ABSTRACT
Neurons connect together to form networks. The operation of neural networks, even those containing just a few distinct types of nerve cell, is poorly understood in general. This is arguably the most serious problem for contemporary neuroscience because large regions of the nervous system (e.g., the cerebral cortex) apparently consists of the same circuit repeated millions of times. How the same circuit serves functions as diverse as those of the cerebral cortex is currently a mystery. The scale of the difficulty is illustrated by Caenorhabditis elegans, a small nematode worm. This animal has just 302 neurons and the circuit diagram of its nervous system is completely known virtually down to the last synapse. Although some aspects of its behavior are beginning to be understood in terms of its network operations (e.g., chemotaxis) most of its behavior cannot yet be modeled.
