One more reason to get a good night’s sleep
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0:01 - 0:02Sleep.
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0:02 - 0:05It's something we spend about
a third of our lives doing, -
0:05 - 0:09but do any of us really understand what it's all about?
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0:09 - 0:11Two thousand years ago, Galen,
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0:11 - 0:13one of the most prominent medical researchers
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0:13 - 0:14of the ancient world,
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0:14 - 0:16proposed that while we're awake,
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0:16 - 0:20our brain's motive force, its juice,
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0:20 - 0:22would flow out to all the other parts of the body,
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0:22 - 0:26animating them but leaving the brain all dried up,
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0:26 - 0:28and he thought that when we sleep,
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0:28 - 0:30all this moisture that filled the rest of the body
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0:30 - 0:32would come rushing back,
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0:32 - 0:34rehydrating the brain
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0:34 - 0:36and refreshing the mind.
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0:36 - 0:39Now, that sounds completely ridiculous to us now,
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0:39 - 0:41but Galen was simply trying to explain
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0:41 - 0:43something about sleep
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0:43 - 0:45that we all deal with every day.
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0:45 - 0:47See, we all know based on our own experience
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0:47 - 0:50that when you sleep, it clears your mind,
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0:50 - 0:51and when you don't sleep,
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0:51 - 0:54it leaves your mind murky.
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0:54 - 0:57But while we know a great deal more about sleep now
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0:57 - 0:59than when Galen was around,
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0:59 - 1:01we still haven't understood why it is that sleep,
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1:01 - 1:04of all of our activities, has this incredible
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1:04 - 1:07restorative function for the mind.
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1:07 - 1:08So today I want to tell you about
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1:08 - 1:10some recent research
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1:10 - 1:12that may shed new light on this question.
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1:12 - 1:16We've found that sleep may actually be
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1:16 - 1:18a kind of elegant design solution
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1:18 - 1:21to some of the brain's most basic needs,
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1:21 - 1:22a unique way that the brain
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1:22 - 1:25meets the high demands and the narrow margins
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1:25 - 1:30that set it apart from all the other organs of the body.
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1:30 - 1:33So almost all the biology that we observe
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1:33 - 1:36can be thought of as a series of problems
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1:36 - 1:38and their corresponding solutions,
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1:38 - 1:41and the first problem that every organ must solve
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1:41 - 1:44is a continuous supply of nutrients to fuel
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1:44 - 1:46all those cells of the body.
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1:46 - 1:48In the brain, that is especially critical;
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1:48 - 1:50its intense electrical activity uses up
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1:50 - 1:53a quarter of the body's entire energy supply,
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1:53 - 1:55even though the brain accounts
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1:55 - 1:58for only about two percent of the body's mass.
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1:58 - 2:00So the circulatory system
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2:00 - 2:02solves the nutrient delivery problem
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2:02 - 2:05by sending blood vessels to supply nutrients
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2:05 - 2:08and oxygen to every corner of our body.
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2:08 - 2:11You can actually see it in this video here.
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2:11 - 2:13Here, we're imaging blood vessels
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2:13 - 2:16in the brain of a living mouse.
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2:16 - 2:18The blood vessels form a complex network
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2:18 - 2:20that fills the entire brain volume.
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2:20 - 2:22They start at the surface of the brain,
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2:22 - 2:25and then they dive down into the tissue itself,
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2:25 - 2:28and as they spread out, they supply nutrients
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2:28 - 2:33and oxygen to each and every cell in the brain.
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2:33 - 2:36Now, just as every cell requires
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2:36 - 2:38nutrients to fuel it,
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2:38 - 2:41every cell also produces waste as a byproduct,
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2:41 - 2:43and the clearance of that waste
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2:43 - 2:45is the second basic problem
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2:45 - 2:48that each organ has to solve.
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2:48 - 2:50This diagram shows the body's lymphatic system,
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2:50 - 2:53which has evolved to meet this need.
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2:53 - 2:56It's a second parallel network of vessels
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2:56 - 2:58that extends throughout the body.
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2:58 - 3:00It takes up proteins and other waste
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3:00 - 3:02from the spaces between the cells,
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3:02 - 3:04it collects them, and then dumps them into the blood
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3:04 - 3:07so they can be disposed of.
