Science2014-06-09 6:43 PM

睡眠是如何强化突触并有益记忆的  Sleep promotes branch-specific formation of dendritic spines after learning

论文摘要 

科学家们长期以来就知道,睡眠可帮助增进学习及记忆,尽管这一过程是如何发挥作用的则一直晦暗不明,尤其是当睡眠被显示会减少脑中的突触数或神经连接时。(寻找睡眠与记忆之间有某种联系的研究人员会期待看到睡眠时突触数会有所增加。) 

Guang Yang及其同事最近在该领域中取得了进展;他们证明,教小鼠学习一种新的运动技能——如在某根杆子顶部保持平衡——会引起它们脑中新的树突棘的形成(树突棘的数目与神经突触数是相关的)。这提示,在哺乳类动物脑中的突触变化是学习的基础。 

如今,为了探索睡眠是否会影响突触变化,Yang等人用一种技术来观看活体小鼠运动皮层中的树突棘。他们训练小鼠学习不同的技能。有些小鼠可在学习后马上得到睡眠;另外一些小鼠则要经历一段8小时的睡眠剥夺时间。睡眠可引起新树突棘数的增加。剥夺睡眠则适得其反。实际上,睡眠剥夺的影响是如此之强,它能压制额外训练的效果;即使当睡眠剥夺小鼠得到对某技能的更严格的训练,但它们仍然比那些得到休息的对等小鼠所长出的新突触棘要少。 

Yang等发现,与新学技能有关的神经活动会在睡眠时被重新激活。研究人员说,这一重新激活与突触棘生长相关联,这就是睡眠是如何促成记忆增进及改善行为执行的。他们的结果提示,睡眠可导致新突触的生长。以往的研究显示,在睡眠时突触数的减少通常与特殊的训练——如在本研究中的训练——无关。 

Yang等人提出,也许在最近的经验中形成的突触会在睡眠时得到强化,而代表较为遥远记忆的突触则会在睡眠中被下调,以在脑中给其它的、资讯更为相关的突触腾出位置。一则《观点栏目》文章提出了更多的见解。 

Abstract 

How sleep helps learning and memory remains unknown. We report in mouse motor cortex that sleep after motor learning promotes the formation of postsynaptic dendritic spines on a subset of branches of individual layer V pyramidal neurons. New spines are formed on different sets of dendritic branches in response to different learning tasks and are protected from being eliminated when multiple tasks are learned. Neurons activated during learning of a motor task are reactivated during subsequent non–rapid eye movement sleep, and disrupting this neuronal reactivation prevents branch-specific spine formation. These findings indicate that sleep has a key role in promoting learning-dependent synapse formation and maintenance on selected dendritic branches, which contribute to memory storage. 

To sleep, perchance to remember

Many researchers believe sleep helps us consolidate our memories, but no one knows quite how. Yang et al. investigated the precise role of sleep in changing mouse brain structures (see the Perspective by Euston and Steenland). When mice learned motor tasks, small protuberances—or “spines”—formed on some of the dendritic branches of specific brain neurons. These spines represent the physical correlate of a memory. But the neurons grew and retained these spines better when the mice slept after learning the task. Neurons that fired during learning fired again during subsequent slow-wave sleep, allowing the mice to conserve the newly formed spines—and memories.

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