Scientists have discovered a way to restore the memories of mice by using a special treatment that utilizes light, finding memories that were previously “lost” deep within the brain.

The study, published in the journal Science, allowed the mice to simply “reactivate” memories they had been suppressing, suggesting that those who have lost memories after brain trauma may not have lost their memories at all, but simply lost hte ability to find them again, according to a Washington Post report.

The finding opens up exciting new possibilities for treating brain trauma victims and restoring memory that had previously seemed to have been gone forever, but maybe hasn’t gone anywhere.

Scientists used what is known as optogenetics, which allows them to pick out specific neurons and then use an engineering virus to introduce a special protein to those neurons, which makes those brain cells sensitive to blue light. Then, scientists can tweak those neurons on and off whenever they want to, according to the report.

The scientists experimented by creating a traumatic incident for the mice by shocking them repeatedly inside an enclosure, and noted which neurons were stimulated by the experience. Then, they used optogenetics to make those neurons light sensitive for a new batch of mive before running the same shock test on them.

Then, they used a drug called anisomycin to cause retrograde amnesia, causing the mice to stop being afraid of the shock chamber. Then researchers used blue light to activate the neurons that held the memories, and they began to fear the chamber again.

Unfortunately, the discovery won’t help humans with amnesia in the near future. One reason is that it is invasive work with ethical concerns, but there are other obstacles as well. However, it does provide some hope for the future.