Neurobiologists have discovered a mechanism by which the constantly changing brain retains memories.

They have found that the brain co-opts DNA methylation, the same machinery by which cells stably alter their genes to specialize during embryonic development.

In this process, molecules called methyl groups are attached to genes, which switches them off. Conversely, lack of methyl groups enables the genes to remain activated.

Using drugs that inhibit methylation, the researchers showed that methylation was necessary for rats to form such memories and that the level of methylation directly controlled the activity of genes known to either suppress or promote memory formation.