A team of scientists has discovered how the region of the brain — typically active when a person sees a face — becomes active when people who've been blind since birth touch three-dimensional models of a face with their hands, according to a recent study published in the journal Proceedings of the Academy of Sciences of the United States of America.
Face-sensitive brain sector reacts to faces for people blind since birth
More than 20 years ago, neuroscientist Nancy Kanwisher and others realized how a small section of the brain near the base of the skull reacts more strongly to faces than to other objects appearing in our vision. This area of the brain is called the fusiform face area, and is thought to be a specialized face-identifying region.
In the new study, Kanwisher and her colleagues show how the same region of the brain goes active in people who've lived without sight since birth when they make physical contact with a 3D model of a face with their hands, according to a blog post on MIT's website.
"That doesn't mean that visual input doesn't play a role in sighted subjects — it probably does," said Kanwisher, according to the MIT blog post. "What we showed here is that visual input is not necessary to develop this particular patch, in the same location, with the same selectivity for faces. That was pretty astonishing."
As senior researcher of the study, Kanwisher is also the Walter A. Rosenblith Professor of Cognitive Neuroscience — in addition to being a member of the MIT McGovern Institute for Brain Research. N. Apurva Ratan Murty is lead author of the study and an MIT post-doctoral fellow. Other authors of the paper include Aude Oliva, a senior research scientist and co-director of MIT's Quest for Intelligence, in addition to MIT's director of the MIT-IBM Watson AI Lab. Santani Teng — another author — is a former post-doctoral fellow at MIT, and Anna Mynick and David Beeler are both former lab technicians.
Brain activity in people born blind possibly key to other mysteries
The study of people born blind has helped researchers answer longstanding questions about how different parts of the brain specialize. In the face-sensitive region, scientists wanted to look at face perception — but similar mysteries abound other aspects of human cognition, said Kanwisher, according to the MIT blog.
"This is part of a broader question that scientists and philosophers have been asking themselves for hundreds of years, about where the structure of the mind and brain comes from," said Kanwisher. "To what extent are we products of experience, and to what extent do we have built-in structure? This is a version of that question asking about the particular role of visual experience in constructing the face area."
Studying tactile touch of 3D face models helps us learn how brains specialize
This latest research builds on the work from a 2017 study by researchers based in Belgium. In it, subjects living with congenital blindness were scanned with functional magnetic resonance imaging (fMRI) while they heard a number of sounds — some adjacent to faces (like chewing or laughing), and others not. This study discovered higher responses in the FFA regions when face-related sounds played than it did to unrelated sounds like bouncing balls or clapping hands.
MIT wanted to study the effects of tactile experience in the new study to measure how blind people's brains react to faces. They did it with a ring of 3D-printed objects including hands, chairs, mazes, and faces — rotating each object so the subjects could interact with all of them while in the fMRI scanner.
As neurology advances, we're likely to find more and more ways specialized areas adapt to lacking or missing modes of perception (like blindness, deafness, and others). Whether each perception is learned or "built-in," there's no shortage of surprising discoveries awaiting in the study of the human brain.