Behave: The Biology of Humans at Our Best and Worst

by Robert M. Sapolsky

What can neuron 1 learn? How to recognize that particular guy. Neuron 5 is equally specialized. But what can neuron 3 learn? How Victorian gentlemen dressed. It’s the neuron that will help you identify the Victorian in the quartet below: Neuron 3’s knowledge is general and comes from the overlap of the first layer’s projections. Neurons 2 and 4 are also generalist neurons, but they’re less accurate because they have only two exemplars each. So neuron 3 is at the convergent center of this network. And the fanciest parts of the brain are wired up in a way that resembles this fairy-tale circuit, writ large—at the same time, neuron 3 is a more peripheral element in some other circuit sending projections to it (say, a circuitry that would be drawn perpendicular to this page), neuron 1 is at the very center of some other network in the fourth dimension, and so on. All of these neurons are embedded within multiple networks.