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3:07 - 3:08But if you look really closely at this diagram,
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3:08 - 3:10you'll see something
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3:10 - 3:12that doesn't make a lot of sense.
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3:12 - 3:15So if we were to zoom into this guy's head,
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3:15 - 3:17one of the things that you would see there
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3:17 - 3:21is that there are no lymphatic vessels in the brain.
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3:21 - 3:24But that doesn't make a lot of sense, does it?
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3:24 - 3:28I mean, the brain is this intensely active organ
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3:28 - 3:30that produces a correspondingly
large amount of waste -
3:30 - 3:33that must be efficiently cleared.
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3:33 - 3:36And yet, it lacks lymphatic vessels, which means that
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3:36 - 3:37the approach that the rest of the body takes
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3:37 - 3:39to clearing away its waste
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3:39 - 3:42won't work in the brain.
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3:42 - 3:45So how, then, does the brain solve
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3:45 - 3:46its waste clearance problem?
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3:46 - 3:50Well, that seemingly mundane question
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3:50 - 3:53is where our group first jumped into this story,
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3:53 - 3:55and what we found
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3:55 - 3:58as we dove down into the brain,
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3:58 - 4:01down among the neurons and the blood vessels,
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4:01 - 4:03was that the brain's solution
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4:03 - 4:05to the problem of waste clearance,
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4:05 - 4:07it was really unexpected.
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4:07 - 4:10It was ingenious,
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4:10 - 4:13but it was also beautiful.
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4:13 - 4:15Let me tell you about what we found.
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4:15 - 4:17So the brain has this large pool
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4:17 - 4:21of clean, clear fluid called cerebrospinal fluid.
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4:21 - 4:22We call it the CSF.
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4:22 - 4:26The CSF fills the space that surrounds the brain,
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4:26 - 4:28and wastes from inside the brain
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4:28 - 4:30make their way out to the CSF,
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4:30 - 4:33which gets dumped, along with
the waste, into the blood. -
4:33 - 4:34So in that way, it sounds a lot like
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4:34 - 4:37the lymphatic system, doesn't it?
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4:37 - 4:40But what's interesting is that the fluid and the waste
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4:40 - 4:41from inside the brain,
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4:41 - 4:44they don't just percolate their way randomly
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4:44 - 4:46out to these pools of CSF.
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4:46 - 4:50Instead, there is a specialized network of plumbing
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4:50 - 4:54that organizes and facilitates this process.
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4:54 - 4:56You can see that in these videos.
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4:56 - 4:59Here, we're again imaging into the brain
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4:59 - 5:00of living mice.
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5:00 - 5:02The frame on your left shows
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5:02 - 5:04what's happening at the brain's surface,
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5:04 - 5:06and the frame on your right shows
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5:06 - 5:08what's happening down below the surface of the brain
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5:08 - 5:10within the tissue itself.
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5:10 - 5:12We've labeled the blood vessels in red,
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5:12 - 5:14and the CSF that's surrounding the brain
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5:14 - 5:16will be in green.
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5:16 - 5:18Now, what was surprising to us
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5:18 - 5:21was that the fluid on the outside of the brain,
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5:21 - 5:24it didn't stay on the outside.
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5:24 - 5:27Instead, the CSF was pumped back into
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5:27 - 5:29and through the brain
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5:29 - 5:32along the outsides of the blood vessels,
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5:32 - 5:34and as it flushed down into the brain
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5:34 - 5:36along the outsides of these vessels,
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5:36 - 5:39it was actually helping to clear away,
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5:39 - 5:41to clean the waste from the spaces
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5:41 - 5:44between the brain's cells.
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5:44 - 5:46If you think about it,
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5:46 - 5:50using the outsides of these blood vessels like this
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5:50 - 5:52is a really clever design solution,
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5:52 - 5:55because the brain is enclosed
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5:55 - 5:57in a rigid skull
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5:57 - 5:59and it's packed full of cells,
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5:59 - 6:02so there is no extra space inside it
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6:02 - 6:05for a whole second set of vessels
like the lymphatic system. -
6:05 - 6:06Yet the blood vessels,
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6:06 - 6:08they extend from the surface of the brain
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6:08 - 6:11down to reach every single cell in the brain,
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6:11 - 6:12which means that fluid
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6:12 - 6:15that's traveling along the outsides of these vessels
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6:15 - 6:19can gain easy access to the entire brain's volume,
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6:19 - 6:21so it's actually this really clever way
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6:21 - 6:25to repurpose one set of vessels, the blood vessels,
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6:25 - 6:28to take over and replace the function
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6:28 - 6:31of a second set of vessels, the lymphatic vessels,
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6:31 - 6:34to make it so you don't need them.
