(NaturalNews) Has a bad experience ever made you cringe when thinking about returning to the place where it happened? Or have you had a good experience that perpetually evokes fond memories of a certain smell or taste? These and other positive and negative emotion associations may seem permanently engrained into your psyche, but new research has found that they can be turned on and off through brain cell manipulation.

Publishing their findings in the journal Nature, researchers from the Massachusetts Institute of Technology (MIT) have discovered that brain circuits can be activated and altered to invoke memories in varying emotional contexts. In other words, positive associations with a thing or place can be changed into negative ones, and vice versa.

The idea is that individuals who have experienced trauma, for instance, can be reprogrammed to no longer suffer when presented with memories or places associated with that trauma. And in the same way, positive experiences, such as going to the beach with friends, can be turned negative through activating certain receptors that basically signal new information in your brain.

"Emotion is intimately associated with memories of past events and episodes, and yet the 'valence' - the emotional value of the memories - is malleable," said Prof. Susumu Tonegawa from the Riken-MIT Center for Neural Circuit Genetics, lead author of the study.

'Massaging' brain cells to alter the perception of memories

Prof. Tonegawa and his team have been researching the subject for years, having learned several years ago that memories can be labeled based on where they're stored in the brain, and turned on or off to evoke certain emotions. If the memory is a negative one, that labeled memory can be activated at any time, creating those same emotions in an instant.

Several years later, that discovery was expanded to include memories of places, which can also be conjured up and made to be associated with either positive or negative emotions. The location where a loved one died, for instance, can be reactivated in a new context to eliminate all associations of its negative context.

For the latest research, Prof. Tonegawa and his team subjected male mice to a negative experience, in this case a series of small electric shocks given in a specific room. Naturally, these mice became afraid of the room based on their experience in it, a recollection of memory that the team labeled "optogenetics" for the purpose of the study.

After subjecting the mice to the shocks, the team put the mice in a different room and, by sending a blue light into their brain, effectively "reactivated" the original, fearful memory. They then gave the mice the option of having the blue light switched on or off, which they naturally chose to have turned off based on its negative association.

But the scenario changed when the team recreated the experience for the mice with a positive emotional cue, which in this study was the introduction of female mice as company. The team then observed that the mice chose to have the blue light switched on, as it stimulated neurons now associated with a positive experience.

"We changed the way the mice react to a memory, without any drugs," added Dr. Roger Redondo, a study co-author. "[This] occurs without the mice ever being brought back to the original place where the memory was formed. All the manipulation is done from within the brain."

Based on these findings, the team hopes to learn more about which, and how many, cells are associated with memories, and how these cells are best adjusted to trigger a flip in the way they're perceived, either positive or negative.

Sources for this article include:

http://www.bbc.com

http://newsoffice.mit.edu

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