The Tale of the Dueling Neurosurgeons: The History of the Human Brain as Revealed by True Stories of Trauma, Madness, and Recovery

by Sam Kean

  Through autopsy work, neuroscientists have determined what sort of brain damage causes alien hand. First, victims probably suffer damage to sensory areas. Those areas provide feedback whenever we move our arms voluntarily, and without that feedback, people simply don’t feel as if they’ve initiated a movement themselves. In other words, victims lose a “sense of agency”—a sense of being in control of their actions.

  Magnetic grasping usually involves the dominant right hand and usually requires additional damage to the frontal lobes. The job description for the frontal lobes includes suppressing impulses from the parietal lobes, which are curious and capricious and, as the lobes most intimately involved with touch, want to explore everything tactilely. So when certain parts of the frontal lobe go kaput, the brain can no longer tamp down these parietal impulses, and the hand begins to flail and grab. (Neurologically, this flaring up of suppressed impulses resembles the “release” of the snout reflex in kuru victims.) And because the grasping impulse springs from the subconscious, the conscious brain can’t always interrupt it and break the hand’s grip.

  Hand-to-hand combat—with one hand undoing the other’s work (pants up/pants down)—usually arises after damage to the corpus callosum, damage that disrupts communication between the left and right hemispheres. The left brain moves the right side of the body, and vice versa. But proper movement involves more than just issuing motor commands; it also involves inhibitory signals. When your left brain tells your right hand to grab an apple, for instance, the left brain also issues a signal through the corpus callosum that tells your right brain (and thus, left hand) to cool it. The message is, “I’m on it. Take five.” If the corpus callosum suffers damage, though, the inhibition signal never arrives. As a result the right hemisphere notices that something’s going on and—lacking orders not to—lurches with the left hand to get in on the action. It’s really an excess of enthusiasm. And because most people perform most tasks with their right hands, it’s usually the left hand that jumps in late and causes this type of alien anarchy. Overall, if magnetic grasping usually involves the dominant half of the brain asserting its dominance even more, then left hand–right hand combat usually involves the weaker half rebelling and trying to win equal status for itself.

  The presence of left/right conflict within the brain explains more than just alien hand. Hemispatial neglect usually arises after damage to the right hemisphere. Hence, Woodrow Wilson couldn’t notice anyone to his left, and it’s usually the left side of flowers and clocks that victims omit when doodling. The reason for this is cranial asymmetry. For whatever reason, the right hemisphere has superior spatial skills and does a better job mapping the world around us. So if the left brain falters, the right brain can compensate and monitor both sides of the visual field, thereby avoiding hemispatial neglect. The left brain, however, can’t reciprocate: it can’t make up for the loss of the right brain’s spatial skills if the right brain falters. As a result, half the world disappears.

  William O. Douglas’s refusal to acknowledge his illness had a similar root cause. Douglas almost certainly suffered damage to areas in the right parietal lobe that monitor touch sensations such as pain, skin pressure, and limb position; without these touchy-feelies, it’s hard to tell that your body parts aren’t moving properly. Moreover, these right-brain areas also detect discrepancies. If you issue a command (Lift the left arm), and nothing happens because that arm is paralyzed, that’s a discrepancy, and your right parietal lobe should send out an uh-oh alert. But if a stroke knocks out the uh-oh alert system, the brain will struggle to catch discrepancies, even blatant ones. It’s like disabling a fire alarm. As a result, Douglas didn’t recognize—in some sense couldn’t recognize—that his whole left side couldn’t move.

  (In extreme cases, this lack of sensation and inability to detect discrepancies will lead a stroke victim to outright reject her paralyzed limbs. That is, she’ll claim that she can’t control her inert arm or leg because—despite its being attached to her own body—the limb actually belongs to someone else, a spouse or a mother-in-law, say. One victim, when shown her own wedding band on the very fingers she was disavowing, claimed the ring had been stolen. Another victim in a hospital complained that medical students kept slipping a cadaver arm under his sheets as a sick joke.)

