What is it about the human brain that allows it to be the basis for all the complexities of the human mind, including not only language, reasoning and memory but emotion and intuition as well? How can this apparently small organ, weighing an average of three pounds, effortlessly accomplish many tasks, such as face and voice recognition, that are quite difficult for extremely sophisticated computers?

The basis for all these remarkable accomplishments is the great complexity of the connections between the elementary units that make up the brain – the neurons, or nerve cells. First of all, there are billions of neurons in the brain. Second, each individual neuron makes contact with about ten thousand other neurons, so that the actual number of connections between the neurons in the brain is astronomical.

Moreover, there are at least two different levels of connections involved. The brain can be subdivided into a number of modules – large-scale units consisting of some tens or hundreds of thousands of neurons. We do not know exactly how many such modules there are, but a fair estimate would be on the order of hundreds. Within each of these modules all the neurons are connected with all the other neurons, either directly or at one or two removes. It is because of the intricate connections among the individual neurons in each module that we call the modules neural networks.

How do these modules work?

Each module or network of this sort is responsible for one aspect or stage of some particular mental process, such as recognizing familiar faces or finding the right words for the sentences you are planning to say.