Organizing Principles of the Brain

Modified: 2020-06-10

One way to think of the organization of the brain is to think of a tube or a long balloon with bumps on it. The brain is made up of neurons, and they are organized in a particular way. One organizing principle of the brain is redundancy. Redundancy means that different parts of the brain each contribute to solving the same problems. For example, vision is mediated by the eye, the superior colliculus, and various layers of the occipital cortex. Evolution is the reason for brain redundancy. As new parts of the brain evolved and took over old brain functions, the old areas that mediated those functions still retained some control over those functions.

Another organizing principle is bilateral symmetry. The plane of symmetry divides the brain into a right and a left half. This particular symmetry is very widespread throughout the animal kingdom. Try to think of animals that do not show this left-right symmetry, they are rare. A starfish is an example of an animal that is not. It is radially symmetrical. The brain has left-right bilateral symmetry. Every brain structure we will discuss, with very few exceptions, comes in a left and a right half. So, there is a right hypothalamus and a left hypothalamus, a right hippocampus and left hippocampus, and so on.

Finally, there is an evolutionary organization. The areas nearest to the spinal cord end are the oldest, while the areas furthest from the spinal-cord end are the newest. The oldest areas are not only shared by all animals, but those areas are also the most important for survival because they control basic functions related to survival, such as breathing and heart rate. Should you sever your medulla, an area in the brain stem, in an accident, for example, you will probably not survive. On the other hand, should you sever part of your neocortex, the newest part of the brain, you will probably lose some brain function, but you are quite likely to survive.

Back to Chapter 3 Lectures