Unthinkable

by Helen Thomson

  * * *

  It’s difficult to imagine what a hallucination feels like unless you have experienced one yourself. I say this with some degree of conviction because a few months ago, early in the morning and alone in bed, I was woken by two strangers entering my room.

  I was paralyzed with fear, I felt wide awake, yet I couldn’t move my body. One of the strangers, a man, walked to the opposite side of the room, while the other, a woman, sat down at the bottom of my bed. As she did so, I felt the covers brush across my legs. Later, I discovered that I had been experiencing what’s known as a hypnopompic hallucination. These appear during the transitory period between a sleeping state and wakefulness, and probably occur due to certain parts of the brain remaining in REM sleep—the period in which we dream the most—while other areas become fully conscious. For me, it had a distinct feeling of objective reality. It was far closer to the experience of someone actually being in the room than the experience of dreaming they were there.

  This distinction is supported by some evidence. In 1998, Dominic Ffytche, a senior lecturer in old-age psychiatry, and his colleagues at King’s College London scanned the brains of people experiencing visual hallucinations. They found that the areas of the brain that were active are also active while viewing a real version of the hallucinated image. Those who hallucinated faces, for example, activated areas of the fusiform gyrus, known to contain specialized face-recognition cells active when we look at real faces. The same was true with hallucinations of color and written words. When the team asked the participants to imagine faces, or colors and words, there was nowhere near as much activity in the corresponding areas of the brain. It was the first objective evidence that hallucinations were less like imagination and more like real perception.4

  As well as hynopompic hallucination, like the one I experienced, another common hallucination is seeing shapes or hearing sounds as you drift off to sleep at night. Or seeing visions of loved ones during a period of grieving. But the kind of hallucination that I am most intrigued about—and the one that reveals most about the brain—is that which crops up in people who have recently lost a sense.

  Several years ago, my mum called me to tell me that my grandmother had started seeing people. Eighty-seven years old, she began to hallucinate after her already poor sight got worse due to cataracts. Her first visitors were women in Victorian dress, shortly followed by young children who danced around her bedroom. Sometimes all she saw was a plain brick wall. My nan was not, it seemed, bothered by these hallucinations; she knew they weren’t real, despite their vividness, but was intrigued by what they meant.

  She was experiencing a common condition in those with failing sight called Charles Bonnet syndrome. Bonnet, a Swiss scientist born in 1720, became interested in hallucinations when his grandfather started to experience visions soon after his eyesight began to fail. One day, his grandfather was sitting in an armchair talking to his two granddaughters. Suddenly two men appeared. They were, by all accounts, wearing magnificent cloaks of red and gray with hats trimmed with silver. When he asked his grandchildren why no one had told him they would be coming, the elder Bonnet discovered that only he could see them.

  Over the next month, his visions appeared on many occasions. Sometimes they were further beautiful visitors, other times they were pigeons or butterflies, sometimes simply oversized carriages. Bonnet’s grandfather apparently enjoyed what he referred to as “the theater in his mind,”5 watching these apparitions for several months before they disappeared completely. Bonnet later experienced the same condition when he too lost his sight in old age.

  It was a similar story for Max, a man I interviewed for the BBC in 2014. Max was in his seventies when Parkinson’s disease destroyed the nerves that send information from the nose to the brain. Despite his loss of scent, one day he suddenly noticed the smell of burning leaves. He was on holiday at the time and so glanced around his hotel room, wondering what could have caused the strange aroma. He was convinced there was a family of skunks around.

  “It was so strong,” he said. “It gave me this strange sensation in my throat that I couldn’t get away from.”

  Over the next few weeks, the aromas intensified, ranging from burnt wood to a horrible onion-like stench. They stuck around after he returned home too, sometimes persisting for hours.

  “When they’re at their most intense they can smell like excrement. It’s so powerful it makes my eyes water.”

