[Editors] MIT reports new insights in visual recognition

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MIT team reports new insights in visual recognition
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For Immediate Release
THURSDAY, APR. 1, 2004
Contact: Elizabeth A. Thomson, MIT News Office
Phone: 617-258-5402
Email: thomson at mit.edu

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CAMBRIDGE, Mass.--MIT scientists are reporting new insights into how 
the human brain recognizes objects, especially faces, in work that 
could lead to improved machine vision systems, diagnostics for certain 
neurological conditions and more.

Look at a photo of people running a marathon. The lead runners' faces 
are quite distinct, but we can also make out the faces of those farther 
in the distance.

Zoom in on that distant runner, however, "and you'll see that there's 
very little intrinsic face-related information, such as eyes and a 
nose. It's just a diffuse blob. Yet somehow we can classify that blob 
as a face," said Pawan Sinha, an assistant professor in the Department 
of Brain and Cognitive Sciences (BCS). In contrast, performing this 
task reliably is beyond even the most advanced computer-recognition 
systems.

In the April 2 issue of Science, Sinha and colleagues show that a 
specific brain region known to be activated by clear images of faces is 
also strongly activated by very blurred images, just so long as 
surrounding contextual cues (such as a body) are present. "In other 
words, the neural circuitry in the human brain can use context to 
compensate for extreme levels of image degradations," Sinha said.

Past studies of human behavior and the work of many artists have 
suggested that context plays a role in recognition. "What is novel 
about this work is that it provides direct evidence of contextual cues 
eliciting object-specific neural responses in the brain," Sinha said.

The team used functional magnetic resonance imaging to map neuronal 
responses of the brain's fusiform face area (FFA) to a variety of 
images. These included clear faces, blurred faces attached to bodies, 
blurred faces alone, bodies alone, and a blurred face placed in the 
wrong context (below the torso, for example).

Only the clear faces and blurred faces with proper contextual cues 
elicited strong FFA responses. "These data support the idea that facial 
representations underlying FFA activity are based not only on intrinsic 
facial cues, but rather incorporate contextual information as well," 
wrote BCS graduate student David Cox, BCS technical assistant Ethan 
Meyers, and Sinha.

"One of the reasons that reports of such contextual influences on 
object-specific neural responses have been lacking in the literature so 
far is that researchers have tended to 'simplify' images by presenting 
objects in isolation. Using such images precludes consideration of 
contextual influences," Cox said.

The findings not only add to scientists' understanding of the brain and 
vision, but also "open up some very interesting issues from the 
perspective of developmental neuroscience," Sinha said. For example, 
how does the brain acquire the ability to use contextual cues? Are we 
born with this ability, or is it learned over time? Sinha is exploring 
these questions through Project Prakash, a scientific and humanitarian 
effort to look at how individuals who are born blind but later gain 
some vision perceive objects and faces.

POTENTIAL APPLICATIONS

Computer recognition systems work reasonably well when images are 
clear, but they break down catastrophically when images are degraded. 
"A human's ability is so far beyond what the computer can do," Meyers 
emphasized. "The new work could aid the development of better systems 
by changing our concept of the kind of image information useful for 
determining what an object is."

There could also be clinical applications. For example, said Sinha, 
"contextually evoked neural activity, or the lack of it, could 
potentially be used as an early diagnostic marker for specific 
neurological conditions like autism, which are believed to be 
correlated with impairments in information integration. We hope to 
address such questions as part of the Brain Development and Disorders 
Project, a collaboration between MIT and Children’s Hospital" in 
Boston.

This work was supported by the Athinoula A. Martinos Center for 
Biomedical Imaging, the National Center for Research Resources and the 
Mental Illness and Neuroscience Discovery (MIND) Institute, as well as 
the National Defense Science and Engineering Graduate Fellowship, the 
Alfred P. Sloan Foundation and the John Merck Scholars Award.

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