Within the visual cortex of the adult brain, a small region is specialized to respond to faces, while nearby regions show strong preferences for bodies or for scenes such as landscapes.
Neuroscientists have long hypothesized that it takes many years of visual experience for these areas to develop in children. However, a new MIT study suggests that these regions form much earlier than previously thought. The findings were published in the Current Biology journal on November 15.
In a study of babies ranging in age from two to nine months, the researchers identified areas of the infant visual cortex that already show strong preferences for either faces, just as they do in adults.
More than 20 years ago, MIT scientists used functional magnetic resonance imaging (fMRI) to discover the fusiform face area: a small region of the visual cortex that responds much more strongly to faces than any other kind of visual input. They have also identified parts of the visual cortex that respond to bodies and landscapes.
A longstanding hypothesis is that it takes several years of visual experience for these regions to gradually become selective for their specific targets. In 2017, a study reported the first successful use of fMRI to study the brains of awake infants. That study, which included data from nine babies, suggested that the fusiform face area did not show a strong preference for human faces over every other kind of input, including human bodies, faces of other animals, or landscapes.
However, that study was limited by the small number of subjects, and also by its reliance on an fMRI coil that the researchers had developed especially for babies, which did not offer as high-resolution imaging as the coils used for adults.
For the new study, the researchers wanted to try to get better data, from more babies. They built a new scanner that is more comfortable for babies and also more powerful, with resolution similar to that of fMRI scanners used to study the adult brain. After going into the specialized scanner, along with a parent, 90 babies watched videos that showed either faces, body parts such as kicking feet or waving hands, objects such as toys, or natural scenes such as mountains.
Based on the collected data, the analysis revealed that specific regions of the infant visual cortex show highly selective responses to faces, body parts, and natural scenes, in the same locations where those responses are seen in the adult brain.
