What is blind vision?

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Jonah Lester
What is blind vision?

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 objects and the place where they are, as if they could somehow process this information. It is an interesting phenomenon called: blind vision. A phenomenon that we will explain in detail below.

Contents

  • A case of blind vision
  • Understanding what blind vision is
  • Brain pathways involved in blind vision
    • Links of interest

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. As a result, Ricardo is unable to see anything. When conducting an exam, professionals ask him if he is able to see an object that they are holding in front of him. It 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 as if he were seeing it. We'd 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, in a non-conscious way, even though the ability to visualize is impaired.

We have always assumed that blindness is a lack of vision caused by the malfunction of a single visual processing pathway: the visual cortex, located in the occipital lobe. Today, however, we know that there are more than 30 areas in the primate and human brain that are involved in vision processing, specialized in components as diverse as color, depth or movement. Vision is much more complex than scientists themselves previously imagined.

For this reason, when some of these areas involved in visual processing are damaged, selective vision problems occur. Distortions in vision that are not necessarily linked to an eye problem or a problem in the visual cortex that produces a visualization deficit.

Although it may seem strange to us, what we think we consciously see 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 capable, on the contrary, of correctly perceiving and processing what they see, that is, they know that they see something, but they cannot know what it is or what what they see implies. as some of these different areas of visual processing are damaged. These people arguably 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 which 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 ocular retina and sent through the optic nerve to later diverge in two parallel pathways. One of these pathways, the most archaic cerebrally speaking, goes to the subcortical structures, such as the superior colliculus in the brainstem. This structure manages to orient the eyeballs towards new stimuli in the environment that appear suddenly or protrude.

Evolutionarily speaking, the newest way is the one that projects to 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 to the temporal lobes, which are in charge of remembering or deciding "what the object is" according to the previously stored information..

Simply speaking, we could say that the information processed in the new pathways is perceived as conscious, while the information in the more archaic pathways can act in a way that seems independent of our conscious perception..

Blind vision would occur when there is damage to the visual cortex. 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 around us. This is the so-called blind vision.

It can also happen that the visual cortex is intact, but the temporal lobe is damaged. In this way the person could see but would be unable to know what he is seeing. 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 https://www.scientificamerican.com/article/when-blindness-is-in-the-mind/

Neuroscientist brings light to the blind - and to vision research. Lea Winerman. 2012. https://www.apa.org/monitor/2012/12/neuroscientist-sinha


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