From autopsies, researchers have long known that some people die with sharp minds and perfect memories, but their brains riddled with the plaques and tangles of Alzheimer's disease. New research shows that those people have a larger part of the brain called the hippocampus."This larger hippocampus may protect these people from the effects of Alzheimer's disease-related brain changes," said study author Deniz Erten-Lyons, MD, with Oregon Health and Science University in Portland, and member of the American Academy of Neurology. "Hopefully this will lead us eventually to prevention strategies."For the study, researchers evaluated the brains of 12 people who had sharp memories and thinking skills at the time of death, but whose autopsies showed a high amount of Alzheimer's plaques. Their brains were compared to those of 23 people who had the same amount of plaques in their brains, but had been diagnosed with Alzheimer's disease before death.Researchers found the volume of the hippocampus part of the brain was 20 percent greater in the cognitively intact group compared to the Alzheimer's disease group with dementia. There were no other demographic, clinical or pathological differences between the groups and the results remained the same regardless of gender, age, and total brain volume.The research will be presented at the American Academy of Neurology 60th Annual Meeting in Chicago, April 12 -- April 19, 2008.The study was supported by grants from the Department of Veterans Affairs and the National Institute on Aging.