BLINDNESS CHANGES BRAIN STRUCTURE

See How Here

Brain structure

The brain has plasticity. Because of this ability to change, blindness can cause the structure of the brain to change. It causes other senses to be heightened by using the area that is normally for sight for other sensory signals. Coordination is different in seeing people than in blind people. Obviously hand-eye coordination would not be useful to someone who could not see.They end up developing memory-hand coordination. People are able to be taught to "see" images through sound, even though they are blind. The brain can do some pretty amazing things.

How should vision work?

  • rays of light are processed through the cornea
  • to the aqueous
  • to the pupil
  • to the lens
  • to the vitreous
  • rods and cones in the retina then receive the light
  • rays begin to be processed
  • light energy causes chemical changes in the retina
  • those cells then produce electrical activity
  • ganglion cells detect edges, color or shadows
  • nerve fibers from the retina cells join together to form the optic nerve
  • Most projections from the retina travel through optic nerve to the thalamus into the lateral geniculate nucleus
  • each optic nerve meets at the optic chiasm
  • medial nerves of optic nerves cross
  • lateral nerves stay on the same side
  • overlap of nerve fibers allows for depth perception.
  • electrical impulses are sent to the visual cortex through the optic nerve
  • The optic nerve sends information via the thalamus to the cerebral cortex
  • visual cortex processes electrical impulses
  • files the information for future reference or sends a message to a motor area for action

(Murray, n.d.)

Science Bulletins: Brains Process Sounds into Sight

Brain development differences in blind people

  • plasticity allows other sensory input to be processed in usual vision processing location
  • visual cortex is in use when people are engaged in auditory and tactile tasks "That tells us that the visual cortex in the blind takes on these functions and processes sound and tactile information which it doesn't do in the sighted. The neural cells and fibers are still there and still functioning, processing spatial attributes of stimuli, driven not by sight but by hearing and touch (Georgetown University Medical Center, 2010)."
  • sensory inputs go to unused portions of the brain in the blind
  • larger frontal lobe (University of California - Los Angeles, 2009)
  • sensory substitution occurs
  • smaller splenium
  • larger isthmus
  • larger non-occipital white matter
  • larger hippocampus
  • reduced gray and white matter volume in primary visual areas
  • less volume in cingulate region
  • greater volume in cerebellum
  • deficits in prmary and secondary visual cortices (Leporé, Voss, Lepore, Chou, Fortin, Gougoux, Lee, Brun, Lassonde, Madsen, Toga,& Thompson, 2010)
Pawan Sinha on how brains learn to see
Understanding Blindness and the Brain (Brian Wandell, Stanford University)

References

Georgetown University Medical Center. (2010, October 10). People blind from birth use visual brain area to improve other senses: Can hear and feel with greater acuity. ScienceDaily. Retrieved December 2, 2015 from www.sciencedaily.com/releases/2010/10/101006131203.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


Murray, M. (n.d.). Our Sense of Sight. Retrieved from https://faculty.washington.edu/chudler/eyetr.html


University of California - Los Angeles. (2009, November 19). Blindness causes structural brain changes, implying brain can re-organize itself to adapt. ScienceDaily. Retrieved December 1, 2015 from www.sciencedaily.com/releases/2009/11/091118143259.htm