A routine act of walking on a crowded street is difficult for a visually impaired. Some people, however, have this navigational feat. It is blindsight, “a weird ability to respond to visual information despite having no conscious knowledge of seeing anything.” Beatrice de Gelder, a cognitive neuroscientist, says that the brain has number of alternate routes that can be mobilised when the main avenues to vision are blocked. Though we tend to concentrate on major visual systems in the brain, we may have hidden resources. In a carefully conducted experiment de Gelder found that a visually impaired man (rendered completely blind by several strokes) could walk unaided through obstacles lying on the way. The experiment suggested that some amount of information is transmitted from the man’s undamaged eyes to a more primitive part of his brain, which operates beneath the level of consciousness. The previous experiments by the group (using brain scanning to recognise fearful, angry or joyous faces by observing increased activity in amygdala region) had suggested that the mind could subconsciously process some visual information.
Our conscious vision depends on a region of the brain called the primary visual cortex. If it is damaged how can one see? How could people see without knowing that they can see? Experts say that this feat is possible due to the auditory assistance. Some blind people are known to possess the capability to sense the reflection of sound waves and that assists them to locate obstacles. de Gelder, however, thinks echolocation is not efficient for small objects. Various kinds of experiments have revealed that people can unconsciously detect a wide range of visual attributes, including colour, simple shapes, simple motion, and the orientation of lines or gratings. Large shapes, as well as very fine detail, seem hard to detect.
The relation between seeing and knowing is more complicated than we commonly assume. For instance, people with normal sight have blind spot, although they are not usually aware of this. For some visually impaired people, loss of sight is certainly not the end of sight. They can see with a special eye. They lose eyesight but in exchange get many other extraordinary abilities. Some can hear well. “My ears were hearing no better, but I was making better use of them,” writes a blind author. Some can see the world around them through their newly acquired hyperactive visual imagination. They discover the world by continuously visualising the surroundings. Some eyes can see the soul.