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標題: | 強化視覺工作記憶表徵的上而下調控持續時間的閾限 The Threshold of Top-Down Modulation Duration for Enhancing Visual Working Memory |
作者: | Kuan-Yao Huang 黃冠堯 |
指導教授: | 葉怡玉 |
關鍵字: | 視覺工作記憶,注意力,回溯線索,由上而下的控制,刷新, visual working memory,attention,retro-cue,top-down control,refreshing, |
出版年 : | 2012 |
學位: | 碩士 |
摘要: | 人們藉由注意力從龐大的訊息世界中,攫取重要的訊息來處理。根據過去研究,注意力分為內在注意力與外部注意力,其中內在注意力主要藉由上而下的控制、刷新以及重複處理以保護或是增強視覺工作記憶中的表徵。然而,過去研究尚未釐清由上而下控制有效運作所需的最短時間,以及表徵強弱對此作用時間的影響。本篇研究使用回溯線索於改變偵測作業,在實驗一裡記憶畫面刺激呈現180毫秒,回溯線索於記憶畫面消失後的800毫秒出現,持續於螢幕上的時間作為由上而下控制持續時距的操控(100、300、500及700毫秒),也加入中性線索以了解有效線索相對的效應。結果發現過短的時距(100 毫秒)會對表徵造成干擾,且需足夠的時距(700 毫秒)才能產生由上而下控制的效益。實驗二則延長記憶畫面刺激所呈現的時間(300 毫秒)以增強表徵,結果發現表徵較強時不受由上而下控制所影響,也發現短時距情況裡的干擾現象並未出現。實驗三延長表徵維持至回溯線索出現的時距(1000 毫秒)使強表徵隨著時間衰弱。結果發現由上而下控制的助益在500和700毫秒的情況裡均為顯著,亦即,強化表徵所需的持續時間閾限也跟著縮短。實驗四和實驗五則採用受試者內設計控制受試者的變異,分別操控記憶畫面的登錄時間而讓回溯線索於畫面消失後800毫秒時呈現以及操控回溯線索出現的時間而讓登錄時間固定於300毫秒。此二實驗的結果和實驗一到實驗三的結果相符。總結而言,由上而下的控制強化視覺工作記憶表徵的持續時間有其最小閾限,且此閾限會受表徵強度所影響。 Internal attention reflects top-down control of representations. Through refreshing representations and recurrent processing, internal attention can protect and strengthen the representation in visual working memory. However, whether there is a minimum duration for top-down control to effectively modulate visual working representations remains unclear. Moreover, whether representation strength influences this minimum duration has not been explored. The aim of this study is to address these two issues using a change detection paradigm while varying the duration for top-down control to modulate a representation cued by a spatial indicator. In Experiment 1, a memory array of four colored shapes was presented for 180 ms, a retro cue was shown 800 ms after array offset, and the duration for retro cueing until the display of a test array was manipulated to be 100, 300, 500, or 700 ms. The retro cue could be 100% valid for indicating the item to be tested or neutral that was uninformative of the to-be-tested item. The participants’ task was to detect whether there was any change between the two arrays. The minimum duration for retro cueing to benefit memory performance was operationally defined as the threshold for top-down modulation to effectively protect visual short-term memory. The results showed cueing cost when the duration was too short (100 ms) and benefit when the duration was long (700 ms) compared with the performance in the neutral-cue condition. The threshold was 700 ms. In Experiment 2, we increased the encoding time to 300 ms for strengthening stimulus representations. Neither the cost nor the benefit was observed. In Experiment 3, the interval between the offset of memory array and retro cueing was lengthened to 1000 ms so that strong representations may decay to weaker ones. The results showed that the threshold for top-down modulation to effectively protect memory representations was 500 ms. In Experiment 4, a within-subject design was adopted to investigate the impact of encoding time on memory performance using an interval of 800 ms between the offset of the memory array and the retro cue. In Experiment 5, a within-subject design was adopted to examine the effect of cue onset time on the performance of stronger representations that resulted from 300 ms encoding time. The results of these two experiments replicated the results from Experiment 1 to Experiment 3. In sum, top-down modulation needs a minimum duration for effectively protecting visual working memory. Moreover, this threshold depends on the representation strength. It appears that the strength of visual working memory representations must be in a certain range for top-down modulation to bring forth the benefits. Future research should explore this range using more rigorous methods to manipulate representation strength. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/62394 |
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顯示於系所單位: | 心理學系 |
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