Sleeping after learning really does give the memory a boost.
Researchers found that sleeping after learning encourages the growth of dendritic spines, which connect brain cells and pass on information, an NYU Langone Medical Center news release reported.
The finding suggests that the combination of sleep and learning causes physical changes in the motor cortex, which is responsible for voluntary movements.
"We've known for a long time that sleep plays an important role in learning and memory. If you don't sleep well you won't learn well," senior investigator Wen-Biao Gan, PhD, professor of neuroscience and physiology and a member of the Skirball Institute of Biomolecular Medicine at NYU Langone Medical Center, said in the news release. "But what's the underlying physical mechanism responsible for this phenomenon? Here we've shown how sleep helps neurons form very specific connections on dendritic branches that may facilitate long-term memory. We also show how different types of learning form synapses on different branches of the same neurons, suggesting that learning causes very specific structural changes in the brain."
Researchers have long-believed that while we sleep the brain replays memories that were created throughout the day.
The researchers looked at mice that were genetically engineered to "express a fluorescent protein in neurons," the news release reported. They used laser-scanning microscope to view thise fluorescent protein in the motor cortex. This allowed the researchers to track the "image and growth" of the mice's dendritic spines along individual dendrite branches as the rodents learned skills such as balancing on a spin rod.
The team trained one group of mice on the spin rods and then had them sleep for seven hours; a second group trained for the same period of time and then stayed awake for seven hours.
The team found that the sleep-deprived mice had less dendritic spine growth than those who slept after training.
"Now we know that when we learn something new, a neuron will grow new connections on a specific branch," Doctor Gan said in the news release. "Imagine a tree that grows leaves (spines) on one branch but not another branch. When we learn something new, it's like we're sprouting leaves on a specific branch."