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6:34 - 6:36And what's amazing is that no other organ
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6:36 - 6:38takes quite this approach
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6:38 - 6:41to clearing away the waste from between its cells.
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6:41 - 6:46This is a solution that is entirely unique to the brain.
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6:46 - 6:49But our most surprising finding
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6:49 - 6:51was that all of this,
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6:51 - 6:53everything I just told you about,
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6:53 - 6:56with all this fluid rushing through the brain,
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6:56 - 7:01it's only happening in the sleeping brain.
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7:01 - 7:02Here, the video on the left
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7:02 - 7:04shows how much of the CSF is moving
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7:04 - 7:08through the brain of a living mouse while it's awake.
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7:08 - 7:10It's almost nothing.
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7:10 - 7:11Yet in the same animal,
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7:11 - 7:15if we wait just a little while until it's gone to sleep,
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7:15 - 7:17what we see is that the CSF
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7:17 - 7:20is rushing through the brain,
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7:20 - 7:22and we discovered that at the same time
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7:22 - 7:25when the brain goes to sleep,
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7:25 - 7:27the brain cells themselves seem to shrink,
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7:27 - 7:29opening up spaces in between them,
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7:29 - 7:31allowing fluid to rush through
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7:31 - 7:34and allowing waste to be cleared out.
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7:34 - 7:37So it seems that Galen may actually have been
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7:37 - 7:39sort of on the right track when he wrote about
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7:39 - 7:42fluid rushing through the brain
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7:42 - 7:43when sleep came on.
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7:43 - 7:47Our own research, now it's 2,000 years later,
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7:47 - 7:49suggests that what's happening is that
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7:49 - 7:51when the brain is awake
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7:51 - 7:53and is at its most busy,
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7:53 - 7:55it puts off clearing away the waste
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7:55 - 7:58from the spaces between its cells until later,
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7:58 - 8:00and then, when it goes to sleep
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8:00 - 8:03and doesn't have to be as busy,
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8:03 - 8:05it shifts into a kind of cleaning mode
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8:05 - 8:07to clear away the waste
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8:07 - 8:08from the spaces between its cells,
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8:08 - 8:11the waste that's accumulated throughout the day.
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8:11 - 8:13So it's actually a little bit like how you or I,
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8:13 - 8:16we put off our household chores during the work week
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8:16 - 8:18when we don't have time to get to it,
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8:18 - 8:21and then we play catch up on all
the cleaning that we have to do -
8:21 - 8:24when the weekend rolls around.
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8:24 - 8:27Now, I've just talked a lot about waste clearance,
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8:27 - 8:28but I haven't been very specific
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8:28 - 8:30about the kinds of waste
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8:30 - 8:32that the brain needs to be clearing
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8:32 - 8:35during sleep in order to stay healthy.
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8:35 - 8:36The waste product that these recent studies
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8:36 - 8:39focused most on is amyloid-beta,
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8:39 - 8:42which is a protein that's made
in the brain all the time. -
8:42 - 8:44My brain's making amyloid-beta right now,
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8:44 - 8:46and so is yours.
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8:46 - 8:48But in patients with Alzheimer's disease,
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8:48 - 8:51amyloid-beta builds up and aggregates
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8:51 - 8:53in the spaces between the brain's cells,
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8:53 - 8:56instead of being cleared away
like it's supposed to be, -
8:56 - 8:58and it's this buildup of amyloid-beta
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8:58 - 9:00that's thought to be one of the key steps
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9:00 - 9:03in the development of that terrible disease.
