Patient H.M. (16 page)

Eventually, surgeons began using electrical stimulation
during
the operations, helping them identify the functional components of the brain before they made their irrevocable cuts, ensuring that they wouldn't, for example, inadvertently slice away the patient's ability to hear or taste or see. And while electrically stimulating the brain became an essential part of making brain surgery safer, it also became a key tool in exploring the organ's subtle geography. Neurosurgeons became neural cartographers, charting out not just the broad contours of the motor cortex, for example, but all the intricate differentiations within it, right down to which part of the brain controlled the fingers as opposed to the toes.

In 1950, when Brenda Milner arrived at the Montreal Neurological Institute, Wilder Penfield, the institute's founder and chief neurosurgeon, was the king of the mapmakers.

Like anyone interested in how the brain works, Milner had seen and studied Wilder Penfield's “homunculi” illustrations. These illustrations, published in Penfield's bestselling book,
The Cerebral Cortex of Man,
and reproduced in dozens of academic and nonacademic publications, were simple but powerful guides to neuroanatomical function. There were two diagrams, each showing a grotesque cartoon figure of a man draped over a portion of a human brain. In the first diagram, the man represented the motor cortex, which is a narrow strip of neural tissue about three-quarters of an inch wide that arches over the top of one side of the brain, dips slightly in the middle, then proceeds down over the next hemisphere. Since the motor cortex is more or less equally represented bilaterally, Penfield's diagram showed only one hemisphere. At the very top, his homunculus dipped its toes into the chasm between the hemispheres, the so-called central sulcus, because that is the portion of the cortex that would cause Penfield's patients' toes to twitch when he stimulated it with his electrode. Next, in predictable nursery-rhyme order, came the ankles, knees, hips, and trunk, right up to the homunculus's shoulder, which rests on the spot right where the brain's flattish top begins to slope noticeably downward. Then things got strange. First of all, instead of proceeding from the shoulders to the neck, as you might expect, Penfield's homunculus was for the moment headless, as the elbows and wrist came next, draped over the next centimeter or so of motor cortex. And then, blown out of all proportion, occupying more space than the entirety of every other part of the body that came before it: the hand. The hand was enormous. Just the heel of the palm took up more cerebral real estate than the entire leg, and its thumb would dwarf Little Jack Horner's. The tip of the thumbnail occupied a spot about halfway down the cortex, and about a millimeter below it the homunculus's head finally made its appearance. The brow was truncated, almost Neanderthal, because Penfield was only able to elicit brow twitches from a lilliputian patch of neurons. Its ears were tiny, almost invisible, for the same reason. Its mouth, however, was almost as gigantic as its hand. Penfield had discovered, through the application of electric shocks to the brains of his patients, that “the cortical representations of the act of eating” were spread widely across a large portion of the surface of the motor cortex, so that applying an electrode to one spot might cause, for example, “mastication with movement of tongue,” while giving a jolt to another spot nearby might cause “mastication with vocalization.”

Penfield's second homunculus complemented his first and represented the somatosensory as opposed to the motor cortex, using another cartoon to illustrate the portions of the brain that govern our sense of touch. The somatosensory cortex was roughly the same size as the motor cortex and lay just behind it. If you looked at a girl wearing two headbands, one behind the other, the somatosensory cortex would lie under the second one, slightly closer to the back of her head. Penfield's careful mapmaking had revealed that the cortical representation of the different body parts along the somatosensory cortex ran almost exactly parallel to the cortical representation of those same body parts along the motor cortex. So if he jolted a point on a patient's motor cortex that caused the patient's ankle to flex, then applied the electrode to a point about a half-inch behind the first one, the patient would usually feel as though someone were touching his ankle. There were a few exceptions. For example, Penfield's motor cortex homunculus lacked genitalia, while his somatosensory homunculus had a little penis nestled in the central sulcus, just below its toes.

