Lost Memories In Alzheimer's Patients May Be Recoverable: Study

Mice with early-stage Alzheimer's disease show that some memories are still stored in their brains, yet scientists at the Massachusetts Institute of Technology find that they cannot be accessed due to their conditions.

With the help of optogenetics, a method to activate brain cells with light, scientists found that some missing memories may exist. However, they have not been unlocked.

Earlier, MIT experts located cells that stored particular memories, and manipulated cells, called engrams, so that they could implant false memories, activate current ones or change emotions tied to memories.

Some mice with retrograde amnesia could not remember quickly, but their brains still formed new memories. It is not clear whether such patients really lose their memories or not.

While optogenetics is seen to be too "invasive," techniques such as deep brain stimulation tend to affect too many areas of the brain simultaneously.

"The important point is, this a proof of concept," said Dr. Susumu Tonegawa, director of the RIKEN-MIT Center for Neural Circuit Genetics, said in a press release. "That is, even if a memory seems to be gone, it is still there. It's a matter of how to retrieve it."

For the study, published in the journal Nature, three groups of mice were studied. Two were engineered to develop Alzheimer's disease, while the third was a healthy group of mice.

All three groups of mice were lowered into a chamber, where their feet were "shocked". An hour later all mice got afraid to be lowered into the same chamber. The following day, the Alzheimer's mice forgot their fear, but the healthy mice remained fearful.

Scientists also checked whether memories had got stored in the brain for a longer time, even though they remembered them in shorter time-frames. They tagged engram cells linked with the chamber experience to get activated by light. They then put the mice into a new chamber and activated the engram cells. It hence caused the rodents to be afraid of "feet shock."

Also assessing whether optogenetics could make them remember things on their own, scientists gave them three hours of the technique to activate their brain cells and then put them in the original chamber a week later. The mice got shocked in the chamber, remembering what had caused their fears.

"The big message is that there is a way to strengthen these memory cells," Dheeraj Roy, a doctoral student at MIT and lead author of the study, told the Boston Herald. "If we had a way of restoring the memory of patients, we think this could have a huge impact on society."