One side of your brain might be giving you nightmares


Study explores what controls emotions while we sleep. Nick Carne reports.


What your brain does while you sleep might be the cause of angry dreams, research suggests.

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Researchers believe they have identified a pattern of brain activity that predicts anger experienced during dreaming.

It they are right, this might help explain the neural basis of the emotional content of nightmares, which are associated with mental and sleep disorders such as anxiety, depression and insomnia.

While humans experience emotions both while awake and while dreaming, there has been only limited research into the brain mechanisms underlying the affective component of dreams.

In the recent study, Pilleriin Sikka and colleagues at University of Turku, Finland, University of Skövde, Sweden, and University of Cambridge, UK, discovered a shared emotional mechanism between the two states of consciousness.

The researchers obtained electroencephalography recordings from 17 healthy individuals during two separate nights in a sleep laboratory.

After participants reached rapid eye movement (REM) sleep – the point where dreams are most vivid – they were woken and asked to describe their dreams and rate the emotions they experienced.

It was discovered that those who displayed greater alpha-band brain activity in the right frontal cortex, as compared to the left, both during evening wakefulness and during REM sleep experienced more anger in dreams.

This neural signature – called frontal alpha asymmetry (FAA) – has been linked to anger and self-regulation during wakefulness.

“We show that individuals with greater FAA (i.e. greater right-sided alpha power) during rapid eye movement (REM) sleep, and during evening wakefulness, experience more anger in dreams,” the researchers write in a paper published in the journal JNeurosci.

“FAA may thus reflect the ability to regulate emotions not only in the waking but also in the dreaming state.”

There were limitations to the study – notably that it was carried out under laboratory conditions – but the researchers suggest their findings “provide support for theories according to which dreaming is a realistic simulation of waking life”.

They stress, however, that on the strength of this study alone it is not possible to say whether the particular neural activation accompanying dream anger supports a certain function, such as to experience threatening situations or negative affective states in order to better deal with them in waking life.

  1. http://dx.doi.org/10.1523/JNEUROSCI.2884-18.2019
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