The most important distinctions between Penfield's maps of the motor cortex and the somatosensory cortex, however, were the methods by which the maps were obtained. Penfield had been able to chart the motor cortex by simple observation: When he stimulated a point on the patient's brain, he would note what part of the patient's body moved, and make a record of it. The mapping of the somatosensory cortex, however, required the active participation of the patient. Patients would have to report to Penfield where, exactly, they felt as though their bodies were being touched. And this meant, of course, that the patients had to be conscious.

Penfield was not the first neurosurgeon to operate on conscious patients. In the late 1800s, a British surgeon named Victor Horsley found that patients could withstand brain surgery while awake so long as large amounts of cocaine were first injected into their dura. By Penfield's time, local anesthesia was almost the norm, injections of synthetically derived novocaine having supplanted the coca-plant-based alternatives. But although Penfield was not the first to keep his patients awake on the operating table or to stimulate their brains electrically, a unique combination of reportorial meticulousness and operative approach made his work groundbreaking. While other surgeons typically operated through small holes in the skull and could therefore only see a small portion of the surface of the brain, Penfield preferred to open a large “bone flap,” roughly five by four inches, exposing a prodigious expanse of cortex that he could then cut or stimulate at will. This allowed him to make more progress in charting the mysterious territories inside our skulls than any who'd come before him.

As early as 1928, Penfield began to muse about the possibility of “an institute where neurologists could work with neurosurgeons and where basic scientists would join the common cause, bringing new approaches.” He lobbied for it relentlessly until, in 1934, with the help of millions of dollars from the Rockefeller Foundation, the Montreal Neurological Institute finally opened its doors. There was nothing like it: a place where scientists and medical doctors were thrown together and jumbled about until the distinctions between them blurred. Neurosurgeons, neurologists, psychiatrists…each approached the study of the brain from a different angle, and at the Neuro they could combine their individual strengths, and compensate for their individual weaknesses, in pursuit of a common cause. And that cause was straightforward and far-reaching: The Neuro, Penfield hoped, “would open the way to brain physiology and psychology. And then, sometime perhaps, we would make a more effective approach to the mind of man.”

When Brenda Milner walked through the front door of the Neuro in 1950, it had already established itself as one of the world's leading centers for the interdisciplinary study of the brain. Penfield's ambitions for the place were literally carved in stone: One of the first things Milner saw, climbing up the steps into the atrium, was a huge marble statue of the goddess Nature, who was coyly pulling open her robes, naked underneath, symbolically revealing herself to science. The statue, like the rest of the atrium, was commissioned personally by Penfield in collaboration with an architect, and as Milner looked around, her eyes would have caught on dozens of other subtle messages hidden around the room, a secret code readable only by those fluent in the language of the brain. A decorative design on the ceiling revealed itself, upon closer inspection, to be an artistic representation of the cells of the cerebellum, and in the center of the ceiling was the institute's logo, an emblem of a ram's head surrounded by odd symbols. Only a few of those entering here would remember that Aries, the astrological ram, ruled over the brain, and fewer still that the odd symbols were hieroglyphs lifted from the Edwin Smith Papyrus and considered to be the first written representations of the word
brain.

Her degree adviser, Donald Hebb, had given Milner two directives prior to her arrival. One, to be as helpful as possible. Two, don't get in anyone's way. She would recall spending her first couple of weeks there “hugging the walls.” Eventually, however, it dawned on her that to follow the first directive she would have to ignore the second, and so she began to step forward and speak up. This was not easy. Wilder Penfield turned fifty-nine in 1950, but he was if anything a more willful, and intimidating, presence than ever. Still big and muscular—he'd been a first-string tackle on the football team at Princeton University—Penfield dominated the Neuro in a very real sense. Every week, he convened a staff meeting in a conference room on the third floor to discuss the status of the institute's patients and research. Dozens of neurosurgeons, neurologists, and electroencephalographers would crowd in, though only the four or five people Penfield considered to be his stars were allowed to sit at the table with him; the rest were relegated to chairs around the periphery of the room. Whenever somebody in attendance said something that displeased him, Penfield would remove his glasses and deliver a hard stare. His subordinates learned to fear that stare in a visceral, Pavlovian way. But for all his occasional bullying, Penfield respected, without prejudice, brilliance. If you stood up to him, and could support yourself with solid facts and arguments, he would back down. And although Brenda Milner, with her sylph-like proportions and gentle, Cambridge-educated accent, was physically unintimidating, her mind quickly revealed razor-sharp claws. Penfield had been hesitant to invite a psychologist into his institute at all—he considered the field wishy-washy and unscientific, dominated by sex-obsessed Freudians—but it wasn't long after Milner's arrival that he asked her to join him at the conference table.

