Some people truly believe they don't exist - and that could be useful for AI research

But the condition is so rare that it's still far from fully understood. Though it's undeniably horrific for those experiencing it, Cotard's Syndrome presents a fascinating conundrum for those studying the disorder. The condition's central contradiction -- how can someone articulate the thought that they don't exist? A 2013 case study of a Cotard's sufferer showed low activity in the brain network associated with awareness of the body. It's only one example (as with much of Cotard's Syndrome research, because the condition is so rare), but unpacking how the brains of those with the syndrome work offers hints as to how normally-functioning brains develop a sense of existence.