Cotard delusion

Is there anything stranger than an otherwise-sane person wholeheartedly believing he or she is dead? Cotard delusion, otherwise known as walking corpse syndrome, is an extremely rare condition whereby people wake up one day and think they have died, that they no longer exist, or that their flesh is rotting off. It's all in their head, of course, but there's a physical cause nonetheless : The brain region involved in facial recognition has become disconnected from the regions involved in emotion. When the person looks in the mirror, they recognize themselves, but they don't have the usual emotional response. 

Their appearance has lost its association with their sense of self, and this cognitive dissonance results in the sense that they do not exist, or have died.