The brain might be said to be in touch more with itself than with anything else.
—GERALD EDELMAN,Bright Air, Brilliant Fire
When Benjamin Rush—physician, father of American psychiatry, and signer of the Declaration of Independence—attempted to explain voice-hearing in 1812, he wasn’t sure where exactly the source of the experience could be found. He was positive the experience pointed to an underlying disease. He wrote in Medical Inquiries and Observations, upon the Diseases of the Mind, one of the earliest psychiatric texts, that there were many people who “fancy they hear voices” as the result of “a morbid affection.” But he hedged his bets as to the disease’s location. Voice-hearing was caused, he wrote, by “a change in the natural actions of the brain, or of the organs of hearing.” The brain or the ear: Rush wasn’t committing.1
Nearly two hundred years later, scientists aren’t so circumspect. The brain is now the undisputed center of inquiry into the mystery of voice-hearing. Open a recent scientific text on hallucinations and you will be met with such esoteric terms as “axonal conduction time,” “increased density of GABA(A) receptors in the superior temporal gyrus,” and “cortico-(thalamo)-cortical interactions.” Yet the brain is not where a scientific inquiry into voice-hearing properly begins. In order to understand what causes voices to be conceived immaculately, the first thing one has to do is understand what causes voices according to the normal rules of the world. The path to voice-hearing begins with the human voice.
Imagine a husband and wife seated across from each other in a living room. The wife wants to say something to her husband. When she finds the words, the first step she takes is to release her breath from the inflated lobes of her lungs into the branched tubing of her respiratory system. The main channel in this system is the trachea. It is approximately eight inches long, rigid, and segmented like the hose of a shower nozzle. Its purpose, in this case, is to serve as the conduit for the breath toward the first obstacle necessary for the production of speech: the vocal cords.
Vocal cords are not really cords; they don’t work in the manner of guitar strings. Rather, they are thin, muscular flaps, reminiscent of labia, that block the top of the trachea like the lid of a truck’s horn. When one wants to breathe, these flaps are loose. When one wants to speak, they form a barrier by pressing together, sealing off the throat from the breath. Its progression stanched, the breath accumulates behind the vocal cords. The pressure builds. Before long, the pressure becomes so great that the vocal cords can no longer maintain their seal, and they release—not all at once but fluidly, periodically, the way the length of an earthworm ripples as it moves across the soil. With speech this event never occurs in isolation. As the breath makes its dash upward, the pressure below the vocal cords decreases rapidly, and the cords, their strength regained, seal together again. More breath creates more pressure, which again builds. Another breaking point is reached, the cords again release, the pressure drops, the cords seal, and so on in a rapid, alternating dance of advance and retreat.
By this process between flesh and breath is created the basic mechanical component of sound: the movement of an object. All sound—a voice, a G-minor chord on a banjo, the hum of a refrigerator—is made because of the movement of an object. When an object moves, it causes an alteration in air pressure, a pulsing of molecules. A sound that exists because of a uniform and constant alteration in air pressure, as in the ringing produced by a tuning fork, is called a pure tone. With the complicated apparatus of the human vocal system, such a pure sound is impossible to create; it would elude even the practiced control of a trained singer. Speech, however, does not require purity; speech requires variety capable of expressing content, and therefore, in addition to the vocal cords, the respiratory system is outfitted with a series of muscles with Latinate names—the depressor anguli oris, the posterior cricoarytenoid, the sternocleidomastoid—whose purpose in speech production is to manipulate the flow of breath as it passes through the body.
After the wife’s breath passes the vocal cords, it makes its way through this muscular assembly line, all the while being shaped into the words she has decided to speak. After passing her lips—the last of the muscles—it shoots into the room like steam from a teakettle. Breath collides with air, completing the first of two alchemic steps on the way to speech: the transformation of breath into molecular movement. The air molecules in front of her mouth compress and open in pulses tuned to her words. These pulses travel forward and outward like an inflating balloon, moving toward their target.
At this point in the process, the voice becomes hard to define. Is the converted breath, hovering in the air between speaker and listener, yet a voice? Is it audible? It is enough to state that at this point the voice has taken leave of the wife’s possession. She is no longer its owner or master. She has pushed it out into the world. It is independent.
