The Occipital Lobes and Their (Dys)Function
Because the occipital lobes are located at the back of the skull, they are not as frequently injured as other parts of the brain. However their role is extremely important when it comes to the survivor’s vision or lack thereof. Essentially, this region of the brain is the visual cortex–the portion concerned with all things visual.
The curious thing about the occipital lobes is that no matter which side of is damaged, the field of vision is affected more or less equally on both sides. Unlike the frontal or parietal lobes, where injury to one side or the other has a greater effect on either motor movement or some other ability, any significant injury to the occipital lobes produces more or less a unified change in vision.
And although the occipital lobes aren’t frequently injured, any significant trauma to the brain can cause a drastic change in vision or the prevalence of scotomas–or blind spots–in the field of view.
“The Peristriate region of the occipital lobe is involved in visuospatial processing, discrimination of movement and color discrimination (Westmoreland et al., 1994).”
Visuospatial processing is like misjudging how far away you are from the doorjam when going through it. Discrimination of movement and color discrimination are both kind of self-explanatory, but an example of discriminating movement is like when you are looking at something far-off about dusk or in the dark, and you don’t notice it moving. That’s when I have noticed this challenge. For those with more pronounced deficits to the occipital lobes, the problems may be exacerbated. For the color discrimination, that’s simply not being able to tell the difference between different shades or hues. Like navy blue and black, charcoal and gun-barrel gray, etc… My wife would say that I have serious problems in this area–I can’t tell the difference between bone, eggshell, ivory or off-white, even though she says she can. I have to take her word for it, because I seriously can’t tell.
If the occipital lobe is damaged, it can cause visual hallucinations and illusions. To differentiate, hallucinations occur when their is not external stimuli, while illusions may take the form of specific objects the survivor sees, but there is a change in either the size of the object or of its color. Additionally, there may be problems with “word blindness,” or alexia–the inability to understand the written word–when the occipital lobes sustain injury.
While the occipital lobes are located in the back of the skull and don’t get injured as often as the frontal lobes or the parietal, they are extremely important regarding all things visual–damage to this area of the brain can produce significant problems for the BI survivor.