The brain’s “waste disposal system” may kick in after intense neural activity – and it might be possible to turn on the process intentionally.

大脑可能会在强烈的神经活动后，启动“废物处理系统”——而且有可能有意地启动这一过程。

Until recently, this system was thought to activate only during sleep, but now researchers have seen it ramping up in people after they watch flickering chequerboard patterns on a screen.

直到最近，人们一直认为这个系统只在睡眠时激活，但现在研究人员发现，在人们观看屏幕上闪烁的棋盘图案后，这个系统就会活跃起来。

The finding provides a tantalising hint that people may be able to deliberately flush out waste products from their brain by staring at intense visual stimuli, says Laura Lewis at Boston University in Massachusetts.

马萨诸塞州波士顿大学的劳拉·刘易斯（Laura Lewis）说，这一发现提供了一个诱人的暗示，即人们可能能够通过强烈的视觉刺激，来有意排出大脑中的废物。

“The real surprise was that they found it in awake people,” says Edoardo Rosario de Natale at the University of Exeter in the UK, who wasn’t involved in the work.

“真正令人惊讶的是，他们在清醒的人身上发现了它。”英国埃克塞特大学的爱德华多·罗萨里奥·德·纳塔莱说，他没有参与这项研究。

The brain’s waste disposal system involves cerebrospinal fluid （CSF） being pumped into the brain and leaving through a network of fine tubes called the glymphatic system, which was only discovered in 2012.

大脑的废物处理系统，将脑脊液（CSF）泵入大脑，并通过叫做胶状淋巴系统（glymphatic）的细管网络离开，胶状淋巴系统在2012年才被发现。

Since the glymphatic system’s discovery, there has been a surge of research aiming to understand how boosting fluid flow could help improve brain health, but much of how the system functions in people is still unclear.

自从胶状淋巴系统被发现以来，关于促进液体流动将如何帮助改善大脑健康的课题，业界做了大量研究，但该系统在人体内的大部分功能仍不清楚。

Lewis’s team took advantage of a new brain-scanning technique, using existing magnetic resonance imaging machines, that highlights any CSF that has newly entered into the fourth ventricle of the brain, a cavity at the base of the head. Fluid that enters this chamber drains out through the glymphatic system.

刘易斯的团队使用了一种新的大脑扫描技术，利用现有的磁共振成像仪，突出显示任何新进入大脑第四脑室的脑脊液，大脑第四脑室是头部底部的一个腔。进入这个腔室的液体通过胶状淋巴系统排出。

They asked 20 volunteers to watch a screen inside the scanner that displayed a pattern known to cause high brain activity: a flickering black- and-white spiral chequerboard. The display was turned on and off at 16-second intervals for about an hour, apart from during short breaks.

他们要求20名志愿者观看扫描仪内的屏幕，屏幕上显示了一种已知会引起大脑高度活动的图案：一个闪烁的黑白螺旋棋盘。除了短暂的休息时间外，显示屏以16秒的间隔打开和关闭，持续约一个小时。

When the pattern was shown, this caused a rise in blood flow to the brain’s visual centres, as expected. When the screen went dark, blood flow reduced and CSF flow into the brain increased.

当显示图案时，正如预期的那样，流向大脑视觉中心的血液增加。当屏幕关闭时，血流减少，而脑脊液流入增加。

The brain-scanning technique couldn’t reveal if the fluid left through the glymphatic vessels, nor if there was a reduction of waste products within the brain. These are questions that need to be tackled next, says Rosario de Natale. “This is opening a new door.”

脑部扫描技术无法显示液体是否通过脑血管离开，也无法显示大脑中的废物是否减少。纳塔莱说，这些都是接下来需要解决的问题。“现在正在打开了一扇新的大门。”

“It’s still an open question whether the fluid goes directly into the brain tissue or if it sloshes around in the ventricle. But we definitely think that it has an effect on fluid in the rest of the brain,” says team member Stephanie Williams, also at Boston University.

“液体是直接进入脑组织，还是在脑室中流动，这仍然是一个悬而未决的问题。但我们可以肯定，它对大脑其他部分的液体有影响，”团队成员、同样来自波士顿大学的斯蒂芬妮·威廉姆斯说。

“We’re very interested now to understand the effect of these changes in fluid flow and how it intersects with brain health,” says Lewis.

刘易斯说：“我们现在对这些液体流动变化的影响，以及它与大脑健康的相互作用，非常感兴趣。”