The study was conducted by scientists at the European Molecular Biology Laboratory (EMBL), Monterotondo, Italy, and the University Pablo Olavide in Sevilla, Spain.
"This is the first time that a pathway in the brain has been linked to forgetting, to actively erasing memories," said Cornelius Gross from EMBL.
“One explanation for this is that there is limited space in the brain, so when you're learning, you have to weaken some connections to make room for others.
"To learn new things, you have to forget things you've learned before."
The study concentrated on the region of the brain responsible for forming memories, the hippocampus, where information enters through three different routes. When memories are cemented, connections between neurons along the main route become stronger.
However, when the scientists blocked this main route in the mice being tested they could no longer learn to associate a sound to a consequence, and anticipate that consequence (a Pavlovian response).
The only way the mice could retrieve that memory is if they had learned that association before the scientists stopped information flow in the main route.
This confirmed that this route is involved in forming memories, but is not needed for recalling those memories.
But blocking that main route had a surprising outcome. It resulted in the connections along it being weakened, and the memory being erased.
Moreover, the active push for forgetting was only found to occur in learning situations. The scientists tried blocking the main route into the hippocampus under other circumstances, and the strength of its connections did not change.
The study is published in Nature Communications
Learning a challenging task can dismantle brain barriers, says study
When the brain attempts to learn something new, it is also actively trying to forget, indicates new research.