Amnesia is one of the most gruesome diseases, as it turns oblivion into our worst enemy rather than our friend in need that always kills sorrow and makes life go on with a fresh start. Amnesia digs deeper into our memories, turning our brains into chaotic machines, unable to make relevant connections that can construct our reality.
A recent study published in Science reveals how a team of researchers was able to reactivate suppressed memories, indicating that retrograde amnesia, with lost memories after brain trauma, are more a problem of memory retrieval than actual loss of data.
The study was performed on mice and it seems that our memories are never lost but rather wait silently in distant corners of our brains, until they’re rediscovered again. Scientists have reached this conclusion through optogenetics, a process that involves using light to control neurons that are genetically sensitive to light stimuli.
The entire study consisted of using light waves in explicit neurons that were introduced to a special protein through an engineered virus. Once exposed, brain cells become sensitive to blue light, allowing scientists to turn on and off particular neurons, thus particular brain functions that involve memory.
To demonstrate the experiment, mice were exposed to bad memories by shocking them repeatedly in a particular enclosure. The neurons that reacted where then picked out and stimulated whenever mice were re-living the memory. This finding helped in alternative groups of mice that were exposed to the so called “memory engram” that was then through blue light to emphasize or suppress the effect, before training them with the same shock.
After the emphasis on a certain memory, connected to particular groups of neurons was made, researchers went through a complex process to make it all disappear, exactly the way they might do to a person with retrograde amnesia. This was performed through a drug called anisomycin that was injected to some of the mice, messing with memory formation.
Conclusion is that they stopped being afraid of the shock chamber, the number one bad memory provider. After that, blue light waves were used to activate the neurons holding back that particular repressed memory. The fear reaction came back immediately.
With this complex piece of research, scientists managed to discover particular links in the brain that can be stimulated for memory retrieval. The engram cells in one part of the hippocampus are strongly connected to another part of the same structure, which makes this pattern of connectivity survive drug treatments.
On the other hand, the amygdala, the fear based region of the brain where memories can be found, is involved in the network. This is how memories can be retrieved, with this chain of alternative connections that becomes active once exposed to light.
“These findings provide striking insight into the fleeting nature of memories, and will stimulate future research on the biology of memory and its clinical restoration”, declared lead author, Susumu Tonegawa.
Image Source: united-academics.org