  Capgras syndrome also makes more sense with left/right discord in mind. The drastic conclusions of Capgras victims have always puzzled scientists. Losing the emotional connection to a loved one no doubt causes angst. But why confabulate imposters? Why doesn’t logic intervene? The answer seems to be that full-blown Capgras actually requires two lesions: one to the face-emotion circuit, a second to (we’re seeing a pattern here) the right hemisphere. According to this theory, the left and right hemispheres work together to help us understand the world. The right brain specializes in gathering sensory data and other simple facts. The left brain, meanwhile, prefers interpreting those data and spinning them into theories about how the world works. In a normal brain, there’s a necessary give and take between these processes. For instance, if the left brain gets too fast and loose in forming a theory, the right brain can check it with a cold, hard fact and prevent a nutty idea from taking hold.

  With Capgras, the sudden loss of emotional glow feels threatening and demands an explanation, which is the left brain’s bailiwick. And if only the face-emotion circuit had suffered damage, the right brain would have supplied the relevant facts (this still looks like Dad, still talks like him) and guided the left brain to a sensible conclusion. When the right hemisphere suffers damage, though, that counsel disappears. So there’s nothing to stop the left brain from twisting the facts to fit a preconceived notion. And given how cherished the belief that’s being challenged is—whether you still feel love for Mom and Dad and your own children—it’s no wonder that the brain prefers to spin tales of imposters and worldwide conspiracies rather than give it up. True, the conclusion seems to violate common sense, but common sense depends on intact brain circuits.

  In light of brain discord many delusions seem, if not rational, at least comprehensible. They’re simply the failings of a fragile brain. Sadly, though, explaining to a patient what causes his delusion rarely helps relieve it: given its nature, you can’t talk someone out of a delusion so easily. (It’s similar to how an optical illusion still fools us even when we know it’s a trick. Our brains can’t help it.) In fact, arguing with the victims of a delusion can backfire. Because if proved wrong, they’ll often double down and blurt out something even wilder. You tortured that memory out of my sister. I’m trying out for the Redskins.

  Some delusions run so deep that they fray the very fabric of the victim’s universe. With so-called Alice in Wonderland syndrome—a side effect of migraines or seizures—space and time get warped in unsettling ways. Walls recede when approached, or the ground suddenly feels spongy beneath their feet. Worse, people feel themselves shrinking down to six inches in height or sprouting up to twelve feet tall. Or their heads feel swelled up, like cranial balloons. Alice victims

  * basically become the incarnations of fun-house mirrors, probably due to malfunctions in the parietal lobe areas responsible for body posture and position. Schizophrenics can experience severe delusions, too, like “delusional bicephaly”—what you might call Siamese twin disorder, the feeling of having an extra head. In 1978 an Australian schizophrenic killed his wife with his erratic driving. Two years later he suddenly found her gynecologist’s noggin perched on his shoulder, whispering to him. Lord knows why, but the man took this as a sign that the gyno had diddled his wife, so he tried to guillotine the doctor’s head with an axe. When this failed, he started shooting at the head with a gun and shot his own head by accident. (The subsequent brain damage from the bullet did “cure” him of this delusion.)

  Victims of Alice in Wonderland syndrome feel stretched or shrunk, much like Alice herself.

  Perhaps the most absurd delusion—in the Sartre/Camus/existentialist sense of absurd—is Cotard
syndrome, in which victims insist, absolutely swear, that they’ve died. Also known as walking dead syndrome, it usually strikes older women, and often emerges after an accident: they’re convinced that their suicide attempts succeeded, or that they died in the car wrecks that sent them to the hospital. The seemingly blatant fact that they’re sitting there, telling you all this, doesn’t impinge; these are people who can hear Descartes’s cogito ergo sum and say, Not so fast. Some even claim they can smell their own rotten flesh; a few have tried to cremate themselves. And in some cases, their delusions plumb the very depths of nihilism. As the first doctor to describe the syndrome, Jules Cotard, said: “You ask them their name? They don’t have a name. Their age? They don’t have an age. Where they were born? They were never born.” Neurologists disagree about the explanation for Cotard, although most feel, as with Capgras syndrome, that two parts of the brain must be malfunctioning simultaneously. One theory interprets Cotard as Capgras turned inward: people feel no “glow” about themselves, and that deadness convinces them that they have in fact died, logic be damned.

