Neuroscientists from the University of Cambridge in England monitored the brain activity of 16 volunteers as they repeatedly listened to a voice saying a nonsense word.  What the researchers discovered was that, while the brain struggled to process the word at first, after just 14 minutes of repetition, the same network of neurons that recognize words a person already knows began to quickly recognize the nonsense word. 

And that was just by listening to the word.  The researchers believe if the volunteers had been asked to repeat the word, they would have also developed a permanent neural connection to the part of the brain responsible for speech.