Sleep is one of those things that has an absence as powerful as its presence. A lack of sleep comes with its own face – eyelids that hang, eyes that are redder and more swollen, darker circles, paler skin, wrinkles or fine lines, and a wilting mouth. It is a face that is often identified by others as being sad, communicating, perhaps, that they should go gently. There are also major changes that we can’t see. The brain is shaped by every experience, and a scarcity of pillow time is a heavyweight when it comes to having an influence.

Being able to tell what is important is vital to effectively reading people and situations, but a lack of sleep causes us to lose our neutrality. New research has found that one night of limited sleep is enough to wreak havoc with the brain’s ability to tell what is important, leading it to see everything as significant. It also is enough to weaken our ability to regulate our emotions, and it causes problems for cognitive processing. We will always struggle to learn, remember, attend, judge, solve problems or make decision when we’re wrestling with a lack of sleep.

The research. What they did.

For the study, researchers kept 18 adults awake all night. Following their sleepless night, researchers mapped the brains of the participants who were asked to identify the direction of travel of small yellow dots that moved over distracting images. The images were chosen because of their different emotional impacts – ‘positively emotional’ (a cat), ‘negatively emotional’ (a mutilated body), or ‘neutral’ (a spoon).

After a good night’s sleep, the participants were quicker and more accurate in identifying the direction of the dots hovering over the neutral images. Brain scans revealed the brain responded differently, depending on whether the images were neutral or emotional.

In contrast, when the participants were sleep deprived, they performed badly for both the neutral and the emotional images. According to brain scans, there was very little difference to the way their brains responded to the emotional and the neutral images.

‘It could be that sleep deprivation universally impairs judgement, but it is more likely that a lack of sleep causes neutral images to provoke an emotional response.’ –Ben-Simon, Researcher, Tel Aviv University.

In the second part of the study, researchers tested concentration, and the degree to which emotional things or neutral things caused distraction. After only one night of a lack of sleep, participants were distracted by every image – neutral and emotional. On the other hand, the participants who had plenty of sleep were only distracted by the emotional images.

Interestingly, brain scans revealed that the part of the brain involved was the amygdala. The amygdala is key to the detection of threat and the activation of the fight or flight response. It’s a big player in anxiety and in any situation that involves confrontation (fight) or avoidance (flight).

What it means.

Without sleep, we’ll struggle to tell the difference between the things that could hurt us and the things that won’t. Our brains give as much weight to something neutral as it does to something more emotional. Understandably, this can lead to a bucketload of trouble.

‘We may experience similar emotional provocations from all incoming events, even neutral ones, and lose our ability to sort out more or less important information. This can lead to biased cognitive processing and poor judgement as well as anxiety.’ -Professor Talma Hendler, Tel Aviv Universisty’s Sagol School of Neuroscience.

Our brains are constantly scanning the environment for threats. We’re all wired to do this and it’s important to keeping ourselves safe. It does this beautifully, but sometimes it can do it too much. Not only does a lack of sleep tend us towards being cranky or irritable, it also puts our brain on high alert.

Being able to read the environment and respond appropriately is critical to having healthy relationships and to living well. The problem with having a brain that’s so quick to interpret things as potential trouble, is the heightened tendency to respond to harmless things as though they could be a problem.

It’s no surprise then, that when we’re tired, we can be fragile or quick to temper when something is said or done, much to the confusion of the innocent ones in the line of fire. It also makes it clear why it’s so important to catch plenty of peaceful zzz’s the night before something difficult – an exam, an interview, a date. Our brains love sleep, they adore it, and given that we’re completely reliant on our brains to walk us through life as seamlessly as we can, one of the best things we can do for ourselves is to make sure we get plenty of uninterrupted, blissful pillow time.