A key brain region responds to faces similarly in infants and adults
Study suggests this area of the visual cortex emerges much earlier in development than previously thought.

Date:
November 15, 2021
Source:
Massachusetts Institute of Technology
Summary:
In a functional magnetic resonance imaging study of babies ranging
in age from two to nine months, researchers have found regions of
the infant visual cortex that show strong preferences for either
faces, bodies, or scenes, just as they do in adults.



FULL STORY ========================================================================== 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. 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, bodies, or 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 John W. Jarve Professor of Brain and Cognitive
Sciences, a member of MIT's McGovern Institute for Brain Research,
and the senior author of the new study.

Using functional magnetic resonance imaging (fMRI), the researchers
collected usable data from more than 50 infants, a far greater number
than any research lab has been able to scan before. This allowed them
to examine the infant visual cortex in a way that had not been possible
until now.

"This is a result that's going to make a lot of people have to really
grapple with their understanding of the infant brain, the starting point
of development, and development itself," says Heather Kosakowski, an MIT graduate student and the lead author of the study, which appears today
in Current Biology.

Distinctive regions More than 20 years ago, Nancy Kanwisher, the Walter
A. Rosenblith Professor of Cognitive Neuroscience at MIT, used 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.



========================================================================== Since then, Kanwisher and her colleagues have also identified parts of
the visual cortex that respond to bodies (the extrastriate body area,
or EBA), and scenes (the parahippocampal place area, or PPA).

"There is this set of functionally very distinctive regions that are
present in more or less the same place in pretty much every adult," says Kanwisher, who is also a member of MIT's Center for Brains, Minds, and Machines, and an author of the new study. "That raises all these questions about how these regions develop. How do they get there, and how do you
build a brain that has such similar structure in each person?" One way
to try to answer those questions is to investigate when these highly
selective regions first develop in the brain. A longstanding hypothesis
is that it takes several years of visual experience for these regions
to gradually become selective for their specific targets. Scientists
who study the visual cortex have found similar selectivity patterns in
children as young as 4 or 5 years old, but there have been few studies
of children younger than that.

In 2017, Saxe and one of her graduate students, Ben Deen, reported the
first successful use of fMRI to study the brains of awake infants. That
study, which included data from nine babies, suggested that while infants
did have areas that respond to faces and scenes, those regions were not
yet highly selective.

For example, the fusiform face area did not show a strong preference
for human faces over every other kind of input, including human bodies
or the faces of other animals.

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, the
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.

The researchers recruited nearly 90 babies for the study, collected
usable fMRI data from 52, half of which contributed higher-resolution
data collected using the new coil. Their 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. The selectivity for natural scenes, however, was not as strong as for faces or body parts.

The infant brain The findings suggest that scientists' conception of
how the infant brain develops may need to be revised to accommodate the observation that these specialized regions start to resemble those of
adults sooner than anyone had expected.

"The thing that is so exciting about these data is that they revolutionize
the way we understand the infant brain," Kosakowski says. "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." Because their data on the area of the brain that
responds to scenes was not as strong as for the other locations they
looked at, the researchers now plan to pursue additional studies of that region, this time showing babies images on a much larger screen that will
more closely mimic the experience of being within a scene. For that study,
they plan to use near-infrared spectroscopy (NIRS), a non-invasive imaging technique that doesn't require the participant to be inside a scanner.

"That will let us ask whether young babies have robust responses to
visual scenes that we underestimated in this study because of the visual constraints of the experimental setup in the scanner," Saxe says.

The researchers are now further analyzing the data they gathered for this
study in hopes of learning more about how development of the fusiform face
area progresses from the youngest babies they studied to the oldest. They
also hope to perform new experiments examining other aspects of cognition, including how babies' brains respond to language and music.

The research was funded by the National Science Foundation, the National Institutes of Health, the McGovern Institute, and the Center for Brains,
Minds, and Machines.

========================================================================== Story Source: Materials provided by
Massachusetts_Institute_of_Technology. Original written by Anne
Trafton. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Heather L. Kosakowski, Michael A. Cohen, Atsushi Takahashi,
Boris Keil,
Nancy Kanwisher, Rebecca Saxe. Selective responses to faces,
scenes, and bodies in the ventral visual pathway of infants. Current
Biology, 2021; DOI: 10.1016/j.cub.2021.10.064 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211115123518.htm

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