The research team was able to implant optical fibers into genetically engineered mice to deliver pulses of light into their brains. Using this technique, known as optogenetics, the team was able to alter the response of individual neurons.
Dr. Xu Liu, one of the lead authors of the study, said the research could one day provide insight to how humans produce false memories themselves. In studies conducted in the 70’s as to how eyewitnesses remembered events, the results showed that just the way a question was asked had the potential to alter a person’s recollection of the event.
“If you want to grab a specific memory you have to get down into the cell level,” said Dr. Xu Liu to BBC. “Every time we think we remember something, we could also be making changes to that memory – sometimes we realize, sometimes we don’t. Our memory changes every single time it’s being recorded. That’s why we can incorporate new information into old memories and this is how a false memory can form without us realizing it.”
Recalling memories, Liu said, is similar to piecing together a puzzle or assembling letters to make a word.
“In the English language there are only 26 letters, but the combinations of letters make unlimited words and sentences, this is also true for memories,” Liu told BBC News. “There are so many brain cells and for each individual memory, different combinations of small populations of cells are activated.”
How could a memory be implanted into a mouse?
- A mouse was put in one environment (blue box) and the brain cells encoding memory were labelled in this environment (white circles on the above image)
- These cells were then made responsive to light
- The animal was placed in a different environment (the red box on the top image) and light was delivered into the brain to activate these labelled cells
- This induced the recall of the first environment – the blue box. While the animal was recalling the first environment, they also received mild foot shocks
- Later when the mouse was put back into the first environment, it showed behavioural signs of fear, indicating it had formed a false fear memory for the first environment, where it was never shocked in reality
Some scientists are already thinking of practical applications of the research. A possibility in the future is erasing memories, said Rosamund Langston from Dundee University to BBC News.
“Episodic memories – such as those for traumatic experiences – are distributed in neurons throughout the brain, and in order to make memory erasure a safe and useful tool, we must understand how the different components of each memory are put together. “You may want to erase someone’s memory for a traumatic event that happened in their home, but you certainly do not want to erase their memory for how to find their way around their home.”