Memory is a tricky thing. There are experiences that we store in our minds and can access later. Some memories are referred to as “long-term,” meaning that they are important enough to be stored for later. Others are “short-term,” which means that they are only kept in the mind for a brief time.1
For Alzheimer’s patients, the problem arises when they lose their long-term memories. That’s where our memories tend to fail us. But the reason isn’t what most of us think. It’s not always that our memories are gone. The memories often remain intact, stored where they always were in the brain. The problem is that we no longer have the ability to access them.
This poses an interesting prospect for neuroscientists – especially those interested in the memory loss typically associated with Alzheimer’s disease and dementia. The questions they have started asking may change the way that we treat Alzheimer’s: Instead of attempting to slow down or halt impairment, why not try to re-access old memories?
Recovering Lost Memories
Groundbreaking research from the Massachusetts Institute of Technology (MIT) published in the journal Nature shows that activating old memories might be key in battling Alzheimer’s. A team at MIT’s Picower Institute for Learning and Memory used mice to test how effective a technique called “optogenetics” might be in helping mice with Alzheimer’s recall forgotten memories.2
The researchers took two groups of mice, one genetically engineered to have Alzheimer’s and the other with healthy minds, and exposed both to an electrical foot shock in a distinct chamber. An hour later, both groups still showed fear when placed in the same chamber. But after a number of days, the Alzheimer’s mice no longer showed any fear of the shock chamber, suggesting that they had forgotten the experience.
Earlier research from MIT had shown that the reason Alzheimer’s patients cannot access memories is due to the fact that when they generate a memory, they do not grow “dendritic spines.”3 These spines are what allow neurons to communicate with one another. If a new memory were a house, Alzheimer’s patients would be building houses completely inaccessible by road.
Now for the kicker: when the Alzheimer’s mice were exposed to optogenetics – a treatment in which light activates select brain cells – they again showed fear when placed in the chamber where they had initially received shocks. The implications are huge, but the MIT team cautioned to be patient, and that the treatment would not be available in humans for a number of years.
Dr. Susuma Tonegawa, the senior author of the Nature study, explained, “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.”4 For now, scientists will focus on how best to refine optogenetics. Right now, it is too invasive for humans. Until the light treatment can target a specific region of the brain, its use will be limited to animal trials.
A New Frontier In Alzheimer's Research
Of course, that doesn’t keep curious and optimistic minds from speculating. If memories in many Alzheimer’s patients are stored but inaccessible, a treatment like optogenetics would enable a recovery previously thought to have been impossible. This offers a real ray of hope for anyone who has seen a loved one suffer from cognitive decline or may be genetically predisposed to Alzheimer’s themselves.
So, like Dr. Tonegawa, we should be hopeful about this research, but also remember that its real-world results might be a long time off. Until then, we should do our best to keep our minds sharp and our bodies healthy.