They found an old doctor in Switzerland who had two strokes and became completely blind, but now when he walks around, he avoids obstacles in his path and doesn't even know that he's doing it.
TN has what is known as blind sight, according to de Gelder. Even though the primary part of his brain that processes visual information is destroyed, he still has more primitive parts of his brain intact, and these are capable of doing some visual processing. After all, one of the most basic functions of the visual system is to help an animal avoid obstacles or predators. TN still has some visual abilities — he's just not aware he has them.
Steven Hackley, an associate professor of psychological sciences, says studying patients such as TN will tell scientists about the nature of consciousness.
"The idea is that by comparing the same mental process when it is conscious and when it is not, it will be possible to determine which parts of the brain are essential and how consciousness arises," Hackley says.