A Patient’s Bizarre Hallucination Points to How the Brain Identifies Places

A Patient’s Bizarre Hallucination Points to How the Brain Identifies Places

The colors in this image indicate the brain regions that were activated more by pictures of houses than other categories (such as faces, body parts, tools, or abstract patterns). Yellow indicates stronger activation than red. The dashed line shows the plane of the virtual brain slice on the right-hand side. Note: The patient’s brain is viewed from below so that the right hemisphere of his brain appears on the left side of the image. (Mégevand et.al.)

Dr. Pierre Mégevand was in the middle of a somewhat-routine epilepsy test when his patient, a 22-year old man, said Mégevand and his medical team looked like they had transformed into Italians working at a pizzeria — aprons and all. It wasn’t long, the patient said, before the doctors morphed back into their exam room and business-casual attire. But that fleeting hallucination — accompanied by earlier visions of houses, a familiar train station and the street where the patient grew up — helped verify that a certain spot, in a certain fold in the brain, is a crucial node in the brain’s process of recognizing places.

In the 1950s, the Canadian neurosurgeon Wilder Penfield made a set of remarkable observations in the course of operating on epilepsy patients. As he moved a stimulating electrode around parts of the temporal and frontal lobes of the brain to locate the source of a patient’s seizures, the patients sometimes reported vivid hallucinations. The work was an early contribution to scientists’ understanding of which parts of the brain do what.

Since then, researchers have developed new methods like fMRI for studying the human brain in action without picking up a scalpel. These tools have given them a much better understanding of how the brain is organized — suggesting, for example, that one particular patch of the temporal cortex specializes in processing faces, while another nearby patch specializes in places. Very few studies, however, have tested these findings by stimulating those parts of the brain to see what people experience.

In the new study, Mégevand and colleagues report what happened when they stimulated a brain region thought to be important for the perception of places — the so-called parahippocampal place area — in one particular patient.

“At first we were really stunned. It was the first time in 70 patients that someone gave such a detailed, specific report,” said Mégevand, a post-doctoral research fellow at The Feinstein Institute for Medical Research in Manhasset, New York.

His team’s findings appear in the April 16 issue of The Journal of Neuroscience. The patient’s hallucinations came as Mégevand and his medical team were tickling electrodes they had placed in his brain in search of the origin of his epilepsy, which had been difficult to control. The patient had started suffering epileptic seizures after contracting West Nile virus when he was 10.

In this patient, Mégevand’s collaborator, Ashesh Mehta, director of epilepsy surgery at the Feinstein Institute, drilled tiny holes in the skull through which he inserted 2-inch long electrodes and guided them to specific points on unique folds in the brain tissue. Even with that level of precision, results can be difficult to reproduce from patient to patient, Mehta says. That’s because everyone’s brain is different, and a variation of millimeters can make a certain hallucination-producing spot hard to pinpoint across patients.

“What was groundbreaking was everything worked the way it was supposed to work,” Mehta said.

The research follows that of Stanford University neurologist Josef Parvizi, who two years ago showed that electrodes placed another spot in the brain were crucial in a patient’s processing of faces.

That study includes a video of the patient’s reaction (below). “You just turned into somebody else. Your face metamorphosed,” the patient marveled. “That was a trip.” Parvizi published another study last year showing that stimulating yet another part of the brain “gave patients the will to persevere hardship.”

This type of ongoing research “is a perfect way for us to explore the functional architecture of the human brain,” Parvizi said. He describes the Feinstein Institute team’s paper as “elegant,” but stresses that the findings do not prove that certain parts of the brain are entirely responsible for the processing of faces, places or anything else. Instead, he says, it only shows that these spots are critical links in networks of neurons responsible for a certain task.

Back in New York, Mehta says he expects to make additional discoveries as his team continues their epilepsy research and treatment. “As we’re stimulating more and more of the brain, we’re finding more unique little spots,” he said.

Still, with these findings come more questions.

For example, Mégevand says, was the pizzeria hallucination the result of an electrode placed partly between neurons that process faces, and those that process places? The patient owned a pizzeria with his family, he says. So was that scene part of an old memory, or something he’d never seen before? Those are questions Mégevand says he hopes to answer going forward.

“If he had been working in a sushi place, maybe we would have been wearing different garb,” Mégevand chuckled.