In an earlier experiment, one of the authors of the new paper, Dr. Alan Pegna of Geneva University Hospitals, found that the same African doctor had emotional blindsight. When presented with images of fearful faces, he cringed subconsciously in the same way that almost everyone does, even though he could not consciously see the faces. The subcortical, primitive visual system apparently registers not only solid objects but also strong social signals.
Held, the MIT neuroscientist, said that in lower mammals these midbrain systems appeared to play a much larger role in perception. In a recent study of rats in the journal Science, researchers demonstrated that cells deep in the brain were in fact specialized to register certain qualities of the environment.
They include place cells, which fire when an animal passes a certain landmark, and head-direction cells, which track which way the face is pointing. But the new study also found strong evidence of what the scientists, from the Norwegian University of Science and Technology in Trondheim, called “border cells,” which fire when an animal is close to a wall or boundary of some kind.
All of these types of neurons, which exist in some form in humans, may have assisted T.N. in his navigation of the obstacle course.
In time, and with practice, people with brain injuries may learn to lean more heavily on such subconscious or semiconscious systems, and perhaps even begin to construct some conscious vision from them.
“It's not clear how sharp it would be,” Held said. “Probably a vague, low-resolution spatial sense. But it might allow them to move around more independently.”