Page 49 - Artificial Intelligence in the Age of Neural Networks and Brain Computing

36 CHAPTER 2 Mind, Brain, Autonomous Agents, and Mental Disorders

FIGURE 2.3
A model macrocircuit of an emerging unified theory of visual intelligence. Its processing
stages begin at the retina and end in the prefrontal cortex, and include both the What and
the Where cortical processing streams. The bottom-up, horizontal, and top-down
interactions between model processing stages are needed to overcome the computational
weaknesses that each processing stage would experience if it acted alone, due to
complementary computing.

4. THE WHAT AND WHERE CORTICAL STREAMS ARE
COMPLEMENTARY

The category learning, attention, recognition, and prediction circuits of the ventral,
or What, cortical processing stream for perception and cognition [9,10] are compu-
tationally complementary to those of the dorsal, or Where and How, cortical
processing steam for spatial representation and action [9e11]. One reason for
this What-Where complementarity is that the What stream learns object recognition
categories that are substantially invariant under changes in an object’s view, size, and
position. These invariant object categories enable our brains to recognize valued
objects without experiencing a combinatorial explosion. They cannot, however, locate