That's much of a topology thing...our brain may be a CPU, but we have neurons throughout much of our body, processing extremely low level sensory inputs into richer information that brains can process at a higher level.

And different species have very different neural topologies: I've heard it described that Octopoda act more like an eight-member swarm intelligences than an intelligent eight-armed creature. Because their neural density is much more diffuse in their arms, they do so much more processing there, and the central brain acts more like a coordination unit than anything.