You may be wanting to forget shameful moments of your bad life but imagine how beneficial forgetting would be for the victim of a rape ...

Researchers have revealed that the memory of a traumatic event could be wiped out, even if other associated recollections would not be modified.

This has been recently proven in rats by a researcher in the Laboratory for the Neurobiology of Learning, Memory and Communication (CNRS/Orsay University), collaborating with an American team. The results of this research could be employed to cure patients affected by post-traumatic stress.

Recalling an event stuck in the long-term memory initiates a reprocessing phase: the recollection then turns sensitive to pharmacological disturbances before being stored again in the long-term memory. So, could a drug therapy wipe out the initial memory, and only that memory?

The researchers trained rats to be frightened of two different sounds, by making them listen to these sounds just before applying an electric shock to their paws. The next day, half of the rats were administered a drug that provokes amnesia for events recalled from memory, and they were exposed to just one of the sounds again.

When the team played both sounds to the rats next day, those which had not ingested the drug were still frightened of both sounds, while those on drugs were no longer afraid of the sound they had heard under the drug's influence.

Recalling the unpleasant memory of the electric shock linked with the sound played while rats were on drugs thus revealed that the memory was wiped out by the chemical, leaving unaffected the memory linked with the other sound.

The team also recorded the neuronal activity of rats in the amygdale, an brain nucleus linked to emotional memory. Remembering the traumatic memory increased significantly neuronal activity but this was decreased in drugged rats. Thus the chemical disturbance of the memory recalled wiped out selectively this memory, and only this memory.

This research is the first one to prove that a memory can be affected or even wiped out at the cellular level, permanently and independently of other memories linked to it.