Way back in 1997, in a textbook I edited on Applied Concepts in Vision Therapy, I indicated that the notion of dual visual processing systems had a certain yinyang feeling to it. As pointed out by Maunsell, the notion of dual processing is typically attributed to Trevarthen, a developmental psychobiologist. Trevarthen’s notions were heavily influenced by Roger Sperry, well-known for his experimental work with split-brain patients. As an interesting aside, Trevarten’s interests ultimately led him to significant work in the field of Autism.
Dual system theories were extended in the ’70s and ’80s by Ungerleider and Mishkin into distinct physiologies for ambient and focal vision and by Milner and Goodale as dual action streams for perception and action, originally conceived as dorsal and ventral streams of vision. Different iterations of these concepts have been applied to Optometry by Padula, Garzia, Solan, and Groffman.
In multiple conversations with Dr. Marie Marrone, a former SUNY Resident in Vision Therapy, we explored how these dualities are reflected in the balance between central and peripheral awareness. I was reminded of this duality today while reading a very nice discussion paper which begged the question as to how independent our visual streams are for perception and action. I think you’ll enjoy reading it: The Illusion of Independent Visual Streams – Cognitive Neuroscience 2010
– Leonard J. Press, O.D., FCOVD, FAAO