Wilder Penfield | Wilder Penfield redrew the map of the brain — by opening the heads of living patients

Wilder Penfield redrew the map of the brain — by opening the heads of living patients

Even in 2018, Wilder Penfield’s approach to treating epilepsy seems like something out of a science fiction movie. Penfield — the celebrated Canadian-American neurosurgeon whose 127th birthday is celebrated today in a Google Doodle — pioneered the technique of removing a portion of the skull while a patient was still awake.

Penfield developed the method, called the “Montreal Procedure,” in the 1930s. It helped him pinpoint the source of the seizure in the brain so he could remove it, and relieve patients of debilitating attacks.

But his work in epilepsy also increased our understanding of the architecture of the brain, mapping how its folds and areas relate to sensations in the body.

Penfield’s surgeries helped epilepsy patients

Descriptions of Penfield’s Montreal Procedure are an odd thing to behold. Patients stay calm and awake while the surgeon literally electrocutes their brain.

Keeping the patients awake was crucial to the success of the procedure. Often in epilepsy, seizures originate from one scarred or damaged region of brain tissue. The brain surgeon’s goal is to identify that tissue while protecting healthy parts.

With the skull open and the brain exposed, Penfield would probe the brain’s surface with a small electrode. If he touched an area of the brain that related to feeling in the fingers, patients would report numbness in their fingers. Prodding different areas of the brain with small electrical impulses could get patients to suddenly retrieve memories, see flashes of light, or smell an odor. The electrode would essentially turn on, or off, the brain circuitry involved in those sensations and perceptions.

People with epilepsy often get “auras” — an odd, specific sensation (a smell, or taste, or thought) before a seizure. If Penfield found the area of the brain that produced the aura, he could remove it, which then greatly reduced the risk of seizures in patients.

Penfield could do this while patients were awake because, ironically, the brain itself has no pain receptors. And local anesthesia allowed him to remove part of the skull without causing much pain.

In treating epilepsy, Penfield sketched a new map of the brain

The Montreal Procedure helped many deal with the debilitating effects of epilepsy, but it also opened up a whole new avenue of understanding how the brain works. Since the electrical impulses would temporarily turn on, or off, a function of the brain, by slowly, meticulously, prodding the brains of his patients, Penfield was able to develop a map of brain function.

Here’s a photograph from a 1937 Penfield report — it’d not for the extremely faint of heart.

American Neurological Association

Each number in the image corresponds to a particular brain function and sensation Penfield mapped. No. 18 corresponds to “Slight twitching of arm and hand like a shock, and felt as if he wanted to move them,” according to the report. At No. 8, the patient “felt sensation of movement in the thumb,” but it didn’t actually move. At No. 13, the patient felt “numbness all down the right leg.”

This was the first time areas relating to speech were mapped, McGill University, which employed him, explains on its website.

In some instances when Penfield prodded a person’s brain, they would suddenly experience a detailed personal memory. This was among the first evidence to suggest that there are physical structures for memory in the brain. One of Penfield’s patients, when prodded with an electrode, responded, “I hear voices. It is late at night, around the carnival somewhere — some sort of traveling circus. I just saw lots of big wagons that they use to haul animals in.”

Penfield and his colleagues used this brain map to develop a homunculus, a cartoon drawing of a human body, sized proportionally to the amount of brain space devoted to each body part.

Sensory and motor homunculus models at the Natural History Museum, London.

 Dr. Joe Kiff /Wikipedia

As the homunculus shows, we use a lot of our brainpower for dexterity (see the huge hands), speech (see the giant lips and tongue), smell, and sight. And we don’t have a whole lot of mental hardware devoted to our chests.

Penfield’s explorations of the brain helped scientists target the malfunctions that led to speech disorders and problems with memory. And the Montreal Neurological Institute, which Penfield co-founded at McGill, became a premier surgical treatment center for epilepsy.

He’s also made an impression on popular culture. Science fiction author Philip K Dick named a device to control emotions of people the “Penfield mood organ.”

Penfield was borne in Spokane, Washington, but did most of his groundbreaking work at McGill in Canada, where he’s celebrated as a national hero. In 1934, he gained Canadian citizenship, and he later became known as “the greatest living Canadian.” He was immortalized in a 60-second Canadian television spot that depicted one of his patients, mid-surgery, declaring, “I smell burnt toast!” during the procedure. Hence the toast in today’s Google Doodle.