Recovering memories lost to Alzheimer’s

Neuroscientists have long believed that Alzheimer’s disease destroys the brain’s ability to store memories, wiping away all trace of the people, events, and knowledge that make up the fabric of a person’s life. But a new study suggests that memories lost to the progressive neurological disorder aren’t gone forever, but merely rendered inaccessible. Researchers at MIT put two groups of mice—one healthy and the other genetically engineered to have Alzheimer’s-like symptoms—inside a box and gave them mild shocks to the feet. When mice in the control group were later placed back inside the box, they displayed fear—a sign that they recalled the trauma of the shock. But the ones with Alzheimer’s seemed unfazed, suggesting they had forgotten the experience. After pinpointing the brain cells associated with short-term memory, the researchers stimulated the forgetful mice with highfrequency bursts of light. Known as optogenetics, the technique effectively restored the animals’ memories by prompting their brain cells to grow small buds called dendritic spines, key components of neural circuitry that connect with other cells and allow the transmission of information. After the treatment, the mice once again feared the box. The findings could lead to new Alzheimer’s treatments that target compromised recall mechanisms in the brain—an entirely new approach to the disease. “Even if a memory seems to be gone, it is still there,” study author Susumu Tonegawa tells The Washington Post. “It’s a matter of how to retrieve it.”