人們在提取記憶時，大腦會因為欲提取記憶的性質不同，而對線索做不同處理，以增進提取效果，這種現象稱為記憶提取導向（retrieval orientation）。本篇研究的目的為探討提取在不同情緒背景下登錄的中性物品時，是否也可以觀察到不同的記憶提取導向。實驗中使用三種情緒圖片（中性、負向、正向）當背景，搭配中性物品圖片作為學習材料，測驗時則以物品圖片作為提取線索。實驗一中每次學習會經歷一種情緒背景，之後進行再認測驗。結果顯示，雖然搭配三種不同的情緒背景，受試者對中性物品圖片的提取表現沒有顯著差異，但是從物品圖片呈現後 500 毫秒開始一直持續到 2000 毫秒，在右側額葉的頭皮電極處可以觀察到中性背景相對於情緒性背景有更為正走向的記憶提取導向效果，另外，800 毫秒到 1200 毫秒之間，正向背景相較於負向背景在整個右半腦區的電極也可以觀察到更為正走向的記憶提取導向效果。為了探討實驗一觀察到的記憶提取導向是否可以根據情況隨時轉換，抑或是在一段時間內只能維持一種導向，實驗二的學習階段設計出現兩種情緒（中性+正向或是中性+負向），並於測驗時提供表情線索讓受試者作排除作業：若物品圖片曾於學習階段出現過，而且當時搭配背景的情緒與表情線索代表的情緒一致時，回答「舊」；情緒不一致或不曾出現過則回答「新」。結果發現，無論在何種情緒背景組合下，受試者對中性物品圖片的提取表現都沒有顯著差異，但是從物品圖片呈現開始一直持續到 600 毫秒，整個頭部（不包含額極處）的電極都可以觀察到情緒性背景相對於中性背景有更為正走向的記憶提取導向效果，另外，700 毫秒到 1400 毫秒之間，額極（frontal pole）處的電極也可以觀察到情緒性背景相對於中性背景有更為正走向的記憶提取導向效果。綜合本篇論文兩實驗的結果說明：欲提取在不同情緒背景下登錄之物品時，大腦會採取不同的記憶提取導向以增進提取效果，所採用的導向可以是一個延續持久的狀態，也可以因應情況需要隨時轉換。這些記憶提取導向在頭皮上的分布不同，影響因素可能是正負向性、激發水準，或是正負向情緒感受，各因素影響的時間也不同。;Different forms of processing are applied to physically identical retrieval cues based on the characteristics of memory that people try to retrieve. This phenomenon is called “retrieval orientations”. The purpose of the present study is to investigate whether the different retrieval orientations adopted for objects encoded modulated by different emotional contexts. In the present study, emotionally neutral object pictures superimposed on neutrally, negatively, or positively valenced background pictures were used as study materials, and object pictures without background were used as retrieval cues. In Experiment 1, subjects would experience one of the three emotional backgrounds in each study phase and then finished a recognition test. The results showed that although the memory performance of object pictures had no significant difference, different emotional contexts during study phase still let subjects adopt different retrieval orientations when trying to retrieve those objects. Objects encoded in neutral backgrounds elicited more positive-going event-related potentials (ERPs) than encoded in emotional backgrounds from 500 ms to 2000 ms over the right frontal scalp. In addition, objects encoded in positive contexts elicited more positive-going ERPs than encoded in negative contexts from 800 ms to 1200 ms over the right hemisphere scalp. The retrieval orientations observed from Experiment 1 were steady and maintaining states. For investigating whether our brain can switch retrieval orientations frequently, we let subjects experience two emotional contexts (neutral + positive or neutral + negative) during each study phase in Experiment 2, and gave expression cues during test phase for subjects to do exclusion tasks. The results showed that from the onset of object pictures to 600 ms, objects encoded in emotional contexts elicited more positive-going ERPs over the whole scalp (not including the frontal pole). On the other hand, the same phenomenon was also observed over frontal pole scalp from 700 ms to 1400 ms. To summarize the results of two experiments, we could conclude that different retrieval orientations were adopted when subjects tried to retrieve objects encoded in different emotional contexts. These orientations could be maintaining states, or switch to another frequently in response to task demands. Their distributions over scalp were different; the affected factor may be valence, arousal, or positive or negative feelings. These factors influenced retrieval orientations in distinct time-window.
