(CBS) Twenty-four years ago, 60 Minutes introduced viewers to George Finn, whose talent was immortalized in the movie "Rainman." George has a condition known as savant syndrome, a mysterious disorder of the brain where someone has a spectacular skill, even genius, in a mind that is otherwise extremely limited.

Morley Safer met another savant, Daniel Tammet, who is called "Brain Man" in Britain. But unlike most savants, he has no obvious mental disability, and most important to scientists, he can describe his own thought process. He may very well be a scientific Rosetta stone, a key to understanding the brain.

Scientists say a memory feat like this is truly extraordinary. Dr. V.S. Ramachandran and his team at the California Center for Brain Study tested Daniel extensively after his Pi achievement.

What did he make of him?

"I was surprised at how articulate and intelligent he was, and was able to interact socially and introspect on his own—abilities," says Dr. Ramachandran.

And while that introspection is extremely rare among savants, Daniel’s ability to describe how his mind works could be invaluable to scientists studying the brain, our least understood organ.

"Even how you and I do 17 minus nine is a big mystery. You know, how are these little wisps of jelly in your brain doing that computation? We don't know that," Dr. Ramachandran explains.

It may seem to defy logic, but Ramachandran believes that a savant’s genius could actually result from brain injury. "One possibility is that many other parts of the brain are functioning abnormally or sub-normally. And this allows the patient to allocate all his attentional resources to the one remaining part," he explains. "And there's a lot of clinical evidence for this. Some patients have a stroke and suddenly, their artistic skills improve."

That theory fits well with Daniel. At the age of four, he suffered a massive epileptic seizure. He believes that seizure contributed to his condition. Numbers were no longer simply numbers and he had developed a rare crossing of the senses known as synesthesia.

"I see numbers in my head as colors and shapes and textures. So when I see a long sequence, the sequence forms landscapes in my mind," Tammet explains. "Every number up to 10,000, I can visualize in this way, has it's own color, has it's own shape, has it's own texture."

For example, when Daniel says he sees Pi, he does those instant computations, he is not calculating, but says the answer simply appears to him as a landscape of colorful shapes.

"The shapes aren't static. They're full of color. They're full of texture. In a sense, they're full of life," he says.

Asked if they’re beautiful, Tammet says, "Not all of them. Some of them are ugly. 289 is an ugly number. I don't like it very much. Whereas 333, for example, is beautiful to me. It's round. It's…."

"Chubby," Safer remarks.

'It's—yes. It's chubby,' Tammet agrees.

Yet even with the development of these extraordinary abilities as a child, nobody sensed that Daniel was a prodigy, including his mother, Jennifer. But he was different.

"He was constantly counting things," Jennifer remembers. "I think, what first attracted him to books, was the actual numbers on each page. And he just loved counting."

Asked if she thinks there’s a connection between his epilepsy and his rare talent, she tells Safer, "He was always different from—when he was really a few weeks old, I noticed he was different. So I'm not sure that it's entirely that, but I think it might have escalated it."

Daniel was also diagnosed with Asperger’s Syndrome—a mild form of autism. It made for a painful childhood.

"I would flap my hands sometimes when I was excited, or pull at my fingers, and pull at my lips," Tammet remembers. "And of course, the children saw these things and would repeat them back to me, and tease me about them. And I would put my fingers in my ears and count very quickly in powers of two. Two, four, eight, 16, 32, 64."

"Numbers were my friends. And they never changed. So, they were reliable. I could trust them," he says.

And yet, Daniel did not retreat fully into that mysterious prison of autism, as many savants do. He believes his large family may have actually forced him to adapt.

"Because my parents, having nine children, had so much to do, so much to cope with, I realized I had to do for myself," he says.

He now runs his own online educational business. He and his partner Neil try to keep a low profile, despite his growing fame.
Scientists say a memory feat like this is truly extraordinary. Dr. V.S. Ramachandran and his team at the California Center for Brain Study tested Daniel extensively after his Pi achievement.