(Newswire.net — September 1, 2014) — A new study from MIT has shown that neuroscientists can reverse the emotional association of specific memories by manipulating brain cells with optogenetics – a technique that uses light to control neuron activity and literally pin down cells in the brain that carry the information.
“Emotion is intimately associated with memories of past events and episodes, and yet the ‘valence’ – the emotional value of the memories – is malleable,” said the study’s senior author Prof Susumu Tonegawa, a Nobel-winning immunologist who is the paper’s senior author and director of the RIKEN-MIT, Center for Neural Circuit Genetics at MIT’s Picower Institute for Learning and Memory.
The researches established good and bad memories in the mice (with food rewards, or light shocks) and recorded the parts of the brain that dealt with the location (hippocampus) of those events, and the emotional recording part (amygdala).
Neuroscientists have devised a technique for switching the emotional association of a memory from bad to good by directly manipulating the neurons that encode it. To switch the memories, when the mice returned to the location where they received the shock or food, they triggered the location memory of the other event. The mice then displayed behaviours of consistent with the opposite memory (quickly moving from, or remaining calm in the current location).
Prior to the memory altering procedure, when the researchers put the mouse in the enclosure where he’d received the shock and used a pulse of laser light to reactivate the memory in his brain, the mouse avoided the area where he’d gotten zapped.
But when they did this after the memory altering procedure, the mouse spent more time in that area and even sniffed around a bit, as if looking for his lady friends. His memory of this place, it seems, had changed from bad to good.
Such memories have two components that are encoded by different parts of the brain. The memory of where it happened is encoded by the hippocampus. The emotional component—the memory of whether it was good or bad—is encoded by the amygdala.
The results, described in the August 27 issue of Nature, demonstrates that a neuronal circuit connecting the hippocampus and the amygdala can be manipulated.
By manipulating this circuit with light, scientists believe they can change or erase memory and even help treat conditions such as post-traumatic stress disorder in humans.
“One may be able to develop methods that help people to remember positive memories more strongly than negative ones,” says Susumu Tonegawa.
A separate study by researchers at Harvard published in PLOS ONE has demonstrated that xenon, a noble gas typically used in humans as an anesthetic, can disrupt the process in which traumatic memories are re-encoded.
However, if that sounds like a promising therapy for disorders like PTSD, don’t hold your breath.
The methods, which include genetically altering neurons and inserting an optical fiber into the brain, won’t be used in people anytime soon, if ever. But this study, and others like it, are illuminating the neural mechanisms of memory in unprecedented detail, and showing that it’s possible to activate, alter, or even create memories just by tweaking the right neurons.