Scientists produce false memories in mice

Scientists have pulled off the plot of Inception - with mice!
Researchers have successfully implanted false memories of an event that never actually took place into a mice brain, showing it is possible to create inaccurate recollections of the past.
Massachusetts Institute of Technology (MIT) scientists have shown that they can plant false memories in the brains of mice.
They also found that many of the neurological traces of these memories are identical in nature to those of authentic memories.
"Whether it's a false or genuine memory, the brain's neural mechanism underlying the recall of the memory is the same," said Professor Susumu Tonegawa, senior author of the paper published in journal Science.

The study also provides further evidence that memories are stored in networks of neurons that form memory traces for each experience we have - a phenomenon that Tonegawa's lab first demonstrated last year.

Neuroscientists have long sought the location of these memory traces, also called engrams. In the pair of studies, Tonegawa and colleagues showed that they could identify the cells that make up part of an engram for a specific memory and reactivate it using a technology called optogenetics.
Episodic memories - memories of experiences - are made of associations of several elements, including objects, space and time. These associations are encoded by chemical and physical changes in neurons, as well as by modifications to the connections between the neurons.

Where these engrams reside in the brain has been a longstanding question in neuroscience.
Tonegawa's lab turned to optogenetics, a new technology that allows cells to be selectively turned on or off using light.
The researchers engineered mouse hippocampal cells to express the gene for channelrhodopsin, a protein that activates neurons when stimulated by light.
They also modified the gene so that channelrhodopsin would be produced whenever the c-fos gene, necessary for memory formation, was turned on.
In last year's study, the researchers conditioned these mice to fear a particular chamber by delivering a mild electric shock.
As this memory was formed, the c-fos gene was turned on, along with the engineered channelrhodopsin gene. This way, cells encoding the memory trace were "labeled" with light-sensitive proteins, researchers said.

The next day, when the mice were put in a different chamber they had never seen before, they behaved normally.
However, when the researchers delivered a pulse of light to the hippocampus, stimulating the memory cells labelled with channelrhodopsin, the mice froze in fear as the previous day's memory was reactivated.