The Brain Mechanism Underlying Lexical Representation And Processing In Chinese-English Bilinguals

Four experiments were conducted to investigate the brain mechanism underlying lexical representation and processing in Chinese-English bilinguals by using fMRI (functional magnetic resonance image) techneque. In Experiment 1, the perceptual processing task of searching for a radical (or a letter) embedded in the stimuli was adopted to address the relationship of the perceptual representation between English and Chinese stimuli. It was found that the striate area, gyrus occipitalis medius, gyrus fusiformis, gyrus postcentralis, lobulus parietalis superior were activated by both Chinese characters and English single words. The gyrus temporalis medius and gyrus rectus and anterior gyrus cinguli were only activated by Chinese stimuli while gyrus precentralis were only activated by English stimuli. In Experiment 2, the semantic representation was addressed by using the semantic category classification task. It was found that the left gyrus temporalis medius as well as the left gyrus fusiformis were activated by both Chinese and English stimuli. But activation induced in the frontal and parietal lobes were different. For example, we found that the left gyrus frontalis superior /medius were activated only by the Chinese stimuli, while the right gyrus frontalis inferior, the supplementary motor area as well as the lobulus parietalis superior on both sides were activated only by the English stimuli. We further tested the difference in the semantic processing by using synonym judgement task within or cross languages in Experiment 3. It seemed that there was no significant difference between these two conditions. The brain mechanism of translation was investigated in Experiment 4. It was found that the common brain areas activated by the conversion from Chinese to English and that from English to Chinese were the left gyrus frontalis medius and the gyrus fusiformis. It was also found that there were some differences between these two kinds of processing.The conclusions: 1) the results support the hypothesis that the two languages have independent perpetual representations but share a common semantic system. 2) The manner of automatic processing or semantic processing of the English stimuli is different from that of the Chinese stimuli. The former is more dependent on the semantic information while the latter more dependent on phonologic processing. 3) Compared to Chinese, English invloves more of the right hemisphere during lexical processing. 4) The mechanism underlying translating Chinese to English is different from that underlying translating English to Chinese. The former is mainly a controlled process while the latter an automatic process.