To live on a day-to-day basis is insufficient for human beings; we need to transcend, transport, escape; we need meaning, understanding, and explanation; we need to see overall patterns in our lives. We need hope, the sense of a future. And we need freedom (or at least the illusion of freedom) to get beyond ourselves, whether with telescopes and microscopes and our ever-burgeoning technology or in states of mind which allow us to travel to other worlds, to transcend our immediate surroundings. We need detachment of this sort as much as we need engagement in our lives.

Ecstatic seizures shake one’s foundations of belief, one’s world picture, even if one has previously been wholly indifferent to any thought of the transcendent or supernatural. And the universality of fervent mystical and religious feelings—a sense of the holy—in every culture suggests that there may indeed be a biological basis for them; they may, like aesthetic feelings, be part of our human heritage.

Given the outlandish quality of some hypnopompic images, their often terrifying emotional resonance, and perhaps the heightened suggestibility that may go with such states, it is very understandable that hypnopompic visions of angels and devils may engender not only wonder or horror but belief in their physical reality. Indeed, one must wonder to what degree the very idea of monsters, ghostly spirits, or phantoms originated with such hallucinations. One can easily imagine that, coupled with a personal or cultural disposition to believe in a disembodied, spiritual realm, these hallucinations, though they have a real physiological basis, might reinforce a belief in the supernatural.

A smudge on the wall is an object of limitless fascination, multiplying in size, complexity, color. But more than that, one sees every relationship it has to the rest of the universe; it possesses, therefore, an endless variety of meanings, and one proceeds to entertain every possible thought there is to think about it.

In the normal process of reading text or scores, what is initially deciphered in the early visual system goes on to higher levels where it acquires syntactical structure and meaning. But in hallucinations of text or scores, caused by anarchical hyperactivity in the early visual system, letters, proto-letters or musical notation appear without the normal constraints of syntax and meaning—providing a window into both the powers and the limitations of the early visual system.

Until the eighteenth century, voices—like visions—were ascribed to supernatural agencies: gods or demons, angels or djinns. No doubt there was sometimes an overlap between such voices and those of psychosis or hysteria, but for the most part, voices were not regarded as pathological; if they stayed inconspicuous and private, they were simply accepted as part of human nature, part of the way it was with some people. Around the middle of the eighteenth century, a new secular philosophy started to gain ground with the philosophers and scientists of the Enlightenment, and hallucinatory visions and voices came to be seen as having a physiological basis in the overactivity of certain centers in the brain.

I remember having twice been in danger of my life, and each time the awareness of the danger occurred to me quite suddenly. On both occasions I felt “this was the end,” and while otherwise my inner language proceeded with only indistinct sound images and slight lip movements, in these situations of danger I heard the words as if somebody was shouting them into my ear, and at the same time I saw them as if they were printed on a piece of paper floating in the air.

We apprehend a piece of music as a whole. Whatever the initial processes of musical perception and memory may be, once a piece of music is known, it is retained not as an assemblage of individual elements but as a completed procedure or performance; music is performed by the mind/brain whenever it is recollected; and this is also so when it erupts spontaneously, whether as an earworm or as a hallucination.

I would feel that I had made a crazy ascent into the stratosphere but had come back empty-handed and had nothing to show for it; that the experience had been as empty and vacuous as it was intense.

It is known that Lewis Carroll had classical migraines, and it has been suggested (by Caro W. Lippman and others) that his migraine experiences may have inspired Alice in Wonderland’s strange alterations of size and shape.

There are also descriptions of ecstatic seizures in The Devils, The Brothers Karamazov, and The Insulted and the Injured, while in The Double there are descriptions of “forced thinking” and “dreamy states” almost identical with what Hughlings Jackson was describing at much the same time in his great neurological articles. Over and above his ecstatic auras—which always seemed to Dostoevsky revelations of ultimate truth, direct and valid knowledge of God—there were remarkable and progressive changes in his personality throughout the later parts of his life, his time of greatest creativity. Théophile Alajouanine, a French neurologist, observed that these changes were clear when one compared Dostoevsky’s early, realistic works with the great, mystical novels he wrote in later life. Alajouanine suggested that “epilepsy had created in the person of Dostoevsky a ‘double man’ . . . a rationalist and a mystic; each having the better of the other according to the moment . . . [and] more and more the mystical one seems to have prevailed.”

