Brain Regions - part2 (OLI)


All animals have adapted to their environments by developing abilities that help them survive. Some animals have hard shells, others run extremely fast, and some have acute hearing. Human beings do not have any of these particular characteristics, but we do have one big advantage over other animals—we are very, very smart.

The Cerebral Cortex

You might think we should be able to determine the intelligence of an animal by looking at the ratio of the animal’s brain weight to the weight of its entire body. But brain size is not a measure of intelligence. The elephant’s brain is one-thousandth of its body weight, but the whale’s brain is only one-ten-thousandth of its body weight. On the other hand, although the human brain is one-sixtieth of its body weight, the mouse’s brain represents one fortieth of its body weight. Despite these comparisons, elephants do not seem 10 times smarter than whales, and humans definitely seem smarter than mice.

The key to the advanced intelligence of humans is not found in the size of our brains. What sets humans apart from other animals is our larger cerebral cortex the outer barklike layer of our brain that allows us to so successfully use language, acquire complex skills, create tools, and live in social groups. In humans, the cerebral cortex is wrinkled and folded rather than smooth, as it is in most other animals. This creates a much greater surface area and size and allows increased capacities for learning, remembering, and thinking. The folding of the cerebral cortex is called corticalization.

Although the cortex is only about one tenth of an inch thick, it makes up more than 80% of the brain’s weight. The cortex contains about 20 billion nerve cells and 300 trillion synaptic connections. Supporting all these neurons are billions more glial cells (glia), cells that surround and link to the neurons, protecting them, providing them with nutrients, and absorbing unused neurotransmitters. The glia come in different forms and have different functions. For instance, the myelin sheath surrounding the axon of many neurons is a type of glial cell. The glia are essential partners of neurons, without which the neurons could not survive or function.

The cerebral cortex is divided into two hemispheres, and each hemisphere is divided into four lobes, each separated by folds known as fissures. If we look at the cortex starting at the front of the brain and moving over the top, we see first the frontal lobe (behind the forehead), which is responsible primarily for thinking, planning, memory, and judgment. Following the frontal lobe is the parietal lobe, which extends from the middle to the back of the skull and is responsible primarily for processing information about touch. Then comes the occipital lobe, at the very back of the skull, which processes visual information. Finally, in front of the occipital lobe (pretty much between the ears) is the temporal lobe, responsible primarily for hearing and language.

The brain's cerebral cortex is divided into two hemispheres (left and right), each of which has four lobes (temporal, frontal, occipital, and parietal). Complex processes such as planning, interpreting sensory input, and learning are controlled by specific cortical areas.

Functions of the Cortex

When the German physicists Gustav Fritsch and Eduard Hitzig (1870/2009) applied mild electric stimulation to different parts of a dog’s cortex, they discovered that they could make different parts of the dog’s body move. They also discovered an important and unexpected principle of brain activity. They found that stimulating the right side of the brain produced movement in the left side of the dog’s body, and conversely, stimulating the left brain affected the right side of the body. This finding follows from a general principle about how the brain is structured, called contralateral control. The brain is wired such that in most cases the left hemisphere receives sensations from and controls the right side of the body, and vice versa.

Fritsch and Hitzig also found that the movement that followed the brain stimulation occurred only when they stimulated a specific arch-shaped region that runs across the top of the brain from ear to ear, just at the front of the parietal lobe. Fritsch and Hitzig had discovered the motor cortex, the part of the cortex that controls and executes movements of the body by sending signals to the cerebellum and the spinal cord. More recently, researchers have mapped the motor cortex even more fully by providing mild electronic stimulation to different areas of the motor cortex in fully conscious participants while observing their bodily responses (because the brain has no sensory receptors, these participants feel no pain). As you can see in the following figure, this research has revealed that the motor cortex is specialized for providing control over the body: The parts of the body that require more precise and finer movements, such as the face and hands, also are allotted the greatest amount of cortical space.
The portion of the sensory and motor cortex devoted to receiving messages that control specific regions of the body is determined by the amount of fine movement that area is capable of performing. Thus, the hand and fingers have as much area in the cerebral cortex as does the entire trunk of the body. 


