The researchers believe that brief bursts of electrical activity in this area, called "sleep spindles", somehow block external sounds form reaching any parts of the brain that might wake a person up.
You bring somebody in the sleep lab, you put electrodes on their scalp and you see what these — what sort of electrical activities you get in the brain.
把人叫来睡眠实验室，把电极贴在他们的头皮上，你就能看到-，他们有什么脑电活动。
3
It is the movement of potassium (and also sodium) ions that causes the electrical impulses that nerve cells carry-including the impulses found in slow-wave sleep.