SCIENTISTS TRYING to understand how the brain responds to
visual objects can't agree on what they see. At the heart of this controversy
is the human face and how the brain perceives it.
The brain tissue in question-which becomes activated when people look at a
face-is called the fusiform gyrus. In a brain scan, this area lights up, or
becomes active, more powerfully than it does when volunteers look at other
objects. Some scientists believe that the fusiform gyrus was designed
specifically to help humans recognize faces.
But more recently, a number of new studies suggests that this brain tissue
is more likely called on for the processing of a visual skill. Yes, it is used
to help people recognize faces, but as a skill, one that people have been
practicing over and over again since birth.
Scientists made the connection between the fusiform gyrus and its role in
the recognition of faces after several dozen patients with damage to this
tissue lost their ability to identify once- known faces. When high-resolution
brain scans came on the scene, it was time to figure out whether this tissue
was in fact specialized for faces.
At the Cognitive Neuroscience Society meeting in Manhattan last week, a
panel of scientists on both sides of the debate presented their arguments.
On one side is Nancy Kanwisher of the Massachusetts Institute of
Technology, who first proposed that the fusiform gyrus was specifically
designed to recognize faces-and faces alone-based on her findings using a
magnetic resonance imaging device. Then, Isabel Gauthier, a neuroscientist at
Vanderbilt University in Tennessee, talked about her research, showing that the
fusiform gyrus lights up when looking at many different kinds of objects
people are skilled at recognizing.
The debate has been going on for years. Gauthier, during her doctoral
student days at Yale, asked Kanwisher whether she could spend some of her
post-doctoral training in Kanwisher's laboratory at MIT. Gauthier's doctoral
work had shown that the fusiform gyrus becomes activated when people become
expert at looking at certain objects-faces, chairs, cars-any category where
there are many visually similar objects.
In a series of experiments carried out during her tenure at MIT, Gauthier
did brain scans of 19 men who were either expert in cars or birds. As she
expected, this area of the brain, the fusiform gyrus on the right side, became
activated when the men looked at familiar faces, but it also became active when
the bird-watchers looked at birds or car enthusiasts looked at vehicles.
"There is no good evidence that humans have an innate specialization for
faces," Gauthier said during a recent telephone interview.
It wasn't Gauthier's intention to prove Kanwisher wrong, but she felt they
both would learn a lesson. "In science, we rarely work with people who disagree
with us," Gauthier explained. "It pushes you to look at your data in many
different ways. It wasn't always easy. In the end, we still disagreed, but it
was a valuable experience."
Kanwisher, a professor in the department of brain and cognitive sciences at
MIT, says she stands by her data and that of others who have had similar
"The fusiform responds much more strongly to faces than to any other
object. Its primary role is in the recognition of faces," Kanwisher said.
What the area actually does when it looks at a face is still not known. It
could be that it just recognizes faces as a category, or it could actually help
the person distinguish individual faces, Kanwisher said.
She said that patients without the ability to recognize faces do not have
difficulty recognizing other objects they are familiar with.
One patient with diffuse brain damage, detailed in the work of Morris
Moscovitch at the University of Toronto, has difficulty recognizing objects,
but his ability to identify faces remains solid. "It shows that these two
functions are separate," Kanwisher said.
The MIT scientist declined to be a part of Gauthier's published results,
which appeared last year in Nature Neuroscience.
At the heart of the issue is the hope of unraveling the mystery of visual
"I don't think anyone can be equivocal on any side of the debate," said
Moshe Barr, a scientist at Harvard who moderated the debate. "There is more
than meets the eye. And the jury is still out."
Gauthier's new study suggests that the processing of facial information
may, in fact, be a skill that some people just don't practice.
In a new study, which appears in the April issue of the Archives of General
Psychiatry, Gauthier teamed with lead investigator Robert Schultz of the Yale
Child Study Center to test whether this region of the brain would behave
differently in people with autism. According to the study, the autistic people
did not have more activity in this region for faces when compared to other
objects. Gauthier thinks this makes sense if her theory is correct that this
area gets strengthened with practice. People with autism generally don't look
at faces, Gauthier said, adding that the fusiform gyrus finding is not a cause
of autism, but an effect of the underlying biology of the disorder.
James Haxby of the National Institute of Mental Health has studied how the
brain recognizes many categories of things-faces, houses, shoes, chairs, etc.
"We see a unique pattern with each category that might help us explain how the
brain represents objects," Haxby said. "Our findings suggest that the
representation of faces and other objects overlap."
He finds that even weak brain signals in this region are important to the
visual representation of objects. Many brain mappers have focused on large
responses and failed to factor in these weaker responses, Haxby said.