I was recently interviewed about brain and city evolution by “Gladelic: A Quarterly Magazine of Intuitive Intelligence”. Here’s the beginning…
Mark, why have you chosen to focus your study on the neocortex (its importance in the aspect of human evolution) how did you come to comparing cities and brains?
Despite the brain’s complexity, our gray matter is essentially a surface, albeit convoluted in our case. Bigger brains expand the surface area of the gray matter, with only a meager increase in the thickness of gray matter. Cities, too, are surfaces, because they lie on the Earth. Our cortex has ample white matter wiring that “leaps” out of the gray matter to faraway parts of the brain, and these long-range connections are crucial to keeping the entire cortex closely connected. For cities, highways are the white matter axons, leaving the surface streets to efficiently connect to faraway spots. I began to follow these leads, and to flesh out further analogies: synapses and highway exits; axon wire thickness and number of highway lanes; axon propagation velocity and average across-city transit speed.
I found similar scaling laws governing how network properties increase as surface area increases. For example, in each case, the number of conduits (highways and white matter axons) increases as surface area to approximately the 3/4 power, and the total number of “leaves” (exits and synapses) increases as surface area to approximately the 9/8 power.
Despite the radically different kind of network, they are in some respects similar enough, and each has been under selection pressure over time to become more efficiently wired. The selection pressure for brains was, of course, natural selection, which involved lots and lots of being eaten. And the selection pressure for cities was teems of political decisions over many decades to steer a city to work better and better as it grew.
The rest of the interview is at Gladelic (half way down). More about my city-brain research can be found here: http://changizi.wordpress.com/category/cities-shaped-like-brains/
Mark Changizi is a professor of cognitive science at Rensselaer Polytechnic Institute, and the author of The Vision Revolution (Benbella Books).
