This revised edition of Oliver Sacks's book is considerably expanded with additional case histories, new findings and practical information on treatment. In a new chapter, illustrated with startling colour paintings by migraine patients, Dr Sacks discusses similiarities among the visual hallucinations, or auras, that often precede a migraine and those that are induced by hallucinogenic drugs or deliria. Drawing on recent advances in chaos theory and neural stimulation, he describes these "hallucinatory constants" and what they reveal about the working of the brain. This is a comprehensive view of one of mankind's complex disorders.