The Brain Basis of Human Vision
published: Oct. 12, 2011, recorded: April 2006, views: 462
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Nancy Kanwisher’s breakthrough scanning research reveals “a teeny part of an answer to the big question of what kinds of brains we have,” she says. Her work depends on functional MRI, a way of imaging people’s brains that detects areas of high neural activity. Kanwisher focuses on vision, to which almost 1/2 of the human cortex is dedicated. “Before fMRI, we knew almost nothing about how that part of the brain was organized,” says Kanwisher. In some of her earliest work, she put her subjects in the fMRI machine, showed them pictures of faces and objects and scanned their heads. She found an area that lit up exclusively in response to the faces. She has found other regions since then, “kind of mind-blowing, because nobody predicted them.” There’s brain circuitry devoted to places and spatial layouts, and another distinct region that responds selectively to body parts like feet, elbows and knees.
Kanwisher has shown that our “minds contain at least a small number of very specialized mechanisms to process very specific kinds of information.” There are lots of questions remaining, though, like determining which mental functions get “their own private piece of cortex and which don’t.” Fruits and vegetables for instance, don't seem to merit their own special brain area. Kanwisher would like to know how these mechanisms arise during development -- whether in response to genetic wiring or environmental stimuli -- and how they change during adulthood.
During exchanges with audience members, Kanwisher says she doesn’t believe that “every mental function of interest happens in one little bit of the brain, because the range of human experience is too broad and varied to fit each into its own little patch.” She dismisses as “baloney” assertions about fundamental cognitive differences between men and women. She also answers questions about scanning in animals, infants and children; evolutionary pressure of brain development; and the limitations of fMRI.
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