The brain is structurally made up of a number of layers, each with its own role, both functually and in evolution.
First, you have the spinal cord. This runs from the base of the spine up into the brain, sending sensory information from the body to the brainstem, and receiving signals to the muscles from the brainstem.
Next, the brainstem, which is wrapped around the top of the spinal cord. This receives signals along the spinal cord, and sends back the automatic responses to those signals. It is here that all of your habitual reactions usually occur. These include making your heart beat, regulating your breathing, and a whole host of other autonomic reactions. Research has shown that not only can you take deliberate control of these functions, but you can also train in new reactions as well. This piece of the brain is shared by every creature with more than a minimal nervous system.
Wrapped around the brainstem is the olfactory lobe. This layer provides elementary processing for signals from the nose. This is where automatic reactions to smells occur.
Wrapped around the olfactory lobe and the rest of the brainstem is the limbic system, where the emotions reside. This area is shared by all mammals. When you are emotionally out of control, this is the part of the brain that is in charge.
As the limbic system developed, so did memory and learning. however, most of the thinking was still done in response to smell, so the rhinencephalon (literally "nose brain") developed to provide better processing of these signals. It is from this that the cortex developed.
The cortex handles at a basic level planning, comprehension of the senses, and coordinates movement. It has two layers, and it was on top of this that several newer layers formed into the neocortex.
The neocortex sits on top of the rest of the brain, and is where our main thinking happens. It is sometimes refered to as the seat of discrimination, and is where abstraction is done. Humans have more of this than any other species on this planet.
last modified 04:23 2003/08/14