Since its introduction in 1846, anesthesia has allowed for medical miracles. Limbs can be removed, tumors examined, organs replaced—and a patient will feel and remember nothing. Or so we choose to believe. In reality, tens of thousands of patients each year in the United States alone wake up at some point during surgery. Since their eyes are taped shut and their bodies are usually paralyzed, they cannot alert anyone to their condition. In efforts to eradicate this phenomenon, medicine has been forced to confront how little we really know about anesthesia’s effects on the brain. The doctor who may be closest to a solution may also answer a question that has confounded centuries’ worth of scientists and philosophers: What does it mean to be conscious?

On a warm afternoon in Madison, Wisconsin, last spring, a psychiatrist was pointing an electromagnetic gun at my brain.

“Put your arm in your lap,” he said.

I obeyed. My head was dressed in a 60-electrode, high-density EEG-recording device. The doctor stood behind my chair, eyeing a digitized MRI of my brain and gliding the gun over my scalp until he found his target: my motor cortex.


I tried.

The gun clicked. My forehead muscles twitched. My arm leapt out of my lap, straight into the air, as if yanked by invisible puppet strings. “Do it again,” I said.

This process is called transcranial magnet stimulation, or TMS. It is the key to a device that Giulio Tononi, one of the most-talked-about figures in anesthesiology since Nassib Chamoun, hopes will provide a truly comprehensive assessment of consciousness. If successful, Tononi’s device could reliably prevent anesthesia awareness. But his ambitions are much grander than that. Tononi is unraveling the mystery of consciousness: how it works, how to measure it, how to control it, and, possibly, how to create it.

Tononi is unraveling the mystery of consciousness: how it works, how to measure it, how to control it, and, possibly, how to create it.

At the heart of Tononi’s work is his integrated-information theory, which is based on two distinct principles, as intuitive as they are scientific. First, consciousness is informative. Every waking moment of your life provides a nearly infinite reservoir of possible experiences, each one different from the next. Second, consciousness is integrated: you can’t process this information in parts. When you see a red ball, you can’t experience the color red separately from the shape of the ball. When you hear a word, you can’t experience the sound of it separately from its meaning. According to this theory, a more conscious brain is both more informative (it has a deeper reservoir of experiences and stimuli) and more integrated (its perception of these experiences is more unified) than a less conscious one.

Compare the brain to New York City: just as cars navigate the city’s neighborhoods via a patchwork of streets, bridges, tunnels, and highways, electrical signals traverse the brain via a meshwork of neurons. Tononi’s theory predicts that in a fully conscious brain, traffic in one neighborhood will affect traffic in other neighborhoods, but that as consciousness fades—for instance, during sleep or anesthesia—this ripple effect will decrease or disappear.

In 2008, in one of several experiments demonstrating this effect, Tononi pulsed the brains of 10 fully conscious subjects with his electromagnetic gun—the equivalent of, say, injecting a flood of new cars into SoHo. The traffic (the electromagnetic waves) rippled across Manhattan (the brain): things jammed up in Tribeca and Greenwich Village, even in Chelsea. Tononi’s EEG electrodes captured ripples and reverberations that were different for every subject and for every region of the brain, patterns as complex and varied as the traffic in Manhattan on any given day.

Tononi then put the same subjects under anesthesia. Before he pulsed his gun again, the subjects’ brain traffic seemed as busy as when they were conscious: cars still circulated in SoHo and Tribeca, in Greenwich Village and Chelsea. But the pulse had a drastically different effect: This time, the traffic jam was confined to SoHo. No more ripples. “It’s as if [the brain] has fragmented into pieces,” Tononi told me. He published these findings in 2010, and also used them to file a patent for “a method for assessing anesthetization.”

I first encountered Giulio Tononi in 2011, at an American Society of Anesthesiologists conference, where he gave the final lecture. His voice—with an erudite Italian accent suitable for narrating the audio tour at the Sistine Chapel—echoed throughout the auditorium. His blond hair was parted in a zigzag across his head. He wore a brown suit with silver studs on the lapels, a white shirt, and a bolo tie. Here, speaking to a rapt audience of mostly American anesthesiologists, was an Italian neuroscientist dressed as if he were from Wyoming.
“Anesthesia: the merciful annihilation of consciousness,” Tononi said, a PowerPoint presentation projected behind him. “The one we devoutly wish for in the proper circumstances. Now, just like sleep takes consciousness away and gives it back, so does the anesthesiologist. Every day. He taketh and giveth.”

