Slow-wave sleep (SWS) is often referred to as
the first stage of deep sleep and consists of non-rapid eye
movement.

Slow-wave sleep
gets its name because
electroencephalography, or more commonly known EEG, is synchronized
producing slow frequency waves. This is the time that we are
getting the most rest as the neurons that control our brain are
able to relax.



EEG
can be used to diagnose sleep disorders and other
conditions such as epilepsy, by monitoring and recording sleep
patterns. EEG shows up on a graph similar to what you might think a
lie detector looks like, the wider the waves the more unrestful
sleep.



Slow-wave sleep is important for memory. This period of sleep is
usually dreamless which means you unconsciously focus on your
memory consolidation. Not only does this stage of sleep build up
mental energy, it rejuvenates your physical energy too. Muscle
activity decreases significantly, similar to your brain allowing
for rest, recovery and growth.


Fun Fact: You are asleep and your phone rings waking you up. If
you manage to answer it, it is likely that the person phoning will
know you've just been asleep. Sounding groggy and struggling to
make conversation is due to SWS slowing down your response to
stimuli.