By Lisa Van Cleve
Blindness and Brain Structure
Affected Brain Structures
- Visual cortex can change from processing visually to processing language (Massachusetts Institute of Technology, 2011).
- Auditory cortex is almost twice the size as compared to most sighted individuals (Lepore, 2009).
- White matter in visual and somatosenory areas is also increased (Lepore, 2009).
- Myelination in the corpus callosum is also affected depending upon early versus late onset of blindness (Lepore, 2009).
- Increased volume in the cerebellum (Lepore, 2009).
(Above) Visual Pathway in the Brain
What this means...
When a person is blind, non-visual areas of the brain can increase and even take on different functions as a possible way to compensate for reduced areas normally devoted to vision. This kind of compensation is particularly evident in young children as gain or loss of brain matter depends on when blindness occurred (University of California, 2009). Affected areas of the frontal lobe might be the reason for enhance skill dominance in certain areas.
Research has found that the occipital lobe is also active with hearing, smell, and touch sensations.
Vision development of sighted individuals
- Can only focus on objects 8-10 inches from the face at birth.
- Tracking or moving of the eyes and eye-hand coordination at 8 weeks.
- Depth perception and decent color vision around 5 months of age.
- Can perceive distances well and throw things with precision between 9-12 months.
- (American Optometric Association, 2015)
Above is about a man named Paul who was born prematurely and lost his vision shortly after birth. This is his account of how he and others who are blind do not see a world of darkness but a functional spatial map. They visualize as others can see, with the lack of color. Sounds and echoes help generate the spatial map and give the ability to navigate their world.
Vision Development in those with Blindness
- During sensitive periods, the brain can re-wire itself to adapt to the lack of function, showing great plasticity of the brain, called cross-modal plasticity.
- Visual cortex is taken over by other senses.
- Increased blood flow to areas with greater brain activity, such as the auditory cortex.
- Brain is made-over to allow adaption to the environment.
- (Bates, 2012)
- Lepore, N., Voss, P., Lepore, F….Thompson, P. M. (2009). Brain structure changes visualized in early- and late-onset blind subjects. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2764825/
- MassachusettsInstitute of Technology. (2011, March 1). Parts of brain can switch functions: In people born blind, brain regions that usually process vision can tackle language. ScienceDaily. Retrieved March 16, 2016 from www.sciencedaily.com/releases/2011/02/110228163143.htm
- University of California - Los Angeles. (2009, November 19). Blindness causes structural brain changes, implying brain can re-organize itself to adapt. ScienceDaily. Retrieved March 16, 2016 from www.sciencedaily.com/releases/2009/11/091118143259.htm