At last, the husband receives the voice. He has had little choice in the matter. The pinna—the part of the ear, made of folds of cartilage, that juts out from the head—is intended to help voices in their search for a destination. Try to stop yourself from hearing a voice once it is spoken. You won’t be able to run fast enough. The human voice is adept at finding its entrance, and once it breaches the barrier of the ear, all is lost. The barbarians have entered the castle.
Paradoxically, the only way to describe the voice now is as the province not of the wife’s body but of the husband’s. Having made its way into his ear and into the thin tube of the auditory canal, it responds to the confinement as water does in a hose: with speed. It races headlong, until it crashes into the taut sheath of flesh known as the tympanic membrane. In response, that membrane booms like the instrument from which it takes its name. It vibrates and echoes, mimicking the complex vibrations of the air.
Beyond the tympanic membrane lie three minuscule bones that rest lightly against one another so that the movement of one causes a movement in the next. It is a Rube Goldberg–ish setup, the single purpose of which is the second alchemic step necessary for communication: the transformation of molecular movement into an electrical impulse. Why evolution has fitted human beings with so jerry-rigged a system for hearing is anyone’s guess, but it is a strangely efficient system. The hammer strikes the anvil, which strikes the stirrup, which strikes a tiny organ like a pin striking a bell. Very little energy is lost.
The bell that is struck is the cochlea, a snail-shaped, hair-lined, fluid-filled device and one of the triumphs of evolution. The cochlea is so ornately constructed that despite two thousand years of direct observation, biologists have been able to discern only a minute fraction of what it does. What is well known is that in the cochlea, molecular movement is converted to electricity. The movement of the fluid within the shell of the cochlea causes the hairs along its twisting length to vibrate. This vibration in turn stimulates the slender cells of the auditory nerve.
The auditory nerve is the final pathway to the brain. It transports the electrical signal of speech across the axons of its component neurons and into an upper section of the brain known as the primary auditory cortex, which processes sound and also is involved in the production and comprehension of language. This lump of inert matter absorbs the incoming electrical impulses, which are transmitted along the neurons in linear fashion and then branch out in a complex network, and somehow converts them into the comprehension of a voice. The hearer hears.
The wife has said, “I want a divorce.”
This single sentence completed the journey from first breath to comprehension in approximately one second. It was a deft manipulation of physics and biology, traversing space and time and several hundred body structures. But the long path of the voice was only prologue. A voice does not begin its true existence until after the brain of the hearer has absorbed and converted the electrical signals of the neurons. The voice then spreads, via the brain’s complex neural network, into wider and deeper areas of the brain. The brain copies the external voice, discards the original, and then remakes the copy in its own image based on the meaning the voice might have for the brain and its owner. The brain molds the voice over and over again like a child playing with a lump of clay. The voice both deviates from the original that produced it and becomes inseparable from what it is stimulating.2
It is easier to see how the brain digests and incorporates a stimulus in a symptom that is halfway between normal speech and voice-hearing. Tinnitus is the perception of buzzing, ringing, hissing, or other simple sounds in the absence of external sounds. In the majority of tinnitus cases, a source of the buzzing can be found in some damage to the microscopic hairs in the cochlea. An “external”—meaning outside the central nervous system—defect is the cause of tinnitus. There is a source for the disorder, and thus the noise can be turned off—theoretically, at least.
But the brain quickly wrests control of the stimulus. The noise produced by a faulty cochlea is processed by the brain like a voice, and as usual the brain has much to say. The mere damage of cilia in the inner ear in short order implicates a wide range of areas in the central nervous system, even areas as far from the ear as the frontal lobes. It is as if the original stimulus were a burglar ducking into a house of mirrors to elude capture. Several tinnitus studies have shown that the more a sufferer tries and fails to find a cure for the noises in his head, going from doctor to doctor for advice, the louder and more persistent the noises become. The sense of frustration becomes inexorably linked to its cause, feeding it. Researchers call this the “headless chicken” phenomenon.3
The pathetic futility of this cycle is heightened by the fact that the stimulus itself, even before it reaches the brain, is a chimera. A voice that is heard is never the same as the voice that is spoken. As a sound wave travels, it weakens. It comes across obstacles and is reflected, refracted, and modified. What is more, the pinna—the external flap of the ear—further alters the sound entering the auditory canal.4 In the end, there is no such thing as a true sound or a true voice.
