visual patterns = shape of the visual network architecture

Cave art and acid trips: The math they didn't teach you in school | WBEZ:

"Basically, as excitation ripples through our neural networks, it makes actual patterns in there – often stripes or a regular series of blobs – of firing or resting neurons. Then, because of the way our visual network is designed, those patterns appear to our eyes as spirals, funnels and tunnels, honeycombs or cobwebs. In fact, those four patterns seem to be pretty much it: Our brain architecture is capable of producing only variations on those four themes."