Axmacher Nikolai, Haupt Sven, Fernández Guillén, Elger Christian E, Fell Juergen
Department of Epileptology, University of Bonn, 53105 Bonn, Germany.
Cereb Cortex. 2008 Mar;18(3):500-7. doi: 10.1093/cercor/bhm084. Epub 2007 Jun 14.
Two step theories of memory formation assume that an initial learning phase is followed by a consolidation stage. Memory consolidation has been suggested to occur predominantly during sleep. Very recent findings, however, suggest that important steps in memory consolidation occur also during waking state but may become saturated after some time awake. Sleep, in this model, specifically favors restoration of synaptic plasticity and accelerated memory consolidation while asleep and briefly afterwards. To distinguish between these different views, we recorded intracranial electroencephalograms from the hippocampus and rhinal cortex of human subjects while they retrieved information acquired either before or after a "nap" in the afternoon or on a control day without nap. Reaction times, hippocampal event-related potentials, and oscillatory gamma activity indicated a temporal gradient of hippocampal involvement in information retrieval on the control day, suggesting hippocampal-neocortical information transfer during waking state. On the day with nap, retrieval of recent items that were encoded briefly after the nap did not involve the hippocampus to a higher degree than retrieval of items encoded before the nap. These results suggest that sleep facilitates rapid processing through the hippocampus but is not necessary for information transfer into the neocortex per se.
记忆形成的两阶段理论认为，初始学习阶段之后是巩固阶段。有人提出，记忆巩固主要发生在睡眠期间。然而，最近的研究结果表明，记忆巩固的重要步骤在清醒状态下也会发生，但在清醒一段时间后可能会饱和。在这个模型中，睡眠特别有利于在睡眠期间及之后短暂恢复突触可塑性并加速记忆巩固。为了区分这些不同观点，我们记录了人类受试者海马体和鼻周皮质的颅内脑电图，同时他们检索在下午“小憩”之前或之后或在无小憩的对照日获取的信息。反应时间、海马体事件相关电位和振荡伽马活动表明，在对照日，海马体参与信息检索存在时间梯度，这表明在清醒状态下存在海马体-新皮质信息传递。在有小憩的那天，检索在小憩后短暂编码的近期项目，与检索在小憩前编码的项目相比，海马体的参与程度并没有更高。这些结果表明，睡眠有助于通过海马体进行快速处理，但对于信息本身转移到新皮质来说并非必要。
