In 1973, psychologist David Rosenhan conducted a controversial and now-famous experiment. Rosenhan instructed eight healthy people to go to emergency rooms around the United States and pretend to hear voices. The voices were not threatening, nor did they instruct these people to act in any dangerous way. Despite that they lacked any other symptoms or psychiatric history, all eight were admitted — some for weeks —
"Hallucinations,'' Oliver Sacks's 13th book, answers this question.
In this fascinating and engaging "anthology of hallucinations," Sacks uses the unique mixture of patient anecdote, memoir, scientific information, and broad reference to literature, art, music, history, and philosophy that has characterized all his work to explore various types of visual, auditory, tactile, and other illusory sensations — excluding those caused by mental illness.
Sacks begins by describing Charles Bonnet syndrome, a condition in which people with impaired eyesight experience visual hallucinations. Bonnet was an 18th-century naturalist who associated his grandfather's visions of floating blue handkerchiefs and ghostly house guests with his blindness. Sacks notes that Bonnet attributed such hallucinations in a sane person "to continuing activity in what he postulated were visual parts of the brain — an activity drawing on memory now that it could no longer draw on sensation." This was a radical notion in an era before it was understood that different areas of the brain control different functions.
Now, of course, this concept is widely familiar, and it seems that virtually any human trait — empathy, depression, an appetite for sugar, a fondness for Bach — can be traced to a few millimeters of cerebral cortex and a couple of neurotransmitters. Still, as Sacks demonstrates in "Hallucinations,'' the extent to which even transient and subtle brain injury can affect our perceptions, and the ways in which our life experiences can alter the brain, are surprising. He devotes chapters to the hallucinations caused by migraine, epilepsy, drug use and withdrawal, delirium, narcolepsy, and Parkinson's disease. He also details the phantom sights, sounds, smells, and feelings that people may experience after an amputation, a profound loss or trauma, or a period of sensory deprivation, such as incarceration.
Though Sacks provides much scientific information in "Hallucinations'' — which, like all his books, is heavily footnoted and meticulously referenced — he is never reductive. He resists the temptation to explain all hallucinations in neuro-anatomical terms and allows for the possibility of mystery. For example, a blind patient of Sacks's with Charles Bonnet syndrome hallucinates unwelcome visitors in fancy dress. The intruders mostly appear at night, pouring through the walls of the patient's nursing home by the hundreds, the women in "beautiful green hats" and "gold-trimmed furs." Sacks sees the nocturnal intensification of the woman's hallucinations not only as a neurological phenomenon, but as a Proustian one: He's reminded of how the bells of Combray seemed to ring louder at night in "Remembrance of Things Past.''
Similarly, Sacks considers the hallucinations sometimes associated with religious and artistic inspiration as both neurological phenomena, and something more. It's long been speculated that Joan of Arc had temporal lobe epilepsy, and it's well known that Dostoevsky suffered from the disease. Yet, Sacks points out, "[e]cstatic or religious or mystical seizures," such as might cause the visions that both Joan and Dostoevsky had, "occur in only a small number of those who have temporal lobe epilepsy." He suggests that while a seizure may affect "parts of the brain that serve to mediate religious feeling," certain people may have, based on their life stories as much as on their neural circuitry, a predisposition to such hallucinations.
Life stories have always been the most compelling part of Sacks's work, whether his patients' in "The Man Who Mistook His Wife For a Hat'' and "An Anthropologist on Mars'' or his own in memoirs such as "Uncle Tungsten,'' and "A Leg to Stand On.'' Readers may find "Hallucinations'' a bit lacking in this regard, since most of the clinical anecdotes here are quite brief.
But a whole chapter of "Hallucinations'' centering on his regular use of amphetamines, morphine, and LSD in the 1960s, is vintage Sacks. Ranging from De Quincey to Timothy Leary, from acetylcholine to Coleridge, Sacks both informs us about the history and pharmacology of hallucinogens, and moves us with an intimate account of his coming of age as a doctor and as a writer.
Suzanne Koven, a primary care internist at Massachusetts General Hospital, writes the monthly "In Practice" column for the Globe. She can be reached at
firstname.lastname@example.org ; read her blog on Boston.com/health.