A new research suggests that ‘lost’ memories are just hiding in the brain waiting to be re-discovered again, well in mice, anyway. A published study by researchers in Science last Thursday mentioned their success in reactivating memories they had blocked. The research indicated that in retrograde amnesia, memories that are lost due to brain trauma, could be more of a retrieval operation rather than a complete lose of memory.
Optogenetics is a process which harnesses light to control neurons which have been genetically sensitized to light. Scientists use the light to choose specific neurons which were treated with a special protein using an engineered virus. Once the brain cells are subjected to this particular protein, the cells become sensitive to blue light, allowing researchers to turn specific neurons on and off at will.
In creating traumatic memories, the mice were subjected repeatedly to shocks inside an enclosure. Neurons were then picked out and stimulated when the mice start to re-live the bad memories and made those neurons together which are called “memory engram” light sensitive in new group of mice before exposing them in the same shock treatment.
Then the researchers made those bad memories disappear the way they might do to a person with retrograde amnesia. A drug called anisomycin was then injected to some of the mice, which messed up their memory formation. Those mice stopped being afraid of the shock chamber, until the blue light were used by researchers to activate the neurons that holds the repressed memory. Then their fear reaction return.
The researchers then concluded, that “lost” memories could still make engrams active in the brain, based on their findings.