Do you remember the bad things that happened to you in life? Sure, you do, powerfully. But the good news is that it is possible to write over them and get a laundry bag of feel-good emotions.

Researchers from Japan and the US have found it out. There are strings that help to create psychotherapeutic fixes for mental bugs, such as depression or Post Traumatic Stress Disorder (PTSD). There are new roads you could walk on to treat these traumas, or even mild problems.

The study has been led by Howard Hughes Medical Institute investigator Susumu Tonegawa at the Massachusetts Institute of Technology (MIT), and published in the August 28, 2014, issue of "Nature." It

looks into optogenetics, a brain breakthrough that shone a light on memories.

The "contextual information" about events, i.e. logs of where and when they happened, is entered into the brain's hippocampus. The feelings are stored in the brain's emotional storehouse, the amygdala.

Emotional memories are powerful when the connexions between the two are strong. "It depends on how strongly the (good or bad aspect) dominates... there is competition between the two circuits' connection strengths," research leader Susumu Tonegawa said.

Their tests began with simple mice. They got some shots of algae protein in parts of the brain that were alert to light. To document good and bad memories, one set of male mice got to hang out with females, leaving behind some feel-good memories. Another group got quick electric shocks to create bad memories. The mice could then recollect their memories when the scholars shone light pulses to revive their memories.

Even while they were on their trips, the scientists switched the experiences to swap their emotions. The happy mice got electric shocks, while the shocked one got to meet the pretty females. The new emotion overcame the earlier ones.

New tests showed that the earlier fear memories had been wiped out. They could do it by pulling smart strings on the hippocampus. The new experience strengthened or weakened the links between the context in the hippocampus, as well as the memories in the amygdala.

Excited by their breakthroughs, they hope that they can treat depression, or PTSD, suffered by people with traumatic memories, such as war survivors. "In the future, I would like to think that with new technology we will be able to wirelessly control neurons in the brain, without intrusive tools like electrodes," said Tonegawa, who won the Nobel Prize for Physiology and Medicine in 1987.