On the next slide, Tononi projected Michelangelo’s The Creation of Eve, which was captioned: And the LORD God caused a deep sleep to fall upon Adam, and he slept: and he took one of his ribs, and closed up the flesh instead thereof. “A quote from the very first surgical procedure that was done with anesthesia,” Tononi said. “The operation was reasonably successful, it seems.”

This tendency toward grandiloquence dates back at least to adolescence. As a teenager in Trento, a city in northern Italy, where his father was mayor, Tononi wrote a letter to Karl Popper, a famous European philosopher, asking him whether he should devote his life to studying consciousness. Popper wrote back with encouragement and sent an inscribed copy of one of his books. Tononi considered approaching the subject through mathematics or philosophy, but ultimately decided that medicine would provide the best foundation. So he attended medical school, became a psychiatrist, and moved to New York for a fellowship under the physician Gerald Edelman. Although Edelman had won a Nobel Prize for his work in immunology, he had by that point pivoted to neuroscience. With Edelman, Tononi began publishing extensively on consciousness. He moved to Madison in 2001, and is now the Distinguished Chair in Consciousness Science at the University of Wisconsin.

When I visited Tononi in June to participate in one of his consciousness studies, he invited me to a dinner party at his home, 15 minutes outside Madison. These dinners are legendary among his research fellows, many of them Ph.D.s and M.D.s from Italy or Switzerland. I arrived at a luxurious log cabin replete with a tractor, an indoor swimming pool, and an outdoor pizza oven. Hanging over the oven was a wire sculpture in the shape of the Greek letter phi, which Tononi has chosen as the symbol for his consciousness theory and as the title of his latest book. The letter was also engraved on his bolo tie and commemorated on the license plate of his car.

He served a multicourse dinner featuring pasta made from scratch, pizzas cooked in the outdoor oven, a well-paired rosé, and absinthe. Midway through the second course, he asked each of his guests a question: whether we believed in free will, and why. I said that I didn’t. I argued that if we are made of atoms based on physical laws, which form molecules ruled by chemical laws, which compose cells that abide by biological laws, how could there be free will? Tononi only smiled. If his theory of integration is correct, my logic is flawed, and free will can exist.

Tononi is to his neuroscientist peers as the 18th-century philosopher Immanuel Kant was to his empiricist counterpart David Hume. Like most modern neuroscientists, Hume saw only the “easy problem.” He proposed that consciousness was nothing more and nothing less than the bundling of various bits of experiential knowledge, or, as he called them, “perceptions.” Using this logic, my physiological argument against free will could stand.

Kant, however, believed that the mind is more than an accumulation of experiences of the physical world. Like Descartes 150 years earlier and David Chalmers 200 years later, Kant focused on the “hard problem,” making the logical argument that something beyond sensory inputs must account for the subjectivity of conscious experience—what Kant called “transcendental” consciousness. Tononi’s theory hinges on a similar conception of consciousness as something more than the sum of its experiential parts—leaving room, then, for the possibility of free will.

The amount of integrated information in the brain—the quantity of consciousness—is what Tononi calls phi. He believes he can approximate it with a combination of his TMS‑EEG technology and mathematical models. Many well-known philosophers and neuroscientists, however, remain skeptical. Chalmers has praised Tononi for his bold attempt to quantify consciousness, but he doesn’t think Tononi has come any closer to solving the hard problem. And even Tononi admits that, in scientific-research time, his theory is still in its infancy. What Tononi has made progress on is neither the easy nor the hard problem: it’s the practical problem. He is currently developing a machine that has the potential to end anesthesia awareness once and for all. Like the BIS monitor, the device would provide a numerical assessment of a patient’s awareness, and would be simple and compact enough to become a regular fixture in operating rooms. Unlike the BIS monitor, it would also be relevant outside the operating room. Whereas the BIS is rooted in data specific to surgery, Tononi has developed a comprehensive theory of consciousness that could, with appropriate technological tweaks, be applied in any number of medical, scientific, or social settings.

