They regulate basic functions such as sleep and wakefulness and are essential for life itself. In mammals such as the mice used in the Cornell work, the largest area of the brain, the cerebral cortex, overlays this region. The cortex, a convoluted mass of cells, modulates just about everything beyond basic body regulation, especially integration of all the body functions and the more mysterious activities of intelligence, consciousness, and mind. Based on extensive research on victims with head injuries, neurobiologists also know that the brain can be roughly divided into areas that correspond to certain functions. Because of this specialization, damage to cells and tissue in those are-as alters the brain's ability to responds appropriately to that type of stimulus.
Brain tissue is made up of billions of tiny cells, called neurons or nerve cells.
Chemical and electrical signals pass among these neurons and are responsible for everything the body does, everything from thought to movement. Some of these fingers are dendrites, filaments that receive messages from other neurons. Other filaments are axons, which carry signals away from the cell to other cells. Together, the dendrites and axons make up a network that can relay signals throughout the brain and all over the body. Thus the wiring of the brain echoes that of an electronic circuit, but it is much more complex.