How can one examine such an elusive shape-shifter? In his philosophical treatise On Being Blue, William Gass (paraphrasing the poet Rainer Maria Rilke) explains the difficulty inherent in examining an object of desire: “Love requires a progressive shortening of the senses: I can see you for miles; I can hear you for blocks; I can smell you, maybe, for a few feet, but I can only touch on contact, taste as I devour. And as we blend, sight…blurs.”5 A similar blurring occurs as we follow a voice into the brain. The quality of our understanding of a voice moving toward the brain decreases asymptotically, until the lines of sense and experience appear as one even if they are not. The voice becomes inscrutable, describable only in the language of metaphor.
And when a voice is emotive, it also becomes intractable. For our jilted husband, only time, perhaps, will dull the influence of the voice he heard, turning it into a brittle husk, like the shell of a cicada on a tree. Until then, however, the presence of the voice—what psychologists refer to as an “auditory image”—will continue to make itself known whenever it so chooses: while he is walking down the street, while he is driving to work, while he is lying in bed. Until such time as it decides otherwise, he will be subservient to the internal life of his wife’s words, and within his skull the setting will forever be the living room in which they were first spoken.
If normal voice-hearing leads to the point that all experience is internal, hallucinated voice-hearing begins there. Hallucinated voice-hearing conflates source and destination. All preliminary steps are bypassed. There is no breath, no manipulation of air, no movement of bones or cochlea, not even a stimulation of the auditory nerve. With voice-hearing the brain, working alone in its watery chamber, creates a voice out of nothing but its own duplicitous silence. And it does so with such reality and finesse that the individual whose brain is engaging in such operations experiences the voice as if it were external.
How is this possible? How can the brain create a voice in the absence of an external stimulus? How can the brain bypass the structures of the auditory system so successfully that it can produce not just sound but a voice, complete with modulation in pitch, tone, and volume, and with emotional tenacity? How can the brain transcend the external world?
These questions have puzzled observers for thousands of years. The most common solution to them has of course been religious. The Greek historian Plutarch, for example, wrote of Socrates that his voices were a privilege granted because of his spiritual superiority: “Now the voice that Socrates heard was not, I think, of the sort that is made when air is struck; rather it revealed to his soul, which was, by reason of his great purity, unpolluted and therefore more perceptive, the presence and society of his familiar deity, since only pure may meet and mingle with the pure.”6
The spiritual interpretation of what causes voice-hearing has been even more popular in its negative form. Heinrich Krämer and Jakob Sprenger’s Malleus Maleficarum, a guide to witchcraft and sorcery first published in 1487, took great pains to describe the vocal capabilities of demons:
Devils have no lungs or tongue, though they can show the latter, as well as teeth and lips, artificially made according to the condition of their body; therefore they cannot truly and properly speak. But since they have understanding, and when they wish to express their meaning, then, by some disturbance of the air included in their assumed body, not of air breathed in and out as in the case of men, they produce, not voices, but sounds which have some likeness to voices, and send them articulately through the outside air to the ears of the hearer.7
Since the medicalization of mental experience, the demonic taint associated with voice-hearing has largely faded away, but the spiritual view has not. Many voice-hearers today explain their experiences in terms of some mystical communion with another person, usually dead. This type of explanation predominates when a voice occurs only once. For example, Kim Callahan Hedden, a Washington, D.C.–based writer, heard a voice when she was thirty-eight years old and waiting for laboratory results that would tell her whether she had cancer. One day at work Hedden went to the bathroom and, while washing her hands, heard a “flat, woman’s voice…as though she were tired and old,” say, “You will be OK.” After she heard the voice, her fears about her health disappeared, and she soon learned that her lab results were negative. The voice, Hedden thinks, was that of the murdered daughter of a retired senator who had his office directly across the hall from her own. “I believe very strongly that certain spaces can be inhabited by voices,” she told me.
