Your sleeping brain does many complicated things. It flushes out toxins and shapes and organizes your memories and thoughts. It also regulates your sleep and wake cycles, allowing you to pass in and out of the different stages of sleep.
On a good night, you’ll pass through several of these light and deep sleep cycles, with your brain activity characteristically ramping up and down during each of these phases.
During a formal sleep study, called a polysomnography, your doctor will be able to see — via your brain waves — how often and efficiently you pass through these stages. To do this, they hook you up to an electroencephalogram (EEG), which evaluates electrical brain activity.
They’ll also monitor your oxygen levels to ensure that you don’t stop breathing while you’re sleeping. If you do, you could have sleep apnea — a serious and debilitating condition that can lead to heart disease and stroke.
Read the full article at source: Scientist: Here’s why sleep tracking apps don’t work – Tech Insider