Scientists discover how brain erases unwanted memories

Researchers from the Cambridge University tested if suppressing memories or substituting them with more desirable memories could erase them and whether these tactics could engage distinct neural pathways.

To test this possibility, researchers used functional magnetic resonance imaging to examine the brain activity of volunteers who had learned associations between pairs of words and subsequently attempted to forget these memories by either blocking them out or recalling substitute memories.

Although the strategies were equally effective, they activated distinct neural circuits. During memory suppression, a brain structure called dorsolateral prefrontal cortex inhibited activity in the hippocampus, a region critical for recalling past events.

On the other hand, memory substitution was supported by caudal prefrontal cortex and midventrolateral prefrontal cortex - two regions involved in bringing specific memories into awareness in the presence of distracting memories.

"This study is the first demonstration of two distinct mechanisms that cause such forgetting: one by shutting down the remembering system, and the other by facilitating the remembering system to occupy awareness with a substitute memory," said lead study author Roland Benoit.

"A better understanding of these mechanisms and how they break down may ultimately help understanding disorders that are characterised by a deficient regulation of memories, such as posttraumatic stress disorder," Benoit said in a statement.

"Knowing that distinct processes contribute to forgetting may be helpful, because people may naturally be better at one approach or the other," he said.

The study was published in the journal Neuron.