Most of us probably know at least a few of those uber-Zoomers. Older people you can describe as “sharp as a tack” at the age of 80, 90 and beyond.

Well, now researchers have found they have certain brain characteristics that differ from their peers who show more typical age-related memory loss.

Scientists from Northwestern University's Cognitive Neurology and Alzheimer's Disease Center identified 12 people aged 80 and older who did as well or better on memory tests as people who were 20 to 30 years younger. They dubbed them "SuperAgers."

MRI scans showed that the cortex of SuperAgers was thicker than a comparison group of people aged 80 and older. The cortex is the outer layer of the brain involved in memory, attention and other thinking abilities.

Brain scans also showed that people in their 80s and 90s who exhibited more typical memory declines had a thinner cortex. At the same time, SuperAgers also had a larger cingulate cortex, another brain region also involved in attention and memory, than even the middle-aged participants.

Researchers still have to figure out the chicken or egg question: does retaining brain volume protecs thinking abilities, or does maintaining thinking abilities protects brain volume.

The study is published in the current issue of the Journal of the International Neuropsychological Society.