Sleep strengthens memory, but not the bad ones! Scientific studies have found that shorter naps do not increase fear-related memories

*For medical professionals only

What if the pressure is too much? Just get some sleep
.
What should I do if I encounter something scary? Just get some sleep
.
What if a terrifying memory lingers in the brain? Just get some sleep
.
This is the method we commonly use to stabilize people, and it is also the ostrich method
that we often use when we encounter major changes.

But does sleeping really work?

With the deepening of the research on the relationship between sleep and memory, people gradually realize that sleep has the function of
consolidating new memories.
Therefore, after some major events, we will see words in various channels advising everyone not to go to sleep immediately, so as not to deepen the fear memory and cause secondary harm
to the parties.

But in fact, according to the available research results, the consolidation effect of sleep on this conditioned fear memory is inconclusive, some studies believe that sleep has no effect on emotional memory consolidation, and some studies believe that sleep enhances the fear response
.

Dr.
Yuri G.
Pavlov and his research team from the Institute of Medical Psychology and Behavioral Neurobiology at the University of Tübingen made healthy subjects receive conditioned fear memory, compared the subjects' response to re-exposure to fear conditions after a 2-hour nap or corresponding waking time, and found that sleep did not enhance the subjects' fear-response behavior, nor did it affect brain event-related potentials (ERP); Fear memories are gradually consolidated over time and are independent of whether or not to nap.

The study was published in Cognitive Affective & Behavioral Neuroscience
.

Fear is a strong, repressive emotional experience
.
After experiencing certain events that trigger intense fear, some people develop pathological fear responses and form fear conditioning as fear memories are formed
.
Panic disorder, specific phobias, and post-traumatic stress disorder (PTSD) are all fear-related disorders
.

Fear conditioning is a kind of associative learning, the neutral stimulus received by the person (such as sound) and the aversive stimulus (such as electric shock, noise) are repeatedly paired, and the neutral stimulus will also produce the same fear conditioning of the aversion stimulus
.
Neutral stimuli are also called conditioned stimuli, and aversion stimuli are also called unconditioned stimuli
.

To subside or attenuate this fear conditioning, you can compete with the original fear memory and further form new memory associations
by extinction learning, that is, constantly repeating conditioned stimuli.

On this basis, the formation, consolidation and regression of fear memory become an important basis
for the treatment and targeted intervention of fear-related diseases.
Sleep plays a crucial role in memory formation, helping to consolidate declarative memory (facts and personal experiences) and procedural memory (skills), while it is unknown whether emotional fear memories can be consolidated after
sleeping.

Trial design CS: neutral stimulus, US: aversion to stimulation

In this study, the researchers designed neutral stimuli and aversion stimuli
using different frequencies of sound.
CS+ indicates a neutral stimulus paired with an aversion stimulus, and CS- indicates a neutral stimulus that is not paired with an aversion stimulus
.

Participants construct a fear conditioning by repeatedly receiving neutral and aversion stimuli, followed by a 2-hour nap or corresponding waking time, followed by extinction learning (receiving only neutral stimuli and not aversive stimuli), or reacquisition (50% or 100% pairing of neutral and aversion stimuli).

Fear responses are evaluated
by subjective evaluation and neural association evaluation (i.
e.
, event neural potential, ERP).

The study excluded volunteers with a history of neurological or psychiatric illness, medication, and smoking, and ultimately included 18 participants with an average age of 24.
7 years
.

Participant ERP changes

Through observation, it can be found that the subject's ERP changes significantly after receiving aversion to malignant stimulation, and if only neutral stimulation is received, the ERP remains in a relatively stable state; During the same period, there was a significant difference in the ERP of CS+ and CS- in the subjects, and the difference between CS+ and CS- became larger
after sleep or wakefulness intervals.
At the same time, no effect of sleep on extinction learning was observed.

This means that after the fear conditioning is formed, the fear response is enhanced whether the participant goes to sleep or remains awake, regardless of sleep or wakefulness
.

Subjective evaluation of fear memories by subjects

Subjective assessments of fear memory were also not affected
by sleep or waking states.
However, exploratory correlation analysis showed that negative ratings of CS+ subjects were associated with
higher sleep quality during the reacquisition phase.

Overall, studies have demonstrated that fear memories or fear responses consolidate over time, and this consolidation is not
related to sleep.
After fear conditioning is formed, neither extinction learning nor reacquisition is affected
by the subject's sleep state.

Although this study also has a small sample size and sleep is designed to be only a nap, the results still remind us that our understanding of sleep and memory should indeed be updated
.
Further, how to prevent and treat fear-related diseases needs more exploration by scientists
.

In any case, I hope that everyone will not be imprisoned by fear memories and can have the courage to look forward to the future
.

References:

[1] Pavlov Y G, Pavlova N V, Diekelmann S, et al.
Fear memory in humans is consolidated over time independent of sleep[J].
bioRxiv, 2022.

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AuthorWang Xuening