| 摘要: | 在過去的研究中，當人們要短暫地記住語言材料，語音被認為是唯一用來短暫記住訊息的編碼 (Baddeley, 1974)。然而在對病人的研究裡發現，語意在短期記憶中也扮演了一定的角色(Martin et al., 1994)。本研究利用中文具有許多同音字的特性，希望能夠讓受試者在短暫記憶語言刺激材料時，無法依賴音的訊息區辨同音字，並且同時要求受試者記住同音字的意義，以作為最後判別目標字(probe)有否出現在記憶列的依據。在實驗1b中，左腦有兩個區域對於受試者在記住同音字時，相對於記住不同音的字(可用音的訊息區辨)有較高的活化，分別是左側的額葉中迴(left middle frontal gyrus, BA 9)和頂葉上迴(left superior parietal lobe, BA 7)。由於判別目標字是否和任一記憶列中的同音字為相同字的作業(identity judgment task)，無法確保受試者只使用了語意訊息，受試者可能也利用了字形作為短暫記住同音字的依據。於是實驗2b我們操弄了相似字形和不同字形的同音字，發現受試者的確受到相似字形的影響，使得反應時間較長於記住不同字形的同音字。實驗三，我們試圖要分離三種訊息對於短期記憶的影響(字音、字形、字意)，結果發現當受試者被要求記住中文單字的字意時，三種訊息都會被激發。另一方面，當我們同時操弄字形及字音，並且請受試者對於相同的刺激材料做相同字(identity judgment task)以及相同音(homophone judgment task)的判斷，受試者對於相同字的判斷會受到語音的影響，而對於相同音的判斷則會被字形所影響。意即，當受試者可以用語音訊息作為編碼時，語音仍舊在短期記憶中扮演了重要的角色。然而，當受試者只需要利用語音訊息完成作業，字形的效果也會被彰顯。此結果顯示了在中文裡，儘管語音對於記住中文字是重要的，字形也影響了受試者提取或短暫記住字音的表現。Phonology has been assumed to play a dominant role in verbal shot-term memory (VSTM), nevertheless, semantic contribution is not thought to play a role in VSTM. Martin et al. (1994) reported two patients revealing functional dissociation between phonological and semantic short-term memory. In this thesis, three experiments were conducted. Experiment 1a sought to establish a valid paradigm for the following fMRI study (Experiment 1b). The STM task (identity vs. homophone judgment) and the memory load (1 character vs. 4 characters) were manipulated. The results demonstrated that the difficulty of the two memory tasks was not significantly different, and the manipulation of memory load was effective. In Experiment 1b, the results were compatible with previous findings in showing an involvement of the left middle frontal lobe (BA 9) and the left superior parietal lobe (BA 7) in reading Chinese characters and retaining homophonic Chinese characters in VSTM. In Experiment 2a, an identity judgment task and a homophone judgment task were employed. Visual similarity and the pronunciation among the stimuli were also manipulated. The results showed a visual similarity effect in the homophone judgment task, which suggested that the phonology of Chinese characters was heavily influenced by the visual form (i.e., the radical and its position). A phonological similarity effect was also found in the identity judgment task that supported that phonology in VSTM played a dominant role in Chinese. In Experiment 2b, only homophones were included in the identity judgment task, and the visual similarity effect was observed. In Experiment 3, an identity judgment task and a lexical-decision task (LDT) were conducted. The results showed a main effect of the probe types and that of the relatedness in accuracy. However, no significant difference was found in the analysis of the mean reaction time. It showed that three kinds of the probe (i.e., semantic, orthographic, and phonological) were equally primed by the to-be-remembered character. The results from the current study highlight semantic and orthographic contribution to VSTM. The neural network that supported the VSTM of Chinese homophones might include the brain regions that were associated with orthographic processing in addition to semantics. |
