• Scientists study activity in the brain with a tool called electroencephalography ( EEG), that measures electrical signals coming from neurons.
• The brain is not turned off while you sleep - there is a lot of activity going on, even if you’re not aware of it. You cycle through four d...

• One of the systems in the brain that wakes us up is the reticular activating system (RAS) - a part of your brain located just above your spinal column that acts like a gatekeeper or filter for your brain, making sure it doesn’t have to deal with more information than it can handle.

When your brain is asleep, it shifts between deep and light stages. If your alarm clock goes off during a deeper stage of sleep, it takes longer for all the parts of your brain to wake up.