My experience with the electrode cap and TMS gun in Tononi’s lab offers a rough guide to how his awareness monitor might work. First, an anesthesiologist would dress your head with electrodes, which would transmit EEG data to a processor. After putting you under, she would monitor the drugs’ effects by using a paddle attached to a high-voltage generator to repeatedly blast your brain with electromagnetic waves. The EEG processor would monitor your brain’s reaction to each blast, calculating the complexity of patterns and the degree of integration and ultimately displaying a numerical phi value—your level of consciousness. Returning to the New York metaphor: if the traffic jam stayed in SoHo, the machine would display a low value, and the anesthesiologist could relax; if it spread to other neighborhoods, the machine would display a high value, and she might want to administer more drugs.

While this device is still millions of dollars and many trial hours away from implementation, Tononi and his Italian colleague Marcello Massimini have tested and validated an approximation of phi in multiple settings, and are preparing to publish their findings. The method has already been used by some clinics in Europe—not on anesthetized patients, but on vegetative ones. What if Terri Schiavo’s family had been able to ascertain that she was, in fact, completely unconscious, more so than she would have been even under heavy anesthesia? These clinics are calculating phi to assess whether comatose patients experience consciousness, and if so, how much. Of course, this application has troubling risks; a flaw in Tononi’s theory could lead families to turn off life support for a still-conscious person. But if the theory holds up—if Tononi has successfully managed to quantify consciousness—it could deliver these families from uncertainty. It could also change the way we think about animal rights, upend the abortion debate—possibly even revolutionize the way we think about artificial intelligence. But before any of that, it would fulfill the promise first offered in the ether dome more than a century and a half ago: an end to the nightmare of waking surgery.

In his recently published book, Phi, Tononi narrates a literary tour of his theory of consciousness through a fictionalized protagonist: Galileo. In one of the last chapters, Galileo encounters a diabolical machine that surgically manipulates the brain to produce pure sensations of pain. Tononi calls it “the only real and eternal hell.” The creator of the machine asks: “What is the perfect pain? Can pain be made to last forever? Did pain exist, if it leaves no memory? And is there something worse than pain itself?”

For George Wilson, a Scottish chemist who had his foot amputated in 1843, before the dissemination of anesthesia, pain gave way to something seemingly beyond physical sensation, something articulable only in spiritual, nearly existential terms. Wilson described his experience in a letter several years after his surgery:

Of the agony it occasioned I will say nothing. Suffering so great as I underwent cannot be expressed in words, and fortunately cannot be recalled. The particular pangs are now forgotten, but the blank whirlwind of emotion, the horror of great darkness, and the sense of desertion by God and man, bordering close upon despair, which swept through my mind and overwhelmed my heart, I can never forget, however gladly I would do so.

While subduing consciousness is the most urgent aspect of Tononi’s work, he is especially animated when discussing consciousness in its fullest, brightest state. In his office in Madison, he described a hypothetical device called a “qualiascope” that could visualize consciousness the same way telescopes visualize light waves, or thermal goggles visualize heat. The more integrated the information—that is, the more conscious the brain—the brighter the qualiascope would glow. Using the device in an operating room, you would watch a patient’s consciousness fade to a dull pulse. If he woke up mid-operation, you might see a flicker.

But if you turned your gaze away from the operating room, you would gain an astonishing perspective on the universe. “The galaxy would look like dust,” Tononi told me. “Within this empty, dusty universe, there would be true stars. And guess what? These stars would be every living consciousness. It’s really true. It’s not just a poetic image. The big things, like the sun, would be nothing compared to what we have.”


In an experiment on vegetative patients, researchers pulsed one subject’s brain with electro­magnetic waves on three different days as the subject emerged from a coma. The resulting EEG patterns reflected Giulio Tononi’s theory of consciousness: they became more complex and widespread as the patient became more conscious.

Presented by

Joshua Lang is a medical student at the UC Berkeley–UCSF Joint Medical Program.

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