Scientists at the University of Copenhagen have recently discovered that salt levels in the brain can dictate whether we are in a state of sleep or wakefulness. The finding has important implications for treating psychiatric diseases like schizophrenia, as well as patients that suffer from convulsive fits and post-anesthetization confusion.
Maiken Nedergaard, who is the senior author in the study, and his team published their work in the journal Science last week.
Salts are essential in the normal functioning of all cells of the human body. It was previously shown by the first author of the study, Fengfei Ding, that a combination of neuromodulators could influence the levels of salt levels in the brain. This new work argues that salt levels are in fact changing the levels of neuromodulators and consequently brain activity between sleep and wake cycles.
Neuromodulators are neurotransmitters capable of relaying messages around the brain. An example of one of these complex molecules is adrenaline--known for being central in the “fight-or-flight” response. On the other hand, salts are simple ions and were not previously thought to have the role the researchers have reported.
In a series of mouse experiments, the Copenhagen researchers were able to control whether a mouse was asleep or awake by altering the levels of salt in their brains. The fine balance of salt levels between when we are awake and asleep is thought to sensitize (or desensitize) neurons in order to increase (or decrease) their firing.
"These salts play a much larger and much more decisive role than hitherto imagined," says Nedergaard. "The discovery reveals a completely new layer of understanding of how the brain functions. First and foremost, we learn more about how sleep is controlled. It may, however, also open up for a better future understanding of why some people suffer convulsive fits when staying awake all through the night.
"It's much simpler than previously believed in brain research," Nedergaard continued. "The research conducted used to focus only on the brain's neural activity as a means of mapping and analyzing complicated processes such as being asleep or awake. Our study shows that the brain uses something as simple as changing the level of salts to control whether we are asleep or awake. This discovery reveals that studying only neurons in order to understand brain activity is not enough. We must include all the supportive cells, especially the so-called astrocytes, which regulate the level of salts in the brain. 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."