The condition is known among brain researchers as hyperthymesic syndrome, based on the Greek word thymesis for "remembering" and hyper, meaning "more than normal."
McGaugh told ABC News' Lee Dye that while the brains of these people are able to perform amazing feats of recall, it is still not fully understood exactly how this occurs. One hypothesis is that the "wiring" of the brains of those with hyperthymesia is set up in such a way that their brains are better able to organize and categorize information for later access.
Past this, however, researchers are stumped.
"In order to explain a phenomenon you have to first understand the phenomenon," McGaugh said. "We're at the beginning."
Memory can likewise be exceedingly fragile. Perhaps no one is more familiar with this fact than 57-year-old Beki Propst, who 10 years ago experienced a grand mal seizure that robbed her of a lifetime of memories.
"Everyone I knew before says my personality is the same," Propst told ABCNews.com. "But I don't know if I'm the same person."
Details of Propst's case continue to baffle doctors. What they do know is that a devastating "electrical storm" in her brain caused her declarative memory to be wiped clean. Facts, events, dates, acquaintances and even her identity were wiped away. As Propst describes it, "If I was a computer, it would be like my hard drive was erased."
David Ewing of Centennial Neurology in Greeley, Colo., Propst's doctor, said that it is remarkable that Propst has adjusted so well to her new life, which, in a way, began slightly more than 10 years ago. The seizure, he says, effectively disconnected the area of her brain in which her memories were stored.
"The area is still there, still intact," he said. "But it was like someone threw a breaker switch. ... She had a single general event, after which she woke up and all of her memories were wiped out."
Since the event, however, Propst has rebuilt her life. Her persistence in rejoining the work force has led to stable employment as a custodian at a state facility. She enjoys strong relationships with her family. And she has written a book, "Absent Memories: Moving Forward When You Can't Look Back," which documents her experiences.
"Every single person I met said, 'You need to write a book about this,'" Propst said. "I thought, 'What the heck, what do I have to lose?'"
While Propst's experience is rare, there have been numerous documented cases in which an injury has led to long-term amnesia.
Traumatic events in the brain can have other unusual effects as well. For 52-year-old Canadian Rosemarie Dore, a stroke on the left side of her brain in 2006 led to a very unusual side effect -- she began to speak with a different accent.
Specifically, Dore, who lives on the Western side of Lake Ontario, adopted a distinctively eastern Canadian accent. She has never been to that region, and she does not know anyone from that part of the country.
"[There was a] nurse that was from Newfoundland," Dore told ABC News. "She comes down the hall, and she come into the room and she says, 'Who's the Newfie here?'" referring to Newfoundland.
"I said, 'There's nobody here like that.'"
"And she said, 'I think I'm talking to her.'"
Though rare, foreign accent syndrome is not entirely undocumented in medical literature. Researchers who have studied the syndrome estimate there are only as many as 60 legitimate recorded cases.