Information for Caregivers

How Blindness Effects the Brain

Blindness Affects the Structure of the Brain

Blindness has a significant impact on the structure of the brain. The brain has the ability to reorganize its structure to accommodate changes, which is also known as neuroplasticity. A prime example of the brain's potential for neuroplasticity can be found in individuals with blindness. One of the areas that is most severely affected in the brains of individuals with blindness is the visual cortex, more specifically, visual cortical neurons. When the eyes and brain are deprived of light, these neurons lose their dendritic spines (Breedlove & Watson, 2013). In addition, a reduction in synapses also occurs as a consequence of blindness (Breedlove & Watson, 2013).

Video: What is Cortical Visual Impairment

The following video provides an in-depth exploration of cortical visual impairment.


https://youtu.be/t4exCMip0_Y

Big image

Other Impacts on Brain Structure

Blindness not only leads to the rearrangement of neurons in the brain's visual systems, but in other systems as well. In the article by Lepore et al. (2010) the author's write that blindness impacts auditory systems. For example, they found a region of the auditory cortex to be twice as big in the brain's of blind individuals than of sighted individuals (Lepore et al., 2010). Furthermore, some research shows that the systems usually used for visual processing may be used for auditory and tactile purposes in blind individuals (Lepore et al., 2010).


Follow this link to the article by Lepore et al., which contains useful information of how blindness affects the brain: http://www.ncbi.nlm.nih.gov/pubmed/19643183

A Comparison: Brain development of Sighted vs. Blind Individuals

Differences in Brain Function

One of the most significant ways in which the brain of a blind individual develops differently than sighted individuals in how different regions of the brain are used. For example, in sighted children the visual cortex is used excessively for processing visual images. However, in some blind children this same region has developed to process language (Lepore et al., 2010). In other words, the brains of some blind children demonstrate impressive neuroplasticity by modifying the function of the visual cortex to include the processing of non-visual tasks.

Video: Looking Inside the Adaptive Brain of the Blind

The following video discusses the brain's ability to reorganize itself in the case of both ocular blindness and blindness caused by damage to the visual cortex.


https://videocast.nih.gov/Summary.asp?File=19243&bhcp=1

Differences in Brain Connectivity

One of the connective differences in blind and sighted individuals relates to axonal connections in the visual cortex. For example, sighted individuals have three main connections stemming from the visual cortex to the rest of the brain ("NIH", 2016). Each of these connections has a different function, they are: spatial processing, object processing, and attention processing ("NIH", 2016). However, in individuals with cortical visual impairment or CVI, the object processing connection is present and intact, but the other two, spatial and attention, are missing ("NIH", 2016). Interestingly, individuals with ocular blindness not only have all threes connections intact, they also show a hyper connectivity, which may be the process that underlies compensatory behavior in the visual cortex (e.g. the visual cortex functioning to process language or auditory information) ("NIH", 2016).


The National Institutes of Health websites features an interesting article on neuroplasticity as it relates to blindness: https://obssr.od.nih.gov/neuroplasticity-in-blindness-what-it-tells-us-about-the-mechanisms-of-blindness/

Differences in Brain Structure

Differences in brain structure exist between sighted and blind individuals. For example, visual regions of the brain are smaller in volume in blind individuals than in sighted ones ("University of California - Los Angeles", 2009). Conversely, non visual areas, such as the frontal lobes, are larger in the brains of blind individuals than sighted individuals ("University of California - Los Angeles", 2009).
Big image

References

University of California - Los Angeles. (2009, November 19). Blindness causes structural brain changes, implying brain can re-organize itself to adapt. ScienceDaily. Retrieved June 8, 2016 from www.sciencedaily.com/releases/2009/11/091118143259.htm


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



Neuroplasticity in blindness: what it tells us about the mechanisms of blindness. (2016). NIH: Office of Behavioral and Social Science Research. Retrieved from https://obssr.od.nih.gov/neuroplasticity-in-blindness-what-it-tells-us-about-the-mechanisms-of-blindness/


Merabet, L.B. (2015). Looking inside the adaptive brain of the blind [Video File]. Retrieved from https://videocast.nih.gov/Summary.asp?File=19243&bhcp=1



Perkins School of the Blind. (2015, October 2) Part 2: Cortical/Cerebral Visual Impairment - What is it? with Darick Wright and Barry Kran. Retrieved from https://youtu.be/t4exCMip0_Y