It was previously thought that Alzheimer's was primarily caused by the build up of sticky amyloid plaques in the brain which stop neurons from firing.
But drugs to clear the plaques have so far failed to bring any improvement to sufferers.
Many scientists believe that the amyloid plaques trigger a 'cascade effect' of other symptoms meaning that by the time they are spotted it is already too late.
Researchers at Penn State University have now discovered that those plaques may be triggering overproduction of a chemical that drives memory loss by preventing a key part of the brain from functioning.
