Neuroscientists have long believed that it takes many years for a baby to develop the part of the brain responsible for the visual experience. Previous studies had shown that infants did have areas that respond to faces and scenes, but those regions were not yet highly selective. However, that study was very limited (only nine babies were examined) and relied on a functional magnetic resonance imaging (fMRI) coil that did not offer high-resolution imaging as the coils used for adults.
This time, with a more powerful fMRI, MIT researchers were able to collect valuable data from more than 50 babies, ranging from two to nine months. This new approach allowed them to examine the visual cortex like never before.
A small region within the visual cortex of the adult brain is in charge of responding to the image of faces. Nearby regions show a preference for body shapes or landscape scenes. In the new study, researchers identified areas of the infant visual cortex that already show strong preferences for faces, bodies, or natural scenes— just as they do in adults.
“These data push our picture of development, making babies’ brains look more similar to adults, in more ways, and earlier than we thought,” says Rebecca Saxe, the senior author of the new study.
What is a functional resonance magnetic imaging (fMRI)?
Functional magnetic resonance imaging (fMRI), a technique used since the 1990s, measures brain activity by detecting changes associated with blood flow. Since neuronal activation and blood flood work in unison, when an area of the brain is in use, blood flow to that region also increases.
fMRI is the preferred mapping technique for researchers since it does not require people to undergo surgery, ingest substances, or be exposed to ionizing radiation. Physicians also use fMRI to assess the viability of brain surgery or similar treatment. It can also be used to study the functionality of a diseased or injured brain.
The study involved getting the babies with a parent into a specialized scanner. Once there, the babies watched videos of faces, body parts, objects, or natural scenes. From the 92 babies recruited for the experiment, 52 provided usable information, and half of these contributed higher-resolution data. Faces were shown to have stronger selectivity.
“The thing that is so exciting about these data is that they revolutionize the way we understand the infant’s brain,” says Kosakowski, an MIT graduate student and the lead author of the study. “A lot of theories have grown up in the field of visual neuroscience to accommodate the view that you need years of development for these specialized regions to emerge. And what we’re saying is actually, no, you only really need a couple of months.”
Another MIT study led by Kanwisher in 2020 showed that the same regions of the brain are also functional in people who have been born blind. By touching a three-dimensional body of a face with their hands these regions became active.
“It’s suggestive of this very interesting story that the brain wires itself up in development not just by taking perceptual information and doing statistics on the input and allocating patches of brain, according to some kind of broadly agnostic statistical procedure,” Kanwisher said. “Rather, there are endogenous constraints in the brain present at birth, in this case, in the form of connections to higher-level brain regions, and these connections are perhaps playing a causal role in its development.”