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To many people, hallucinations imply madness, but in fact they are a common part of the human experience. These sensory distortions range from the shimmering zigzags of a visual migraine to powerful visions brought on by fever, injuries, drugs, sensory deprivation, exhaustion, or even grief. Hallucinations doubtless lie behind many mythological traditions, literary inventions, and religious epiphanies. Drawing on his own experiences, a wealth of clinical cases from among his patients, and famous historical examples ranging from Dostoevsky to Lewis Carroll, the legendary neurologist Oliver Sacks investigates the mystery of these sensory deceptions: what they say about the working of our brains, how they have influenced our folklore and culture, and why the potential for hallucination is present in us all.
were plausible, though not always entirely accurate from what she remembered sensing before her loss. Sometimes they were not really there at all: Our kitchen was being revamped, and the electrics blew one evening. My husband assured me that all was safe but I was very worried about a possible electrical fire that might start.… I woke up in the middle of the night and had to get up to check the kitchen because I thought I could smell electrical burning.… I checked everywhere I could see in the
inhibit people from acknowledging that they have hallucinations; perhaps for this reason musical hallucinations have long been considered rare—but it is now realized that this is far from the case.9 Musical hallucinations can intrude upon and even overwhelm perception; like tinnitus, they can be so loud as to make it impossible to hear someone speak (imagery almost never competes with perception in this way). Musical hallucinations often appear suddenly, with no apparent trigger. Frequently,
factors additionally predispose to hallucination. In 1922 the French neurologist Jean Lhermitte described the sudden onset of visual hallucinations in an elderly patient—people in costume, children playing, animals around her (she would sometimes try to touch them). The patient had insomnia at night and drowsiness in the daytime, and her hallucinations tended to come at dusk. Though this lady had dramatic visual hallucinations, she had no visual impairments and no lesions in the visual cortex.
happy, occasionally angry, though she could not connect his expressions with any of her own moods. Silent, motionless, ever changing, these hallucinations were almost continuous throughout her waking hours (“They are 24/7,” she said). They did not occlude her vision but were superimposed like transparencies over the left half of her visual field. “They have been getting smaller lately,” she told me. “Kermit the Frog is tiny now. He used to occupy most of the left half, and now he’s down to a
anything, they increased and became more intense than ever. They had something of the character of a Jane Austen novel, or perhaps a Masterpiece Theatre version of one, unfolding in a leisurely way. These visions were very detailed, with all the characters dressed, behaving, and talking as they might in Sense and Sensibility. (This astonished me—for I have never had much social sense or sensibility, and my taste in novels inclines more to Dickens than Austen.) I would get up at intervals during