BW: What kind of scientific aspects?
PS: Fairly soon after that experience, I realized that there is an amazing scientific opportunity in providing treatment for such a child: getting a window into visual learning. Cases of congenital blindness are just so rare in the Western world, it is hard to have a systematic, scientific program to study. It’s an amazing domain of research, but it’s also a challenging domain because of the paucity of subjects.
BW: In 1981, scientists Hubel and Wiesel were given the Nobel Prize concerning the “critical period for sight.” They suggested that an animal deprived from light for a long period of time would never be able to see. Doesn’t your work challenge those notions?
PS: In the initial phases of Project Prakash, given that we went in with the assumption that maybe the critical-period idea was going to hold strictly, we were pleasantly surprised every time we’d see evidence of significant visual improvement. I don’t think Hubel and Wiesel themselves pushed for its application in the human domain, but it was natural that, in the absence of direct human data, other researchers would extrapolate from their study.
BW: How do you test for what the children are able to see after their operations?
PS: The simplest thing you can do with a child that is beginning to see is simply track how well they do at a task. Imagine that you had a collection of 50 face images, and 50 nonface images. You show them these 100 images soon after they gain sight, and a week after they gain sight, and so on, and you try to determine what was their performance at discriminating faces from nonfaces. We’re trying to understand what is the kind of information that goes into children’s interpretation of the visual world.
BW: Why are faces so important?
PS: I don’t have any direct evidence, but the theoretical position we are taking: Dynamic information is significant for this learning. If you look at the motion characteristics of objects in the real world that a child is likely to encounter, faces are up there in terms of being dynamic entities. Faces are mostly in motion. Both the head is moving and the internal facial features have their own types of movement, while most of the rest of the world is fairly static. So motion helps the brain focus attention on the face and also helps to segregate the facial regions from the rest of the regions. I believe that’s why face-learning comes about so very quickly. Because there are few other things in the natural environment that can compete with the face, just in terms of its dynamic characteristics.
BW: Have you done any brain imaging with the children? Is there a way to gauge the changes in their visual learning?
PS: The thing that we can say with confidence, even at this early stage: We see tremendous plasticity in the brain. So from a week after treatment, you see significant reorganization in the visual cortex. We image their brains soon after surgery, and a month, or multiple months after surgery. We see how the patterns of response can change over time. The plasticity happens over a very large swath of the brain. It goes along with the behavioral findings — that the brain maintains its ability to learn, and to be plastic well into life.
This article was originally published in the Summer 2011 issue of Brain World Magazine.