New research offers a tantalizing hope that memory loss — a signature and heartbreaking symptom of Alzheimer's Disease — may be reversed one day.
Scientists at the Massachusetts Institute of Technology have discovered a way to retrieve old memories in mice with early Alzheimer's symptoms.
In their experiment, described in the online journal Nature, the MIT scientists studied the behavior of mice that had been genetically altered to have Alzheimer's symptoms and a group of healthy mice.
All the mice were placed in a chamber, where they were given a foot shock. An hour later, the mice were put in the chamber to see if they remembered the shock.
They did. They all exhibited fear when they were in the chamber — indicating that they had all formed new memories associating the chamber with the foot shock.
But several days later, when placed in the chamber once again, only the healthy mice were afraid. The mice with the Alzheimer's symptoms seemed to have forgotten the foot shock incident.
The researchers then set out to see if they could get the Alzheimer's mice to access that "lost" memory using a technique called optogenetics to stimulate the brain. They tagged brain cells that store specific memories — in this case, the one associated with the fearful experience — with a light-sensitive protein. Then they shined light on the brain cells storing the fearful experience. The mice instantly showed signs of fear, indicating that their memory of the foot shock had been reactivated.
While optogenetics has not been used in humans, the study offers hope that treatments may be developed to help people in the early stages of Alzheimer's access memories previously thought to be gone forever.
