Here’s a nice depiction of the two streams hypothesis of the visual system from a talented artist on the autistic spectrum, with the cat’s eyes representing the visual cortex. In fact, the way this autistic artist operates through picture thinking is represented very well, as you can see here: http://autisticandawesome.wordpress.com/2012/08/05/the-visual-system-part-2/
Look at the painful description this person gives of reading text: “I hate learning that way, from big blocks of text with few pictures, the text separate from the pictures that the text describes. I hate textbooks. I hate their text, and I hate their pictures. Their text is long and boring, and their pictures are ugly and cluttered. It is hard for me to learn anything that I don’t already know from the text and pictures of a textbook.”
Follow this stream of consciousness back to the textbook I quoted extensively from in the previous post – and you’ll get a clue that our autistic artist has difficulty integrating the dorsal and ventral streams. More specifically, our artist’s self-description sounds like Dorsal Stream Dysfunction (DSD). Chapter 7 by Dutton et al explains why reading may be difficult due to crowding of the text, or complexity of the visual scene. Hence our artist’s whimsical and liberally spaced renditions. Dutton et al note that plus spectacle lenses which would normally not be prescribed based on acuity needs can help DSD patients with problems accessing text on the basis of crowding or clutter.
There’s a question that parents ask that’s been around as long as the TV itself: Why does my child insist on getting so close to the television? In some instances it’s due to uncompensated refractive issues, but in some cases it is due to a shallow dorsal stream. As Dutton et al note regarding DSD: “Seeing objects in the distance is difficult, as the further away things are, the more visual information there is in the scene. For this reason, children with dorsal stream dysfunction like to get very close to the television, presumably so that they can give visuial and auditory attention to the individual elements of a moving scene.”
You can read a great overview of Dorsal Stream Dysfunction and the DSD tree at this website: