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Does sleep affect our emotions and memories?

24 November 2011

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Sleep has been linked to reduced activity in the part of the brain that processes emotions and memory, according to a report published in the journal Current Biology.

A total of 34 healthy adults were shown emotional images, twice, 12 hours apart. They were asked to rate how emotional they found the images on a scale of one to five at each viewing. Sleep tests, including functional magnetic resonance imaging (MRI) scans and electroencephalogram (EEG) scans, were used to measure the amount of brain activity during the tests. Half of the people were allowed to sleep between viewing the images, whereas the other half remained awake.

The researchers specifically looked at part of the brain called the amygdala. This part of the brain is thought to process emotions and memory.

Researchers found that when people had slept, their emotional response to the same stimuli was not as strong. This was because the amygdala activity was reduced during sleep. There was an increase in amygdala activity in those who stayed awake between viewing the images and there was no change in their second set of ratings.

Interestingly, the researchers suggest that these results could be because of chemical changes in the brain that occur during a stage of sleep known as rapid eye movement (REM), when you’re most likely to dream.

Dr Layla McCay, Assistant Medical Director, Bupa, commented: “This is an interesting report, but we can’t necessarily draw any firm conclusions from it. Only a very small number of people were looked at and it’s difficult to suggest that viewing emotionally charged images could replicate the same feelings caused by real-life experiences and traumas. While people may have been affected by the images, they aren’t necessarily a true representation of real life and can’t directly prove that sleep helps to ease painful memories.

“Despite lots of research, sleep remains a bit of a mystery to us. However, we do know that sleep is vital for our wellbeing. If you’re having trouble sleeping, there are several things you can do to help you nod off. Make sure that your mattress is comfortable and that the temperature isn’t too hot or cold in your bedroom. It’s also important to establish a good sleep routine by relaxing before bedtime and just using your bedroom for sleeping – not eating or watching TV. It also helps to go to bed at the same time each night – even at the weekend.”

A total of 34 adults aged 18 to 30 were looked at. They were shown 150 emotionally stimulating images. The researchers also conducted a control test using 150 new images that people hadn’t seen before, to confirm that the changes between those who slept and those who stayed awake weren’t affected by the time of day.

Key facts

  • There are different types and stages of sleep that make up the sleep cycle. Non-rapid eye movement (non-REM) sleep has four stages, which occur during light sleep and deep, or slow-wave, sleep.
  • The second type is rapid eye movement (REM) sleep. During REM sleep your brain is active. Your eyes move rapidly from side to side but the rest of your body will be relaxed. This is the time when you dream.
  • An MRI scan is a technique that uses powerful magnets, radio waves and computers to produce detailed images (or scans) of the inside of the body.
  • An EEG is a test that measures the electrical activity of the surface of the brain. It’s used by doctors to help diagnose different brain conditions, including sleep problems.

How can we help you?

Worried about the effects of an unhealthy lifestyle?

Get checked out with a Bupa Health Assessment. Our assessments are designed to help you understand and manage your health. Call 0845 600 3458 quoting ref HFS100 to book an appointment today.

Read the study

Van der Helm E, Yao J, Dutt S, et al. REM sleep depotentiates amygdala activity to previous emotional experiences. Curr Biol 201. doi: 10.1016/j.cub.2011.10.052

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