Milner, David & Goodale, Melvyn first proposed that
the visual system splits into a dorsal and a ventral systems.
Studying the difference between these two functional roles of the visual system, the French neurologist Marc Jeannerod had advanced the theory that there are two information processing systems for visual input: the "semantic processing system" (that yields a perceptual representation of the object) and the "pragmatic processing system" (that yields a motor representation of the same object).
The "dorsal" visual system that is common to most animals helps the animal carry out the orienting function: to detect movement (typically, either danger or food) and to guide action. The ventral visual system of the human brain is relatively distinct from the dorsal system and is related to the "semantic processing system" that analyzes and "recognizes" the object. This allows the human brain to carry out more sophisticated actions in response to a visual act. Human vision therefore originated when the functions of orientation and identification got separated.
TM, ®, Copyright © 2005 Piero Scaruffi