The harrowing flashbacks experienced by people with post-traumatic stress disorder when recalling a memory of normal daily life are an example of what can happen when two memories become linked. By targeting specific brain cells, researchers have separated memories in mice without affecting how each memory is recalled individually.

Kaoru Inokuchi at the University of Toyama in Japan and his colleagues gave mice a mildly harmful chemical along with a sweetener, and then administered electric shocks at the same time as the animal heard a sound. The authors then gave the sweetener and made the sound at the same time to link the two memories. A specific group of neurons in the brain's amygdala stored this memory link. Suppressing the activity of these brain cells unlinked the memories, but the mice were still able to recall the individual memories.

The results suggest that a therapy targeting these brain cells could one day help people with post-traumatic stress disorder.

Science 355, 398–403 (2017)