A Tale of Two Engrams: Roles of the Hippocampus and Amygdala in Contextual Fear Conditioning

雙痕記：海馬與杏仁核在情境恐懼制約中的角色

This review focuses on the research for physiological psychology of fear memory done in our laboratory, specifically on the roles of the amygdala and hippocampus in contextual fear conditioning. We present findings to suggest that the hippocampus is involved not only in representing the context of conditioning but also in associating it to an electric shock. The hippocampal GABAergic and cholinergic systems mediated the context representation and context-shock association respectively. These findings demand revising the prevailing model of contextual fear conditioning: In short, the brain may store two engrams for the context-shock association in such conditioning, one relying on the amygdala for a simple reflexive association of CS and US, while the other on the hippocampus for combinatorial binding of all cues in a conditioning episode. These findings, in relating to those from the local and other laboratories, invite re-thinking on the concept of functional localization in the brain.

此論文回顧本生心實驗室對杏仁核與海馬在情境恐懼學習中不同角色的研究結果。我們發現海馬不僅參與情境表徵的形成，也參與情境與電擊的聯結，這有別於目前流行模式之預測。這兩個功能分別由海馬內的伽瑪胺基丁酸與乙醯膽鹼系統負責。易言之，對於情境恐懼制約學習，腦中會形成兩個情境電擊聯結表徵：在杏仁核形成簡單的CS-US反射式聯結以支援快速反應，而在海馬形成一整合式的組態表徵以支援靈活因應。這一恐懼聯結有雙重記憶表徵的發現，在合併考量本地與國際的生心研究成果下，促使吾人重新思考生理心理學中所謂腦功能區位化的意涵。