Do bad memories still haunt you? Well, two studies have found that the bad memories can be history in real terms as they can be replaced with the good ones, opening new ways for traumatic stress treatment.
Two research teams on Wednesday reported that the bad remembrance can be erased or rewired and replaced with the once-happy memory so that a painful and distressed recollection is physically linked to the joyous one in the brain
The researchers used lab rodents for both the studies. The basis of the studies was a phenomenon called reconsolidation which was discovered in the 1990s.
Reconsolidation means when a memory is recovered, its physical symptoms are so changeable in the brain that it can be altered.
“Recalling a memory is not like playing a tape recorder. It’s a creative process,” said Susumu Tonegawa, lead author of one of the studies who is from the Massachusetts Institute of Technology.
In the first part, the MIT team gave male mice were kept in isolation and given electric shock in order to create bad memories for the animals and in the second part they were kept with their female partners, making a happy memory.
The brains of the mice were engineered so that the neurons could be activated with light. This technique is known as optogenetics.
The scientists reactivated the regions of the memories using lasers. The region where memories encoded is called the hippocampus.
When socializing memory was active, they got a shock, and when they were given shock memory the mice got active and started playing with females.
The shock memory became physically linked to brain neurons encoding pleasure, while the socializing one is connected to neurons encoding fear.
This change of brain wiring and its finding were reported in the journal Nature.
In another study, the researchers at the McLean Hospital in Boston exploited the flexibility of reactivated memories to omit them completely.
The rats were trained about lights: a flash of light leads a shock. The lights were turned on and the memory was reactivated. Animals were then immediately given an anesthetic called xenon gas that blocked molecules involved in formation of the memory. And the trained rats that were not given xenon remembered everything.
The second study was reported in the journal PLOS One: The rats forgot that light precedes a shock.