In a discussion of the history of voice-hearing, the reason for much of the experience’s content, and the reactions of hearers, the belief that voices have a spiritual source external to the self is central. When discussing the science of voice-hearing, however, the spiritual view is, by definition, moot. We now live at a time when we have the tools and the knowledge, paltry though they still are, to confirm a suspicion that goes back to ancient Greece: that the brain is the source of all cognitive processes and thus the source of all its offshoots, that nothing—no movement, no thought, no belief, no idea, no feeling of love or hate or desire or fear—can exist without the brain. No matter our religious beliefs, the unassailable physical fact is that the phenomenon must have a neurological correlate that, in theory, we can explain, chart, and describe. Any scientific exploration of voice-hearing is bound by what the neuropsychologist Christopher Frith and his colleagues have called “a fundamental assumption”: “[F]or every mental state…there is an associated neural state.”8
Unfortunately, accepting the brain’s centrality in causing voices has not helped solve the mystery of how—or why, if such a question can be asked—it does so. There are two main obstacles blocking an answer to the question “What causes voice-hearing?” The first is the complexity and elusiveness of the brain. The second is the extraordinary complexity of voice-hearing itself, which not only manifests itself in an array of forms but implicates an array of psychological and, thus, neurological faculties.
First, the brain. The cerebral cortex—the eighth-of-an-inch-thick sheath of topographically erratic tissue that deals with “higher” brain functions such as speech and thought—contains approximately ten billion individual neurons interwoven with one another in a three-dimensional network and in constant communication by way of chemical transfers across microscopic gaps called synapses. In the cerebral cortex, which makes up a minute fraction of the brain’s matter, there are approximately one million billion connections between neurons. The possible combinations of connections within the cerebral cortex approach incalculability. And the brain is not a static organ. It is alterable, dynamic, less a computer, to which it is too often compared, than an entire atmosphere, with innumerable molecules rocking and sparking and calming with unpredictable constancy. A further obstacle is that the brain is largely self-referential. It is constructed in such a way that the majority of its matter only receives input from and gives output to other parts of the brain. This brain matter neither directly influences nor is directly influenced by the outside world. In other words, much of the brain speaks to itself alone.9
The secrecy of the brain’s activity has led some scientists to seek a less internal solution to voice-hearing. These scientists suggest that rather than the brain creating something out of nothing, voice-hearers must be misinterpreting information, something we all do from time to time. They cite evidence that voice-hearers subvocalize—that they subtly and unconsciously move their vocal apparatus when they think, which would suggest that their voices are in fact produced by their own quiet whispering. Some researchers would seem to have proven the so-called whisper hypothesis, as the philosophers G. Lynn Stephens and George Graham have dubbed it, quite dramatically.10 In 1949, Louis Gould, a psychiatrist, published a report in which a patient’s subvocalizations neatly matched his hallucinations. Gould wrote:
The subvocal speech continued, “She knows. She’s the most wicked thing in the whole, wide world. She knows everything. She knows all about aviation.” At this point [the patient] stated audibly: “I heard them say that I have a knowledge of aviation.”11
In 1981, two psychiatrists were even able to coax a patient into gradually increasing the volume of his whispering until he was having a conversation with his voice at a normal volume.12
Might subconscious whispering be the cause of voice-hearing? It would certainly make things simpler if it were. To eliminate voices, one would merely have to instruct a voice-hearer to block his own ability to whisper and thus dam the river feeding the hallucinations. Indeed, this is what some clinicians have done, with positive effect. They have told patients to open their mouths wide, thus otherwise engaging their vocal cords, or to hum to themselves. And yet there is convincing evidence that the whisper hypothesis cannot provide an overarching explanation for voice-hearing. Many voice-hearers, for example, hear their voices coming from distant parts of the room and not from their bodies. Furthermore, the whisper hypothesis does not explain auditory hallucinations that are not made of voices. One voice-hearer I interviewed, a sports journalist based in Chicago, sometimes hears not just voices but full orchestras in his head. Certainly this man, whose voices are the result of a seizure disorder incurred after a fall down a flight of stairs in childhood, is not capable of playing full symphonies under his breath. Finally, in 1981, neurologist Edmund Critchley reported on congenitally deaf psychiatric patients who insisted, through sign language, that they heard audible voices in their head. These men and women had never heard speech before and therefore could not possibly hear their own whispers.13 It seems that although subvocalization is often the case, it does not provide a satisfactory framework to think about voice-hearing in general. The answer has to lie inside the brain.
