The power of the nap to help us control our emotions

When her daughter was in preschool age, Rebecca Spencer experienced something that many parents and caretakers know well: the power of a nap.

Without a nap, her daughter was dizzy, grumpy, or both at the same time.

Spencer, a sleep neuroscientist at the University of Mbadachusetts in Amherst, USA, wanted to explore what lies behind this anecdotal experience.

"Many people realize that a child without a nap is emotionally deregulated," he says. "This led us to ask ourselves a question:" Do naps really help to deal with emotions? "

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Scientific research has already shown that in general, sleep helps us understand emotions. In fact, he plays a key role in coding the information extracted from the day's experiences. It is therefore essential to preserve memories.

And the emotional memories are unique because of the way they activate the body of the amygdala: the emotional core of the brain.

"Activating the body of the tonsil is what allows you to remember the day of your wedding and your parents' funeral more than any other day of work," Spencer said.

The body of the amygdala attributes to these memories a meaning, so that they are treated longer during sleep and that they are repeated more than other unimportant memories.

The result is that emotionally important memories are easier to recover in the future.

But by influencing the treatment of memories, dreams can also change their power.

"Sleep is especially effective at transforming emotional memory," said Elaina Bolinger, Emotion and Sleep Specialist at the University of Tuebingen, Germany.

In a recent study, Bolinger and his colleagues showed both negative and neutral images to children 8 to 11 years old. The children showed their emotional reaction by choosing simple drawings representing people.

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Later, some children slept and others did not. The researchers controlled their cerebral physiology with electrodes from the next room.

The next morning, the children saw the same pictures, as well as new ones. And compared to the children who stayed awake, the children who had slept controlled their emotional reactions better.

This research suggests that sleep helps to crystallize emotional information and control what we feel. And this effect occurs quickly.

"Much of the current research indicates that a single night's sleep is already useful," Bolinger said. "It's useful for the treatment of memories, but also for emotional regulation in general."

But all the dream is not the same.

Types of sleep

Rapid eye movement paradoxical sleep is badociated with emotional memories, and having more REM sleep allows people to better evaluate the intentions of others and to remember emotional stories.

One theory suggests the absence of noradrenaline, a stress hormone, during REM sleep. Temporarily released from this hormone, the brain can process memories without stress.

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Simon Durrant, head of the sleep and cognition laboratory at the University of Lincoln, England, points to another aspect.

The prefrontal cortex is the most developed part of the brain: it is there that Durrant says "the human impulse to keep calm and not react immediately to things".

Upon waking, it is the part that keeps the body of the tonsil under control and, therefore, the emotions. During sleep, this connection is reduced.

"In a sense, during REM sleep, emotion is endemic."

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But Spencer thinks that non-paradoxical sleep also plays an important role. Slow Sleep (SWS) is the first phase of sleep that consolidates memories and is particularly effective when processing neutral memories.

Spencer's research suggests that the amount of SWS activity during sleep affects the transformation of emotional memories.

Naps consist mainly of non-REM sleep. And a recent article co-written by Spencer seems to be the first to show that naps, not just nighttime sleep, contribute to the treatment of emotional memory in children.

Without taking a nap, the children showed a bias for the emotions. With the nap, they reacted in a similar way to neutral stimuli and emotional stimuli.

In summary, he badures that "if they do not take a nap, children become hypersensitive to emotional stimuli" because they have not consolidated the emotional baggage of this day.

Spencer thinks that naps also contribute to the treatment of emotions in adults, but not to the same extent. An adult has a more mature hippocampus and, therefore, a greater ability to preserve his memories. Not sleeping does not hurt them too much.

However, it is only up to a certain point. Spencer's research on aging suggests that "we need to consolidate our memories more often as we get older".

It is interesting to note that older adults show a preference for positive memories, while young adults tend towards negative ones.

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This may be because children and adolescents focus on negative experiences because they contain essential information to learn: from the dangers of fire to the risk of accepting a drink from a stranger.

But towards the end of life, people give priority to the positive. They also have less paradoxical sleep, the type of sleep that will save the most negative memories, especially in depressed people.

Therapeutic Uses

Sleep researchers are also badyzing the potential of some facets of sleep to treat post-traumatic stress disorder (PTSD).

One study suggests that sleeping within 24 hours of a traumatic experience makes these memories less painful later. Sleep therapy can help people with anxiety to remember that they have eliminated their fear.

On the contrary, sleep therapy, in which people are deliberately deprived of sleep, is spreading as a method of treating depression.

Insomnia can in some cases have a protective effect. Spencer notes that "after a trauma," the natural biological response in these conditions is to suffer from insomnia ".

Thus, it can sometimes be good that the lack of REM sleep alters the brain's ability to consolidate emotional memories.

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"There is evidence that people with longer REM sleep tend to be more depressed," says Durrant. The expert thinks that this is because a subgroup of depressed people is restoring negative memories during REM sleep.

"I do not think I will be able to solve this problem," he says of all the potential clinical applications of sleep therapy and wakefulness.

But it is clear that some types of decision making improve after sleep, partly because of the way sleep regulates all this whirlwind of feelings.

Bolinger clearly explains: in general, "sleep helps to feel better".

In the end, the best recipe for a broken heart or a troubled mind can be a nap.

Read the original story in English on BBC Future.

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