A brain area that recognizes faces remains functional even in people who have been blind since birth, researchers say. The finding, presented at the Society for Neuroscience meeting this week, suggests that facial recognition is so important that evolution has hardwired it into the human brain.
"It's all inborn," says Josef Rauschecker, a professor of neuroscience at Georgetown University Medical Center. "The structures are all there because nature has put them there."
Rauschecker was part of a team that studied the brains of six blind people, including Jeannette Gerrard, a retired government worker who lives in Washington, D.C. Gerrard has always relied on voices to identify people, and says that faces were never that important to her.
"I knew what my face looked like by touch," she says, "and I figured a face was a face."
So she was intrigued when researchers from Georgetown asked her to take part in an experiment that would eventually allow her to see faces using sound.
First, the scientists had Gerrard learn to use a special headset fitted with a small camera. By moving her head, Gerrard could make the camera scan across a drawing.
The device produced sounds. And as lines or curves came into the camera's view, those sounds would change. The concept is a bit like tapping your way along a wall to find a stud behind the plaster.
With practice, Gerrard was able to interpret more complex sound patterns that revealed more complicated shapes. Eventually, "I could identify a face by listening to those sounds," Gerrard says.
To find out how Gerrard was doing this, the Georgetown scientists put her in a brain scanner. The idea was to watch Gerrard's brain while she was using sounds to recognize a simplified drawing of a face, says Paula Plaza, who was in charge of the experiment. "Our interest was looking into the brain," she says. "What part of the brain is responsible for this perception?"
The team compared brain scans from the six blind people with the scans from 10 sighted people who were looking at the face drawings with their own eyes. The results were almost identical. In both groups, the image caused lots of activity in the left fusiform face area, a region of the brain "that always lights up when you see a face," Rauschecker says.
In sighted people, the fusiform face area is connected to the brain's visual system, he says. But in blind people it appears to be wired to circuits that process sounds. "So there is substantial reorganization in the brain of the blind," Rauschecker says.
What's remarkable is that despite this reorganization, the brain of a blind person retains the module devoted to facial recognition, Rauschecker says. That strongly suggests that the ability to recognize faces comes more from nature than from nurture, he says.
ARUN RATH, HOST:
The human brain is amazing at recognizing faces. It took decades for computers to get anywhere near as good. That's because most brains include an entire region that specializes in faces. But what about the brain of someone who has never seen a face? NPR's Jon Hamilton reports on a study of people who have been blind since birth.
JON HAMILTON, BYLINE: Seeing a face is one way to recognize a person. But Jeannette Gerrard, who is blind, says she relies on voices.
JEANNETTE GERRARD: Oh yeah, anybody, oh yeah. Doesn't matter who they are, and I would know if there was something wrong or, you know - you know, by their voice.
HAMILTON: Gerrard is a retired government worker who lives in Washington, D.C. She says faces have never been that important to her.
GERRARD: I knew what my face looked like by touch, you know, and things of that sort. And I figured a face was a face.
HAMILTON: So she was intrigued when researchers from Georgetown University asked her to take part in a study that would let her see faces using sound. The scientists had Gerrard wear a special headset.
GERRARD: And there was these goggles or something, and it had a little camera that fit up on top of the nose part.
HAMILTON: By moving her head, Gerrard could make the camera scan across a drawing. And as lines or curves came into view, the device would play sounds that changed in pitch and volume.
(SOUNDBITE OF VISUAL HEADSET INTERFACE SOUNDS)
HAMILTON: The concept is a bit like tapping your way along a wall to hear where a stud is behind the plaster. With practice, Gerrard learned to interpret more complex sound patterns.
(SOUNDBITE OF VISUAL HEADSET INTERFACE SOUNDS)
HAMILTON: These revealed geometric shapes, letters and even faces.
GERRARD: So I could identify a face by listening to those sounds.
HAMILTON: To find out how Gerrard was doing this, the Georgetown scientists put her in a brain scanner. Paula Plaza, who was in charge of the experiment, says the idea was to watch Gerrard's brain while she was using sounds to recognize a face.
PAULA PLAZA: Our interest was looking into the brain. What part of the brain is responsible for this perception?
HAMILTON: In other words, what area of the brain did a blind person use to identify faces? To make sure the results would be meaningful the team scanned the brains of six blind people who'd learned to recognize faces through sound. They also scanned 10 sighted people who were looking at the drawings with their own eyes. Plaza says the results were clear.
PLAZA: The activation of the blind group looks like when sighted were seeing a face.
HAMILTON: When sighted or blind people recognized a face, there was lots of activity in a place called the fusiform face area. Josef Rauschecker, another member of the Georgetown team, says the area was discovered in the 1990s.
JOSEF RAUSCHECKER: It's turned out to be a very reliably activated region of the brain that always lights up when you see a face.
HAMILTON: But Rauschecker says the fusiform face area, or FFA, is usually connected to the brain's visual system.
RAUSCHECKER: Normally, in a sighted person, the FFA is not activated by sounds, you know? So there is substantial reorganization in the brain of the blind.
HAMILTON: A reorganization that takes brain areas usually reserved for vision and instead uses them to process sounds. Rauschecker says what's interesting is that despite all this rewiring, the brain of a blind person retains a working module devoted to recognizing faces.
RAUSCHECKER: What seems to happen in the blind participants is that they still have that module at their disposal. It's still functioning. It's still looking for faces. But the input is now coming through the auditory channel.
HAMILTON: Rauschecker says recognizing faces is so important that evolution appears to have hardwired it into our brains. The Georgetown team presented their findings this week at the Society for Neuroscience meeting in Washington, D.C. Jon Hamilton, NPR News. Transcript provided by NPR, Copyright NPR.