updated 11/17/2008 3:40:39 PM ET 2008-11-17T20:40:39

A handful of people reach old age with razor-sharp brains. Scientists call them "super aged."

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But what makes them special?

In a new study, researchers examined the brains of five dead people who were considered super aged because after age 80 they had performed higher on memory tests than others their age. The scientists compared these brains to those from some "normal," non-demented elderly folks who had died.

The super aged brains had fewer fiber-like tangles than the brains of people who had aged normally.

The tangles consist of a protein called tau that accumulates inside brain cells and is thought to eventually kill them, the researchers explained in what they're calling a preliminary finding. Tangles are found in at least moderate numbers in the brains of all elderly people, but they are more prevalent in the brains of Alzheimer's disease patients.

"It was always assumed that the accumulation of these tangles is a progressive phenomenon through the aging process. But we are seeing that some individuals are immune to tangle formation and that the presence of these tangles seems to influence cognitive performance," said Changiz Geula, principal investigator of the study and a research professor of neurology at the Cognitive Neurology and Alzheimer's Disease Center at Northwestern's Feinberg School in Illinois.

The findings were presented yesterday at the Society for Neuroscience annual meeting in Washington, D.C.

Geula said the lower number of tangles in the super aged appears to be the critical difference in maintaining memory skills.

Some of the super aged in the study performed memory tasks at the level of people who were about 50 years old. For example, after being told a story, super aged subjects were able to remember it immediately after and still accurately recall its details 30 minutes later. They also remembered a list of 15 words and recalled these words equally well when tested after 30 minutes.

Geula said new research will focus on what makes cells in super aged brains more resistant to tangle formation.

"We want to see what protects the brains of these individuals against the ravages that cause memory loss," he said. "Understanding the specific genetic and molecular characteristics of the brains that makes them resistant, someday may lead to the ability to protect average brains from memory loss. "

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