When the psychologist Stephen Pinker was on the TV show The Colbert Report in 2007, Stephen Colbert insisted that he explain, in five words or fewer, how the brain works. Pinker's brilliantly concise response was “Brain cells fire in patterns.” Neurons are different from the cells that make up other bodily organs in that they build up electrical charges; they can pass these on to other neurons that are connected to them. Firing is a kind of electrical discharge. The flow of electrical charge in neurons is only a few millivolts, compared to as much as a billion in lightning flashes, and also differs in being directed along pathways formed by the thousand or so connections that a neuron has with other neurons. These connections are called synapses. Figure 3.1 depicts how one neuron can send messages in the form of electric signals to another neuron by means of synaptic connections.