The fictional Jason Bourne is inspired by Ansel Bourne's real memory trauma. Ansel's "Bourne Identity"-like case was one of the first documented instances of a rare disorder known as dissociative fugue. This is a state in which an individual has lost their former identity. According to psychologists, a physical injury or a lot of stress can trigger this form of amnesia. The victim enters a "fugue state" in which he or she functions completely normally, even though there is no recollection of who he or she is.

Source: ABC News