Staresina Bernhard P, Davachi Lila
New York University, New York, NY 10003, USA.
J Cogn Neurosci. 2008 Aug;20(8):1478-89. doi: 10.1162/jocn.2008.20104.
Although the general role of the medial-temporal lobe (MTL) in episodic memory is well established, controversy surrounds the precise division of labor between distinct MTL subregions. The perirhinal cortex (PrC) has been hypothesized to support nonassociative item encoding that contributes to later familiarity, whereas the hippocampus supports associative encoding that selectively contributes to later recollection. However, because previous paradigms have predominantly used recollection of the item context as a measure of associative encoding, it remains unclear whether recollection of different kinds of episodic detail depends on the same or different MTL encoding operations. In our current functional magnetic resonance imaging study, we devised a subsequent memory paradigm that assessed successful item encoding in addition to the encoding of two distinct episodic details: an item-color and an item-context detail. Hippocampal encoding activation was selectively enhanced during trials leading to successful recovery of either an item-color or item-context association. Moreover, the magnitude of hippocampal activation correlated with the number, and not the kind, of associated details successfully bound, providing strong evidence for a role of the hippocampus in domain-general associative encoding. By contrast, PrC encoding activation correlated with both nonassociative item encoding as well as associative item-color binding, but not with item-context binding. This pattern suggests that the PrC contributions to memory encoding may be domain-specific and limited to the binding of items with presented item-related features. Critically, together with a separately conducted behavioral study, these data raise the possibility that PrC encoding operations -- in conjunction with hippocampal mechanisms -- contribute to later recollection of presented item details.
尽管内侧颞叶(MTL)在情景记忆中的总体作用已得到充分证实,但关于MTL不同亚区域之间精确的分工仍存在争议。有人提出,嗅周皮质(PrC)支持非联想性项目编码,这有助于后期的熟悉感,而海马体则支持联想性编码,选择性地有助于后期的回忆。然而,由于先前的范式主要将项目背景的回忆用作联想编码的衡量标准,因此尚不清楚不同类型的情景细节的回忆是否依赖于相同或不同的MTL编码操作。在我们当前的功能磁共振成像研究中,我们设计了一种后续记忆范式,该范式除了评估两个不同的情景细节(项目颜色和项目背景细节)的编码外,还评估了成功的项目编码。在导致成功恢复项目颜色或项目背景关联的试验中,海马体编码激活被选择性增强。此外,海马体激活的程度与成功绑定的关联细节的数量而非种类相关,这为海马体在领域通用的联想编码中的作用提供了有力证据。相比之下,PrC编码激活与非联想性项目编码以及联想性项目颜色绑定均相关,但与项目背景绑定无关。这种模式表明,PrC对记忆编码的贡献可能是领域特异性的,并且仅限于将项目与呈现的与项目相关的特征进行绑定。至关重要的是,结合另一项单独进行的行为研究,这些数据增加了一种可能性,即PrC编码操作(与海马体机制一起)有助于后期对呈现的项目细节的回忆。