エピソード記憶における時間情報の処理に関連する神経基盤とその障害

Neural Mechanisms Underlying the Processing of Temporal Information in Episodic Memory and Its Disturbance

エピソード記憶とは，日常生活の中で体験する出来事の記憶であり，内容に加えて時間や場所の文脈情報が付随している。先行する脳機能画像研究や神経心理学的研究から，エピソード記憶の時間情報には，①出来事の順序を整理する，②複数の出来事を区別する，③1つの出来事の記憶に含まれている複数の要素を統合する，の3つの側面があり，それぞれ①外側前頭前野皮質，②前頭葉眼窩部，③側頭葉内側面領域が関連していることが示唆されている。

Abstract

Episodic memory is defined as memory for personally experienced events, and includes memory content and contextual information of time and space. Previous neuroimaging and neuropsychological studies have demonstrated three possible roles of the temporal context in episodic memory. First, temporal information contributes to the arrangement of temporal order for sequential events in episodic memory, and this process is involved in the lateral prefrontal cortex. The second possible role of temporal information in episodic memory is the segregation between memories of multiple events, which are segregated by cues of different time information. The role of segregation is associated with the orbitofrontal regions including the orbitofrontal cortex and basal forebrain region. Third, temporal information in episodic memory plays an important role in the integration of multiple components into a coherent episodic memory, in which episodic components in the different modalities are combined by temporal information as an index. The role of integration is mediated by the medial temporal lobe including the hippocampus and parahippocampal gyrus. Thus, temporal information in episodic memory could be represented in multiple stages, which are involved in a network of the lateral prefrontal, orbitofrontal, and medial temporal lobe regions.