以行為及事件相關電位實驗探討情緒情境轉換與事件分割;Behavioral and ERP Studies of Emotional Context Change and Event Segmentation.

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Title:	以行為及事件相關電位實驗探討情緒情境轉換與事件分割;Behavioral and ERP Studies of Emotional Context Change and Event Segmentation.
Authors:	莊千慧;Chuang, Chien-Hui
Contributors:	認知與神經科學研究所
Keywords:	事件邊界;情緒;再認記憶;事件相關腦電位;event boundary;emotion;recognition memory;event-related potentials (ERPs)
Date:	2021-01-29
Issue Date:	2021-03-18 17:35:52 (UTC+8)
Publisher:	國立中央大學
Abstract:	在日常生活中，當我們經歷到知覺或是概念的情境轉換時（即感知到了事件邊界時），我們會將那些所接收到的連續不斷的訊息分割成不同的事件。然而，目前還不清楚的是，當情緒上的情境轉換時，是否也會對於我們的事件記憶有著同樣的處理？為了研究這個問題，我們做了四個學習-測驗的行為實驗及一個腦波實驗。在實驗中，我們操弄了情境圖片的情緒及時間間隔與否。受試者在學習階段需要對情緒性情境圖片做缺口大小判斷，在這之間每八張圖片會根據實驗而有或無一個五秒鐘的時間間隔。之後，受試者對情緒性圖片會有一個預期外的再認記憶測驗。在實驗一中，受試者同時經歷了時間間隔和正負向情境轉換，結果顯示受試者對於事件邊界後的圖片比起其他圖片有顯著較好的再認記憶表現。表示當人們同時經歷了時間間隔及情緒情境轉換時，人們能夠感知到事件邊界。但是還不清楚的是，是否如果只經歷時間間隔或是只經歷情緒情境轉換也足以能讓人們將正在經歷中的訊息分割成為不同事件？因此在實驗二中，受試者在中性的情緒情境下只經歷時間間隔；在實驗三中，受試者則只經歷正負向情緒情境轉換。結果顯示，當受試者只經歷時間間隔時，並沒有展現出事件邊界對記憶的增強效果；而當受試者只經歷情緒情境轉換時，事件邊界對負向圖片記憶的增強效果消失了。比較實驗一和實驗三後發現，結果的不同並不是因為休息而造成的，也就是說休息並沒有影響到對於事件的記憶。接著，我們想了解是否影響受試者在學習階段的編碼會影響人們對於事件邊界的感知？因此在實驗四中，我們增加了學習階段的難度，結果發現受試者並沒有展現出事件邊界對記憶的增強效果。比較實驗三和實驗四後發現，影響受試者的學習階段並不影響我們對於事件的記憶。另外，透過這兩次實驗之間的比較，我們發現事件邊界的記憶增強效果只特定於正向情境，即只有從負向情境轉換成正向情境的情況下，人們才能夠感知到事件邊界。我們推測是否在事件邊界後的正向圖片比起其他正向圖片能記得更好其實是被之前的負向圖片所影響？因此在腦波實驗中，我們用中性圖片取代了正向圖片，發現在事件邊界後的中性圖片並沒有比其他中性圖片記得更好，因此並不支持先前的負向圖片增強了前面的圖片記憶表現的推測。總和這些結果，我們推測這可能是因為負向情緒能使記憶更加鮮明，而導致在負向情境下事件邊界對記憶的增強效果並不明顯。而在腦波結果發現，對於中性和負向圖片都出現一個大的N300，在900毫秒到1900毫秒有一個晚期的LPP；以及在200毫秒到1900毫秒時，邊界後圖片比起邊界前圖片還要來得負。除了這些結果之外，我們發現負向圖片比起正向圖片會引起更大的刺激前之隨後記憶效果，並且這效果在900毫秒到1900毫秒時只出現在邊界後圖片。總結來說，我們的行為結果顯示只有從負向情境轉換成正向情境的情況下，人們才能夠穩定的感知到事件邊界。神經生理結果則顯示，邊界前和邊界後可能存有不同的神經處理機制。;When experiencing a perceptual or conceptual context shift (i.e., experiencing an event boundary), the continuous information we perceived is segmented into discrete events in our daily life. However, whether the change of emotional context also has the same process on our event memories remains unclear. To investigate this question, we manipulated the emotional context images and temporal breaks on our four study-test behavioral experiments and one EEG experiment. Participants studied a series of emotional context images with or without temporal break followed by an incidental recognition task. In experiment 1, participants experienced positive and negative context change along with temporal break. The result showed a significantly better recognition memory for the post-boundary items than the others, indicating that people would perceive an event boundary when they experienced an emotional context change with a temporal break. However, whether the pure emotional context shift or pure temporal break is sufficient for segmenting ongoing information into events remains unclear. Therefore, participants encountered only temporal break with the neutral context in experiment 2 and only positive and negative context shift in experiment 3. These results revealed no boundary enhancement effect when participants only experienced temporal break while the boundary enhancement effect for negative pictures was diminished when participants encountered pure emotional context shift. After comparing Experiment 3 with Experiment 1, we found that the difference between these two experiments was not caused by temporal breaks. Later, we considered whether disturbing encoding phase would impact the perception of event boundaries. In experiment 4, we increased the difficulty of the gap judgment task and found that there was no event boundary enhancement effect. However, after comparing Experiment 4 with Experiment 3, we found that the difference of the results between these two experiments was not caused by increasing the study difficulty. From two comparisons, we found the event boundary enhancement effect was specific to the positive context, thus, we consider whether this enhancement was influenced by the prior negative pictures. To address this issue, we replaced the positive pictures with neutral pictures to test in a more realistic way in EEG experiment. The behavioral results showed that there was no boundary enhancement effect, suggesting that the negative stimuli did not facilitate the later stimuli. For ERP results, we found a large N300 for both neutral and negative pictures, a late LPP started from 900 and lasted to 1900 ms, and a more negative waveform for post-boundary items than pre-boundary items in the time window from 200 to 1900 ms. Besides, the subsequent recognition memory was better for negative pictures than neutral pictures and there was a subsequent memory effect for post-boundary pictures in the time window from 1600 to 1900 ms but not for pre-boundary pictures. In summary, our behavioral results indicated that emotional context shift could be perceived as event boundaries in conditions that the context changed from negative to positive. Neural physiological results suggested that there might involve different processing for pre-boundary and post-boundary.
Appears in Collections:	[College of Science Institute of Cognitive Neuroscience] Electronic Thesis & Dissertation

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