What causes the startling, unbidden perception of something that seems very real but has no material existence outside of our own minds? The “poet-laureate of medicine,” Oliver Sacks, takes us through the looking glass and into the fascinating world of hallucinations. Oliver Sacks, MD, is a physician, best-selling author, and professor of neurology at the NYU School of Medicine. He is best known for his collections of neurological case histories, including The Man Who Mistook His Wife for a Hat (1985), An Anthropologist on Mars (1995), Musicophilia: Tales of Music and the Brain (2007), and The Mind’s Eye (2010). His book Awakenings (1973) inspired the 1990 Academy Award-nominated feature film starring Robert De Niro and Robin Williams. Sacks is a frequent contributor to the New Yorker and the New York Review of Books and a fellow of the American Academy of Arts and Sciences. His newest book is Hallucinations (2012).
Indre Viskontas, a PhD neuroscientist and a Committee for Skeptical Inquiry Fellow, interviewed Sacks for our Center for Inquiry’s Point of Inquiry podcast.
You have a new book out called Hallucinations, and some of our readers may have already come across an excerpt in the New Yorker called “Altered States,” in which you describe some of your own experiences with hallucinogenic drugs. But before we delve into that topic, please tell us what is it that distinguishes a hallucination from other fantastical mental experiences, such as waking dreams or imagination?
Well, hallucinations can occur in full consciousness, unlike dreams, and they are projected externally and appear to have a real and objective reality, unlike imagined objects and people. They are similar to percepts (objects of perception) except they are, as it were, forced percepts in which there’s nothing there to perceive. It’s as if the perceiving parts of the brain have been forcefully activated internally.
I was initially struck by the beginning of your book, where you talk about people who have hallucinations because one of their senses has an absence of stimulation. For example, Charles Bonnet Syndrome, where people who are blind experience visual hallucinations. Tell us a little more about what’s going on there.
First, a lot of my work is done in an old-age home. I see a lot of people who have impaired vision or hearing even though they are intellectually quite intact. And a good proportion—I can’t say exactly but I would think close to a fifth of these people—develop hallucinations in the mode in which they are defective. So the blind and partially blind get purely visual hallucinations. Deaf people get auditory hallucinations, most commonly musical rather than verbal. People who’ve lost their sense of smell can get smell hallucinations.
One might say that people who have lost a limb get limb hallucinations. But I’m not quite sure whether phantom limbs belong in the same category with the others.
I open the book with a description of a patient whom I’ve been following for many years, who became very dear to me, and I was very sad when she died a few weeks ago, just short of her hundredth birthday. She was a remarkable old lady, strong and clear minded.
The nursing home phoned me saying she was apparently hallucinating and they didn’t know what was going on. When I went to see her, she was puzzled. She said, “I’ve been blind for five years. I see nothing. Why am I seeing things now?” I asked, “What sort of things?” She described scenes with animals, with people looking at her, with falling snow and a snow plow. Very vivid visual vignettes, maybe two or three minutes long, and then there would be another one.
I asked if they were like dreams, and she said, “No, they’re like film clips or maybe like going to the theater.” Interestingly, she could never recognize the people or places she hallucinated. And she felt that when they did their thing it was autonomously without any relation to her or to her own thoughts or feelings. This is rather characteristic of hallucinations in Charles Bonnet syndrome. Other hallucinations sometimes are charged with affects (emotions) or the sense of familiarity. But not the Charles Bonnet ones.
You mention that in the case of these visual hallucinations, they were of unfamiliar things. Whereas, I think you also mention that when people have musical hallucinations they are generally of familiar melodies or tunes or music they have heard before. Is that fair to say?
Yes, it’s a very striking difference. I’ve wondered whether it’s because music is an already constructed thing, whether one takes in whole pieces of music as opposed to visual things which may not be completed, unless of course, one is hallucinating a painting or photograph. It’s very much that what one sees has to be constructed like imagining an image. Whereas the musical ones are very much more like memories.
Do you know of any research in which people have looked at what’s going on in the brain during these hallucinations? Say, for example, in the visual hallucinations, there’s some other part of the brain that’s also active that’s doing the imagining or creating the scene.
