"By analyzing the neural networks of the brain, the researchers have found that memories of secondary significance to us are wiped away during sleep, " writes Medical Xpress.
During sleep our brain analyses which neurons contain useful information and which of them contain trivial facts. Those that do not contain beneficial information begin to weaken with time and disappear.
The goal of the researchers' experiments was to discover what kinds of processes our brain performs during sleep. They examined the neurons of lab mice while they slept.
Maintaining neural networks requires a lot of energy and even though the capacity of our memory allows it, our brain wipes away the insignificant memories since their activity is unneeded.
It's much more efficient to retain only the most crucial information. Even in that state the human brain still burns about 20% of the calories we take in.
Lead researcher Ana Gonzalez Rueda explains that discarding certain memories helps the brain prevent over-excitement of the nervous system. It takes a very long period of time before the brain does any actual memory dumping though.