Who are you? It's one of the deepest, most troubling questions in all of human history. Are you a cloud of thoughts? Are you a brain? Is there such a thing as freewill? What is human consciousness and what secrets lay entangled in the spell it casts over our existence?

Mull over these questions enough and you'll wind up second guessing everything from your career path to you choices in breakfast cereal. Nailing down the recipe for the human mind gets even more complicated when your throw in the X factor of parasitic infection.

How much of you is you -- and how much is the work of mind-altering parasites?