Scientists at the Alzheimer's Disease Research Center at Washington University School of Medicine in St. Louis found some study participants whose brain scans revealed brain plaques -- deposits of protein that have been linked to Alzheimer's disease -- still performed well on tests of their cognitive ability. Those doing well on the tests were likely to have spent more years in school.

"The good news is that greater education may allow people to harbor amyloid plaques and other brain pathology linked to Alzheimer's disease without experiencing decline of their cognitive abilities," first author Catherine Roe said in a statement.

The study, published in Archives of Neurology, used the study participants' education levels to approximate a theoretical quality called cognitive reserve developed by regularly challenging and making use of the brain. Neurologists have speculated this quality helps the brain cope with the damage caused by Alzheimer's disease.

The imaging agent Pittsburgh Compound B or PiB was used for positron emission tomography scans to reveal the presence of amyloid plaques. However, Alzheimer's disease is still only conclusively diagnosed through post-mortem brain examination.