activated in 7 bilinguals in Early group, 2 in Midterm group and 3 in Late group. On the other hand, hearing the English story, 4 in Early group, 1 in Midterm group and 0 in Late group had that activation. However, hearing the English task, all focused areas were activated in 0 of the Early group, 5 in the Midterm group and 4 in the Late group. Conclusions: This study demonstrates that broad areas including motor and sensory language areas are activated when hearing immature language and become localized to Wernicke's area through maturing. It's suggested that Broca's area, premotor cortex and other areas are necessary for maturing and plasticity of language. Funding: nothing