Exploratorium Magazine Online
picturing the body

Volume 23, Number 3

 page 2 of 5


Identifying those pieces has led to an explosion of information about how the brain is organized—and knowing the organizational plan is critical to understanding how any system works. Traditionally, physiologists have prospered from the mantra "form follows function." That is, natural selection forces a structure to evolve toward the most efficient design for its particular task. So by studying the design, we can make good guesses about the task.

For instance, if you'd never seen a typewriter before and wanted to figure out how it worked, you'd only have to take it apart. Likewise, draw a blueprint of the digestive tract and you've come a long way toward understanding how the body processes food. But take the brain apart and all you'll get is a mosaic of gray and white tissue—anatomy without obvious purpose. It's a black box instead of a machine; a computer instead of a typewriter.

Like a computer, the brain relies on electronic circuitry to perform its job. It stores data in both short-term and long-term memory. It rapidly sorts and processes information. Like a computer, you can't tell what it does by taking it apart; instead, you have to turn it on. But if it's on, you can't take it apart. Catch 22.

Functional MRI lets us look at what's happening inside the box while it's turned on. With it, we can see exactly what regions of the brain are activated when a specific task is performed, effectively getting form from function. The black box is growing transparent—and its design isn't what we expected.

For example, Kanwisher, who studies how we see things, has demonstrated that one region of the visual cortex is activated when a person is shown a picture of a place, but that a completely different region of the cortex is activated when a person is shown a picture of a face.

"Facial recognition is separated from other things in the visual system," she says. "We are extremely visual organisms. Over a dozen specific regions have been found in the visual cortex alone in the last few years, and more are expected."

Why would our brain use different neurons to recognize faces versus recognizing a familiar building?

"We're extremely social primates," Kanwisher says. "In the evolution of our primate ancestors, it was probably pretty important to survival to know who you were looking at; whether someone was a friend or a foe. It's also possible that facial recognition is simply very different from every other visual task and needs a highly specialized area. Or maybe we just look at faces so much more than anything else that the brain has specialized itself."

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