中英雙語兒童靜息態功能性連結發展變化

Abstract

本縱貫研究探討學齡初期兒童大腦語音處理網路的內在功能網絡及其發展軌跡與中英雙語學習經驗之關係。由於中文與英文在文字與語音對應方式不同，中英雙語兒童可能發展出不同於中文單語兒童的神經功能網絡。過去研究發現，相較於單語兒童，雙語兒童在中文語音處理時，較傾向使用背側語言路徑，且右腦有較強的活化，但雙語經驗如何形塑大腦內在功能連結及其與語音能力發展的關係，仍缺乏縱貫研究證據。本研究於小學一年級及三年級縱貫追蹤40名中英雙語兒童與30名中文單語兒童之聲韻覺識能力變化，並同時以功能性近紅外光譜技術 (fNIRS) 測量靜息態功能性連結 (resting-state functional connectivity, RSFC)。分析結果顯示，雙語與單語兒童於右側顳上迴 (superior temporal gyrus) 之功能性連結呈現不同發展軌跡。雙語兒童的右側前-後顳上迴功能性連結隨年齡時間增強，單語兒童則逐漸減弱。此外，雙語兒童右側前-後顳上迴功能連結增幅越大，其中文聲韻覺識正確率進步越小，顯示增強的功能性連結可能反映因應額外語音處理需求所形成的補償性神經機制。整體而言，長期中英雙語學習經驗與兒童早期識字發展的大腦內在功能連結變化有關，並形塑右側顳上迴及語言網路的不同發展軌跡。

Learning a second language is associated with experience-dependent neuroplasticity during brain development. Because Chinese and English differ in their mappings between print and speech, bilingual experience may be associated with a neural organization distinct from that of monolinguals. Previous neuroimaging studies have shown that Chinese-English bilingual children recruit the dorsal language pathway (i.e., the superior temporal gyrus [STG], inferior parietal lobule [IPL], and dorsal inferior frontal gyrus [dIFG]) more than monolinguals during Chinese phonological processing and exhibit stronger right-hemisphere activation. However, whether bilingual experience is associated with differences in the brain’s intrinsic functional organization and its developmental trajectory during early literacy development remains unclear. The present longitudinal study examined developmental changes in resting-state functional connectivity (RSFC), a task-free measure of intrinsic functional organization, using functional near-infrared spectroscopy (fNIRS). Forty Chinese-English bilingual and 30 Chinese monolingual children were assessed twice, in Grade 1 (6-7 years) and Grade 3 (8-9 years). Phonological awareness (PA) was assessed in both Chinese and English for bilinguals and in Chinese for monolinguals. Results revealed divergent developmental trajectories of connectivity within the right STG. Over the two-year interval, bilingual children showed increased connectivity between the right anterior and posterior STG (aSTG-pSTG), whereas monolingual children exhibited the opposite pattern of decreasing connectivity. Among bilinguals, greater increases in right aSTG-pSTG connectivity were associated with smaller improvements in Chinese PA accuracy, suggesting that strengthened connectivity may reflect a compensatory mechanism supporting additional phonological processing demands. Together, these findings indicate that long-term bilingual experience is associated with differences in the intrinsic functional organization of the developing language network, characterized by a distinct developmental trajectory of right STG connectivity during early literacy development.