Magnocellular (“magno” for short) deficit is related to dyslexia. The magno cells are associated with processing and detecting movement of stimuli coming through your retina. In autopsies of dyslexics and non-dyslexics, the former has a smaller cluster of magno cells that can bring in rapidly changing information. Because of this, images would tend to clump together and an activity like reading proves to be extremely difficult; the brain simply cannot parse out the many images (of text) going into your eyes. Without clean breaks between one word to the next, the words on a page seem to shimmer and jump on a page. It is not surprising to find that people who are dyslexic also do not like crowds or places with lots of movement – city streets, for example, with its many moving cars and people.
Parallel pathways of magno (fast-processing) and parvo (slow-processing) cells
In The User’s Guide to the Brain (page 105) by John J. Ratey, a researcher gives her story of how hard it was for her to believe that her mother is a dyslexic.
No, it couldn’t be, I thought to myself. My mother couldn’t possibly be dyslexic. She had graduated at the top of her class, she’s a perfectionist, and she absolutely loves to learn. How could she of all people be dyslexic?
We often do not realize that dyslexia can happen to anyone, and that being smart and motivated does not mean that it is easy to read. Reading, after all, is not an innate ability. Humans are not born knowing how to read but we certainly are capable of doing so. Dyslexia does not equate the lack of intelligence.