  Sensory loss doesn’t have to be permanent to bring on such hallucinations. Avinash, after all, was in fine health while trekking across the glacier.

  “I knew I wasn’t sick,” he told me. “My heart rate was fine. I wasn’t dehydrated and I’d had enough food. I tried to rationalize it all. I pinched myself, I kept trying to make sure I wasn’t asleep or dreaming. At one point I tripped and cut my hand—the sight of blood made me sure it wasn’t a dream.”

  At some point he started hearing a voice, and felt like there was a presence guiding his every move. “I felt as if it was talking me through things. It was asking me to think carefully, to pick my way through each glacier. It was helping me, guiding me toward where I should be.”

  The whole experience lasted almost nine hours.

  “I asked myself at one point, ‘Am I dead?’ This was a difficult trek—you could have just fallen into a crevice and died and no one would ever have found you. It was only when I passed someone else on the mountain that I knew I was definitely alive. But even when I met up with the rest of my group I still felt strange. It was only after a good night’s sleep that everything went back to normal.”

  Searching for answers to his weird hallucinations, Avinash momentarily wondered whether he had achieved the “savikalpa samadhi”— a state said to be reached by meditation in Buddhist or Hindu tradition through which one is said to lose all human consciousness, and in which the conception of time and space is altered.

  It turns out the answer is far simpler. But to understand more, I needed to speak to Sylvia.

  * * *

  One Friday morning in 2004, the people of Potters Bar were going about their daily business. Minutes from the center of town was sixty-year-old Sylvia, a retired teacher, who was working in her house. All was well, apart from one thing. That wretched noise. The two notes that had started playing earlier that morning, which no one else seemed to be able to hear. Sylvia had initially thought the radio must be playing, but a quick search proved that not to be the case. Fairly fearful of the strange new noise, which got louder throughout the day, Sylvia went to bed, hoping it would be gone by morning. She woke up to find the noise was still there. It droned on and on, dah de dah de dah de. Over weeks, the notes changed, and months later finally became full-blown musical hallucinations—tunes that were constantly in the background, sometimes so loud that they drowned out normal conversation.

  “Please ignore her for a moment,” Sylvia says, as she welcomes me into the house. She’s talking about the golden Labrador sitting quietly in the hall. Sookie is Sylvia’s new hearing dog.

  “Good girl,” she says to the dog. “Now you can go say hello.” Sookie bounds over to me and sticks her nose straight into my pocket. “She thinks you may have treats,” says Sylvia. “It’s always worth a try.”

  Sylvia needs a hearing dog because she is deaf. She finds it difficult to hear speech, and real music sounds awful, distorted by profound hearing loss caused by an ear infection several years earlier.

  Sylvia’s husband, John, waves hello as we walk past a grand piano and through to a bright conservatory at the back of the house. I sit down on a wicker chair, while Sylvia serves up tea and biscuits.

  She takes me back to the Friday morning that it all started. She’d had tinnitus and hissing for a number of years previously. But this was something new. It was the notes C and D going back and forth, she says. “It was very slow at first. I remember thinking, ‘Oh I don’t want that, think about something else.’ The notes grew from there. I’ve never had quiet since.
”

  Gradually over weeks the notes developed into short phrases that would repeat over and over again. Sometimes they would get longer, forming complete melodies from the music she had loved before she lost her hearing.

  “What kinds of tunes do you hear most often?” I ask.

  “It’s mostly classical music, short excerpts. When I could hear properly, I didn’t tend to listen to much else.”

  Even as we sit talking—through the help of a microphone and lip reading—Sylvia’s tunes are playing in her head. If they ever recede, which they sometimes do when she’s focused on a piece of music or concentrating on speaking, they are replaced by a constant B-flat tone and the hiss of tinnitus.

  “Do they resemble any particular instrument?” I ask.

  “They’re a cross between a wooden flute and a bell,” she says. “It’s really strange—you’d expect to hear a sound that you recognize, maybe a piano or a trumpet, but it’s not like anything I know in real life.”

