Memories in the Night: How Your Brain Comes Alive While You Sleep

SleepThe idea that sleep has a reparative effect on the brain is longstanding. Even outside neurology, such a claim seems obvious to anyone who’s ever experienced the bone-deep fatigue of prolonged wakefulness and the refreshment of quality sleep (that is, every vertebrate who ever lived).

But while there’s almost a century of evidence from psychology on things like long-term memory consolidation, we still don’t really know what the physiological mechanism is. As Dr. Anna Majewska, assistant professor, Department of Neurobiology and Anatomy, Center for Visual Science at the University of Rochester Medical Center and post doctoral fellow, Department of Brain and Cognitive Sciences at MIT says, “Sleep serves a million functions. Figuring all those out and how they intersect is very hard.”

We’ve seen research that seems to confirm our suspicions about sleep’s role in neural regeneration. A study published in Neuron called it the “price we pay for plasticity.” As the researchers wrote, the increase in plasticity that happens as we learn and experience inputs (expressed physically as connections between neurons) can’t be sustained for long because it consumes energy, cellular resources, and space. The more it happens, the less efficient and more erratic neural signaling gets, affecting learning and memory (we experience that as being simply tired).

The only answer is to put the brain into an “offline” state where it can consolidate the strength of connections without the constant flow of inputs that happens when you’re awake.

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