Yes, well, there have been some very beautiful studies that have become possible with the advent of functional brain imaging, fMRI, and more recent forms of imaging, tensor imaging, that shows the white matter. If people were hallucinating faces, there tended to be abnormal activity in the so-called fusiform face area in the back of the right hemisphere in the inferotemporal cortex. If, on the other hand, they were hallucinating words or pseudo-words or letters, lexical hallucinations, then the visual word form area in the left hemisphere would be activated. And it looked very much that those systems of the brain involved in perceptual recognition generated hallucinations of that sort if they were being autonomously stimulated or released.
I think the studies of musical hallucinations have not sorted things out quite in this way because people hear [complete] pieces of music. What we find is a very widespread activation of all those parts of the brain, including cerebellum, basal ganglia, premotor cortex, and so forth that are activated when one listens to real music.
In these patients who are experiencing hallucinations in the absence of stimulation, and in particular, those healthy people you described who, after three days in a sensory deprivation chamber, began to hallucinate, it almost seems as though the hallucinations are a comfort rather than something they fear. Did you find that patients over time would learn to control either the content or the expression of their hallucinations?
Usually no control, or very little control, was obtained. But there tended to be accommodation. Once people with Charles Bonnet are reassured that there is no psychiatric or neurological calamity and they’re not on anything hallucinogenic, they may then become quite accepting of the hallucinations. I quote one man who imagined his eyes saying, “We know blindness is no fun so we have concocted this small syndrome as a sort of coda to your sighted life. It’s not much, but it’s the best we can do.” I’m slightly misquoting him, but that’s essentially what he imagined his eyes saying. Charles Bonnet’s grandfather who, as it were, was the original subject, would often compare his hallucinations to spectacles in a theater, and would sometimes like to go in a dark room in the afternoon for a hallucinatory matinee.
I was struck along the same lines by a description of a patient you wrote about. Her name was Gertie C. I believe she was a Parkinsonian patient. Could you tell our readers her story?
Gertie was a patient who had had the sleeping sickness, encephalitis lethargica, and a post-encephalitic syndrome which immobilized her for decades before she was put on L-dopa. She had all sorts of hallucinations, as do other patients on L-dopa. But it also become clear, when she got to know me and trust me (and I followed her for ten years or more) that she had had hallucinations long before she was put on L-dopa, mostly of a rather pastoral sort. She imagined lying in a meadow or floating in water. When she was put on L-dopa, her hallucinations became more social and more erotic, and apparently she got these quite under control so that she did not hallucinate until the evening. When it was time for her to hallucinate at 8:00 PM, she would say to her visitors, firmly but courteously, that she was expecting a gentleman visitor from out of town, and perhaps they could come another day. Her gentleman visitor, an apparition, would come through the window and brought her much comfort, both social and sexual. But she really seemed to have control of this. It never spread out of control, and it had this sort of humor that was engaging.
But she was an old hand at hallucinating. It may be that some schizophrenic patients—she was not schizophrenic—may also get on comfortable terms in this sort of way with their hallucinations. Incidentally, I mentioned in my book another patient who had Parkinson’s disease (not post-encephalitic), and he was also prone to hallucinating visitors. But they never followed him out of the apartment. They were confined to his apartment, and he could get away from them, if he wished, by going outside.
About a year ago I cohosted a television show on the Oprah Winfrey Network, in which I had the opportunity to investigate claims of miracles across the U.S. Several of the episodes included people who reported having had visions of a religious sense. They would be very offended if I intimated at all that they might have been hallucinating. Is there a difference, at least in the medical field, between what people think of as a religious vision and a hallucination?
Well, there is certainly a difference in character. People are often rather quiet about ordinary hallucinations. But with religious experiences, they may become almost evangelical. There’s a book in front of me at this moment which has been much talked about and is on the cover of Newsweek. It’s called Proof of Heaven and subtitled, “A Neurosurgeon’s Journey into the Afterlife,” by a man called Eben Alexander.
He had a nasty bacterial meningitis. He was in a coma for several days. But when he came to, he described an enormously complex so-called near-death experience. These experiences are often rather stereotyped in quality. People may feel they’re in a dark corridor and moving towards some bright light. Feelings of bliss envelop them as they are drawn towards the light. They sense, in a way, that the light is the boundary between life and death. And they would then come back or “float back.” In Musicophilia, I described such a sequence with a subject, another surgeon as it happened, who had been struck by lightning.
