Memory loss is one of the frightening symptoms of Alzheimer’s disease, but researchers now say those “lost” memories may not actually be gone – just inaccessible.
Researchers from Massachusetts Institute of Technology (MIT), including Nobel Prize-winning neuroscientist Susumu Tonegawa, found in their study that those memories may be stored in the brain, locked away.
“The important point is, this is a proof of concept. That is, even if a memory seems to be gone, it is still there. It’s a matter of how to retrieve it,” said Tonegawa in a statement.
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This is the first major study of its kind to look at recall as the issue, rather than the destruction of memories.
Tonegawa said by using optogenetics – flashes of blue light to stimulate nerve cells in the brains of mice – they could recall thoughts lost to them.
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Researchers studied mice genetically engineered to develop Alzheimer’s symptoms and a group of healthy mice. The mice with Alzheimer’s quickly forgot the memory of having their feet electrically shocked when they walked in a chamber. Once the light technique was used activating and stimulating brain cells, the memories of the mice were restored and they showed a fear response to the chamber.
“Directly activating the cells that we believe are holding the memory gets them to retrieve it,” Roy says. “This suggests that it is indeed an access problem to the information, not that they’re unable to learn or store this memory,” said Dheeraj Roy, an MIT graduate student.
In this image of a mouse model of early Alzheimer’s disease, engram cells (green) that encode a fear memory were tagged with a light-sensitive protein. Dheeraj Roy/MIT
In this image of a mouse model of early Alzheimer’s disease, engram cells (green) that encode a fear memory were tagged with a light-sensitive protein.
The research carried out by the RIKEN-MIT Center for Neural Circuit Genetics and published in the journal Nature, provides hope of developing future treatments that might reverse some of the memory loss seen in early-stage Alzheimer’s, the researchers said.