Sleep is a complex neurological process characterized by shifting brain patterns, fluids flushing in and out of the skull, and a drop in body temperature, all with the apparent aim of restoring the brain as its waking functions are disabled.
In this process, the hormone norepinephrine appears to play a significant role, even though it’s released at lower levels during sleep compared to when we’re awake.
“We have learned that noradrenaline causes you to wake up more than 100 times a night,” co-first author Celia Kjærby, an assistant professor from the Center for Translational Neuromedicine, said in a statement.
“Neurologically, you do wake up, because your brain activity during these very brief moments is the same as when you are awake. But the moment is so brief that the sleeper will not notice,” PhD student Mie Andersen, the other co-first author of the study, added.
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“You could say that the short awakenings reset the brain so that it is ready to store memory when you dive back into sleep,” Maiken Nedergaard, a Professor of Glial Cell Biology at the University of Copenhagen, speculated.
Indeed, when the researchers artificially reduced the amplitude of norepinephrine’s oscillation in mice’s sleeping brains, either through genetic engineering or pharmaceuticals, they found that the mice performed worse on memory tests compared to unaltered controls.
