2014英语四级听力练习:慢速英语8.27(2)_大学英语听力

2014英语四级听力练习:慢速英语8.27(2)

　　From Learning English, this is the Health Report.

　　Why do we need sleep?

　　Is bedtime just a time for dreaming? Do our brains turn off for the night? What if I told you that scientists recently discovered that our brains may be just as busy at night as they are during the day?

　　While we sleep, our brains are doing much more than getting ready for the next day. Researchers at the University of Rochester found that the brain may be busy cleaning house -- cleaning out harmful waste materials.

　　As with many studies, the researchers turned to mice for help. They studied mice that had colored dye injected into their brains. They observed the mice brains as they slept and when they were awake. The researchers say they saw that the brains of sleeping mice were hard at work.

　　Working Double Duty

　　Dr. Maiken Nedergaard led the study. The brain expert says our brains perform two very different jobs. It seems they have daytime jobs. Later they moonlight at a nighttime job.

　　Moonlighting is working a nighttime job in addition to a day job. And this study says that is what our brains seem to be doing working an extra job at night without additional pay for overtime.

　　When we are awake, the brain cells are working very hard at processing all the information about our surroundings. Whereas when we are asleep, they work very, very hard at removing all the waste that builds up when we are awake.