Can we determine how the brain causes voices? We have some promising tools for the task in neuroimaging technologies, most notably positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). These technologies allow researchers to observe the brain in vivo—the former by measuring the brain’s metabolization of glucose, the latter by measuring blood flow. Since their development in the 1980s and 1990s, they have helped map the neural bases of thought and have proven to be the strongest forces in the advancement of the brain sciences. The neuroimaging revolution has even led some to pronounce the imminent solution of the mind-body problem. In 1996, Tom Wolfe predicted that the field of neuroscience “is on the threshold of a unified theory that will have an impact as powerful as that of Darwinism a hundred years ago.”14 Some have responded to such vigorous optimism by pointing out that an overreliance on imaging can make us into modern-day phrenologists and that in regard to complex cognitive phenomena, all imaging can do is provide us with a tool to confirm psychological theories. Some have gone even further and argued that no matter how logical a materialist view of the mind is, that view can never be proven with technology or any other scientific advancement, so ineffable is the activity of the mind.
Whether this argument reflects wisdom or defeatism or some combination of the two, the blunt fact is that neuroimaging has not significantly deciphered the physiology of voice-hearing. In 1999, the journal Psychiatry Research Neuroimaging published a review of the neuroimaging of hallucination that began by citing an observation made by Jean-Etienne-Dominique Esquirol, a nineteenth-century French asylum director who, responding to the work of Benjamin Rush and others, introduced an exclusively brain-based model of hallucination. “The site of hallucination,” Esquirol wrote in 1838, “is not in the peripheral organ of sensation, but in the central organ of sensitivity itself; in fact, the symptom cannot be conceived but as a result of something setting the brain in motion.” As Esquirol wrote elsewhere: “In hallucinations everything goes on in the brain.” The authors of the review responded gloomily to this early scientific pronouncement. “More than 150 years since Esquirol’s death,” they wrote, “the exact location of this aberrant functioning remains unclear.”15
The science of voice-hearing has remained static in large part because of the complexity of the phenomenon itself. Hallucinations may simply be too diverse a phenomenon to be pinpointed in the brain. Voice-hearing comes in a range of intensities, from single words to lengthy speeches; it can be the result of an organic or psychiatric disorder, or of no underlying problem at all. By asking, “What causes voice-hearing?” then, we are asking too broad a question. What is more, voice-hearing necessarily implicates a vast system of psychological functions, including perception, emotion, cognition, memory, consciousness, and attention. Unsurprisingly, studies on voice-hearing have exhibited the prominent involvement of diverse sections of the brain: Wernicke’s area, which makes spoken language comprehensible; Broca’s area, which generates speech; Heschl’s area, which aids in hearing; the left parahippocampal region, which is associated with the perception of unexpected stimuli; the thalamus, which relays information for processing in other parts of the brain; the hippocampus, which helps lay down long-term memory; the frontal lobes, which are involved in emotional responses; and so on. There appears to be an extensive network of brain areas associated with voice-hearing. And that network undoubtedly is not uniform from voice-hearer to voice-hearer. In the end, how the brain treats a voice may depend the most on the hearer’s experience of that voice.16
Hearing voices is considered to be one of the strangest of human experiences. Is it? Neuroscience does not allow us to gain an adequate understanding of how voice-hearing works, but by giving us an idea of how the brain operates in general, it does allow us to assess the phenomenon’s strangeness.
