They're called "super-agers" - people in their 80's an 90's who can remember things as well as people in their 50's and 60's. Northwestern University in Chicago started recruiting them last year by putting out a notice inviting elderly people to take memory tests.
In one of the test, Neuroscientist Emily Rogalski asks of the subjects, "I want to tell you to tell me as many of the words as you can remember."
Michael, age 87, was able to remember 8 of the 12 words.
He was entered in the study and given a brain scan. Those brain scans are revealing real physical differences between super-ager brains and brains that are just plain aging. The cortex, the outer layer of the brain, is significantly thicker.
"When you measure the thickness of the cortex you're measuring the health of the brain. So the thicker, the better," says Rogalski.
She says this shows that mental decline is not inevitable. "Maybe it's possible to maintain optimal memory as we age."
But what's the secret? Michael told WTTW, "I've always been very active."
And super-ager Barbara, age 85, says "You've got to get up every day with the idea that this is going to be a great day."
But that doesn't stop her from her daily crossword, her treadmill session, or her active social life.
Other super-agers include a retired neuroscientist who's 96, a 92-year-old Holocaust survivor, and an 81-year-old smoker named Ken with a pack-a-day habit who enjoys hot air ballooning, loves musicals, loves to golf, is learning Spanish, and pours himself a vodka martini before bed.
But whether it's the positive attitude that's keeping their brains healthy, or their healthy brains that are keeping their attitudes positive - that's still a mystery.
They've all agreed to donate their brains to research after they die. Although considering how active they are, that might be awhile.