Cerebral Cortex

The cerebral cortex is the surface layer of the cerebrum. It is about 1/2 inch in thickness, although this varies slightly in different areas of the brain. It is composed of what is referred to as grey matter and white matter. The grey matter of the cerebral cortex is a densely packed region comprising neurons, dendrites and capillary blood vessels. The neurons (nerve cells) are the basic operative units of the brain. Below the grey matter is a thicker inner layer, the sub-cortical layer, which is white in appearance. The white matter is made up of dendrites and myelinated axons. These neural fibers form the billions of connections within the brain by which information in the form of electrical impulses is transmitted to the selective areas of the brain. There are three types of fiber tracts within the white matter: association fibers, commissural fibers and projection fibers. Association fibers belong to a given hemisphere and only conduct neural impulses within their given hemisphere. Commissural fibers connect neurons from one hemisphere to another. Projection fibers form tracts that transmit and receive impulses from neurons in the cerebrum to other parts of the brain and spinal cord