How salts in the brain make us wake up

"Our study shows that the brain uses something as simple as changing the level of salts to control whether we are asleep or awake," says Maiken Nedergaard. (Credit: Kevin Schoenmakers/Flickr)

Salts in the brain appear to play a bigger role than scientists previously thought in how we fall asleep and wake up.

By influencing the level of salts, researchers were able to control a mouse’s sleep-wake cycle.

“The brain is more than a group of neurons that function like a computer.”

“The discovery reveals a completely new layer of understanding of how the brain functions,” says Professor Maiken Nedergaard, co-director of the University of Rochester Center for Translational Neuromedicine and lead author of the study.

“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.”

The study, published in Science, focused on a collection of ions that reside in the cerebral spinal fluid (CSF).

By altering the concentrations of potassium, calcium, magnesium, and proton ions found in the fluid, the researchers observed that they could manipulate the sleep-wake state of mice in the absence of neurotransmitters. Potassium in particular appears to play a key role as the levels of the ion fluctuate rapidly during sleep-wake transitions.

While these shifts in ion concentration outside of brain cells had been known to occur, these changes had always been regarded as a consequence rather than one of the causes of the sleep-wake cycle, as the new study suggests.

“The fact that a simple alteration of extracellular ion composition can wake a sleeping animal up and put a wake animal to sleep is direct evidence for that this mechanism plays a key role in regulating consciousness,” says Nedergaard, who also conducts research at the Center for Basic and Translational Neuroscience at the University of Copenhagen.

“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,” says Nedergaard.

Sources: Mark Michaud for the University of Rochester and Kristine Snedker for the University of Copenhagen

(Note: This story was edited to include additional information provided by the University of Rochester.)