Why do you sometimes forget why you went into a room? If a loved one changes as a result of a brain disorder, are they still the same person? And could a brain disorder enhance your identity rather than damage it? From dementia and brain injury to sleep disorders, coma, and multiple personality disorder, neurologist Jules Montague explores what becomes of the person left behind when the pieces of their mind begin to function differently or go missing. Along the way she answers fascinating questions about how we remember, think, and behave: Why do some memories endure and others fade? And what if rather than losing memories, your mind creates false ones?