Behavioral and fMRI investigations on the effects of phonological and visual similarity of English words on short-term memory in unbalanced Chinese-English bilinguals

• Main Authors: Yin-chen Li, 黎引真
• Other Authors: Denise Hsien Wu
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/59033315049867238942

碩士 === 國立中央大學 === 認知與神經科學研究所 === 101 === Previous findings from readers of alphabetic languages demonstrate that verbal information in short-term memory (STM) is mainly retained by phonological but not visual representation. In contrast, our previous findings from Chinese readers demonstrate the contribution from both phonological and orthographic representation. To investigate whether bilinguals’ STM is delineated by characteristics of the native language or by the to-be-remembered materials, the effects of phonological and visual similarity of English words in native English speakers and in Chinese-English bilinguals were examined. The neural substrates underlying the phonological and visual representations of English words during STM tasks are also compared between native English speakers and Chinese-English bilinguals. Two experiments were conducted in this study. Experiment 1 consisted of two behavioral experiments using a probed serial recall task. The results of the behavioral experiments showed that English speakers’ STM was only hindered by phonological but not visual similarity of English materials, while the STM of Chinese-English bilinguals was affected by both phonological and visual similarity. Furthermore, bilinguals’ proficiency in English seemed to modulate the effect of visual similarity. Experiment 2 was an fMRI experiment employing a similar task with the probed serial recognition paradigm. The neuroimaging results generally showed a left lateralized fronto-temporo-parietal network of verbal STM and a left lateralized fronto-parietal network of the phonological similarity effect (PSE). On the other hand, the results showed a right lateralized and bilateralized fronto-parietal network of the visual similarity effect (VSE) in native English readers and Chinese-English bilinguals, respectively. In general, the activations associated with the PSE and the VSE were more lateralized in the native English participants while being more bilateralized in the Chinese-English participants. The present findings suggest that the representation underlying bilingual verbal STM is jointly determined by features of the first language and proficiency of the second language, and that the behaviorally observable VSE might be associated with the bilateralized fronto-parietal activations.