This is one of the most interesting questions to me about human brains, and as far as I know no significant progress has been made in answering it.

Some people appear to have a capacity for learning, retention and understanding that is well outside the normal range. People like Ramanujan or von Neumann, or Tao. They learn at a speed that far exceeds the speed of what we would consider gifted students, they reach a deep and intuitive understanding of the material, and go on to make many discoveries / inventions of which even one would be enough for an ordinary scientist to be considered successful.

It seems there is something very different about their minds, but just what is it that allows those minds to operate at such a level?