記憶固化之造影研究 －干擾時間差異對固化作用之影響

Abstract

記憶的形成如何從短期變成長期記憶，而其中涉及到的大腦變化是神經科學家長久以來關切的議題。至今多數記憶固化的研究多以動物作為研究對象，而本研究用非侵入性的磁振造影、及平靜狀態實驗（resting state fMRI）來研究人類記憶固化時序上的歷程。15位慣用手為右手並以中文為母語、平均年齡為23歲的受試者參與本實驗。我們利用配對連結典範（pair-association paradigm）進行記憶的干擾作業，使用（幾何圖形－無生命名詞）作為記憶材料；而（幾何圖形－有生命名詞）作為干擾材料，並操弄記憶固化與干擾之間的時間差異（立即干擾、延宕干擾）來研究干擾後、以及24小時後的平靜狀態腦區連結變化。 結果發現，第一、延宕干擾在兩側顳葉下迴（bilateral ITG）以及左側海馬迴（left hippocampus）的活化顯著大於立即干擾，此項功能性連結是由記憶階段而來，不是由干擾階段而來。第二、記憶24小時後的海馬迴仍參與固化作用。第三、左側額葉下迴（left IFG）與左側顳葉中迴（left MTG）在記憶作業中形成語意處理網絡。第四、在延宕干擾的再認作業中，再認學習過的配對在左側顳葉中迴（left MTG）的活化顯著大於再認重組過的配對，推論與提取語意訊息有關。 本研究為第一個利用記憶干擾實驗、操弄干擾時間來研究記憶固化歷程，並利用平靜狀態實驗進行固化歷程分析的人類研究，使我們對於記憶固化歷程的腦區連結改變有更進一步的了解。

Most work on memory consolidation is from animal studies, showing that memory consolidation requires protein synthesis and the growth of new hippocampal synapses within 24 h. However, much less research is done on this issue in the human. In the present study, we examined whether resting BOLD correlations, or functional connectivity, between hippocampal and cortical regions are affected by time-dependent interference during learning. Fifteen right-handed participants participated in the present study (9 males, mean age = 23 years, aged 20-29 years). In the MRI scanner, each participant received two sessions, immediate interference and delay interference. The timing of retroactive interference between a memory task and an interference task was 0 sec (immediate interference) and 30 min (delay interference). A recognition task was given to participants 24 hours after the memory task. We analyzed both resting data and fMRI data. First, the resting results showed that bilateral ITG and left hippocampus were significantly activated in the delay versus immediate comparison. This functional connectivity was from the memory task, not from the interference task. Second, our resting finding suggests that the hippocampus is continuously involved over time rather than fading out in related memory traces after 24 hours memory consolidation. Third, the contrast of the memory versus interference task produced greater activation in left IFG and MTG, which are related to semantic networks. Last, during the retrieval in the recognition task 24 hours after the memory task, the contrast of intact versus recombined pairs produced greater activation in left MTG for retrieving semantic information in the delay interference. The present study was the first study using time-dependent interference paradigm, which was originally from animal studies and now transfer onto human studies, giving us the image of differential rest patterns of interregional interactions during memory consolidation.