为什么有些人有超强记忆力？

STEVE INSKEEP, HOST: On a Monday, it's MORNING EDITION from NPR News. I'm Steve Inskeep.

DAVID GREENE, HOST: And I'm David Greene. Good morning.

Today in Your Health, searching for genes linked to Parkinson's disease. That's in a moment. First, memory and the brain. Scientists have identified a handful of people who have extraordinary memories. How extraordinary? They can remember vivid details about every day of their lives. As Michelle Trudeau reports, researchers are trying to understand how their brains work.

MICHELLE TRUDEAU, BYLINE: Bob Petrella says he had to go through a lot of testing to qualify as someone with superior autobiographical memory. First, there were questions about news events from the past several decades.

BOB PETRELLA: What they would do was they would ask you an event. They would say, like, the O.J. Simpson car chase. And I'd say, you know, June 17th, 1994. Then they would ask what day of the week that was. It was a Friday.

TRUDEAU: Bob scored 55 percent correct on the news events. You and I would be lucky to get 15 percent right. Then he was quizzed about his own life.

PETRELLA: They asked what day of the week was January 1st, 1984, which was a Sunday when the Steelers, my favorite team, lost to the Raiders that day 38-10.

FRANK LANGFITT, BYLINE: Bob Petrella is one of 11 individuals who've now been extensively studied by memory researcher James McGaugh at the University of California, Irvine. The testing has shown that Bob and the others like him don't use memory tricks. They don't have photographic memories. They're not savants. But rather, says McGaugh, other than their remarkable memories, they're remarkably normal.

JAMES MCGAUGH: They're all reasonably successful in what they do. There is a professional violinist. There is Marilu Henner, who is a successful actress. There's a radio news announcer. There's a Discovery Channel producer and so on.

TRUDEAU: Surprisingly, Bob and the group didn't do any better than you and I would on most standard memory tests, like repeating back lists of words or a string of numbers. It's their autobiographical memory specifically that's exceptional. Other types of memory are pretty much normal.

PETRELLA: People like us, we forget normal things. Like, I forgot where I parked my car a couple of months ago coming out of a theater. Or I forget where I left my keys.

TRUDEAU: The researchers have also identified another surprising set of behaviors that these individuals share.

MCGAUGH: Most, if not all of them, have some obsessive compulsive tendencies. They tend to save a lot of objects. They tend to have some repetitive habits. They tend to store things.

TRUDEAU: So in Bob's case...

MCGAUGH: He's germ avoidant. If he drops his keys, he has to wash them. He can't wear shoes that have shoestrings because shoestrings touch the ground.

TRUDEAU: But McGaugh says the obsessive tendencies don't seem to interfere with daily living. It's a tantalizing clue, especially when coupled with the MRI findings that a brain area known to be involved in OCD is larger than normal in these folks. This brain area, called the caudate, may be related to having the repetitive and instant replay of past events. The brain scans also revealed other differences in brain structure.

MCGAUGH: What we've identified are nine regions of the brains of these subjects that differ from those of control subjects.

TRUDEAU: Many of these regions are involved in memory encoding and retrieval. McGaugh says, they're first hints and hopes research on these individuals will reveal how their phenomenal memories work and perhaps how ordinary memory works as well.

For NPR News, I'm Michelle Trudeau.