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Limbic System

The limbic system includes the hippocampus, the amygdala, and the septum. Parts of the limbic system also lie in the thalamus and the hypothalamus. The limbic system processes emotional experience. The amygdala plays a role in aggression and fear, while the hippocampus plays a role in memory.

Cerebrum

The cerebrum, the biggest part of the brain, controls complex processes such as abstract thought and learning. The wrinkled, highly folded outer layer of the cerebrum is called the cerebral cortex. The corpus callosum is a band of fibers that runs along the cerebrum from the front of the skull to the back. It divides the cerebrum into two halves, or hemispheres. Each hemisphere is divided into four lobes or segments: the occipital lobe, the parietal lobe, the temporal lobe, and the frontal lobe:

  • The occipital lobe contains the primary visual cortex, which handles visual information.
  • The parietal lobe contains the primary somatosensory cortex, which handles information related to the sense of touch. The parietal lobe also plays a part in sensing body position and integrating visual information.
  • The temporal lobe contains the primary auditory cortex, which is involved in processing auditory information. The left temporal lobe also contains Wernicke’s area, a part of the brain involved in language comprehension.
  • The frontal lobe contains the primary motor cortex, which controls muscle movement. The left frontal lobe contains Broca’s area, which influences speech production. The frontal lobe also processes memory, planning, goal-setting, creativity, rational decision making, and social judgment.

Brain Hemispheres

Lateralization refers to the fact that the right and left hemispheres of the brain regulate different functions. The left hemisphere specializes in verbal processing tasks such as writing, reading, and talking. The right hemisphere specializes in nonverbal processing tasks such as playing music, drawing, and recognizing childhood friends.

Roger Sperry, Michael Gazzaniga, and their colleagues conducted some of the early research in lateralization. They examined people who had gone through split-brain surgery, an operation done to cut the corpus callosum and separate the two brain hemispheres. Doctors sometimes use split-brain surgery as a treatment for epileptic seizures.

Control of the Body

Because of the organization of the nervous system, the left hemisphere of the brain controls the functioning of the right side of the body. Likewise, the right hemisphere controls the functioning of the left side of the body.

Vision and hearing operate a bit differently. What the left eye and right eye see goes to the entire brain. However, images in the left visual field stimulate receptors on the right side of each eye, and in-formation goes from those points to the right hemisphere. Information perceived by the right visual field ends up in the left hemisphere.

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