The opening of “Remember This,” Joshua Foer’s excellent 2007 National Geographic piece about people with extreme memories and those of us with more average neural connections governing the data and images we retain:

“There is a 41-year-old woman, an administrative assistant from California known in the medical literature only as ‘AJ,’ who remembers almost every day of her life since age 11. There is an 85-year-old man, a retired lab technician called ‘EP,’ who remembers only his most recent thought. She might have the best memory in the world. He could very well have the worst.

‘My memory flows like a movie—nonstop and uncontrollable,’ says AJ. She remembers that at 12:34 p.m. on Sunday, August 3, 1986, a young man she had a crush on called her on the telephone. She remembers what happened on Murphy Brown on December 12, 1988. And she remembers that on March 28, 1992, she had lunch with her father at the Beverly Hills Hotel. She remembers world events and trips to the grocery store, the weather and her emotions. Virtually every day is there. She’s not easily stumped.

There have been a handful of people over the years with uncommonly good memories. Kim Peek, the 56-year-old savant who inspired the movie Rain Man, is said to have memorized nearly 12,000 books (he reads a page in 8 to 10 seconds). ‘S,’ a Russian journalist studied for three decades by the Russian neuropsychologist Alexander Luria, could remember impossibly long strings of words, numbers, and nonsense syllables years after he’d first heard them. But AJ is unique. Her extraordinary memory is not for facts or figures, but for her own life. Indeed, her inexhaustible memory for autobiographical details is so unprecedented and so poorly understood that James McGaugh, Elizabeth Parker, and Larry Cahill, the neuroscientists at the University of California, Irvine who have been studying her for the past seven years, had to coin a new medical term to describe her condition: hyperthymestic syndrome.

EP is six-foot-two (1.9 meters), with perfectly parted white hair and unusually long ears. He’s personable, friendly, gracious. He laughs a lot. He seems at first like your average genial grandfather. But 15 years ago, the herpes simplex virus chewed its way through his brain, coring it like an apple. By the time the virus had run its course, two walnut-size chunks of brain matter in the medial temporal lobes had disappeared, and with them most of EP’s memory.”

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Oliver Sacks discussing his pen pal Alexander Luria, the neuropsychologist who authored The Mind of a Mnemonist: