WEDNESDAY, Oct. 24, 2012 — A rare neurological disorder known as prosopagnosia, or face blindness, prevents some people — including prominent neuroscientist and author Oliver Sacks — from recognizing all faces, sometimes including their own.
Face blindness is caused by two tiny areas in the brain that are essential for seeing and recognizing faces, a new Stanford University study published in the Journal of Neuroscience reports. The study is the first to offer direct evidence that these brain areas — the mid and posterior fusiform gyri — are the key to facial recognition, but do not impair perception of other images.
Sacks — who has written extensively about odd and interesting neurological disorders — told the NPR show Radiolab that he once apologized for bumping into an older bearded man, only to realize it was his own reflection in a mirror.
In the study, Stanford neuroscientists "tickled" volunteer Ron Blackwell's brain through electrical pulses. Blackwell volunteered to participate after having electrodes implanted in his brain to help identify the source of his seizures. By chance, two of the electrodes were placed on the right fusiform gyri. When these electrodes were activated, Blackwell said his visual perception of the researcher conducting the study completely shifted.
"You just turned into somebody else. Your face metamorphosed," he said in a video accompanying the study. "Your nose got saggy and went off to the left." But only the face changed; the rest of the researcher's body remained the same. When the electrical impulses stopped, the distorted image vanished.
In addition to identifying which areas of the brain control facial recognition, this shows that abnormal brain activity to these key areas can distort a person's view of faces. These findings held up across multiple faces.
Similar simulation of electrodes has been shown to impair a person's ability to recognize a famous face, the authors report in the study, but this is the first to document face-only distortions in a person's view.
One to 2 percent of the population has prosopagnosia, the National Institute of Neurological Disorders and Stroke report, and the hope is that these results might someday help those patients.
Last Updated: 10/24/2012