How many hours sleep do you get every night? Is your sleep uninterrupted? How does lack of sleep affect the health of your brain?
Sleep is divided into two major phases of brain activity:
- rapid-eye-movement (REM)
- non–rapid-eye-movement (NREM) sleep.
Neuroscientist Dr Sarah McKay says that when you first fall asleep you experience NREM sleep, and then 60 to 90 minutes later, REM sleep kicks in. During the course of a normal night, a healthy adult will experience 4 to 6 consecutive sleep cycles of REM and NREM.
When you’re in NREM sleep, your body is able to move, but your eyes don’t; your breathing and heart rate slow and your blood pressure falls. Blood flow to the brain decreases, and electroencephalograms (EEGs – recordings of brain activity) show slowing of brain activity.
When you cycle into REM sleep, your body becomes immobile and yours eyes move about rapidly. Your blood pressure, heart rate, and breathing rate increase, and blood flow to the brain increases (and my gentlemen readers can attest to blood flow into other areas of the anatomy too). EEG activity also increases and you being to dream.
Neuroscience has shown that NREM sleep is essential for learning and memory. In fact, Dr McKay says that neuroscientists have been gathering evidence for some time that rats need NREM sleep to learn.
In this interview she explains the benefits of an afternoon nap. Sarah says there’s no harm in giving your brain a break if you are tired – but it’s important not to indulge in a long sleep during the day.