There is a neuron in your brain that will respond only to pictures of Jennifer Aniston - provided you have had prior visual exposure to the actress. That neuron does not respond to pictures of Bill Clinton or Halle Berry. Only Jennifer. I used the story to explain the almost ridiculous plasticity of the organ. There is no such thing as Jennifer Aniston in our evolutionary history - she was born in 1969, for heaven's sake - but we are flexible enough to devote an entire cell to her if we have previously encountered her in some fashion.