CAMBRIDGE, Mass. -- Objects that resemble faces are everywhere. Whether it's New Hampshire's erstwhile granite "Old Man of the Mountain," or Jesus' face on a tortilla, our brains are adept at locating images that look like faces. However, the normal human brain is almost never fooled into thinking such objects actually are human faces.
"You can tell that it has some 'faceness' to it, but on the other hand, you're not misled into believing that it is a genuine face," says Pawan Sinha, professor of brain and cognitive sciences at MIT.
A new study from Sinha and his colleagues reveals the brain activity that underlies our ability to make that distinction. On the left side of the brain, the fusiform gyrus an area long associated with face recognition carefully calculates how "facelike" an image is. The right fusiform gyrus then appears to use that information to make a quick, categorical decision of whether the object is, indeed, a face.
This distribution of labor is one of the first known examples of the left and right sides of the brain taking on different roles in high-level visual-processing tasks, Sinha says, although hemispheric differences have been seen in other brain functions, most notably language and spatial perception.
Lead author of the paper, published Jan. 4 in the Proceedings of the Royal Society B, is Ming Meng, a former postdoc in Sinha's lab and now an assistant professor at Dartmouth College. Other authors are Tharian Cherian '09 and Gaurav Singal, who recently earned an MD from the Harvard-MIT Division of Health Sciences and Technology and is now a resident at Massachusetts General Hospital.
Face versus nonface
Many earlier studies have shown that neurons in the fusiform gyrus, located on the brain's underside, respond preferentially to faces. Sinha and his students set out to investigate how that brain region decides what is and is not a face, particularly in cases where an
|Contact: Caroline McCall|
Massachusetts Institute of Technology