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9:03 - 9:06So we measured how fast amyloid-beta is cleared
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9:06 - 9:08from the brain when it's awake
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9:08 - 9:09versus when it's asleep,
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9:09 - 9:11and we found that indeed,
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9:11 - 9:13the clearance of amyloid-beta
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9:13 - 9:18is much more rapid from the sleeping brain.
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9:18 - 9:19So if sleep, then,
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9:19 - 9:21is part of the brain's solution
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9:21 - 9:23to the problem of waste clearance,
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9:23 - 9:26then this may dramatically change how we think
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9:26 - 9:28about the relationship between sleep,
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9:28 - 9:31amyloid-beta, and Alzheimer's disease.
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9:31 - 9:33A series of recent clinical studies
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9:33 - 9:35suggest that among patients
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9:35 - 9:38who haven't yet developed Alzheimer's disease,
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9:38 - 9:41worsening sleep quality and sleep duration
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9:41 - 9:43are associated with a greater amount
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9:43 - 9:46of amyloid-beta building up in the brain,
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9:46 - 9:48and while it's important to point out
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9:48 - 9:50that these studies don't prove
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9:50 - 9:52that lack of sleep or poor sleep
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9:52 - 9:54cause Alzheimer's disease,
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9:54 - 9:57they do suggest that the failure of the brain
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9:57 - 9:59to keep its house clean
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9:59 - 10:02by clearing away waste like amyloid-beta
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10:02 - 10:03may contribute to the development
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10:03 - 10:07of conditions like Alzheimer's.
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10:07 - 10:09So what this new research tells us, then,
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10:09 - 10:11is that the one thing that all of you
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10:11 - 10:13already knew about sleep,
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10:13 - 10:15that even Galen understood about sleep,
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10:15 - 10:18that it refreshes and clears the mind,
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10:18 - 10:20may actually be a big part
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10:20 - 10:22of what sleep is all about.
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10:22 - 10:24See, you and I, we go to sleep
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10:24 - 10:26every single night,
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10:26 - 10:29but our brains, they never rest.
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10:29 - 10:30While our body is still
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10:30 - 10:33and our mind is off walking in dreams somewhere,
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10:33 - 10:35the elegant machinery of the brain
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10:35 - 10:37is quietly hard at work
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10:37 - 10:39cleaning and maintaining
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10:39 - 10:42this unimaginably complex machine.
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10:42 - 10:43Like our housework,
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10:43 - 10:46it's a dirty and a thankless job,
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10:46 - 10:48but it's also important.
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10:48 - 10:51In your house, if you stop cleaning your kitchen
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10:51 - 10:52for a month,
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10:52 - 10:55your home will become completely unlivable
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10:55 - 10:57very quickly.
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10:57 - 10:59But in the brain, the consequences
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10:59 - 11:02of falling behind may be much greater
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11:02 - 11:04than the embarrassment of dirty countertops,
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11:04 - 11:07because when it comes to cleaning the brain,
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11:07 - 11:09it is the very health and function
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11:09 - 11:12of the mind and the body that's at stake,
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11:12 - 11:14which is why understanding these
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11:14 - 11:19very basic housekeeping functions of the brain today
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11:19 - 11:22may be critical for preventing and treating
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11:22 - 11:25diseases of the mind tomorrow.
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11:25 - 11:27Thank you.
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11:27 - 11:29(Applause)
- Title:
- One more reason to get a good night’s sleep
- Speaker:
- Jeff Iliff
- Description:
-
The brain uses a quarter of the body's entire energy supply, yet only accounts for about two percent of the body's mass. So how does this unique organ receive and, perhaps more importantly, rid itself of vital nutrients? New research suggests it has to do with sleep.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TEDTalks
- Duration:
- 11:41
Morton Bast edited English subtitles for One more reason to get a good night's sleep | ||
Morton Bast approved English subtitles for One more reason to get a good night's sleep | ||
Morton Bast edited English subtitles for One more reason to get a good night's sleep | ||
Morton Bast edited English subtitles for One more reason to get a good night's sleep | ||
Morton Bast edited English subtitles for One more reason to get a good night's sleep | ||
Madeleine Aronson accepted English subtitles for One more reason to get a good night's sleep | ||
Madeleine Aronson edited English subtitles for One more reason to get a good night's sleep | ||
Madeleine Aronson edited English subtitles for One more reason to get a good night's sleep |