Researchers have found a link between protein levels in the brain and memory deterioration with age following research on mice.
It is hoped the discovery could lead to treatments to reverse forgetfulness, but study lead Prof Eric Kandel warns that it is a big leap from the mouse to a human brain.
Prof Kandel, from Columbia University Medical Centre, said: "The fact that we were able to reverse age-related memory loss in mice is very encouraging.
"At the very least, it shows that this protein is a major factor, and it speaks to the fact that age-related memory loss is due to a functional change in neurons of some sort. Unlike with Alzheimer's, there is no significant loss of neurons."
Less active with time
The team at Columbia started by analysing the brains of eight dead people, aged between 22 and 88, who had donated their organ for medical research.
They found 17 genes whose activity level differed with age. One contained instructions for making a protein called RbAp48, which became less active with time.
Young mice genetically engineered to have low RbAp48 levels performed as poorly as much older mice in memory tests. But using a virus to boost RbAp48 in older mice appeared to reverse the decline and boosted their memory.
Commenting on the findings, Dr Simon Ridley from Alzheimer's Research UK said: "While the findings may seem clear cut from these studies, in reality people reaching older age may well have a combination of changes happening in the brain - both age-related and those involved in the early stages of Alzheimer's.
"Separating early changes in Alzheimer's from age-related memory decline in the clinic still presents a challenge, but understanding more about the mechanisms of each process will drive progress in this area."