Suppressing unwanted memories could interfere with the creation of new ones.

Michael Anderson of the University of Cambridge, UK, and his colleagues asked volunteers to learn pairs of words such as 'pump' and 'oil'. The participants were then cued by one word and asked to either recall, or purposely not think about, the other word in the pair. Between these trials, people viewed various scenes and had to imagine how an object came to be in the scene. The researchers found that, compared with no memory suppression, participants accurately recalled the object's identity about 45% less frequently if the scene was presented shortly before or after memory-suppression trials. The extent of the forgetting effect correlated with how much hippocampus activity was dampened during the memory-suppression trials. (The hippocampus is an area of the brain that is involved in memory processing.)

This 'amnesic shadow' could help to explain memory lapses that can follow traumatic experiences, when people try to suppress certain memories, the authors suggest.

Nature Commun. 7, 11003 (2016)