Wu, D. 1, 2 & Lin, E. Y. 1, 3
1 Laboratories for Cognitive Neuroscience, National Yang-Ming University, Taiwan
2 Institute of Cognitive Neuroscience, National Central University, Taiwan
3 Institute of Neuroscience, National Yang-Ming University
Previous literature of short-term memory (STM) indicates that verbal materials are dominantly retained in phonological representations while other linguistic information (e.g., orthography, semantics) only contributes to verbal STM minimally if not negligibly. However, accumulating evidence suggests that retention of verbal materials is jointly supported by multiple linguistic components correspondent to orthographic, phonological, and semantic representations in long-term memory. That is, the underlying mechanisms of verbal STM are closely related to those of long-term linguistic knowledge. Similarly, the organization and processing of verbal STM should reflect the characteristics of a specific language to be retained. Because logographic characters of Chinese are visually more complex than alphabetic letters, the correspondence between orthography and phonology is less transparent, and there are abundant homophones, reading and remembering Chinese should rely more on information additional to phonology than reading and remembering alphabetic languages. In behavioral experiments with a probed recognition task, participants’ STM of Chinese characters was clearly affected by orthographic similarity of to-be-remembered stimuli, irrespective of phonological similarity of the materials. Experiments with functional magnetic resonance imaging further revealed that remembering homophonic or orthographically similar characters was associated with higher activation in a left-lateralized network including the brain regions that are sensitive to orthography, consistency, and homophone computation of Chinese characters (i.e., the middle and inferior frontal gyri, the insula, the middle temporal gyrus, and the junction of the fusiform gyrus). Remembering orthographically similar characters also involved bilateral superior and inferior parietal lobules, which might be associated with visuo-spatial processing of STM. The findings from our investigations provide converging evidence for the indispensible contribution of orthographic representations to verbal STM of Chinese characters. These results also suggest that linguistic characteristics of a specific language not only determine the processing mechanisms of that language but also delineate the organization of verbal STM for that language.