Blindness & Brain Structure

Why is brain structure different in the blind?

The Visual Cortex and Changes in Brain Structure.

In those who have eyesight the visual cortex in the brain is stimulated by the things they see. The eyes relay the images to this area of the brain, this area then analyzes the images and determines what it is they are looking at based on experiences. Below is a quick video that gives an overview of the visual pathway in sight-seeing people.


In the blind, this area of the brain is not stimulated by images from the eyes, as the eyes cannot see. It is stimulated instead, by other senses (touch and hearing) used by the blind to judge their surroundings. The normal areas for these senses also have grown to compensate for the lost sense of sight (University of California, 2009). It reorganizes itself to accommodate for the loss of a sense (University of California, 2009). Amazing!


Studies show an enlargement of the core areas of the auditory cortex and other studies show an increase in size of the "planum temporale (an area behind the auditory cortex important in language and music processing) in blind musicians with absolute pitch than those sighted with the same skill" (Hirsch, Bauer, & Merabet, 2015, p. 4).


It is believed that the structural changes that occur in those who are blind is due to the increased reliance on non-visual senses and as a result, "this structural plasticity appears to be associated with non-visual sensory skills within the context of behavioral

compensations" (Hirsch, Bauer, & Mirabet, 2015, p. 5).

Educational Video on The Vision System - Diopsys

Does it matter at what age a person goes blind for changes to occur?

Studies show that depending upon how early or how late blindness occurs, structural changes may be different. "Only the early-blind group differed significantly from the control group in an area of the brain's corpus callosum that aids in the transmission of visual information between the two hemispheres of the brain" (University of California, 2009). Myelination reduction is thought to be the culprit in the reduced volume in certain parts of the brain when a person is blind before the age of 5 (University of California, 2009). The below video explains blindness and the brain.
Can We Restore Sight For The Blind?
Understanding Blindness and the Brain (Brian Wandell, Stanford University)

The blind can see?

Yes. As a matter of fact they can! Just not with their eyes. Some people who are blind use different techniques to gain information about the world around them. The video posted below is an example of a man using echolocation to verify the spaces around him. Pardon the pun, but guess this could be coined "blind as a bat"? In all seriousness, the changes his brain had to make in order for echolocation to be this great of a tool is just awe-inspiring.
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Technological Advancements Helping the Blind Actually "See"

Technology can be such a wonderful thing. As the age of technology advances we are finding out more and more that it is capable of. We have gone from prosthetic limbs to prosthetic/bionic eyes that very well could enable the blind to have visual capabilities.


"The experimental device is made by a company called Second Sight in Santa Clarita, California. It now consists of miniature camera attached to a pair of glasses that sensds a signal to a wireless receiver planted behind the patient's ear. The signal then goes through a tiny wire implanted under the skin, into the eye to an electronic chip attached to the retina itself" (Hreff, 2015, para. 5). If you would like to read more about how the bionic eye glasses work please click the link below.

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References


Educational video on the vision system. (2009). Diopsys. Retrieved from www.youtube.com.


Hirsch, G. V., Bauer, C. M., & Merabet, L. B. (2015). Using structural and functional brain imaging to uncover how the brain adapts to blindness. Annals of Neuroscience and Psychology, 2(5), 1-11. Retrieved from http://www.researchgate.net/publication/281716740_Using_structural_and_functional_brain_imaging_to_uncover_how_the_brain_adapts_to_blindness.


Hreff, Z. (2015). Eye camera may help the blind see. ABC News. Retrieved from http://abcnews.go.com/Technology/CuttingEdge/story?id=97825&page=1.


Kish, D. (2015). How I use sonar to navigate the world. Ted. Retrieved from http://www.ted.com/talks/daniel_kish_how_i_use_sonar_to_navigate_the_world#t-22964.


University of California.(2009). Blindness causes structural brain changes, implying brain can re-organize itself to adapt. ScienceDaily. Retrieved from www.sciencedaily.com/releases/2009/11/091118143259.htm.


Sanford, K. (2015). Can we restore sight for the blind? [video] DNews. Retrieved from www.youtube.com.


Wandell, B. (2009). Understanding blindness and the brain. [video] Stanford University. Retrieved from www.youtube.com.