Elaboration of neural networks: trend toward cephalization: cephalization: Very diffuse, it is the one type of organism that has neurons that are bi-directional: getting a bit more sophisticated. Flatworm: there is a brain developing which allows for. Centralization of sensory reception: we have multiple ganglion that control and centralize, a place to take in information and integrate it to. Cephalpod control the body: nerve core also the ability to have communication between the nerve core. Left side and right side of the body is able to communicate. Annelid: same thing as flat worms, we have an area of centralization, we now have ganglions that run along the body of the worm. Echinoderms: have 5 area where they have ganglion. Chordates: has a brains a core that distributes signal, well developed cranium, nerve cores and ganglion down the body. These are the simplest forms because their neurons not specialized (can function as sensory, interneurons, or efferent).