Areas of the brain involved in visual function
-By Timothy Lyons
There are three main Areas of the brain involved in visual function and in the processing of visual information. These areas are known as the lateral geniculate nucleus (LGN), the striate cortex (SC) and the extrastriate cortex (ESC). The latter two are also known as the visual cortex which is a part of the cerebral cortex (Dragoi & Tsuchitani, 2007) the LGN is a layered structure. It has six main layers of cells. Each layer responds to only one eye. Thus they are considered to be monocular.
The LGN is the main area for input of visual information from the retina. This is the main connection between the optic nerve and the occipital lobe. The SC handles information dealing with visual information and visual perception. The SC is also known as the primary visual cortex. The extrastriate cortex encompasses the entire area of the occipital lobe around the primary visual cortex. The ESC is an area that deals with many purposes. This area deals with motion and is part of the manner in which recognition of motion of the human body takes place (Carson and Birkett 2017; Dragoi & Tsuchitani, 2007).
Problems from damage to areas of the brain involved in visual function
If there is damage or lesions done to the LGN in the brains of humans, problems follow. Lesions in this area results in total vision loss in the part of the field of vision that is opposite that of the area in which the lesion occurred (Dragoi & Tsuchitani, 2007).
The Damage to the area of the ESC can cause a number of problems. First this area is where most color is perceived. Lesions in this area can lead to perceptual deficits such as the failure to recognize objects, the loss of the ability to see colors and the inability to see the movement of objects (Carson & Birkett, 2017; Dragoi & Tsuchitani, 2007). The examples from (Carson & Birkett, 2017) include animals with impaired ability to differentiate colors but who could still see black and white and humans whose damage lead them to see only in black and white and also had no ability to recall what colors looked like. There is also an example of damage that caused an inability to recognize any object while maintaining the ability to tell what color the unidentified object was. Further some damage to this area can result in the inability to read, the inability to identify object while being able to still grab them and even the inability to recognize faces.
According to (Carson & Birkett, 2017) damage to areas in the SC can result in the inability to perceive spatial location orientation and movement. In one case a woman with damage to certain areas was able to see lines of objects but was had great difficulty in picking them up. In another case with animals, damage to these areas lead to the animal not being able to perceive movement in objects such as other animals. Examples of damage in other areas within this same parts of the brain have been responsible for akinetopsia or the inability to see movement and some persons were able to see movement but could not see where things were heading. In one case a person was unable to compensate for the role of the movement of the eyes in vision so that when he moved his eyes the world appeared to move backward.
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