  “But it sounds like a real noise?”

  “Yes, it’s not as if you imagine a tune in your head, it’s like listening to the radio. It manifests as real sound.”

  Soon after her hallucinations started, Sylvia did something very constructive. She wrote them down, keeping a record in a manuscript book of all the tunes that would come and go. She has the rare talent of perfect pitch, which allows her to hear any note and know exactly which note is being played.

  She brings the sheet music to the conservatory for me to read. Some of the pieces are made up of random notes, never going anywhere in particular. Other hallucinations resemble short sections of recognizable tunes—I spot a passage from the traditional Scottish folksong “My Bonnie Lies Over the Ocean.”

  Seeing her hallucinations on paper highlights their repetitiveness. There are pages of notes that wind up and down, up and down. They are like this for most of the day, Sylvia says.

  Years of teaching math allows her to make a quick mental calculation. “If it’s just two or three notes then they can take a second to play before they repeat,” she says, “so that’s what? Hearing the same tiny tune about eighty-six thousand times a day?”

  Sylvia tells me that early on in the evolution of her hallucinations, words began to put themselves to the tunes.

  “I did my utmost to prevent that happening,” she says, “and I managed to make it stop.”

  I ask her why.

  “I didn’t want that happening. I didn’t want words coming into my mind. It just felt a bit close to schizophrenia.”

  SHE’S RIGHT, OF COURSE—hearing voices that are not there is often considered a sign of mental illness. No one knows this better than David Rosenhan, a professor emeritus at Stanford, who in 1973 got himself and seven other completely healthy friends admitted to the mental wards of hospitals across the United States. The point of his experiment was to question the validity of psychiatric diagnosis—but they hadn’t expected it to be so easy. Rosenhan and his colleagues each phoned a hospital complaining of hearing voices. The rest of their medical history and any other life stories were all true. All eight were admitted—seven were diagnosed with schizophrenia, one with manic-depressive psychosis. As soon as they entered the hospital they said their hallucinations had disappeared. It was then up to each individual to convince the staff to discharge them—a task that took between seven and fifty-two days.6

  In fact, most hallucinations are not associated with schizophrenia. When John McGrath, a professor at the Queensland Brain Institute in Australia, analyzed interviews with more than 31,000 people from eighteen different countries, he discovered that hallucinations were fairly common in all age groups. When participants were asked whether they had ever experienced a hallucination, such as hearing voices that other people said did not exist, 5 percent of men and 6.6 percent of women answered yes.7

  I ask Sylvia whether she tells other people about her hallucinations.

  “No, I don’t talk to many people about it. Very early on, I was taught that as sound travels up to the brain it picks up emotions that go with that sound. In other words, if I became constantly irritated by them, the sounds would always cause irritation. If I told them they were unimportant, they would stay insignificant. So I took a conscious decision to belittle them, and not talk to other people about them. I don’t want them to garner an importance. It was the best advice I could have been given—it’s allowed me to live with them.”

  She smiles. “Sometimes I go, ‘Oh shut up,’ and my friends know what I’m talking about, but they can’t possibly put themselves in my shoes.”

  She glances at John as he pops his head into the conservatory. “John, bless him, is a real support in every sort of way, but even he has no idea how dramatic this sound is that’s going on all the time. It gets in the way of his conversation with me. I mishear what he says so much of the time. Sometimes I think he’s said something very funny and he didn’t say it at all. He’s very understanding, but no one can have any idea what this is like unless they’ve experienced it for themselves.”

  * * *

  In fact, there is a way that you can experience something similar for yourself, safely at home. All you need is a table-tennis ball, some headphones and a bit of tape. Cut the ball in half and tape each segment over your eyes. Sit in a room that is evenly lit, find some white noise to listen to over your headphones, sit back and relax.

