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.