TUESDAY, Oct. 23, 2012 (HealthDay News) -- The perception of others' faces changed radically for a man when scientists electrically stimulated key parts of his brain, potentially bringing new insights into how humans recognize others.
Stimulation of two brain nerve clusters involved in facial recognition altered the volunteer's perception of faces, but it did not affect his ability to recognize other body parts or inanimate objects, researchers noted.
The painless mild electrical stimulation was performed with electrodes temporarily implanted in the brain of 47-year-old Ron Blackwell of Santa Clara, Calif. The electrodes were implanted by Stanford University doctors in an effort to pinpoint the site in Blackwell's brain that might be causing his increasingly uncontrollable epileptic seizures.
Two of the electrodes were implanted near two nerve clusters located about a half-inch apart in a brain structure called the fusiform gyrus. These nerve clusters are critical for face perception.
The doctors wanted to find out what would happen if they electrically stimulated these two nerve clusters, and Blackwell agreed to the test.
One unexpected result was a scrambling of Blackwell's ability to recognize others.
"You just turned into somebody else. Your face metamorphosed," he told Dr. Josef Parvizi, associate professor of neurology and neurological sciences at Stanford University's School of Medicine, during a video of the test.
"You almost look like somebody I've seen before, but somebody different," Blackwell said. "... You were someone else. Your whole face just sort of metamorphosed ... it's almost like the shape of your facial features drooped."
"Ron didn't see my face vaporize or go blank. Instead, it just seemed to warp before his eyes," Parvizi added in a Stanford news release.
When the electrical stimulation was halted, Blackwell's distorted image of Parvizi's face immediately returned to normal, according to the report published in the Oct. 24 issue of the Journal of Neuroscience.
The researchers said the findings could prove helpful in treating people with a condition called prosopagnosia, which is the inability to distinguish one face from another. The results may also help improve understanding of why some people are much better than others at recognizing and remembering faces.
The U.S. National Institute of Neurological Disorders and Stroke has more about prosopagnosia.