"Transient states of depersonalisation are appreciably commoner during migraine auras. Freud reminds us that "... the ego is first and foremost a body-ego ... the mental projection of the surface of the body." The sense of "self" appears to be based, fundamentally, on a continuous inference from the stability of body-image, the stability of outward perceptions, and the stability of time-perception. Feelings of ego-dissolution readily and promptly occur if there is serious disorder or instability of body-image, external perception, or time-perception, and all of these, as we have seen, may occur during the course of a migraine aura."