Tag Archives: hallucinations

Lit Review: Hallucinations, by Oliver Sacks

Finally, something worth posting here.  I wrote another book review for our newsletter.  I didn’t enjoy writing about this book as much as the previous one I reviewed because there wasn’t too much wrong with it.  Not that there was a ton I disagreed with in Consciousness, but there were some pretty controversial topics covered in it that were more fun to discuss.  Anyway…


Oliver Sacks

Alfred A. Knopf (New York), 2012

“Thus the matter of belief is, in all cases, different in kind from the matter of sensation and perception, and error is in no way analogous to hallucination.  A hallucination is a fact, not an error; what is erroneous is a judgment based upon it.”

–Bertrand Russell, Theory of Knowledge (1913)

            One astonishing revelation of the human mind uncovered by the study of neuroscience is the fragility of our perception of reality: a mild imbalance in the activation of certain neuronal circuits from drug use or psychiatric disease is often sufficient to evoke profound alterations in sensation and perception.  We call the precepts that form in the absence of external reality hallucinations.  Despite the stigmas associated with them, drug users and the mentally ill are far from the only people who experience hallucinations.  In fact, hallucinogenic experiences are a nearly universal phenomenon.  As Dr. Oliver Sacks illustrates in his most recent book Hallucinations, they can provide deep insight into how the human brain functions.

            Dr. Sacks has a gift for crafting a compelling narrative out of the human nervous system, and he accomplishes this in Hallucinations by combining medical history, scientific background, fascinating (and sometimes downright bizarre) case studies of his patients, as well as his own personal experience.  Perhaps because he experienced it himself, Dr. Sacks begins by describing a common (yet little recognized) condition called Charles Bonnet Syndrome (CBS) that afflicts older people suffering from visual impairment.  CBS is marked by the experience of a wide spectrum of intensely vivid, complex visual hallucinations.  Patients report seeing anything from faces, common objects, repetitive patterns, and even rows of text or sheet music.  Often times a “scene” composed of hallucinatory people and objects will play in the patient’s visual field. 

            Patients with CBS are not united by dementia or mental illness, as many doctors mistakenly diagnose.  Rather, they suffer from deficits in the visual field.  The visual damage that yields CBS hallucinations can arise in the eye (due to macular degeneration, for example) or in the brain, especially in areas of the cortex associated with the visual pathway.  Dr. Sacks describes the pioneering research of British psychiatrist Dominic ffytche, who, using fMRI, discovered a “striking correspondence” between the particular hallucinatory experiences of CBS patients and specific portions of the visual pathway that become activated while the patient is hallucinating.  For instance, hallucinations of faces were associated with activation of the fusiform gyrus and the superior temporal sulcus, brain areas known to be specialized for the representation of faces and facial features, respectively. 

            As the remainder of Hallucinations uncovers, there are hallucinations for every perceptual experience—those of sound, smell, touch and taste, as well as complex, multimodal hallucinations involving a combination of the senses—and their origin is in the brain.  Dr. Sacks devotes chapters to describing visual auras seen by sufferers of migraines and epilepsy, and even recounts his own experiences while under the influence of hallucinogenic drugs to hilarious effect.  The recurring theme of the book is that the vast majority of people who experience hallucinations are not crazy; the patients Dr. Sacks describes are instead treated as privileged observers of singular neurological phenomena.

Dr. Sacks ascribes an almost romantic quality to hallucinations, frequently citing patients who describe their experiences as comforting and even inspiring.  Among the more interesting segments are his discussions of how hallucinatory experiences may have contributed to works of art and literature, including myths and certain religious beliefs.  “Hallucinations,” writes Dr. Sacks, “beyond any other waking experience, can excite, bewilder, terrify, or inspire, leading to the folklore and the myths (sublime, horrible, creative, playful) which perhaps no individual and no culture can wholly dispense with.”  As Dr. Sacks brilliantly illuminates in Hallucinations, the brain often separates our sense of what is real and what is illusory with a fuzzy line.