Scientists at the University of York, in collaboration with the University of East Anglia, have shown that sleep deprivation interferes with the brain’s ability to restrict unwanted memories.
As we enter the trenches of the assessment period, more and more students are starting to exchange rest for revision and sleep for studying. So it can become increasingly difficult to get the full recommended 8 hours sleep (which may be slightly higher for women).
A new study, published in the journal Proceedings of the National Academy of Sciences, found that limiting the sleep of otherwise healthy participants negatively affected that participant’s ability to suppress bad memories.
These unwanted memories can be fairly tame, like the remembrance of a mildly embarrassing moment or a minor accident. But these memories can also serve as a reminder of traumatic and deeply stressful incidents that the participant has tried to suppress.
Dr Scott Cairney from the University of York’s psychology department said: “Memories of unpleasant experiences often intrude into our conscious mind in response to reminders, but tend to be fleeting and can be put out of the mind again, but we have previously shown that the brain’s ability to suppress such intrusive memories is contingent on obtaining restful sleep.
“Suppression is a very clever function of the brain as it weakens all of the connecting traces of the memory, thereby inhibiting us from joining up all the dots to retrieve the full picture of the experience when it is triggered by an external stimulus.”
The experiment:
A team of psychologists used functional magnetic resonance imaging (fMRI) scans to investigate the brain activity of 85 healthy adults, half of which had experienced a healthy night’s sleep in the sleep lab, and the other half stayed awake all night.
The participants were then asked to observe several different faces, which they had previously seen paired with images of distressing scenes.
For each face, the participant was asked to either recall the scene associated with it, or suppress the memory of the scene.
When attempting to suppress the scene images, the well-rested participants showed more activation in the right dorsolateral prefrontal cortex – a brain region that controls thoughts, action, and emotions – compared to those who stayed awake all night.
The rested participants also showed reduced activity in the hippocampus – a brain region involved in memory retrieval – during attempts to suppress unwanted memories, demonstrating that they could turn off their intrusive thoughts with more ease than the unrested participants.
Dr Cairney explains: “The participants who were sleep deprived were unable to engage the area of the brain that helps us suppress unwanted memories. Consequently, they could not quash memory related processes in the hippocampus that give rise to intrusive thoughts.
“This is really important to our understanding of mental health issues as it is well documented that those who suffer with anxiety, depression or PTSD, also have difficulty with sleep. Now that we have better understanding of the the mechanisms in the brain that can help restrict negative memories and thoughts, we can perhaps work on more targeted treatments and behavioural therapies that help with improving sleep and as a result support the brain in doing what it has so cleverly adapted to doing, allowing us to lead mentally fit lives.”
The results:
The study shows that rapid eye movement (REM) sleep is vital in decreasing next-day brain reactivity to emotional experiences by supporting the activity of the prefrontal cortex.
Sleep (and enough of it) is really important to get you through a tricky exam season. The embarrassing memory of when you tripped up over your shoelaces on school picture day is probably the last thing you want popping into your head when you’re trying to write an essay.