Last week, we wrote about a study out of MIT led by Li-Huei Tsai in which they found that putting mice with multiple signs of Alzheimer’s disease into a room with flashing LED lights reduced the percentage of beta amyloid plaques in the mice brains by 50%. This week, we’re following up to introduce you to a similar study, also out of MIT, that attempted to restore memories in mice with early Alzheimer’s using a form of light therapy called optogenetics.
As you probably know, people suffering from the early stages of Alzheimer’s are often unable to remember recent experiences. Historically, medical professionals believed that those memories no longer exist in the patients’ brains. This MIT study though suggests that those memories aren’t actually gone, but instead just difficult to access. Authors of the study note they were able to stimulate memories once thought gone, in mice with early Alzheimer’s disease, using a technique called optogenetics. Optogenetics involves introducing genes for light-sensitive proteins into the brain to monitor and control their activity with precise light signals. This allows them to control how neurons communicate with one another.
While optogenetics can’t be used in humans yet, the results of this study open the possibility of developing new treatments that may be able to reverse some memory loss often seen in early Alzheimer’s disease. Susumu Tonegawa, Director of the RIKEN-MIT Center for Neural Circuit Genetics at the Picower Institute for Learning and Memory and lead study author, says “even if a memory seems to be gone, it’s still there.” We think this evidence holds hope for the future of Alzheimer’s disease treatment.
The Study Details
Tonegawa and colleagues already knew that mice with retrograde amnesia and impaired memory recall could still form new memories. This made them wonder whether the same could be true in those suffering from Alzheimer’s disease. To test their hypothesis, they studied three groups of mice – a control group of healthy mice and two groups of mice that were genetically engineered to develop Alzheimer’s symptoms.
They exposed all the mice to a chamber with specific sensory details so the mice would recognize it as different from their normal living conditions. They then gave each of the mice an electric shock to the foot. After the initial shock was given, all the mice showed signs of fear when placed in the same chamber an hour later, which indicated that they had formed a memory of the shock they’d experienced in that chamber and were afraid it would happen again.
Several days later, they placed all mice in the chamber again. The control group of healthy mice showed the same fear – they remembered the chamber and what had happened in there. But the mice with Alzheimer’s disease did not appear to remember the shock and showed no signs of fear, despite the natural clues that they were in a place that hurt them (the chamber where they received the shock).
After that, the researchers activated the brain cells they believed held the fearful memory. Dheeraj Roy, lead paper author and graduate student at MIT, says that using optogenetics to directly activate the cells believed to hold the memory seemed to allow the mice to retrieve that memory previously inaccessible. After cell activation, the mice who had previously “forgotten” about the foot shock after initially showing fear when placed in the chamber again showed signs of fear in the chamber.
This provides evidence that in mice with Alzheimer’s disease, memories are just difficult to access rather than lost. Researchers believe this gives hope that human memories may be able to be recalled with treatment. While the procedures MIT researchers used to elicit memories in mice are too invasive to be used on humans, there is hope that somehow, the mice trials will lead researchers to successful Alzheimer’s treatments in the future.
At Home Care Assistance, we focus on non-pharmacological treatments for Alzheimer’s disease and other forms of dementia. Learn more about how we can help here.