I have met one woman like this and had the opportunity to work closely with another. In both of their cases they were in car accidents. I didn't know either of them before their accidents, but I have multiple friends that had known each of them for years or decades prior. In both cases they were described as pretty average before their accidents. Since their accidents they have both become extremely prolific readers [1] , with drastically better memory and cognition [2], and can't sleep more than 4 hours a night if they try.

[1] In the case of my colleague, she read everything she wanted, at which point she read the first Dewey decimal cataloged book in the local library and then started to read each subsequent book in progression. Less than three years after her accident she had almost finished every book in the local library and was already making plans to get a membership at the state's largest library.

[2] Neither have photographic memory, but it is something eerily close; and they make cognitive leaps that never cease to amaze me.