  Called the ganzfeld technique, this kind of sensory deprivation has been used to investigate the appearance of hallucinations for decades. In a paper published in the journal Cortex,8 Jiří Wackermann at the Institute for Frontier Areas of Psychology and Mental Health in Freiburg, Germany, describes some of the hallucinations that occurred in volunteers trying out the technique.

  “For quite a long time there was nothing except a green-greyish fog,” said one participant. “It was really boring. I thought, ‘Ah, what a nonsense experiment!’ Then, for an indefinite period of time, I was ‘off,’ like completely absent-minded. Then, all of a sudden, I saw a hand holding a piece of chalk and writing on a blackboard something like a mathematical formula. The vision was very clear, but it stayed only for a few seconds and disappeared again . . . it was like a window into that foggy stuff.” Later, she saw a clearing in a forest and a woman who passed by on a bike, her long blond hair waving in the wind.

  Another participant felt like she and a friend were inside a cave. “We made a fire. There was a creek flowing under our feet, and we were on a stone. She had fallen into the creek, and she had to wait to have her things dried. Then she said to me: ‘Hey, move on, we should go now.’”

  As I sit back in my own living room, ping-pong balls strapped to my face, I feel much the same way as that first participant. Nothing happened for at least thirty minutes, other than a myriad of random thoughts and waves of sleep. Just as I was wondering whether I should give up, I saw an image coming out from what seemed like a window full of smoke. It was of a man lying curled up next to me. He bent his elbow in this strange way as if presenting it to me. It appeared for a few seconds, then disappeared. It certainly differed from a dream, or from a random image plucked from my imagination. It was an intriguing demonstration of what can occur when our senses are impaired. But why does it happen?

  * * *

  “The brain doesn’t tolerate inactivity,” said Oliver Sacks, when I spoke to him about this back in 2014. “It seems to respond to diminished sensory input by creating autonomous sensations of its own choosing.”

  This was noted soon after the Second World War, he said, when it was discovered that high-flying aviators in featureless skies and truck drivers on long, empty roads were prone to hallucinations.

  Now researchers believe that these unreal experiences provide a glimpse into the way our brains stitch together our perception of reality.

  Although bombarded with thousands of sensations every second of the day, your brain rarely stops providing you with a steady stream of consciousness. Think about all the sounds, smells
and tactile sensations that you can sense right now. Noise from the outside world, the tightness of your socks, the feel of this book against your fingers. Processing everything that you experience in the world all of the time would be a very inefficient way to run a brain. So instead it takes a few shortcuts.

  Let’s use sound as an example. When sound waves enter the ear, they are converted into electrical messages by receptors within the ear canal and transmitted to the brain’s primary auditory cortex. This part of the brain processes the rawest elements of sound, such as patterns and pitch. From here, the signals get passed on to higher brain areas that process more complex features, such as melody, key changes and emotional context.

  Instead of relaying every detail up the chain of command, the brain combines the noisy signals coming in with prior experiences, to generate a prediction of what’s happening in the world.

  If you hear the opening notes to a familiar tune, for instance, you expect the rest of the song to follow. That prediction is passed back to the lower regions, where it is compared to the actual input, and to the frontal lobes, which perform a kind of reality check, before it pops up into our consciousness. Only if a prediction is wrong does a signal get passed back to higher areas, which adjust subsequent predictions.

  You can test this for yourself. Anil Seth, a cognitive and computational neuroscientist at the University of Sussex, suggests listening to sine-wave speech, a degraded version of a speech recording. The first time all you’ll hear is a jumble of beeps and whistles. But if you listen to the original recording and then switch back to the degraded version, you will suddenly be able to make out what is being said. All that has changed is your brain’s expectations of the input. It means it now has better information on which to base its prediction. “Our reality,” Seth once told me, “is merely a controlled hallucination, reined in by our senses.” Or, as psychologist Chris Frith once put it, “A fantasy that coincides with a reality.”9