Consider, for instance, that you are chopping an onion for an omelet, and you accidentally cut your finger. Your finger hurts. Where is the pain, in the finger or in the brain? In his book Complications, the physician Atul Gawande writes of a patient who began to suffer from chronic back pain after a fall at a construction site. Men and women with such pain are common. Chronic back pain, Gawande reminds us, is near epidemic in the United States, “second only to the common cold as a cause of lost work time.” But test after test showed no physical defect in the man’s back. His muscles, spine, disks, nerves—all were in check, all were whole and healthy. His physicians scratched their beards, double-checked their films, consulted one another. The man’s pain was so strong that it caused him to vomit and to defecate in his pants. Was he lying? Did he want to feel pain? Such men and women are also common. Even the man himself suspected impure motives. He felt shame.17
The man’s pain had no “source”: no wound, no burn, no buildup of lactic acid in the muscles. But what we call source is no more than a signal. The pain, if we choose to name the sensation as an entity in and of itself, is always in the brain. That is where the neurons fire and where the information is assembled, no matter the location at which we experience the pain. If it helps, consider the signal a staff member and the brain the president. The information is hurried through the chamber and handed quickly to the president, who announces the fiat: Pain! Sometimes the president gets power-hungry and begins dispatching troops without permission. And why not? Why does the brain need permission when it has power? Exercises in executive prerogative pour forth: itches, hunger, tingles, sweat, erections. And all of it comes from the brain. Need we be concerned with what exists outside?
In 1866, the neurologist Silas Weir Mitchell published an early report of the phenomenon known as “phantom limb” syndrome, disguised as a short story. At a key moment in the story, George Dedlow, a Union soldier, wakes up after having been wounded in battle:
I got hold of my own identity in a moment or two, and was suddenly aware of a sharp cramp in my left leg. I tried to get at it to rub it with my…arm, but, finding myself too weak, hailed an attendant. “Just rub my left calf,” said I, “if you please.”
“Calf?” said he, “you ain’t none, pardner. It’s took off.”
“I know better,” said I. “I have pain in both legs.”
“Wall, I never!” said he. “You ain’t got nary leg.”
As I did not believe him, he threw off the covers, and, to my horror, showed me that I had suffered amputation of both thighs, very high up.
“That will do,” said I, faintly.18
Approximately 80 percent of amputees experience sensation in a limb after it has been severed from the body. They feel the limb in specific positions. They feel pain. One man feels his amputated arm jutting out from his body as if it were the arm of a weather vane; he walks through doors sideways in order to fit through. Others try to walk on a nonexistent leg that absolutely feels as if it is there, and fall.
The first rule of sound is that its production relies on the movement of an object. And what is the brain? It is an organ in constant movement. Its molecules are objects; its current flows. From this movement springs dreams alive with imagery. One psychiatrist has written: “The dream meets the definition of hallucination in every respect and most of us, according to a large body of physiological data, spend from one to two hours dreaming every night.”19 Dreams and dreamlike states—vivid imagery popping into one’s mind—occur so frequently, this psychiatrist writes, that perhaps the question we should ask is not “Why do hallucinations occur?” but “Why don’t they occur more often?”
Voice-hearing is strange, but by degree, not by kind. No mental phenomenon, no matter how strange, is unfamiliar by kind. We are all floating on the careless, rocking sea of the brain. The biologist Gerald Edelman has used a different metaphor for the brain; he likens it to a jungle, a comparison I find apt not just for the intended suggestion of complexity but for the suggestion of competitive balance. The brain is an unstable ecosystem. Feral cats devour reptiles that support the insects that in turn increase the number of reptiles, which in turn increases the number of cats. Canopy trees suffocate smaller flora, and the canopy trees, in competing with one another, allow light to shine through and bring the flora back to life. And so on. Burdened with a like neural environment, we expect minor brutalities to happen—the cresting and dipping sine curve of unwanted thoughts, temporary melancholies, fits of uncontrollable lust, aberrant desires, forgotten memories, hateful fears, intractable longings. Dreams and images. It is only when the brain’s brutalities refuse to abate or are spectacular in appearance that we take note of the unstable complexity that has been there all the time and question the soundness of the system.
And then we question our sanity and are driven by the shame of subservience into silence—or we are further driven to understand. When the latter occurs, where can we turn if the brain refuses to give up its secrets? One of the most sensible criticisms of neuroimaging studies has been that they often scrutinize the brain at the expense of the patient’s experience. The critics of neuroimaging offer technophobes a comforting thought. If you want to understand voice-hearing or any complex psychological phenomenon, you must ultimately, no matter where else you choose to look, make the long pilgrimage to the oracle: the voice-hearer himself.