Different brain pathways in processing Chinese and English by Primary Three Hong Kong pupils based on electroencep-halography coherence analysis

Abstract

A 128-channel electroencephalography (EEG) system was employed to record the electrical brain signals reaching the scalp of test subjects in response to reading mother tongue (Chinese) and second-language ( English) sentences. Half of these test sentences were grammatically correct, while the other half contained syntactical errors. We analysed the coherence in various EEG frequency bands (δ, θ, α, β, γ) among all possible pairs of scalp electrode sites. Since it is well-known that the rest state of the brain, whether eyes open or closed, has an abundance of activities, we studied the difference in coherence (rather than the absolute value) of a subject as he/she reads Chinese and English sentences. We analysed the difference in “cross-talk” between ten different brain regions as the subject responded to the visual stimuli by simplifying the raw difference coherence data into“difference coherence diagrams” pertaining to specific conditions (i. e. correct or incorrect grammar) . We have found, from the responses of 22 Primary Three pupils (mean age nine years), that Chinese syntactic processing is related to strong short-range EEG coherence within the frontal and occipital regions, while syntactic processing of English involved relatively more coherence between EEG signals recorded from the frontal and temporal regions. A gender difference was also found. Boys seemed to show a general left hemispheric preference for syntactic language processing. In particular , the left frontal region was a prominent EEG coherence focus. On the other hand , girls tended to use more bilateral regions for processing both Chinese and English syntax , and the parietal and right temporal regions seem to be particularly strong coherence foci.

通過一系列實驗，讓測試者閱讀母語（中文）和第二語言（英語）的句子，判斷其文法或​​句法結構是否有錯誤。同時用安裝了128個電極貼片的腦電圖（ EEG ）機記錄頭蓋的腦電波。除去記錄過程中的人為現象（如眨眼、眼珠移動等），把測量到的信號分為五個波段（δ，θ，α，β，γ），然後比較每一對電極貼片的電波，作相關性分析。人在靜止、清醒的狀態時，不管開眼或閉眼，腦電圖都有活躍的電信號記錄。而測試閱讀中文或英文時，其相應的腦電反應也混合在靜態的腦電圖中。因此，不管電極貼片測量到的絕對相干值（absolute coherence value），作相干值差異的分析。例如，比較測試者閱讀正確的中、英文句子時相干值的差異。為便於討論，將頭蓋分為十大區域。計算某兩區的相干值時，取兩區間各電極貼片的相干平均值。從而繪製出枕葉與後穎葉在閱讀正確的中文及正確的英文句子時的相干值之差等。即把大量的腦電信號簡化為十區的差分相干圖（difference coherence diagrams）。 22名小學三年級學生參與這項測試。研究顯示，在分析中文句法性質、結構時，測試者用在左、右額葉間及在左、右枕葉間的短程相干去操作。在分析英語句法時，測試者則多用額葉與顳葉間的相干去運作。此外所做的相干分析表明男女有別。男童較多利用左腦去作句法分析，左前額葉區是其突出的腦電圖相干中心點；女童則傾向於用左、右腦思索中文和英文，頂葉及顳葉兩區是其相干的兩個中心。