The cerebral cortex is divided into many different areas, each of which is closely associated with specific mental and behavioral functions. This division of the cortex is based on differences in detailed microscopic structure, anatomical connections, and functional properties (what it does) among different areas.

The idea that different parts of the brain do different things is called localization of function. As described above, this idea comes from phrenology, but the cerebral cortex is now subdivided in a very different way. According to many data, the cerebral cortex is divided into a hierarchy of three kinds of areas: primary sensory areas at the bottom, sensory association areas, and higher order association areas at the top.

Information from each sense (eyes, ears, etc.) reaches the cerebral cortex first and most directly at its own specialized areas called its primary sensory cortex (or area).
As Figure 3-2d above shows, each sense has its own area.

• The visual pathway from the eyes projects (makes connections) most directly to the primary visual cortex on the occipital lobe at the back of the brain.
• The auditory pathway from the ear projects most directly to the primary auditory cortex on the top edge of the temporal lobe, located under the temple pieces of a pair of glasses.
• The somatosensory (soma = body) or touch pathways project most directly to the primary somatosensory cortex on the front edge of the parietal lobe.
• The most direct pathways from the cortex to motor neurons in spinal cord arise from the primary motor cortex.