An individual ant is quite insignificant, but a large group of ants can do quite remarkable things. Likewise, neurons evolved to communicate with each other, and are quite useless except when connected to a network of other neurons.
I’ve always liked to use the ant colony as an anology for brain function. According to this article about swarm intelligence by Carl Zimmer, it may be more than just an anology:
By studying army ants — as well as birds, fish, locusts and other swarming animals — Dr. Couzin and his colleagues are starting to discover simple rules that allow swarms to work so well. Those rules allow thousands of relatively simple animals to form a collective brain able to make decisions and move like a single organism.
Deciphering those rules is a big challenge, however, because the behavior of swarms emerges unpredictably from the actions of thousands or millions of individuals.
This collective brain is capable of performing higher order computational processes, such that the ant colony is endowed with problem-solving and decision-making skills. This behaviour is decentralized – it is self-organizing rather than under the control of any individual within the group.
In his article, Carl discusses the work of Iain Couzin, a mathematical biologist at Princeton who builds computer models of swarms in order to better understand the collective behaviour of animals.
Such models can be applied in many practical situations. For example, Houston-based medical and industrial gas company America Air Liquide uses artificial intelligence software based on the collective behaviour of ants to determine the most efficient routes for delivering their products to 6,000 different locations.
Couzin and his colleagues are using their models to investigate decision-making in groups of people. The feedback observed between individuals in their experimental human swarms, Couzin says, resembles the decision-making mechanisms of the human brain.