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TOM COSTELLO: Every day, we are bombarded by sights, smells,
tastes, textures, and sounds-- senses that allow humans and
animals alike to perceive the world around us - and
survive. With all these sensations coming in, scientists
are trying to solve how the brain is able to process and
organize them. For some animals, including humans, the answer may
lie in one of our most complex senses: vision.
SABINE KASTNER: One third of the primate brain is dedicated to
vision. It is a huge real estate.
COSTELLO: Dr. Sabine Kastner is a neuroscientist at Princeton
University who is funded by the National Science Foundation. She
and her team are studying how the visual system in the brain
is able to weed out important information from a busy
scene in order to perform even simple tasks -
like crossing the street.
KASTNER: And I was thinking to myself - while I was crossing
the street, I was looking for cars, what is known about what
we do, what's going on in the brain when we do just that?
COSTELLO: In all animals, vision begins with the eyes. The retina
acts like a camera's memory card and captures an image of what it
is seeing. The image is then transmitted as electrical
impulses through a bundle of nerve fibers to the thalamus-
the brain's switchboard. From there, these impulses travel to
the visual regions in the cortex, are interpreted, and
then sent to the parts of the brain that control behavior. So
whether it is a person looking for cars or a hawk searching for
prey, they will be able to respond quickly. But how
does the brain know which parts of a scene are important
and which are not?
KASTNER: A fundamental problem that we encounter in vision is
that there are always lots and lots of things around us.
COSTELLO: To test how animals' brains make sense of crowded
visual scenes, Kastner and her team designed experiments
using functional magnetic resonance imaging, or fMRI,
to peek inside the human brain.
KASTNER: So we just took two thousand scenes, they were all
outdoor, street scenes, basically. And we showed them
to human subjects in our scanner.
COSTELLO: The machine sends back three-dimensional images of the
brain in real time, showing the regions of the brain that are
active when the subject sees a place, object, or person.
Another experiment utilizing fMRI studies how the brain
recognizes faces and facial cues, an ability that could help
an animal identify friend or foe.
KASTNER: Nonhuman primates can do these sort of interpretations
just as we can. There's a big difference if a bigger monkey is
angry and wants to come after you in the wild.
COSTELLO: The results from Kastner's experiments point
to the crucial role played by complex networks
of cells, called neurons, that transmit information
throughout the brain.
KASTNER: Most of the operations that the brain is performing
involves networks. That means that there are many, many areas
involved that often somehow span the entire brain.
COSTELLO: To help neuroscientists like Kastner
better understand these networks, they are beginning to
collaborate with mathematicians, computer scientists, and
physical scientists to create theoretical and computational
models of these complex networks. These collaborations
will help scientists understand how these biological systems
play key roles in perception.
KASTNER: And this is what applied mathematicians,
physicists, statisticians, computer scientists really have
the background to do. So they can give us
models of what these computations in these
nodes may be.
COSTELLO: Understanding the brain's networks will help
scientists understand how animals perceive the world
around them, and could even contribute to the development of
new technologies, for instance, more advanced facial recognition
technology. This also could lead to better treatments for brain
disorders, like ADHD and schizophrenia. Although the
brain's visual system is riddled with mystery, dedicated
neuroscientists like Kastner are providing a clearer picture of
all that the brain can do.
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