The motor cortex sends out messages to specific parts of the body and the somatosensory cortex receives information from different parts of the body, namely the skin’s sensory receptors as well as from the movements of different body parts. As shown in the figure above, the motor cortex is at the back of the frontal lobe. The somatosensory cortex is located at the front of the parietal lobe, adjacent to the motor cortex. Again, the more sensitive the body region, the more area is dedicated to it in the sensory cortex. Our sensitive lips, for example, occupy a large area in the sensory cortex, as do our fingers and genitals.

Other areas of the cortex process other types of sensory information. The visual cortex is the area located in the occipital lobe (at the very back of the brain) that processes visual information. If you were stimulated in the visual cortex, you would see flashes of light or color, and perhaps you have had the experience of “seeing stars” when you were hit in or fell on the back of your head. The temporal lobe, located on the lower side of each hemisphere, contains the auditory cortex, which is responsible for hearing and language. The temporal lobe also processes some visual information, providing us with the ability to name the objects around us.

As you can see in the preceding figure, the motor and sensory areas of the cortex account for a relatively small part of the total cortex. The remainder of the cortex is made up of association areas in which sensory and motor information are combined and associated with our stored knowledge. These association areas are responsible for most of the things that make human beings seem human—the higher mental functions, such as learning, thinking, planning, judging, moral reflecting, figuring, and spatial reasoning.



Did I get this

The somatosensory cortex (an area just behind the motor cortex that receives information from the skin’s sensory receptors and movements from different body parts) is located in:
frontal lobe OR parietal lobe OR occipital lobe OR temporal lobe
The parietal lobe houses the somatosensory cortex, which receives information sent from our senses.


The auditory cortex is responsible for hearing and language is located in:
frontal lobe OR parietal lobe OR occipital lobe OR temporal lobe
The temporal lobe houses the auditory cortex, which processes the sounds we hear.


The motor cortex sends messages to specific regions of the body to create movement is located in:
frontal lobe OR parietal lobe OR occipital lobe OR temporal lobe
The frontal lobe houses the primary motor cortex, which sends signals to move our muscles.


Grandma had a stroke that damaged her left frontal lobe. We can expect she will:
  • have difficulty controlling movements on the right side of her body
  • neglect sensations on the left side of her body
  • have difficulty controlling movements on the left side of her body
  • have difficulty detecting sensations on the right side of her body
Given the contralateral organization of the brain, damage to the left hemisphere typically affects the right side of the body. Furthermore, the frontal lobe houses the primary motor cortex, which sends signals to move our muscles.


Carbon monoxide poisoning often damages the occipital lobe of the brain. What might we expect when this part of the brain is damaged?
  • problems processing visual information
  • problems feeling touches to the skin on the opposite side of the body
  • problems retrieving long-term memories
  • problems moving parts of the body on the same side at the damage
The occipital lobe houses the visual cortex, which processes images that we see.


Gretchen recently reported randomly hearing songs, and voices from the past. An MEG (magnetoencephalography) revealed she had a tumor causing neurons in the _________ lobe to occasionally fire at random, triggering these auditory illusions.
frontal lobe OR parietal lobe OR occipital lobe OR temporal lobe
The temporal lobe houses the auditory cortex, which processes what we hear.


A new animal is discovered that is more sensitive to pain in its toes than its fingers. If we were to examine the brain of this animal we would notice that _______________.
  • the frontal lobe would have more brain area devoted to the toes than the fingers
  • the parietal lobe would have more brain area devoted to the toes than the fingers
  • the frontal lobe would have more brain area devoted to the fingers than the toes
  • the parietal lobe would have more brain area devoted to the fingers than the toes
The parietal lobe does house the somatosensory cortex, which receives information sent from our senses, and more sensitive regions of the body tend to have more area of the brain devoted to processing.




Kirby recently suffered a stroke. He has recovered much of his functioning, but he finds he still cannot move his left foot even though he can feel pain, cold, etc. to that foot. He also has no problems with his right foot. In this case, it is likely that the ______ of the brain was damaged by the stroke.
right frontal lobe OR left parietal lobe
The frontal lobe houses the motor cortex, which is responsible for controlling movements, and because the brain is organized contralaterally, damage to the right hemisphere typically affects the left side of the body. 


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