Once there, she would never leave.

For Milner, the institute felt like home. Her curiosity and inquisitiveness, the qualities that had animated her since childhood, found a place where they could flourish, where the puzzles she confronted were intoxicatingly difficult and the stakes bracingly high. This didn't mean the day-to-day work situation was idyllic: Penfield allowed Milner access to his patients and provided her with a small office, but for the first several years of her tenure he didn't pay her a dime and she was forced to “borrow” her notebooks and pencils and other office supplies from the University of Montreal. Even some of the basic psychological tests and manuals that formed the bedrock of her work she had to finagle from generous researchers at other institutions, to whom she pleaded poverty in heartfelt letters, since she couldn't afford to pay for them herself. In the end, what mattered to her was the work she was able to do. And the work she was able to do was everything she'd ever dreamed of.

Her basic mandate was to determine whether Penfield's epilepsy surgeries were having any adverse effects on his patients. She was particularly focused on his psychomotor epilepsy patients, the men and women whose seizures were often characterized by moments of inattention, odd behavior, and short periods of amnesia. By employing his stimulating electrode, Penfield had demonstrated that these specific types of epileptic attacks could be reproduced on the operating table by shocking a part of the brain known as the medial temporal lobes. In addition, the institute's new electroencephalography equipment, which allowed researchers to monitor the brain's electrical spikes and discharges in real time noninvasively, without opening the cranium, also indicated that psychomotor seizures often originated in this portion of the brain. So in 1949, Penfield began implementing what to him was the obvious surgical approach to the treatment of these cases: If he could determine that patients' psychomotor seizures originated in a particular hemisphere, he would open up that side of their skulls and perform a “unilateral partial temporal lobectomy,” removing that hemisphere of their medial temporal lobes. The hemisphere he left behind, Penfield hoped, would pick up the slack for its departed twin. Still, removing brain regions whose function he didn't understand, even unilaterally, and even if doing so appeared to have a therapeutic benefit, bothered Penfield. That's why he had asked Donald Hebb to send a psychologist to the Neuro. Brenda Milner's mission was to determine whether these removals Penfield was making were having an effect on his patients. And, if so, what that effect was.

In its most common definition,
temporal
means “of or relating to time.” In the case of the temporal lobes, however, the word is just an anatomical guidepost and refers to the fact that the temporal lobes lie directly behind the parts of the head referred to as the temples. “Medial” means “in the middle,” so the medial temporal lobes are simply the centermost parts of the region.

Penfield's operations focused on a specific portion of the medial temporal lobes, an area usually called the limbic lobe. Here again, the French physiologist Paul Broca, the man who introduced the world to Monsieur Tan, played a critical role: The French word
limbique
means “egg-shaped,” and the limbic lobe, when viewed from the side, appeared roughly oval in shape, so that's what Broca named it. Within the limbic lobe were several other structures whose names also had clear and simple visual inspirations. The amygdala, dense and compact, came from the Latin word for “almond.” The uncus, which ended in a sharp curve, derived from the Latin for “hook.” And in the center of this centermost portion of the brain was the hippocampus, the largest structure of the group. It had a broad, thin-snouted top and a thin, curling tail. Hippocampus is Greek for “seahorse.”