The value of sleep and the power of naps

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Your eyes feel heavy. Slowly they are closing. But wait, it’s only noon, and there is still a lot to do. Would taking a nap help? Or would it mess the rest of your day?

What is sleep, and how is it composed?

Sleep, either at night or during a nap, is made up of 90-minute cycles. Each cycle is made up of 4 phases, while a siesta can last between 5 minutes and 3 hours. It means that it can include complete sleep cycles or just a few sleep phases.

Upon falling asleep, immediately enter phase 1. This phase lasts approximately 2 to 5 minutes. Phase 2 comes right after and lasts about 30 minutes. Here your temperature decreases, muscles relax, and breathing and heart rates become more regular. Your neurons fire in unison and create waves of activity that navigate the cerebral cortex, accentuated by rapid bursts of neural activity, which experts call sleep spindles.

As you entered phase 3, or slow-wave sleep, the undulating waves increase as your neurons fire in coordination. This phase is where the most profound dreaming occurs and lasts between 20 to 30 minutes.

Afterward, you enter REM (Rapid Eye Motion) sleep, which on a nap lasts between 10 to 20 minutes. In REM, the brain is more active; its activity is similar to the one performed while awake. The end of REM indicates a complete sleep cycle.

And then, would a midday nap help you?

It depends on a few factors. Especially considering what phases of sleep your nap would include.

Think of a half-hour nap. It would be primarily a phase 2 sleep. Phase 2 is strongly associated with long-term empowerment. A process that is beneficial to strengthen the synapse between neurons. Something essential for learning.

A nap that lasts between 20 to 30 minutes does not reach the deep sleep of phase 3, which makes it relatively easy to wake up after this. Half to one hour nap has the benefits of phase 2 and leads to the deep sleep of phase 3.

During phase 3, multiple brain regions transfer information from the short-term memory storage area to the long-term memory storage area. Which stabilizes and strengthens long-term memory by pairing the sleep spindles with slow frequency waves.

Phase 3 is the phase of sleep from which it is most difficult to wake up. So while a 30- to 60-minute nap offers cognitive benefits, those benefits typically don’t kick in until about 15 minutes after waking up.

Naps of 60 to 90 minutes enter the REM phase. Being in REM, the prefrontal cortex, responsible for cognitive control and inhibitions, becomes much less active. Meanwhile, the amygdala and cingulate cortex – regions associated with emotions and motivation – remain very busy.

Many researchers have argued that the combination of these factors causes bizarre dreams during REM sleep. Decreased inhibitions and cognitive control can lead to strange associations. And thanks to the activity of the amygdala and cingulate cortex, these associations can be between highly emotionally charged subjects.

Some researchers think that this phase helps us find innovative connections between ideas upon awakening. Since brain activity during REM is closer to being awake, it is usually easier to wake up from REM than from phase 3, even if the nap is longer.

Best time for a nap

The time of day is also crucial. Our need for deep sleep like phase 3 increases progressively throughout the day. So if you take an afternoon nap, you may be depriving yourself of the sleep pressure necessary to sleep at night.

The same does not happen for the REM phase; most periods of REM occur in the morning. So, most morning naps occur in REM. Midday naps have about the same REM sleep and deep sleep, and afternoon naps contain mostly deeper sleep.

It seems the world is divided evenly between those who take naps and those who don’t.

Nappers generally show cognitive benefits from napping, but non-nappers show no difference when taking an eventual nap. Researchers believe this is because nappers have an easier time staying in a light sleep phase and move through the sleep cycle easier. While non-nappers generally experience deeper sleep phases when taking one, making their heads cloggy when they wake up.

So would a nap help? There is only one way to find out.

Info: Sara C. Mednick for TED Ed.