Hallucinations by Oliver Sacks
My rating: 5 of 5 stars

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Hallucinations are among the most captivating, yet misunderstood, phenomena of the mind. In the popular imagination, they are synonymous with losing one’s grip on reality and are considered evidence of a full-blown psychosis. However, there are a great variety of causes and forms of hallucination, many of which occur among the sane. What Sacks provides in this book is a survey of the forms of hallucination through exploration of cases and anecdotes. To emphasize the point that hallucinations aren’t just for the insane, Sacks doesn’t arrange the book around the idea sanity and insanity. Cases of mental illness are peppered throughout, but there are even more cases of people who fully realize that their hallucinated sensory experiences aren’t real. In fact, he starts with Charles Bonnet Syndrome, hallucinations among blind individuals who are often scared to discuss the phenomena for fear they will be labeled insane even though they know they aren’t really seeing anything. (The brain’s abhorrence of under-stimulation is a recurring theme in the book.)

As mentioned, the approach of the book is to discuss cases of hallucination, and not so much to delve into the research on causes and treatments. This anecdotal approach makes the book readable and offers a unique and intimate insight into hallucination, but it doesn’t drill down into the brain science as much as some might like. This will no doubt be a positive for many, and a negative for others. The author describes several of his own hallucinatory experiences related to drug use, drug withdrawal, and migraine headaches. As I understand it, that level of candor was par for the course for Sacks (though this is the first of his books that I’ve read.) At any rate, his personal experience offers a particularly vivid portrait, and moves the book beyond the sterile feel often found in scientific works.

The book consists of 15 chapters, organized by types / causes of hallucination. After an introduction and the aforementioned chapter on Charles Bonnet Syndrome, there’s a chapter on sensory deprivation hallucinations that’s aptly entitled “the prisoner’s cinema.” Chapters three and four are on olfactory and auditory hallucinations, respectively. The fifth chapter focuses on cases of hallucination experienced by those with Parkinson’s Disease. Chapter six is entitled “Altered States,” but it deals largely with drug-induced hallucinations (it should be pointed out other “altered states” of consciousness, notably sleep, are dealt with in other places), and it’s where Sacks’ personal story begins to be detailed. The next chapter deals with migraine headache related phenomena, and—as the author suffered from such headaches—his story is also imprinted on this chapter.

Chapter eight deals with epilepsy, and, like the Sam Kean book that I reviewed yesterday, is entitled “The Sacred Disease.” That name derives from the fact that those who develop temporal lobe epilepsy are sometimes known to become spontaneously hyper-spiritual in the process. In fact, many scientists now believe that Joan of Arc, Saint Paul (the Apostle), and [for my Indian readers] Ramakrishna were afflicted by this ailment. (Not based on their high degree of spirituality, but rather on accounts of sensory phenomena they were said to have experienced.)

Chapter nine examines cases related to hemianopia—a situation in which one occipital lobe is damaged resulting in a kind of “blindness” in half one’s visual field. While people think of blindness as being a problem with the eyes, it’s possible to have perfectly good eyes and optic nerves and be blind (on a conscious level) due to brain’s incapacity to process the input it is receiving. (Incidentally, in his book “Subliminal” Leonard Mlodinow describes engrossing cases of people who were blind due to brain damage, but–owing to a redundant subconscious systems–they could walk around without running into obstacles.)

Chapter ten describes cases associated with delirium, a common cause of hallucinations that can be the side-effect of any number of physical problems including fever, blood sugar imbalance, and liver failure.

The next two chapters are about sleep-related sensory imaginings. Chapter eleven details cases of hypnagogic and hypnopompic imagery, which are what we see as we are on the edge of falling asleep or awaking, respectively. Hypnagogic hallucinations may be as simple as shifting shapes, or more elaborate. If you’ve gotten this far in the book without any experience that corresponds to what Sack’s is describing, you’ll almost certainly have some experience with hypnagogic images. If not, you should stop consciously counting sheep (or whatever other daydreaming you do as you fall asleep) and just watch what your mind projects. You’ll know it when you see it because you won’t be able to control the imagery (though you can distract over it with conscious thought) and—as in dreams—it probably won’t make a lick of sense. Hypnopompic images are quite different, less widely experienced, and often more disconcerting. Chapter twelve presents cases dealing with narcolepsy (random spontaneous falling asleep) and sleep paralysis, a common experience on the trailing edge of sleep in which one can’t move and which often comes with imagined sensations of a more nefarious variety—hence the widespread lore of night hags and the like.

Chapter thirteen scrutinizes cases that are associated with traumatic events from one’s past. These can involve sightings of ghosts of departed loved ones or replays (flashbacks) of the traumatizing event. This chapter, in a discussion of dissociation, also foreshadows the phenomena of out-of-body (OOB) experience that’s dealt with in more detail in chapter 14. The theme of that penultimate chapter is seeing oneself. Beyond OOB, it deals with a variety of hallucinations of oneself, including those in which one’s body appears distorted (i.e. so-called “Alice in Wonderland” Syndrome.)

The last chapter discusses hallucinations in the tactile domain, and, specifically, the most widely investigated form of these phenomena—the phantom limb. Phantom limb syndrome is experienced by amputees, many of whom can still feel the lost limb. This has resulted in nightmarish scenarios in which an awaking patient complains of an itch on the sole of his or her foot only to be shown that they have no legs from the knee down.

There are no graphics in the book, but, because it’s based around cases, it doesn’t need them for clarification of complex ideas. There are footnotes, as well as a bibliography.

I found this book to be absorbing, and I learned a great deal from it. I’d recommend it for anyone who seeks greater insight into hallucinations or unusual mental phenomena more generally.

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