Many of us know what it’s like to suffer through a bad night’s sleep. We toss and turn, our thoughts doing likewise, and no matter how we lie we just can’t get comfortable. Our body is screaming at us to go to sleep but our brains are resolutely refusing to do so.

Many believe this restlessness to be a purely psychological phenomenon; stress, anxiety, worry, planning and simply thinking about your day can all keep us awake at night. There may, however, be an underlying neural mechanism at work which has long been masked by these negative thought processes.

Researchers from the University of Copenhagen, led by Professor Maiken Nedergaard, have discovered that differing levels of salt in the brain determines our sleep-wake cycle.

Sleep-wake cycles have long been thought to exist under the influence of so-called neuromodulators. These are compounds which, as the name suggests, modulate the activity of neurons within the brain in order to wake us up or put us to sleep. Hormones and neurotransmitters are examples of such compounds.

Despite strong evidence for the theory that neuromodulators directly influence our sleep-wake cycle, the mechanism by which this actually works has been very unclear.

Using mice models, the team found that injecting salt into the brain can actually supersede the influence of these neuromodulators. Specifically, higher levels of salt in the brain cause neurons to become hypersensitive to stimulation, whether that be from sound, light or other events in your environment. As a result, these stimuli wake you up.

These findings don’t negate the role neuromodulators play on the sleep-wake cycle. In fact, the results indicate that the reason for varying levels of salt is due to the neuromodulators themselves. Rather than influencing neurons directly, they influence salt levels instead. It is in essence a three step process:

Neuromodulators -> salt -> the sleep-wake cycle

Previous research has been unable to identify this process as studies have mostly focused solely on neuronal activity, and ignored the possibility of extracellular ion levels manipulating how said neurons behave.

So does this mean that if you eat more salt you’ll be able to get up in the morning? Well, probably not. I don’t think your brain or your blood pressure would thank you for that. We have only just discovered this relationship between neuromodulators and sleep, and are a long way off from harnessing said relationship to improve sleep.

As Dr Nedergaard explains, there is an awful lot more to study, and that’s before we begin to even think about research with human participation:

“The brain is more than a group of neurons that function like a computer. The fact that the brain needs 7-8 hours of sleep to function well on a daily basis reveals that there’s much more we need to understand, aside from neurocomputation.”

If you’re lucky enough to have a journal subscription, you can read the original article at Science.