From Abracadabra to Zombies
Many people have hallucinations but don't talk about them for fear of either being labeled as mentally or actually being mentally ill. The kinds of hallucinations people have vary from mundane repetition of patterns to ecstatic and blissful unions with god or nature, from repetitions of what went on during the day to horrendous and terrifying visions of demons and monsters. Several of the topics covered in The Skeptic's Dictionary may involve hallucinations, e.g., visions of angels or demons, hypnagogic and hypnopompic hallucinations, déjà vu and jamais vu, hypnosis, fairies, ghosts, gods, near-death experiences and other out-of-body experiences, and a sense of presence and sleep paralysis. The latter is somewhat of a misnomer since the paralysis and accompanying hallucinations occur upon waking from REM sleep.
Hallucinations may be induced by drugs or by electrical or magnetic stimulation of the brain. They may occur naturally because of fever, sensory deprivation, or injury. Hallucinations occur in otherwise perfectly healthy people and they occur in schizoprenia. Having a hallucination is not a sign of illness, but many illnesses may lead to hallucinations.
In addition to Sacks's eloquent and engaging descriptions of hallucinations in blind and deaf people, parkinsonian hallucinations (often caused by drug treatments that increase dopamine), migraine hallucinations, delerium, narcolepsy, and several other unique hallucinatory experiences, there are hundreds of stories that divide themselves into three categories: those who know they are hallucinating and do not mistake their visions, feelings, or other seeminlgly sensory experiences with some external cause; those who do not believe they are hallucinating but having a real experience with an angel or the divine; and those who aren't sure what to make of their hallucinatory experiences. There does not seem to be a clear cut set of personality traits that one could use to distinguish the ones who know they are hallucinating from the ones who "know" they're not.
Many readers of Hallucinations will be pleased to know that it not uncommon for the bereaved to hallucinate a recently deceased loved one. There will be little comfort, however, for those who hallucinate ogres or demons sitting on their chests. Some will enjoy "mystical" experiences without seeing them as particularly religious, while others will be transformed by such hallucinations, convinced that they have experienced a transcendent being. Some will take their out-of-body experiences as bizarre, perhaps enjoyable, but not indicative of a soul separating from the body, while others will be convinced that their OBE is proof the soul continues to exist after the body decays. Some will even use their phantom limb experience to justify belief in the afterlife. There is no uniformity at all either in the kinds of hallucinations people have or with what they make of them.
Sacks explores what parts of the brain are involved in various hallucinations, though our knowledge in this area is somewhat scant. This is to be expected since hallucinations cannot be willed, but come upon us with or without our assent.
Sacks also explores the main differences between hallucinations and dreams, acts of imagination, and acts of sense perception. Anyone interested in the human brain and how it functions and malfunctions would find this book instructive. It should go without saying that anyone who experiences hallucinations should read this book, if only to discover that you really are not alone.
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