And he had this sort of blissful moment and then he said, “Slam! I was back.” He was back because someone was doing CPR on his heart and his heart started beating again twenty or thirty seconds afterwards. So, his whole cosmic journey only occupied a matter of seconds. Dr. Alexander feels that his cortex was out of action while he was having his visions and therefore it must have been direct supernatural intervention. I think such a claim can’t be sustained and indeed, a few seconds of altered consciousness as one emerges from coma would be enough to give him such a state.
People in these states may insist on their reality and feel their lives are transformed. And, as you say, may get angry if one says it was a hallucination. Of course, hallucinations, being brain events in the absence of any sort of objective world around one, can’t be evidence of anything, much less proof of anything. Certainly the being in heaven hallucination may feel real at the time, but in retrospect, I think many people will almost regretfully say, well, it was a hallucination. It seemed intensely real but it can’t be.
But other people may stick with the feeling that they have been vouchsafed a glimpse of the afterlife or, indeed, they have had quite a long sojourn there. One knows that what one had imagined was not reality. But if it leaks into hallucination, it may [seem to] be. I don’t think hallucinations are evidence of reality any more than imaginings are.
I was struck by how you describe almost a continuum of belief in one’s own hallucinations. You have people who, for example, on one extreme, have Anton’s Syndrome in which they have damage to the occipital lobe and they’re blind cortically. But they deny their impairment—despite overwhelming evidence to the contrary. On the other extreme, you have people who immediately know that their hallucinations aren’t real and they’re skeptical of them. What is the difference between these two sets of people?
Anton’s Syndrome, which I only touch on briefly, does involve all sorts of misconnections from reality testing. But with complex temporal lobe hallucinations, which during surgery can be induced by stimulating the temporal lobe cortex in the right place, can produce what Dr. Penfield, a pioneering neurosurgeon, called “experiential hallucinations,” which seem intensely real. Although there may be a sort of doubling of consciousness, so the patient can say, “I know I am in Dr. Penfield’s operating room, but I am also at the corner of 25th and First Avenue in South Bend, Indiana.”
They might feel an intense sense of similarity in their investing somehow the present. I think one has to think in terms of various levels. These Charles Bonnet hallucinations are relatively low down in the ventral visual pathway. But by the time one comes to these temporal lobe hallucinations, one is finding co-activation of the amygdala and the hippocampal systems. This then may invest them, certainly, with a strong sense of emotion and familiarity. Also, to some extent, of [a sense of] reality.
You also describe—in the temporal lobe epilepsy patients—ecstatic hallucinations.
These so-called “ecstatic” hallucinations have been described for many years in the medical literature, and in the general literature. You have only to read Dostoyevsky’s descriptions of his own seizures—descriptions he also splits among many of his characters. He would suddenly be arrested and cry, “God exists! God exists!” He would feel that he was in heaven and that everything was unified and made sense. It could sometimes be followed by convulsions, but he said for five seconds of this state he would give his whole life.
In these ecstatic hallucinations, there is a sudden transport of joy and also a sense of being transported to heaven or into communication with God. These seem intensely real to people and very pleasurable. There was an interesting study a few years ago when there was an attempt to treat some patients with ecstatic seizures. A lot of them refused to take medication, and some of them even found ways of inducing their own seizures.
If a seizure is pleasant, usually there is spiking in the right temporal lobe at the same time as people are having their divine vision. They may be a bit out of touch with the sort of daily reality around them. But lives are being transformed by this.
One of my favorite case histories, which I quote in my book, is of a bus conductor in London who, as he was punching the tickets, suddenly felt that he was in heaven and told this to all of his passengers. He remained in a very elated state for three days. It sounds as if he was in an almost postictal mania. Then he continued on a more moderate level, deeply religious, until he had another bunch of seizures three years later—and he said that cleared his mind. Now he no longer believes in God and angels, in Christ, in an afterlife, or in heaven. Interestingly, the second conversion to atheism carried the same elated and revelatory quality as the first one to religion.