  All these delusions pry open the human mind and expose seemingly solid, seemingly unshakable aspects of our inner selves as really rather tenuous. Hemispatial neglect wipes out half the victim’s world, and he never notices. Capgras victims lose the ability to feel close to people. Alice victims feel their bodies melt into instability. And alien hand syndrome upends our notions about free will, since victims seem to have lost free will for part of their bodies. But if the history of neuroscience proves anything, it’s that any circuit for any mental attribute—up to and including our sense of being alive—can fail, if just the right spots suffer damage.

  Like it or not, delusions can dupe even healthy brains. With nothing more than video cameras and mannequins, scientists can easily induce out-of-body experiences in volunteers. Or they can graft an extra arm onto someone’s torso by simultaneously stroking both her real hand and a dummy hand attached to her. Some inspired setups can make people feel that they’ve changed genders or are shaking hands with themselves. Hi, I’m Sam. Nice to meet you, Sam.

  Even more disarming are a series of experiments that began in San Francisco in the 1980s. A neuroscientist there named Benjamin Libet sat some college students (including his daughter) down in his lab and had them face a timer. He fit them with a helmetlike contraption that recorded the electrical activity in their brains, then told them to hold still. All the students had to do, for the entire experiment, was move one finger. Just whenever they felt like it: wait… wait… tap. Afterward they told Libet the precise moment on the timer when they’d decided to move. He then compared their answers to what the electrical scans said.

  On every scan Libet could see a spike in motor activity not long before the finger moved. Pretty straightforward. The problem started when he looked at when the decision to move had taken place. Because in every case the conscious decision lagged behind—by a good third of a second—the unconscious spike in motor activity. Indeed, the spike was usually almost over before the decision got made. Because causes must precede effects, Libet concluded, reluctantly, that the unconscious brain must be orchestrating the whole sequence, and that the “decision” to move was nothing but a post hoc rationalization—an ego-saving declaration by the conscious brain. Uh, I meant to do that. This experiment has been replicated many times—it’s robust. And in many cases scientists can predict when someone will move before even she knows that.

  Equally unnerving is another set of experiments, which involved stimulating the exposed brains of surgical patients with electricity. When scientists sparked certain motor areas, people’s arms and legs flailed. But unless the person actually saw himself move, he denied he’d done so, since he’d felt no inner urge to. Conversely, sparking other parts of the brain can induce just the urge, even while the arms and legs lie limp. Stronger currents can even induce a false sense of having moved, but again without any actual movement taking place. (One woman said, in all seriousness, “I moved my mouth there, I talked. What did I say?”) In sum, your actions, your desires to act, and your conviction of having acted can all be decoupled and manipulated. None of those three things necessarily follows from the others; they’re more casually linked than causally linked.

  If you’re biting your nails and wondering where free will fits into all this, you’re not alone. These experiments leave little wiggle room, and to many scientists they in fact obliterate free will. In this thinking, the mind’s conscious, decision-making “will” is actually a by-product of whatever the unconscious brain has already decided to do. Free will is a retrospective illusion, however convincing, and we feel “urges” to do only what we’re going to do anyway. Pride alone makes us insist otherwise. And if that’s true,

  * victims of alien hand and other syndromes may have simply lost the illusion of free will for part of their bodies. In some sense, they might be closer to the reality of how the brain works than the rest of us. Makes you wonder who’s really deluded.

  PART V

  CONSCIOUSNESS

  CHAPTER TEN

  Honest Lying

  Almost every structure we’ve examined so far contributes to forming and storing memories. Memory is therefore a wonderful way to see how different parts of the brain work together on a large scale.

  Soldiers buried more than men in the graves of Southeast Asia. While conquering Singapore in February 1942, Japanese soldiers captured 100,000 mostly British POWs, more than they knew what to do with. The military worked thousands of them to death on the brutal Burma–Siam “Death Railway,” a project that required hacking through 250 miles of mountainous jungles and constructing bridges over rivers like the Kwai. Most of the remaining captives, including many doctors, were crowded into the notorious Japanese prison camps. In fact, two British doctors incarcerated in the Changi camp, Bernard Lennox and Hugh Edward de Wardener, realized that their captors were essentially running a gruesome experiment: taking healthy men, depriving them of one nutrient, and watching their brains deteriorate.

