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健忘1.jpg

研究揭示为何老年人更健忘

《中国科学报》 2017-12-18

  

  睡觉时脑电波产生的时机可能影响记忆。

  图片来源:iStock.com/Syldavia

  当人们睡觉时,大脑并不会休息。当神经元相互“对话”时,脑电波会在大脑中传送。如今,研究人员证实,当脑电波无法进行恰当的互动时,人们可能会失去长期记忆。此项工作或许有助于解释为何老年人更加健忘,并且可能带来治疗记忆丧失的新方法。

  为探寻睡眠如何促成老年记忆丧失,美国加州大学伯克利分校神经科学家Randolph Helfrich及其团队让70多岁和20多岁的健康成年人参加了一项记忆测试。参与者被训练将“鸟”等常见且较短的单词同由诸如“jubu”等随机音节结合构成的没有意义的单词匹配起来。一旦他们学会了这种单词——无意义单词的组合,便去玩“记忆”游戏。参与者不得不将配对单词进行两次匹配:一次是在他们掌握该任务的约10分钟后;第二次是从一整晚的休息中醒过来的几小时后。当他们睡觉时,研究人员记录了其大脑中的脑电活动。

  不出所料,和参与的年轻人相比,老年人在早上记住单词对的能力要差很多。脑电活动记录揭示了其中一个原因。两种脑电波——慢波振荡(促进优质睡眠的较大波动)和睡眠梭状波(短波的瞬间爆发)是深度且通常无梦的非快速眼动睡眠的明显标记。但这些脑电波在老年人中并不同步。研究人员在日前出版的《神经元》杂志上报告了这一发现。

  他们认为,这种不合拍的活动扰乱了储存短期和长期记忆的大脑各部分之间的交流。Helfrich介绍说,实际上,储存长期记忆的前额皮质需要告诉海马体——所有记忆最先经过的大脑区域——已作好接收信息的准备。如果大脑电波没有同步,这种交流便会失去,记忆也由此失去。

  为阐明是什么引发了这种不同步,研究人员利用结构磁共振成像(利用无线电波观看内部器官)分析了参与者的大脑。他们发现,产生慢波振荡和长期记忆的大脑区域在年老的参与者中较小。这表明,老年人更加健忘是因为这一区域随着时间的流逝出现萎缩。“这种萎缩足以伤及实时将脑电波聚集在一起从而连夜储存记忆的机制。”Helfrich表示。(徐徐)

责任编辑:李阳阳

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