New York, A research says that now it has been revealed that how Alzheimer's can cause dementia in humans by an experiment with genetically engineered mice.

Researchers from Johns Hopkins University determined that a one-two punch of major biological insults must occur in the brain to cause dementia that is a hallmark of the disease by using a genetically engineered mouse model mimicking the development of Alzheimer's disease in humans.

“In Alzheimer's disease, tau bunches up inside the nerve cells and beta-amyloid clumps up outside these cells, mucking up the nerve cells controlling memory,” said Philip C Wong, Professor of Pathology at Johns Hopkins.

Tong Li, assistant professor of pathology at Johns Hopkins said,“What hasn't been clear is the relationship and timing between those two clumping processes, since one is inside cells and one is outside cells”.

According to new research, the accumulation of beta-amyloid in and of itself is insufficient to trigger the conversion of tau from a normal to abnormal state.

In humans, the lag between development of the beta-amyloid plaques and the tau tangles inside brain nerve cells can be 10 to 15 years or more.

The work suggests that combination therapy designed to prevent both the beta-amyloid plaque formation as well as pathological conversion of tau may provide optimal benefit for Alzheimer's disease.

The authors noted that, “Our mouse model could be used to test new therapies”.