美国国家公共电台 NPR How Deep Sleep May Help The Brain Clear Alzheimer's Toxins

 

MARY LOUISE KELLY, HOST:

Researchers have long been puzzled by the relationship between sleep and Alzheimer's. New research may help solve that puzzle. NPR's Jon Hamilton reports on a study suggesting that the brain waves produced during deep sleep trigger a process that washes away toxins² in our brains.

JON HAMILTON, BYLINE³: People with Alzheimer's often have sleep problems, and sleep problems appear to make people more vulnerable to Alzheimer's. But Laura Lewis of Boston University says there's never been a good explanation for this connection.

LAURA LEWIS: You know, it's been known for a long time that sleep is really important for brain health, but why it is, you know, is more mysterious.

HAMILTON: Lewis was part of a team that wanted to solve the mystery, so they found a way to watch what was going on in the brains of 11 sleeping people. Lewis says one of the things they monitored was the liquid that flows through the brain and spinal⁴ cord. It's called cerebrospinal fluid, or CSF.

LEWIS: And that's when we discovered that during sleep, there are these really large, slow waves occurring maybe once every 20 seconds of CSF washing into the brain.

HAMILTON: Like the oscillations of a very slow washing machine. Earlier studies of animals had found that the flow of CSF increases during sleep and helps carry away waste products, including the toxins associated with Alzheimer's. But Lewis' team was able to see this process occur in the brains of people in real time, and that led to another discovery.

LEWIS: Before each wave of fluid, we would actually see a wave of electrical activity in the neurons. This electrical wave always happens first, and the CSF wave always seems to follow seconds later.

HAMILTON: Suggesting that the electrical wave was triggering each wash cycle. That brain wave was a very familiar one, called a slow wave. Slow waves appear when a person enters the state known as deep sleep, and Lewis says they play a role in both memory and brain disease.

LEWIS: It's already known that people with Alzheimer's disease have less of these electrophysiological slow waves, so they have smaller and fewer slow waves.

HAMILTON: Lewis' study, which appears in the journal Science, suggests that this reduction in slow waves is reducing wash cycles in the brain, and she says that would limit the brain's ability to clear out the toxins associated with Alzheimer's.

LEWIS: It would make sense that if there's large waves of fluid, of CSF, that that might in turn cause mixing and dispersion of all kinds of other fluids in the brain and help with this waste removal process.

HAMILTON: Lewis' team made one more discovery about sleeping brains. As the flow of cerebrospinal fluid increases, blood flow decreases. Less blood in the brain means more room for CSF to carry away waste. Lewis says the brain's self-cleaning system all seems to depend on getting the right kind of sleep.

LEWIS: Some disruption to the way sleep is working could potentially be contributing to the decline in brain health.

HAMILTON: Including Alzheimer's. William Jagust at the University of California Berkeley says the finding fits nicely with other research on sleep and Alzheimer's disease. Jagust was part of a team that studied the relationship between slow wave sleep and a toxin¹ called beta-amyloid, which accumulates in the brains of people with Alzheimer's. He says they found something a bit disturbing.

WILLIAM JAGUST: It's a vicious cycle where amyloid decreases sleep and decreased sleep results in more beta-amyloid.

HAMILTON: Jagust says the new study suggests the increase in amyloid could be the result of less waste removal in the brain. He says it's likely that Alzheimer's, like heart disease, has more than one cause.

JAGUST: There are a bunch of things that are probably contributing to people's likelihood to getting Alzheimer's, and I think sleep is going to turn out to be one of them.

HAMILTON: Jon Hamilton, NPR News.

1 toxin   

n.毒素，毒质

参考例句：

• Experts have linked this condition to a build-up of toxins in the body.专家已把这一病症与体内毒素的积累联系起来。
• Tests showed increased levels of toxin in shellfish.检验表明水生有壳动物的毒素水平提高了。

2 toxins   

n.毒素( toxin的名词复数 )

参考例句：

• The seas have been used as a receptacle for a range of industrial toxins. 海洋成了各种有毒工业废料的大容器。
• Most toxins are naturally excreted from the body. 大部分毒素被自然排出体外。 来自《简明英汉词典》

3 byline   

n.署名；v.署名

参考例句：

• His byline was absent as well.他的署名也不见了。
• We wish to thank the author of this article which carries no byline.我们要感谢这篇文章的那位没有署名的作者。

4 spinal   

adj.针的，尖刺的，尖刺状突起的；adj.脊骨的，脊髓的

参考例句：

• After three days in Japan,the spinal column becomes extraordinarily flexible.在日本三天，就已经使脊椎骨变得富有弹性了。
• Your spinal column is made up of 24 movable vertebrae.你的脊柱由24个活动的脊椎骨构成。