Humans have very highly developed brains when compared to other animals. The cerebrum is the highest and larges brain area in humans. Its outer layer is known as the cerebral cortex. Cerebral cortex contains around 70 percent of the neurons in the central nervous system. The cerebral cortex looks like a giant, wrinkled walnut. It covers most of the visible portions of the brain with a mantle of gray matter. The cortex in lower animals is small and smoth. In humans, it is highly convoluted and the largest brain structure. The fact that humans are more intelligent than other animals is related to this corticalization.
The cortex is composed of two sides or hemispheres. The two hemispheres are connected by a thick band of fibres called the corpus callosum. The left hemisphere of the brain mainly controls the right side of the body. The right hemisphere mainly cotrols left body parts. Thus if a person has an injury or stroke that damages the right hemisphere, the left side of the body will be paralyzed.
In addition to the hemispheres, the cerebral cortex can be divided into several smaller areas, or lobes. The occipital lobes, located at the back of the brain, are the primary visual area of the cortex. The parietal lobes are located just above the occipital lobes. Touch, temperature, pressure and other somatic or bodily sensations are channeled to the somatosensory area on the parietal lobes. The temporal lobes are located on each side of the brain. Auditory information project directly to the temporal lobes, making them the site where hearing registers. The frontal lobes perform a mixture of functions. Olfactory information registers on the underside of the frontal lobes. An arch of tissue running over the top of the brain, called the motor cortex, directs the body's muslces. If the motor cortex is stimulated with an electrical current, muscles in various parts of the body will twitch.
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