If our fears were truly forgettable, many of us would lead better lives. And although the science isn’t quite there yet, researchers at Fudan University in Shanghai have taken a promising step.
Scientists wanted to see if they could erase fear memories in adult mice by transplanting a group of young neurons from mice embryos, called MGE cells, into older brains. MGE cells mature into inhibitory neurons, which travel across the brain and help make parts of the developing mind of a baby mouse (or human) more moldable. The process is partly why young children quickly absorb new information, such as languages.
“When you’re an adult, that period of plasticity closes, and the whole cortex works this way,” said Arturo Alvarez-Buylla, a professor of neurosurgery at the University of California, San Francisco. “But the remarkable thing is that these cells come from a little tiny place inside the brain, they go on this long journey, then they get to the right place and they hook up in exactly the right way to work properly — and this lab in China is taking advantage of that process.”
Previous work from Alvarez-Buylla and many others showed that MGE cells travel across the brain and help reintroduce plasticity into adult mice, but this is the first time scientists leveraged that to erase traumatic memories. By injecting MGE cells into the amygdala with a needle, they created the period of malleability they needed to do the job.
Scientists taught the mice to fear a sound by shocking them every time it was played. The mice would show their fear by freezing. Then the researchers tried to eliminate the fear using extinction training, a method that basically involves playing the sound repeatedly without a shock until the mice get over it. It worked — those with the brain cell transplant froze the least after extinction training, especially when they received it two weeks after the transplant. The findings are promising, but it’s unclear how to apply them to humans.
“Maybe we don’t do such an aggressive surgery on the human amygdala, but perhaps we could someday inject some protein [to] help the amygdala easily learn new behavior,” said Wuzhou Yang, a master’s student at Fudan University and part of the study.
Either way, it could be just a matter of time before we can reintroduce childlike flexibility into our brains. After all, the power to forget is something that many people crave and would pay money to have.
Kelly Kasulis is a journalist living in Boston and the deputy digital editor of The GroundTruth Project. Follow her on Twitter @KasulisK.