Memory Loss Reversed in Lab Test on Mice
Findings May Shed Light on Alzheimer's Disease
July 14, 2005 -- When memory is lost due to dementia such as Alzheimer's
disease, is it gone for good?
Scientists probed that idea in lab tests on mice. The mice were bred to
develop a progressive dementia similar to Alzheimer's disease. The researchers
were able to create mice with a gene that could be "turned off."
Symptoms of Alzheimer's disease occur when brain nerve cells that process
information and memory degenerate and die. Abnormalities such as amyloid plaque
accumulate on nerve cells and tangles of proteins -- called tau -- form in
Tau protein is thought to be responsible for nerve cell death and
When tau protein production was "turned off," the mice's memory
didn't just stop getting worse. It improved.
It's too soon to know if the same could be possible for humans. If so, it
might be possible to recover mental function in the early stages of diseases
such as Alzheimer's, write Karen Ashe, MD, PhD and colleagues in
Since the findings are based on mice, the clinical implications should be
viewed "with caution," they write.
"Most Alzheimer's disease treatments focus on slowing the symptoms or
preventing the disease from progressing," says Ashe in a news release.
"But our research suggests that in the future, we may be able to reverse
the effects of memory loss, even in patients who have lost brain or neural
tissue," she continues.
Ashe is a neurology professor at the University of Minnesota.
About the Study
The tests were done on mice bred to develop Alzheimer's-like dementia.
As dementia settled in, the mice did worse when placed in a water maze -- a
test used to assess learning and memory. The test can help determine
abnormalities in an area of the brain affected by Alzheimer's dementia.
Before dementia, the mice worked to master the maze quickly. They learned to
find a hidden platform where they could get out of the water.
With dementia, the mice forgot the route to the platform.
Then, the researchers laced some mice's food with a drug to turn off tau
production. Afterward, memory improved in those mice.
"The ability to acquire and retain new spatial memories was restored ...
and the improvement was related to the suppression of tau and not [the chemical
used to suppress tau]," write the researchers.
The mice's memory recovery was "surprising," write the
When tau production was curbed, the mice already had "abundant"
brain tangles, had lost a significant amount of brain weight, and had lost
brain cells, the researchers write.
"Thus, neurofibrillary tangles are not sufficient to cause cognitive
decline or neuronal [brain cell] death in this model," write Ashe and