Scientists have made a breakthrough in their efforts to halt the progress of Alzheimer's disease.
A drug being developed at St Andrews University has stopped the death of brain cells in mice.
Researchers have discovered a chemical which prevents the reaction between protein compounds that leads to the death of nerve cells.
In the early stages of Alzheimer's, a toxic protein called amyloid builds up in nerve cells and destroys them, before moving out of the cells and collecting in clumps known as senile plaques.
Dr Frank Gunn-Moore, who led the research, said: "We have shown that it is possible to reverse some of the signs associated with Alzheimer's disease.
"Our research holds a possible key for the treatment of Alzheimer's disease, particularly in its early stages."
Dr Gunn-Moore expressed his hope that it might ultimately be possible to reverse the symptoms of Alzheimer's.
He said it would be another three years before the chemical is developed into a drug, and then several more years before it can be trialled on humans.