In 1899, Gabriel Anton described a singular syndrome in which patients totally blind from cortical damage (usually from a stroke affecting the occipital lobes on both sides) seemed to be unaware of it. Such patients may be sane and intact in all other ways, but they will insist that they can see perfectly well. They will even behave as if sighted, boldly walking in unfamiliar places. If, in so doing, they collide with a piece of furniture, they will insist that the furniture has been moved, that the room is poorly lit, and so on. A patient with Anton’s syndrome, if asked, will describe a stranger in the room by providing a fluent and confident, though entirely incorrect, description. No argument, no evidence, no appeal to reason or common sense is of the slightest use.

There is something about the rapid and spontaneous transformations specific to hypnagogic imagery that suggests the brain is “idling,” as my correspondent Mr. Utter suggested. Neuroscientists now tend to speak of “default networks” in the brain, which generate their own images. Perhaps one may also venture the term “play” and think of the visual cortex playing with every permutation, playing with no goal, no focus, no meanings—a random activity or perhaps an activity with so many microdeterminants that no pattern is ever repeated. Few phenomena give such a sense of the brain’s creativity and computational power as the almost infinitely varied, ever-changing torrent of patterns and forms which may be seen in hypnagogic states.

(Cataplexy, indeed, can scarcely be hidden. I spoke to one man, by chance a friend of the comedian Robin Williams’s, who said that whenever he met Robin, he would lie down on the ground preemptively; otherwise, he was sure to fall down in a fit of laughter-induced cataplexy.)

The “mare” in “nightmare” originally referred to a demonic woman who suffocated sleepers by lying on their chests (she was called “Old Hag” in Newfoundland). Ernest Jones, in his monograph On the Nightmare, emphasized that nightmares were radically different from ordinary dreams in their invariable sense of a fearful presence (sometimes astride the chest), difficulty breathing, and the realization that one is totally paralyzed. The term “nightmare” is often used now to describe any bad dream or anxiety dream, but the real night-mare has dread of a wholly different order; Cheyne speaks of “the ominous numinous” here.

Adler studied a group of Hmong refugees from Laos who had immigrated to central California in the late 1970s and were not always able to perform their traditional religious rites during the upheaval of genocide and relocation. In Hmong culture, there is a strong belief that night-mares can be fatal; this evil expectation, or nocebo, apparently contributed to the sudden unexplained nocturnal deaths of almost two hundred Hmong immigrants (mostly young and in good health) in the late 1970s and early 1980s. Once they were more assimilated and the old beliefs lost their power, the sudden deaths stopped.

A general practitioner in Wales, W. D. Rees, interviewed nearly three hundred recently bereft people and found that almost half of them had had illusions or full-fledged hallucinations of a dead spouse.

I see it often with my patients in hospital, who can show extraordinary courage and calmness in facing the most dreadful diseases but fly into a rage if a nurse is late with a bedpan or a medication. The amorality of nature is accepted, whether it takes the form of a monsoon, an elephant in musth, or a disease; but being subjected helplessly to the will of others is not, for human behavior always carries (or is felt to carry) a moral charge.

The term “shell shock” was coined with the notion that the brains of these soldiers had been mechanically deranged by the repeated concussion of the new high-explosive shells introduced in this war.

the “dark tunnel” is correlated, Nelson feels, with the compromise of blood flow to the retinas (this is well known to produce a constriction of the visual fields, or tunnel vision, and may occur in pilots subjected to high g-stresses). The “bright light” Nelson correlates with a flow of neuronal excitement moving from a part of the brain stem (the pons) to subcortical visual relay stations and then to the occipital cortex.

The near universality of phantom limbs after amputation, the immediacy of their appearance, and their identity with the corporeal limbs in whose stead they appear suggest that, in some sense, they are already in place—revealed, so to speak, by the act of amputation.

Given a suitable prosthesis, the phantom limb will slip into the prosthesis (“like a hand into a glove,” as many patients say)—slip into it and animate it, so that the artificial limb can be used like a real one.