Specialization extends down to single cells
From Ward, Sensation and Perception, 3rd edn., 1989
Center-surround receptive fields of retinal ganglion cells:
On-center cell: Sensitive to light falling in the center of the field
Off-center cell: Sensitive to light falling in the annular surround
Cell functions are specific
Cell functions are complex
Emergent behavior arises from large numbers of elementary functions