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 patients brain is viewed from below so that the right hemisphere of his brain appears on the left side of the image. (Mgevand et.al.)
Dr. Pierre Mgevand was in the middle of a somewhat-routine epilepsy test when his patient, a 22-year old man, said Mgevand and his medical team looked like they had transformed into Italians working at a pizzeria aprons and all. It wasnt 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 brains 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 patients 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, Mgevand 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 Mgevand, a post-doctoral research fellow at The Feinstein Institute for Medical Research in Manhasset, New York.
His teams findings appear in the April 16 issue of The Journal of Neuroscience. The patients hallucinations came as Mgevand 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, Mgevands 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. Thats because everyones 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 patients processing of faces.
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A Patients Bizarre Hallucination Points to How the Brain Identifies Places