Alzheimer’s disease is a progressive mental deterioration where, in its early stages, patients forget recent experiences. As it progresses, more of the memory is lost. Now, new MIT research published in the journal Nature suggests that recent memories are not only still stored somewhere in the brain, they can also easily be accessed.
In their research, the team details that mice that are in the early stages of Alzheimer’s have the ability to form new memories—the same way normal mice can—but are unable to recall them just a few days after.
They tested two strains of mice, one with Alzheimer’s symptoms and the other without, by placing them in a chamber where they received a foot shock. A few days later, they were placed back in the chamber where the normal mice showed fear, while the those with Alzheimer’s didn’t—seemingly demonstrating that they didn’t remember the foot shocks from before.
The MIT neuroscientists behind the study were then able to artificially stimulate these memories using optogenetics. They tagged engram cells (associated with the fear the mice experienced in the chamber) activated by light to prompt natural cues that will recall the experience—this basically shows that these memories can possibly be retrieved.
The ability to activate the cells that scientist believe hold the memories thus means they can be retrieved.
Proof of Concept
“The important point is, this 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,” says Susumu Tonegawa, the Picower Professor of Biology and Neuroscience and director of the RIKEN-MIT Center for Neural Circuit Genetics at the Picower Institute for Learning and Memory.
In the end, the work suggests that access to the specific memory is the problem, not that Alzheimer’s patients are not able to store the memory.
Optogenetics, however, is a technique that isn’t and cannot be used by humans—but the research shows how this could possibly help find future treatments that would reverse the memory loss for early-stage Alzheimer's.