I want to ask you about a personal experience of mine. I don’t think I’ve ever experienced a full-blown hallucination, at least to my knowledge. But you might remember from the conversation we once had at dinner that I am a grapheme-color synesthete. For our readers who are unfamiliar with the term, it means that I see letters and numbers in color. Is this a hallucination?
No, I think that seeing letters and numbers in color or seeing music in color is really a constant physiological happening between two areas of the cortex, a letter-reading one and a color-constructing one. I think this sort of thing, which you can probably verify from your own experience, comes at an early age, and doesn’t change. I suppose one might call it an illusion, in that one sensation is invested with the qualities of another sensation. This can take very complex forms. There’s one professional musician who could taste different pitches—she tuned her violin by taste.
That’s amazing. For me it just feels so natural, yet I know, intellectually, that the appearance of the color doesn’t happen until my brain has somehow understood the symbolic meaning of a letter, for example.
That’s interesting. And if you’re given a sort of a nonsense string of letters, that doesn’t light up at all?
Well, the letters do. But it’s not until—say if I see two intersecting lines, it’s not until my brain decides whether it’s a T or an L that I see the color. If letters are occluded and I don’t know what the letter is, there is no color. It feels instantaneous to me that the color comes on in line with the meaning of the letter. In that way, I wondered if there wasn’t a part of my brain that is overlaying a hallucination. But I can see your point that it’s more of an illusion because it’s unchanging and it’s always present.
Probably if you spoke to another letter-synesthete, you would find that he or she had different colors from you.
Yes, in fact, I’ve been working with an illustrator on a graphic novel. Her name is M.G. Lord. She’s also a synesthete, and we have very heated arguments about what colors the letters should be.
Nabokov discovered when he was a child that he was a synesthete. But he complained to his mother that the letters in the alphabet set were of the wrong color. She agreed with him. But when she said the colors they were to her, the two of them disagreed. In general, synesthetes don’t agree. This is especially striking for musical synesthetes. Liszt and Rimsky-Korsakov both thought [their musical synesthesia] was something absolute. But when they met they found that they saw very different colors and couldn’t agree about anything.
I’d like to wrap up the interview with a more personal note from your own experiences. I was very much struck by one experience you described in which you had taken a hallucinogenic drug and you were waiting for a hallucination to appear. And then nothing happened. Can you describe that experience?
Yes, well, I was living then down on Venice Beach in the early 1960s, and there were a lot of drugs around. And people said to me, if you really want something striking take artane. Artane is a belladonna-like drug which is used in treating Parkinson’s. And they said just take twenty, you’ll still be in partial control. Anyhow, I took these tablets. At first I noticed nothing. I had a rather dry mouth, difficulty accommodating, my pupils were dilated. Nothing else. Then I heard a car door slam and footsteps, and I thought it was my friends Jim and Kathy. They often visited me on Sunday. I shouted “Come in!” and we chatted. I was in the kitchen.
There was a swinging door between the kitchen and the sitting room. I said, “How do you like your eggs done?” And we chatted in the four or five minutes while I prepared their ham and eggs. Then I walked out with the breakfast on a tray and . . . there was no one there. I was so shocked I almost dropped the tray. It hadn’t occurred to me for a moment that all this was hallucinated, at least that their part of the conversation was hallucinated. I thought I’d better watch myself. But this was followed by some even stranger things, including having a conversation with a spider. I think the spider was real enough; there weren’t any visual elements.
But then the spider said, “Hello.” And for some reason it didn’t surprise me any more than Alice was surprised by the White Rabbit. I said, “Hello yourself.” And we had a conversation. Actually, an abstract conversation about some points in analytic philosophy. Many years later, I mentioned this to a friend of mine, an entomologist, the philosophical spider with a voice like Bertrand Russell. He nodded his head and said, “Yes, I know the species.”
What is amazing is that you were expecting it. You were waiting for a hallucination.
Yes. Although I didn’t think it would take that form. I thought it would be all sorts of dramatic visual misperceptions and hallucinations as one may get with LSD or mescaline and those drugs. But this time it was purely auditory, and oddly humdrum although at the same time deeply absurd. I wonder what one would have thought had they seen me talking learnedly to a spider.