The human brain is a remarkable thing; our most complex machines are not even close to competing with our powers of higher consciousness and ingenuity. And yet, those 80 billion or so neurons are also incredibly fragile. If the tiniest thing goes wrong with a particular connection - maybe something misfires, or a certain neural pathway is blocked - things can fall apart very quickly. And, oddly enough, even without any injuries or structural malfunctions, the human brain can get weird all by itself - turns out, it's surprisingly easy to trick it into seeing and hearing things that aren't...