ABSTRACT
This chapter aims to change the reader's mental schema regarding the brain from "terra incognita" to "terra cognita", because the development of a meaningful mental schema of the brain is needed to assimilate research findings on brain functioning. One of the earlier models of brain structure in the twentieth century was proposed by a former US National Institute of Mental Health Brain and Behavior Lab Director, Paul MacLean. He hypothesized that the human brain was "triune," with three structural levels that evolved separately over time. The communication functions of the brain are carried out by the neurons, each of which is composed of a cell body, one axon, and a number of dendrites. Neurons are not attached to each other; rather, there are gaps between the axon and dendrites of each neuron, which are called synapses. The brain is composed of the nerve cell bodies, the fibers, the glia, and the blood vessels.