  No matter his background, every doctor in the camps worked as a surgeon, dentist, psychiatrist, and coroner, and they suffered from the same ailments—dysentery, malaria, diphtheria—that ravaged the troops. They pared down bamboo shards for needles, unstitched parachutes for silk sutures, and drained human stomachs for acids. Monsoons tore through their “clinics”—often just tents draped over poles—and some doctors faced beatings and threats of being boiled in oil if they didn’t cure enough soldiers to meet work quotas. Guards made things worse by restricting sick men to half rations, to “motivate” them to recover. But even among the healthy, the food—mostly plain rice—was never adequate, and led to beriberi disease.

  For as long as people have eaten rice in Asia, doctors there have reported outbreaks of beriberi. Symptoms included heart trouble, anorexia, twitching eyes, and legs so swollen that the skin sometimes burst. Victims also walked with a shuffling, staggering gait that reminded locals of beri, sheep. When Europeans colonized Southeast Asia in the 1600s, their doctors began seeing cases as well; one early report came from Dr. Nicolaes Tulp, the Dutchman later immortalized in Rembrandt’s The Anatomy Lesson. But the number of cases exploded after the introduction into Asia, in the later 1800s, of steam-powered rice mills. The mills removed the outer husks from rice grains, producing so-called white rice. People back then called it polished rice, and cheap polished rice became a dietary staple—or, often, the diet—of peasants, soldiers, and prisoners. During the Russo-Japanese War alone, 200,000 Japanese troops fell victim to beriberi.

  Scientists eventually began to suspect that beriberi was a nutritional deficiency—probably a lack of vitamin B1 (a.k.a. thiamine). In shucking off the nutritious rice husks, the mills stripped out almost all the B1, and many people didn’t get enough thiamine from eating vegetables, beans, or meat. Our bodies use B1 to harvest energy from glucose, the end result of digesting carbohydrates. Brain cells especially rely on glucose for energy, since othe
r sugars cannot cross the blood-brain barrier. The brain also needs thiamine to make myelin sheaths and to build certain neurotransmitters.

  A hospital in a Japanese POW camp in Singapore.

  The first cases of beriberi appeared two weeks after the Changi camp opened, among a few alcoholics cut off cold turkey. Many more cases appeared after another month. Doctors tended to the ailing as best they could and sometimes kept their spirits up by lying about the progress of Allied armies. When all else failed, some doctors ordered men to live or face court-martial (a threat reminiscent of those old medieval laws that made suicide illegal). Nevertheless, by June 1942 there were a thousand beriberi cases in Changi alone. Helpless to stop the epidemic, de Wardener and Lennox started doing autopsies in secret and collecting tissues from the brains of beriberi victims, to study the pathology of the disease.

  Although considered contraband, these tissues and autopsy records were mostly safe inside Changi. But in 1943 Lennox and de Wardener were herded off to different camps near the Death Railway in Siam and had to split their medical stash. Wary of confiscation, Lennox arranged to smuggle the brain tissues out of his camp, only to have them perish in a train wreck. De Wardener guarded the all-important paper records, a four-inch sheaf. But as the war turned sour for Japan in early 1945, de Wardener realized that Japanese leaders wouldn’t look kindly on hard evidence of starving POWs. So when he received another transfer order—and saw guards frisking his fellow-transferees and searching their belongings—he made a hasty decision. He had a metallurgist friend seal his papers inside a four-gallon petrol tin. He then wrapped the tin in a cape and buried the bundle three feet deep in a fresh grave, leaving only the dead soldier as a sentinel. To remember which grave it was—there were so many—he and some friends took compass bearings on a few enormous trees nearby. As he departed camp, de Wardener could only pray that the heat, rot, and miasma of Siam wouldn’t eat through the bundle before he returned. If he returned.