Your eyes get heavy and gradually... close...
It’s only lunchtimeand you still have so much to do.
Would taking a nap help?Or would it derail your day?
Our sleep, both at night and in naps,
is made up of approximately 90 minutesleep cycles with four stages each.
A nap can last anywhere from five minutesto three hours,
so it can include full sleep cyclesor just a few stages.
As you fall asleep, you enter Stage 1:the first two to five minutes of sleep.
Stage 2 comes next, for about 30 minutes.
In Stage 2, body temperature drops, muscles relax,
and breathing and heart rate become more regular.
Your neurons start to fire in unison,
creating waves of activity that sweep across the cortex,
punctuated by rapid bursts of neural activity called sleep spindles.
As you enter Stage 3,or slow wave sleep,
the rolling waves increase as your neuronsfire in coordination.
This phase lasts about 20 to 30 minutesand is where your deepest sleep occurs.
Then, you enter REM sleep, which lastsabout 10 to 20 minutes in a nap.
In REM, the brain becomes more active,more like your brain activity while awake.
The end of REM signals the completion of a sleep cycle.
OK, but will a nap make you feel better?
Well, that depends on a few things—
especially what stages of sleepthe nap includes.
Take a 30 minute nap, which consists mainly of Stage 2 sleep.
Stage 2 sleep is associated with long-term potentiation,
a process that's thought to strengthenthe synapses between neurons,
which is essential for learning.
A 20 to 30 minute nap stops shortof Stage 3′s deep sleep,
making it relatively easy to wake up from.
A 30 to 60 minute nap, meanwhile,has the benefits of Stage 2 sleep
and also takes you into the deeper sleep of Stage 3.
During Stage 3, multiple brain areaswork together to transfer information
from short-term memory storageto long-term storage,
stabilizing and strengthening long-term memory
by coupling sleep spindles with slow waves.
Stage 3 is the most difficult stage to wake up from.
So while a 30 to 60 minute napcan have cognitive benefits,
those benefits often don’t kick in until about 15 minutes after waking up.
60 to 90 minute naps enter the REM stage.
While in REM, the prefrontal cortex,
which is largely responsible for inhibition and cognitive control,
Meanwhile, the amygdala and cingulate cortex,
regions associated with emotion and motivation, are highly active.
Researchers have posited that the combination of these things
leads to bizarre dreams during REM sleep:
the decrease in inhibition and cognitivecontrol might lead to wild associations—
and, thanks to the amygdala and cingulate cortex activity,
those associations can be between emotionally charged topics.
Some researchers think this stage mighthelp us make innovative connections
Because the brain activity duringREM is closer to waking,
it may be easier to wake up from REM than Stage 3,
even though the nap is longer.
Our need for deep Stage 3 sleep progressively increases
you may rob yourself of the sleep pressureneeded to go to sleep at night.
This doesn't happen for REM sleep.
Longer periods of REM occurduring morning hours,
so morning naps are dominated by REM,
midday naps have about equal partsof REM and deep sleep,
and evening naps contain more deep sleep.
On top of all this, it seems that we’re just about evenly split
between nappers and non-nappers.
Nappers consistently showcognitive benefits from napping,
Researchers think this could be because nappers
are able to stay in a lighter sleepand move through sleep stages more easily.
Meanwhile, non-nappers may experiencemore deep sleep while napping,