The ability to form new memories is an essential part of human existence.
Diseases that rob our brains of the ability to form new memories — or retrieve old ones — are painful and disturbing for the afflicted as well as their families.
A new study
of epilepsy patients hints that using deep brain stimulation to enhance the ability to learn new information can help people form better memories, but many experts remain skeptical about how well it would work as a treatment to combat memory loss in people living with Alzheimer’s disease or other forms of dementia.
The hippocampus, the brain’s seat of learning and memory, is the area most affected and devastated by Alzheimer’s. A research team at UCLA's David Geffen School of Medicine, led by neurosurgery professor Itzhak Fried, wanted to see how stimulating cells — both within the hippocampus and in its threshold, the entorhinal cortex — might affect learning and memory. “The entorhinal cortex is the golden gate to the brain’s memory mainframe,” Fried says. “Every visual and sensory experience that we eventually commit to memory funnels through that doorway to the hippocampus. Our brain cells must send signals through this hub in order to form memories that we can later consciously recall.”
A New Discovery
In deep brain stimulation, a battery-operated neurostimulator is surgically implanted in the brain, where it delivers electrical stimulation to targeted areas. The treatment has long been used in Parkinson's disease patients to deliver electrical stimulation to limit tremors, rigidity and walking problems. The subjects of the UCLA study were epilepsy patients. Electrodes had been previously placed in each patient's hippocampus or entorhinal cortex to determine the location of their seizures. Fried's team activated those electrodes while the patients played a virtual taxicab game which asked them to learn and navigate the streets of a city and to find the best routes from one point to another.
The experiment was a success. As it happened, it was not the stimulation of the hippocampus that helped improve the formation of memories in these patients, but rather the threshold of the entorhinal cortex. When those nerve fibers were stimulated during learning, the patients "later recognized landmarks and navigated the routes more quickly,” Fried said. “They even learned to take shortcuts, reflecting improved spatial memory.”
Will It Work for Alzheimer's Patients?
The study offers us intriguing clues into the ways we can affect the brain’s memory mechanisms. But the big question is whether the results can be reproduced for people with Alzheimer's or other brain disorders affecting memory. Patients and families are hopeful, but Dr. William H. Thies, chief medical and scientific officer of the Alzheimer’s Association, urges caution. "The population in the study was very different," being epileptic patients and not Alzheimer's sufferers, he said. Alzheimer’s disease is marked by the accumulation of amyloid-beta clumps, tangles of the protein tau, and the death of brain cells.
Any of these factors could affect whether deep brain stimulation would improve memory function in Alzheimer’s patients. Thies also has practical concerns. "Doing surgery on the 5.4 million people with Alzheimer’s disease is not something you’re going to put at the top of your list.”
The UCLA study still represents an important discovery about how the brain is wired. Fried can envision devices within the brain someday that could be activated when people with declining memory skills need to learn new tasks. But the more promising avenues for people with Alzheimer’s will continue to be lifestyle changes and improved medications. “In the future, we’ll probably be even better at stratifying risk for Alzheimer’s disease and treating it appropriately,” Thies says. “The techniques will continue to become more sophisticated, and more effective.”