Auras and other hallucinations: windows on the visual brain.

Hallucinations in psychologically normal individuals provide a valuable route to studying the neural mechanisms of visual awareness. Migraine auras, epileptic auras and the hallucinations of Charles Bonnet Syndrome are examined in this context. Both similarities and striking differences in content are noted and the extent to which we are currently able to localize the source of these forms of endogenously driven visual awareness is discussed.