A breakthrough study examining how dementia affects mice suggests that people with Alzheimer's disease lose access to their memories but not the actual memories. Researchers hope that this finding can one day help scientists develop a cure for dementia.
For this study, the research team headed by Nobel Prize winner Susumu Tonegawa experimented on mice that had been genetically altered to have symptoms that were similar to Alzheimer's, the leading cause of dementia that affected an estimated 5.3 million Americans in 2015. The researchers were particularly interested in finding a way to get the mice to recall new memories since these types of memories tend to be forgotten within a few days in patients with early signs of Alzheimer's.
The researchers placed the mice into a box and shocked their feet with an electrical current that was not strong enough to be dangerous. To test their recall, the researchers placed the mice into the same box 24 hours later. The researchers observed that mice with Alzheimer's symptoms did not exhibit any signs of fear. Mice without Alzheimer's symptoms, on the other hand, would freeze in fear of being shocked again.
The researchers then attempted to recall the memories that the mice had in regards to the box by stimulating areas of their brain using a method called optogenetics. The researchers used blue light to activate the mice's engram cells, which are linked to memory retention. They then tested the mice's recall by placing them in the same box, as well as a different one, and found that the mice acted fearful in both environments, which suggested that not only was their memory recalled, it was also retained.
"Directly activating the cells that we believe are holding the memory gets them to retrieve it," said lead author Dheeraj Roy, who is a graduate student at MIT. "This suggests that it is indeed an access problem to the information, not that they're unable to learn or store this memory."
The researchers hope that their findings could someday apply to human patients.
"As humans and mice tend to have a common principle in terms of memory, our findings suggest that Alzheimer's disease patients, at least in their early stages, may also keep memories in their brains, which means there may be a possibility of a cure," Tonegawa said.
The study was published in the journal Nature.
