When Karen Byrne woke up from a brain operation to control her epilepsy, she found that her left hand had a mind of his own.
Here's the strange tale of the Alien Hand Syndrome:
Imagine being attacked by one of your own hands, which repeatedly tries to slap and punch you. Or you go into a shop and when you try to turn right, one of your legs decides it wants to go left, leaving you walking round in circles.
Last summer I met 55-year-old Karen Byrne in New Jersey, who suffers from Alien Hand Syndrome.
Her left hand, and occasionally her left leg, behaves as if it were under the control of an alien intelligence.
From Dr. Michael Mosley of BBC Four's The Brain: A Secret History: Link