The dementia associated with Alzheimer's, Parkinson's disease and strokes had previously been linked to low levels of acetylcholine, a chemical that carries signals in the brain.
The new study of 28 young, healthy U.S. adults shows the chemical helps keep old information from getting in the way of learning and remembering new information.
Higher levels of acetylcholine can improve attention, memory and daily activities, the researchers found.
The study is important because cholinesterase inhibitors -- one of the most commonly prescribed drugs for Alzheimer's treatment -- can raise levels of the memory-boosting chemical.
The drugs could help doctors detect early symptoms of Alzheimer's and other disorders in elderly patients in the beginning stages of dementia, said lead author Dr. Alireza Atri of Massachusetts General Hospital/ Harvard Medical School.