The Cerebrum or Neocortex

Now we arrive at the newest part of the brain, the neocortex, cerebrum, or just plain cortex. Cortex means cover in Latin, and neo- means new, hence, new covering. The neocortex is also the largest part of the brain. It is divided up into four or five arbitrary divisions or lobes. The four lobes on the surface are the frontal, parietal, occipital, and temporal. The fifth lobe is underneath the surface lobes, and is called the limbic lobe or limbic system. The following descriptions are cursory; many more functions are present in the neocortex. Also, a great deal of the neocortex's surface is "silent," meaning that no apparent functions can be determined. Those silent areas are called associative areas, and are probably responsible for a great deal of our cognitive capacity.

In the frontal lobe, at its rearmost portion, are areas that control motor functions or movements. The body areas controlled are mapped onto that portion of the cortex, with some parts, notably the hands and lips, receiving more brain tissue than other parts, like the torso, for instance. In other words, the map is asymmetric with respect to the body. If human frontal lobes are directly stimulated on the motor areas, then body movements can be observed. Following the contralateral organization, stimulating the left motor area will result in a movement on the right side of the body.

In the parietal lobe, at its frontmost portion, are areas that monitor sensory information. These areas are directly across a deep sulcus, or division, from the motor areas. The body is also mapped onto the sensory areas of the parietal lobe, but that map (or homunculus) is not exactly like the map of the motor areas. They are, however, very similar. In a similar fashion to the motor areas, stimulation of the sensory areas will result in a sensation on the opposite side of the body.

The temporal lobe receives sensory input from the ears. Thus, sounds are analyzed and interpreted as language. The occipital lobe receive sensory input from the eyes. It analyzes and interprets visual stimuli. The analysis and interpretation of vision is extremely complex and accounts for the largest percentage of the brains's activity. If you were to receive a monthly bill from your brain, the largest portion of that bill would be for vision.

The limbic lobe or limbic system is an ancient cortex, sometimes called the paleocortex (paleo- is Latin for old). The neocortex has taken over most of the limbic system's original functions. Now, the limbic system primarily controls emotional behaviors and memories.

URLs

The External Architecture of the Brain--tutorial, basic, links, graphics

Simply executed tutorial of external anatomy of brain. Provides links to cerebral hemispheres, views of cerebral cortex, the cortex and its layers, division of the cortex into lobes, and specialized areas of the cerebral cortex. http://www.epub.org.br/cm/n01/arquitet/architecture_i.htm

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