Perhaps you have ever observed how some people who totally lack vision and therefore cannot visualize the environment, behave as if they could see. They are people who seem to have a special intuition with which they perceive the objects and the place where they are as if they could process this information in some way. It is an interesting phenomenon called: blind vision. A phenomenon that we will explain in detail below.
- 1 A case of blind vision
- 2 Understanding what blind vision is
- 3 Brain pathways involved in blind vision
A case of blind vision
Ricardo is a person who has suffered damage to the visual cortex that has left him in a state of total blindness. Following this, Ricardo is not able to see anything. Carrying out an exam, professionals ask him if he is able to see an object they hold in front of him. This is a ball that Ricardo claims to be unable to see. However, when asked to touch the ball, he manages to raise his arm and reach it just as if he were watching it. We would be talking about a case of blind vision.
Understanding what blind vision is
It could be said that blind vision is the ability to see through intuition, not consciously, although the ability to visualize is damaged.
We have always assumed that blindness is a lack of vision caused by the malfunction of a single visual processing pathway: visual cortex, located in the occipital lobe. Today, however, we know that there are more than 30 areas in the brain of primates and humans involved in vision processing, specializing in components as diverse as color, depth or movement. The vision is much more complex than the scientists themselves imagined.
That is why, when some of these areas involved in visual processing are damaged they occur selective vision problems. Distortions in vision that are not necessarily linked to an eye problem or a problem in the visual cortex that causes visual impairment.
Although it may seem strange to us, what we think we see consciously through our eyes is not everything when it comes to seeing. That is why people whose visualization capacity is non-existent can act as if they possess a different vision; A blind, intuitive vision.
In the same way, some people who have a good capacity for conscious visualization are not, on the contrary, able to perceive and correctly process what they see, that is, they know that they see something, but they cannot know what it is or what it implies what they see. , since some of these different areas of visual processing are damaged. It could be said that these people suffer from blindness, although they can see.
Brain pathways involved in blind vision
Although we have mentioned that there are many areas involved in vision, as well as pathways and nerves that play an important role, we will try to understand what are the main pathways of vision and how their interactions and deficits can cause blind vision.
The messages of the environment are perceived by the eye retina and sent through the optic nerve to subsequently diverge in two parallel pathways. One of these ways, the most archaic Cerebrally speaking, he goes to the subcortical structures, As the upper colliculus in the Brain stem. This structure manages to orient the eyeballs towards new stimuli in the environment that appear suddenly or protrude.
The newest way evolutionarily speaking is the one that projects the visual cortex where the characteristics of the object such as color or orientation are analyzed. From here, the information can be directed to the parietal lobes in which it is decided how the object is used or the temporal lobes, which are responsible for remembering or deciding “what is the object” according to the previous information stored.
Simply speaking, we could say that the information processed in the new ways is perceived as conscious, while the information of the most archaic ways can act in a way that seems independent of our conscious perception.
The blind vision would occur when there is a visual cortex damage. The information cannot be processed or sent to the temporal or parietal lobes, so there is no conscious perception of what we see. However, if the path that goes to the most archaic areas of the brain is intact, our senses can continue to unconsciously perceive the objects we have around. This is the so-called blind vision.
It may also happen that the visual cortex is intact, but the temporal lobe is damaged. This way the person could see but would be unable to know what he sees. This is the call, visual agnosia.
Links of interest
When Blindness Is in the Mind, Not the Eye. Vilaynur S. Ramachandran, Diane Rogers-Ramachandran. 2008 //www.scientificamerican.com/article/when-blindness-is-in-the-mind/
Neuroscientist brings light to the blind - and to vision research. Read Winerman 2012. //www.apa.org/monitor/2012/12/neuroscientist-sinha.aspx