Hennevin Elizabeth, Huetz Chloé, Edeline Jean-Marc
Laboratoire de Neurobiologie de l'Apprentissage, de la Mémoire et de la Communication, UMR CNRS 8620, Université Paris-Sud, Bâtiment 446, 91405 Orsay Cedex, France.
Neurobiol Learn Mem. 2007 Mar;87(3):416-40. doi: 10.1016/j.nlm.2006.10.006. Epub 2006 Dec 18.
In the course of a day, the brain undergoes large-scale changes in functional modes, from attentive wakefulness to the deepest stage of sleep. The present paper evaluates how these state changes affect the neural bases of sensory and cognitive representations. Are organized neural representations still maintained during sleep? In other words, despite the absence of conscious awareness, do neuronal signals emitted during sleep contain information and have a functional relevance? Through a critical evaluation of the animal and human literature, neural representations at different levels of integration (from the most elementary sensory level to the most cognitive one) are reviewed. Recordings of neuronal activity in animals at presentation of neutral or significant stimuli show that some analysis of the external word remains possible during sleep, allowing recognition of behaviorally relevant stimuli. Event-related brain potentials in humans confirm the preservation of some sensory integration and discriminative capacity. Behavioral and neuroimaging studies in humans substantiate the notion that memory representations are reactivated and are reorganized during post-learning sleep; these reorganisations may account for the beneficial effects of sleep on behavioral performance. Electrophysiological results showing replay of neuronal sequences in animals are presented, and their relevance as neuronal correlates of memory reactivation is discussed. The reviewed literature provides converging evidence that structured neural representations can be activated during sleep. Which reorganizations unique to sleep benefit memory representations, and to what extent the operations still efficient in processing environmental information during sleep are similar to those underlying the non-conscious, automatic processing continually at work in wakefulness, are challenging questions open to investigation.
在一天当中，大脑的功能模式会经历大规模变化，从专注的清醒状态到最深层次的睡眠阶段。本文评估了这些状态变化如何影响感觉和认知表征的神经基础。睡眠期间有组织的神经表征是否仍得以维持？换句话说，尽管缺乏意识觉知，但睡眠期间发出的神经元信号是否包含信息且具有功能相关性？通过对动物和人类文献的批判性评估，回顾了不同整合水平（从最基本的感觉水平到最认知水平）的神经表征。在动物身上呈现中性或显著刺激时对神经元活动的记录表明，睡眠期间仍有可能对外部世界进行一些分析，从而识别与行为相关的刺激。人类的事件相关脑电位证实了某些感觉整合和辨别能力得以保留。人类的行为和神经影像学研究证实了这样一种观点，即记忆表征在学习后的睡眠中会被重新激活并重新组织；这些重新组织可能解释了睡眠对行为表现的有益影响。本文展示了显示动物神经元序列重演的电生理结果，并讨论了它们作为记忆重新激活的神经元相关物的相关性。所回顾的文献提供了一致的证据，表明结构化的神经表征在睡眠期间可以被激活。睡眠特有的哪些重新组织对记忆表征有益，以及睡眠期间在处理环境信息方面仍然有效的操作在多大程度上类似于清醒时持续进行的无意识自动处理的操作，这些都是有待研究的具有挑战性的问题。
