CAMBRIDGE, England — Sleep is restorative and rejuvenating, and, according to new research, the perfect time for reorganization. A new study shows that each night as we rest, our brains strengthen the neural connections that store important information, while weakening the ones that store unimportant information.
When we’re awake, we’re constantly taking in information — sensory input that is processed by the brain. The brain then orders this information into perceivable sensations, such as light waves being interpreted by our eyes, and stores the information for later use. In order for us to remember or learn anything, the brain has to create neural connections to store the data. But if the brain attempted to store and nurture all the information we observe in various ways throughout our days, it would become overloaded.
A team of scientists, led by Ana González Rueda at the University of Cambridge, investigated the mechanisms the brain uses to order and store memory during the slow wave sleep phase — the third phase of sleep that is generally the deepest and most restful, without rapid-eye movement.
“Depending on the experiences of a person and depending on their relevance, the size of their corresponding neuronal connections changes. Those that save important information are larger and those that store the dispensable are small,” Rueda explains in a media release.
Rueda and her team stimulated the neuron connections of mice given a type of anesthesia that brings their brains to a state similar to slow wave sleep in humans. They found that the largest neuronal connections are maintained by the brain, while the smaller ones are left to die. The brain also allows for the storage of different types of information on a day-to-day basis without losing previously stored data. The result is stronger, more consolidated memories.
In other words, González Rueda says, the brain “puts order” to our memories by prioritizing the most important pieces of information and getting rid of the useless ones.
“Although the brain has an extraordinary storage capacity, maintaining connections and neuronal activities requires a lot of energy. It is much more efficient to keep only what is necessary,” she says. “Even without maintaining all the information we receive, the brain spends 20% of the calories we consume.”
The study showed one of the first indications of the electro-physiological aspects of sleep, and provides a new way to study live synaptic plasticity. In future studies, the authors hope to see how the brain operates during the REM phase of sleep, when humans are typically dreaming.
The study was published online March 1, 2018 in the journal Neuron.