Differentiation of Human Medial Prefrontal Cortex Activity Underlies Long-Term Resistance to Forgetting in Memory
Differentiation of Human Medial Prefrontal Cortex Activity Underlies Long-Term Resistance to Forgetting in Memory
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DOI：
10.1523/jneurosci.2290-17.2018
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发表时间：
2018-11-28
影响因子：
5.3
通讯作者：
Davachi, Lila
中科院分区：
文献类型：
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作者：
Ezzyat, Youssef;Inhoff, Marika C.;Davachi, Lila
众所周知，与将学习事件集中在一起相比，随着时间的推移将学习事件分布在一起会在长时间尺度上产生更好的记忆。对这种长期抵抗遗忘的一种解释是，分布式学习导致记忆中的神经分化，这通过消除高度相似的记忆表征来支持对过去经验的检索。情景记忆提取的神经解剖学模型提出，海马和内侧前额叶皮层（MPFC）共同作用，使行为适当的记忆检索。然而，目前尚不清楚这些区域的表征如何共同支持在初始学习后很长时间内对遗忘的抵抗。使用功能磁共振成像，我们测量了分化检索记忆表征后，延长延迟在男性和女性人类参与者。一周后，如果在2天（过夜）内学习，单词-对象关联会被更好地记住，与在一天（同一天）内学习相比，可以在不同的时间背景下学习关联。MPFC检索模式显示分化过夜相对于同一天的记忆，而海马模式反映了关联检索的成功。MPFC的隔夜记忆分化高于联想记忆，高于在全脑范围内检索活性体素组评估的分化。MPFC模式分化中与记忆相关的差异与过夜学习的记忆成功和大脑-MPFC功能连接相关。这些结果表明，跨天的学习信息导致不同的MPFC记忆表征，减少1周后的遗忘，并表明这源于MPFC和海马体之间的持续相互作用。
It is well known that distributing study events over time leads to better memory over long time scales, compared with massing study events together. One explanation for such long-term resistance to forgetting is that distributed study leads to neural differentiation in memory, which supports retrieval of past experiences by disambiguating highly similar memory representations. Neuroanatomical models of episodic memory retrieval propose that the hippocampus and medial prefrontal cortex (MPFC) work together to enable retrieval of behaviorally appropriate memories. However, it is not known how representations in these regions jointly support resistance to forgetting long after initial learning. Using fMRI, we measured differentiation in retrieved memory representations following an extended delay in male and female human participants. After 1 week, word-object associations were better remembered if studied across 2 d (overnight), allowing associations to be learned in distinct temporal contexts, compared with learning within a single day (same day). MPFC retrieval patterns showed differentiation for overnight relative to same day memories, whereas hippocampal patterns reflected associative retrieval success. Overnight memory differentiation in MPFC was higher for associative than item memories and higher than differentiation assessed over a brain-wide set of retrieval-active voxels. The memory-related difference in MPFC pattern differentiation correlated with memory success for overnight learning and with hippocampal-MPFC functional connectivity. These results show that learning information across days leads to differentiated MPFC memory representations, reducing forgetting after 1 week, and suggest this arises from persistent interactions between MPFC and hippocampus.