The brain actually works 24 hours. When you sleep, it is time for your brain to sort out and process information and consolidate your learning experience. Active areas of the brain are alternately excited. But you can't work 24 hours a day. If you don't sleep for a while, you will die. I read a biography that said that the East India Company punished the aborigines during the colonial rule and didn't let them sleep. As a result, those aborigines died in great pain. The brain does consume a lot of oxygen. Some crazy scientists tried to drill holes in the skull and remove the brain bones in order to make their oxygen more abundant, but it didn't seem to be a trend and didn't win the Nobel Prize. Unfortunately, it hurts in vain.