I listening to the latest episode of my favourite science shows on CBC radio and there was an interesting segment about synesthesia.
http://www.cbc.ca/quirks/archives/09-10/qq-2009-09-26.html
Towards the end they mention a possible link between synesthesia, autism, and epilepsy.
Here is a direct link to the mp3 (7.65MB):
http://www.cbc.ca/quirks/media/2009-2010/mp3/qq-2009-09-26_05.mp3

