Key takeaway 1 : Sleep is divided into 90 minutes cycles.

For each completed 90 minutes cycle, REM sleep (or deep sleep) gets increased. In other words, during a sleep cycle, more sleep within that cycle consists of REM sleep. And this is true whether the sleep is interrupted or not. So the more cycles one gets during the night, the more one gets REM sleep.

And this is important because REM sleep and non-REM sleep provide disctinct benefits.

Key takeaway 2 : The neuromodulators at work during sleep bias the role of the sleep phase

Different neuromodulators (norepinephrine, dopamine, serotonine, acetylcholine) are at play during sleep. But their concentration vary during the different phases of sleep. And these concentrations, due to the disctinct roles of these neuromodulators, influence the role of the sleep phase on recovery, learning, …

Key takeway 3 : Non-REM sleep (slow wave sleep) is important for motor-learning & detailed information learning

Non-REM sleep tends to occur during the beginning of the night. And during non-REM sleep, there is about zero acetylcholine, some norepinephrine and a ton of serotonin.

Due to this cocktail, non-REM sleep that occurs early in the night tend to be important for motor-learning as well as detailed information learning.

Key takeaway 4 : REM sleep is important for replaying some encountered events without fear attached to it

During REM sleep, serotonin and norepinephrine are essentially at zero levels.

Norepinephrine is not only the neuromodulator linked to altertness and the desire to move, it's also the chemical linked to fear and anxiety. And therefore, during REM sleep, since norepinephrine levels are at zero, this allows us to replay certain events (e.g. traumatic events or unpleasant events) without the fear being attached to it. One can also live contorted events of the reality (so live new experiences).

REM sleep therefore seems to allow unlearning of emotional events. Or at least, detaching the emotional burden linked to events.

Key takeaway 5 : Lack of REM sleep maks us irritable

Linked to key takeaway 4, lack of REM sleep makes us irritable because we are then unable to unlink the emotional burden from events. Therefore, small things turn into big things. We catastrophize everything.

Key takeaway 6 : Lack of REM sleep makes us lose meaning

During REM sleep, meaning is formed i.e. our brain devises whether it's a good thing to be with someone or somewhere, it associates things together (things and their purposes).

Therefore, lack of REM sleep causes people to be come weird e.g. associate things that are not supposed to be associated together, difficulty to find words, …

And it's crucial for functional human beings to have detailed association. Imagine if everything was bothering you or making you sad, this would become problematic.

Key takeaway 7 : EMDR or Eye Movement Desensitization Reprocessing mimics REM sleep effects

During EMDR protocol, people are asked to remember a traumatic or unpleasant event and at the same time to look laterally with their eyes in a repeating pattern.

The lateral eyes movement has for effect to deactivate the amygdala, which is involved in threat detection, stress, anxiety and fear. This protocol helps people to dissociate the anxiety/stress/fear associated with the event they are trying to remember. Note that the amygdala is not the fear center and that some fears are not associated with the amygdala.

Lateral eyes movement mimic what people usually do when engaging into locomotion (human-driven locomation so walking, running, …) without stress surrounding them (so not running from a bear but rather taking a tour in a quiet forest).

Note that EMDR protocol seems to work better for specific event, not entire traumatic periods.

Key takeaway 8 : Sleep is self-therapy

Getting a good sleep (non-REM and REM) provides one with essential functions to be a well functionning human being. See previous takeaways.

Key takeaway 9 : Sleep consistency matters

It's at least as important (and perhaps more important) to be consistent about sleep than it is to "get enough sleep".

A study showed that for each hour variation (less or more) around the mean, a decrease in 17% performance (for performing an exam) was observed.

This means that people need to adjust their sleep schedule to their needs. It's better to get consistently 6 hours of sleep than getting 6 then 10 then 4 then 6.

Key takeaway 10 : Serotonin supplements can increase the amount of REM sleep

During non-REM sleep, serotonin levels are low. Therefore, taking serotonin supplements or 5-HTP based supplements (precursor to serotonin) lead to increase levels of serotonin and therefore increased percentages of REM sleep.

Take care however that therefore non-REM sleep might be diminished and this has implications too.

Key takeaway 11 : Strength exercises tend to increase non-REM sleep

Resistance exercises tend to increase non-REM sleep (motor learning acquisition) throug their impact on the body. Note that one does not need to exercise close to bed to have this effect. In fact, exercising close to bedtime might lead to sleep disruption or phase shift (see other podcast)

Key takeaway 12 : Lucid dreaming can be influenced

If one desires to experience more lucid dreams, one can try to tether to the reality through a cue.

For example, one can draw a red apple on a notebook for several days before sleep. And then maybe during sleep, one will see a red apple and tie this experience to the reality of drawing the apple and push the conscious state into the sleeping state therefore creating lucid dreaming.