The eyes are very important to humans as it helps to identify distance, predict sizes, read, view and perform other ocular functions in the body. Basically, the eyes are the organ that allows us to see. Humans are visual creatures, and many parts of our body, work with the eyes to function properly, as the eyes help in bringing objects into focus, and depth perception, and enable the brain to identify different visual information.
Talking about the eye sending visual information to the brain and allowing the brain to identify visual information, the visual cortex is responsible for this. The visual cortex is the main cortical region that receives, and processes visual information in the brain, from the retina in the eyes. What happens when the eyes aren't functional, and a person is blind, how does the brain respond, affecting other parts of the body? Have you tried working in the dark? You have to start counting steps, else fall after slipping while walking. You start to ask yourself, how does my brain function without my eye for sight. I was talking to a person who was born blind, he told me he doesn't identify any color, and doesn't known if what he sees is color black. While he wasn't using his eyes, his earing sense was very great. I started to wonder if the loss of sight, allowed for other senses to be heightened. As I continue this post, we will understand why he had a more heightened hearing sense, when his sight was no more.
WIth sight, there are different views, the left visual field, and the right visual field. The right field of the eye will send visual signals to the left side of the eye, and the right visual field of the eye will send signals to the left side of the eye. These angles pick the sides of both the right and left eyes overlapping. The light ray or photons within the light spectrum will hit the retina of the eye. The retina which is made up of photoreceptors Rods and Cones, with Rods detecting low light sensitivity, while the cones detecting high light sensitivity and color. This photon is transduced to sodium potassium neurotransmitter which will be sent to the brain as signals through the optic nerve, and then meet at the optic chiasm, then to the optic tracts where it goes into the brain. In the brain, it reaches the Thalamus, in the Lateral geniculate Nucleus of the Thalamus, where part of the visual processing takes place, from the Lateral geniculate Nucleus of the Thalamus, the signals are sent to the Visual cortex at the back brain (Occipital lobe). The visual cortex is made up of five layers ranging from V1, V2, V3, V4, and V5, with V1 being the primary visual cortex (straite area). the V1 is the visible area of the brain that is attributed to vision, other parts are viewed via microscopy. When visual information gets to V1, it is sent to V2, which then triggers V3, V4, and V5, to enable and interprete visual information.
Neuroplasticity is the ability of the brain to its structure and function, increasing or decreasing the amount of receptors on neurons that binds to neurotransmitters in the brain, as wells as weakening or strengthening the synapses in the brain which allows for the transmission between two or more neurons. With this, can we say that it is possible for the brain to change its structure and function when it has to do with blindness. With blindness, no matter how it comes, either as a result of cortical blindness, damage of the visual cortex, brain tumor affecting the retina, optic chiasma, or optic nerve leading to different types of blindness, causing the brain to start responding to the blindness. When a person goes blind, the brain undergoes neuroplasticity where the brain starts to change its structures and functions. You must have heard that when one sense is lost, other senses become heightened. With visual character, there are two types of plastic changes that occur in the visual cortex, known as Cross-Modal plasticity, which is where there are changes in the structure of the visual cortex, improving hearing, and tactile sensations. This will improve the hearing process as well as feeling process of the person who is blind. The second type of plastic change in the visual cortex is the multimodal plasticity which involves the use of previously existing pathways in the brain for visuals which aren't working anymore for other purposes, improving hearing and tactile sensation. This means that the brain doesn't leave any part of itself without use, so when the brain isn't functioning for visual purposes, it changes itself or uses the pathway for vision to improve other senses.
https://www.sciencedirect.com/topics/neuroscience/visual-pathway
https://www.kenhub.com/en/library/anatomy/the-visual-pathway
https://www.allaboutvision.com/eye-care/eye-anatomy/photoreceptors/
https://www.sciencedaily.com/releases/2009/11/091118143259.htm
https://www.sciencedaily.com/releases/2018/12/181219115622.htm
