Breaking down memories

Memories are not static, unchanging pieces of information stored in the library of the brain. Rather, they are dynamic elements that are remodelled every time they are retrieved. 

A memory comprises a series of proteins that are stabilized and consolidated in the brain’s memory centre (the hippocampus). When a memory is recovered, some of its proteins are broken down and rebuilt before the updated memory is stored again. Working with mice pre-conditioned with a fear memory, Bong-Kiun Kaang and a team from Seoul National University found that degradation of memory proteins is controlled by a system that labels them with a common protein called ubiquitin and degrades them using an enzyme complex called a proteosome¹.

The team found that memory proteins were labelled and degraded within one hour of memory retrieval and that blocking proteosome activity prevented degradation. Protein degradation seems to be important in the reorganisation of memory, allowing the ensuing protein synthesis to rebuild the memory and incorporate new information. Also, protein degradation plays a part in memory extinction, which is the removal or ‘unlearning’ of a memory. Future work will study the signal that stimulates the labelling and degradation of memory proteins.