Blindness and Brain Changes
By: Kara Pengelly
Visual Cortex and Neuroplasticity
In the case of someone experiencing blindness, the portions of the brain that would normally be used to process visual stimuli do not receive the input from the optic nerve. In many cases, a loss of mass in the portion of the brain that utilizes visual stimuli is experienced, but that does not mean that these portions of the brain do not try to adapt and function in a productive manner (Lepore, et al, 2010). For example, a study conducted by UCLA, it was found that the the visual cortex in blind people is active during touch-based reading, whereas this portion of the brain remains inactive in people of normal vision (Mind Hacks, 2007).
A person's ability to adapt to new experiences relates to the degree of neuroplasticity present within his or her individual brain. As the person ages, neuroplasticity is gradually lost, which means that the younger a person is, the better the probability that he or she will be able to adapt to the loss of vision, and will see would-be dormant portions of the brain share in the "workload" of the rest of the brain. Additionally, the volume of the brain that is lost also varies based upon the age of onset (Lepore, et al, 2010).
This image shows the areas of excess and deficit of brain volume for patients who presented with early-onset blindness (Lepore, et al, 2010).
Early- vs. Late-Onset Blindness
The occipital brain region shows differences in the brain structures associated with early- and late-onset blindness (Lepore, et al, 2010).
This image shows the excess in non-occipital white matter by volume (Lepore, et al, 2010).
Early- vs. Late-Onset Blindness
Heightening of Other Senses
Examples of the restructuring include a blind person's ability to locate windows due to a change in temperature, or perceive a person standing outside his or her former line of vision by using sound and a heightened sense of echolocation. Similarly, babies who are born blind exhibit extra hand movements and slapping motions to use sound and touch as a way to navigate their world (Osborne, 2015).
This ability does come at a bit of a cost, however, in the instance that vision an be restored. Over time, the brain re-wires itself to operate as normally as possible in the absence of vision. As such, the brain may resist efforts to restore vision, and even when the efforts are successful, the patient may expect the process to take time before vision is fully restored (Bates, 2012).
For more information about how blindness affects the structure of the brain, explore the following links:
Bates, M., (2012). Super powers for the blind and deaf. scientificamerican.com. Retrieved on March 16, 2016 from http://www.scientificamerican.com/article/superpowers-for-the-blind-and-deaf/
Leporé, N., Voss, P., Lepore, F., Chou, Y.-Y., Fortin, M., Gougoux, F., Thompson, P. M. (2010). Brain Structure Changes Visualized in Early- and Late-Onset Blind Subjects. NeuroImage, 49(1), 134–140. http://doi.org/10.1016/j.neuroimage.2009.07.048
Mind Hacks (2007). The unique construction of the blind brain. mindhacks.com. Retrieved on March 16, 2016 from http://mindhacks.com/2007/04/12/the-unique-construction-of-the-blind-brain/
Osborne, M. (2015). How does becoming blind affect other senses? livestrong.com. Retrieved on March 16, 2016 from http://www.livestrong.com/article/268986-how-does-becoming-blind-affect-other-senses/
University of Texas (n.d.). The primary visual cortex. cs.utexas.edu. Retrieved on March 16, 2016 from https://www.cs.utexas.edu/users/nn/web-pubs/sirosh/pvc.html