The identity of the protein which is key to developing long-term memory has been confirmed. say US scientists.
Scientists believe the mBDNF protein is key to memory formation
The discovery may lead to advancements in treatment for Alzheimer's disease and other people with memory loss.
Scientists have suspected for a long time that the mBDNF protein plays a role in memory development.
But the Institutes of Health team claims in the journal Science to have proved the protein is the key, using experiments on mouse brains.
Protein mBDNF, which stands for mature brain-derived neurotrophic factor, is produced by a chemical reaction involving the enzyme plasmin and proBDNF.
The team carried out a series of experiments on mice brains, which are easy to mutate, to see how the protein affected long-term memory and what was needed to create the protein.
In tests where the mouse brain was incapable of producing mBDNF, long-term memory formation was not possible.
But when the conditions were right to produce mBDNF, the researchers, including teams from Cornell University in New York and the Chinese University of Hong Kong, found long-term memory development was possible.
Dr Bai Lu, of the National Institute of Child Health and Human Development, part of the National Institutes of Health, said the findings had the potential to treat people with Alzheimer's disease.
"The fundamental problem is the part of the brain associated with memory is dying. If you can stop it from dying or improve the functions of memory you can help patients with Alzheimer's disease."
But he admitted doctors were not yet at the stage where they could alleviate memory deficits - as the substance which creates plasmin, which it is thought people with Alzheimer's disease lack, can affect the blood.
The possibility that mBDNF could play a key role in long-term memory was first raised in 1996 and since then doctors have established how the protein is formed during chemical reactions involving plasmin and other proteins
The findings have been cautiously welcomed by scientists in the UK.
Professor Peter Giese, of the Wolfson Institute for Biomedical Research, part of University College London, said it was a "small step forward".
"There are theories that learning defects in the early stages of Alzheimer's disease trigger further degeneration.
"If we could prevent the early learning degeneration we could stop the later neuro-degeneration."
But he warned it would be years before it could become a viable form of treatment.
Dr Susanne Sorensen, head of research at the Alzheimer's Society, added it was "another piece of the puzzle on how we understand memories are laid down in the brain".
"These results may be helpful to the understanding of some aspects of Alzheimer's disease in the long run but are not directly applicable to any development of treatment for Alzheimer's disease at the moment."