题目内容：

    We could learn vocabulary while we are asleep. Researchers showed it is possible 1. (learn) new information while sleeping deeply, and recall this information later. They did tests to see 2. a person could remember new words and their translations while sleeping. The answer is yes. The language areas of the brain remember vocabulary during sleep, especially during deep sleep. While sleeping, our brain switches on for about half a second and then switches3. for half a second. The active state  4.(call) “up-state”. This is how our brain could learn new vocabulary.