What happens when you split a brain in twain?

The two halves of your brain are in constant communication. Severing that communication can have dramatic consequences, but in the 1950s, researchers believed that doing so could be used to treat severe forms of epilepsy. They called the procedure a corpus callosotomy.

At the time, very few people elected to undergo the surgery, but when they did, researchers took interest. A so-called "split-brain" patient provided a rare opportunity to study the brain and how it worked — and in the last several decades, a small group of these patients has managed to become the subject of some of the most intense and impactful neuroscientific research in recent history.

Over on Nature, David Wolman has written a fascinating article on split-brain science and all that it entails — the researchers who pioneered the field, and continue to study it today; the patients who elected to not only undergo the procedure, but agreed to be scrutinized for the rest of their lives; the discoveries that these investigations have brought to light; and the surprisingly human element underscoring the whole affair. Included here is the introduction, but you'll definitely want to read the article in its entirety.

Wolman begins:

In the first months after her surgery, shopping for groceries was infuriating. Standing in the supermarket aisle, Vicki would look at an item on the shelf and know that she wanted to place it in her trolley - but she couldn't. "I'd reach with my right for the thing I wanted, but the left would come in and they'd kind of fight," she says. "Almost like repelling magnets." Picking out food for the week was a two-, sometimes three-hour ordeal. Getting dressed posed a similar challenge: Vicki couldn't reconcile what she wanted to put on with what her hands were doing. Sometimes she ended up wearing three outfits at once. "I'd have to dump all the clothes on the bed, catch my breath and start again."

In one crucial way, however, Vicki was better than her pre-surgery self. She was no longer racked by epileptic seizures that were so severe they had made her life close to unbearable. She once collapsed onto the bar of an old-fashioned oven, burning and scarring her back. "I really just couldn't function," she says. When, in 1978, her neurologist told her about a radical but dangerous surgery that might help, she barely hesitated. If the worst were to happen, she knew that her parents would take care of her young daughter. "But of course I worried," she says. "When you get your brain split, it doesn't grow back together."

In June 1979, in a procedure that lasted nearly 10 hours, doctors created a firebreak to contain Vicki's seizures by slicing through her corpus callosum, the bundle of neuronal fibres connecting the two sides of her brain. This drastic procedure, called a corpus callosotomy, disconnects the two sides of the neocortex, the home of language, conscious thought and movement control. Vicki's supermarket predicament was the consequence of a brain that behaved in some ways as if it were two separate minds.

After about a year, Vicki's difficulties abated. "I could get things together," she says. For the most part she was herself: slicing vegetables, tying her shoe laces, playing cards, even waterskiing.

But what Vicki could never have known was that her surgery would turn her into an accidental superstar of neuroscience. She is one of fewer than a dozen 'split-brain' patients, whose brains and behaviours have been subject to countless hours of experiments, hundreds of scientific papers, and references in just about every psychology textbook of the past generation. And now their numbers are dwindling.

Continue reading over on Nature.