Understanding the Brain

This lecture covers the overall organization of the brain and spinal cord and defines important terms and concepts, focusing on areas of the central nervous system that can be viewed from the outside. Neuroanatomists divide the brain into five major regions from rostral (front) to caudal (back).

We examine how the central nervous system is organized internally, starting with the basic unit: the nerve cell or neuron. The brain and spinal cord are made up of concentrations of neuronal cell bodies called nuclei (gray matter) and bundles of axons coursing between them (white matter).

The hundreds of nuclei in the brain can be grouped into specialized systems for sensation, learning, memory, and other functions. Regions of white matter can also be subdivided into functional types; for example, projection pathways connect different areas, like the motor cortex and the spinal cord.

The cerebral cortex is the outer layer of neurons or "bark" covering the brain. Considered the seat of the mind, it is where cognition and other higher-order functions such as language, intellect, and memory take place. The cortex can be divided into four lobes, each comprised of areas that are associated with specific functions.

This lecture introduces the traditional and modern classification of sensory, motor, and association cortex. One of the crucial discoveries of the past 40 years is that much of what was previously called association cortex is actually sensory in function. For example, there are many more cortical areas devoted to vision than previously thought.