Wiring Optimization in the Brain

The complexity of cortical circuits may be characterized by the number of synapses per neuron. We study the dependence of complexity on the fraction of the cortical volume that is made up of "wire" (that is, ofaxons and dendrites), and find that complexity is maximized when wire takes up about 60% of the cortical volume. This prediction is in good agreement withexperimental observations. A consequence of our arguments is that any rearrangement of neurons that takes more wire would sacrifice computational power.