The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It has up to six layers of nerve cells. It is covered by the meninges and often referred to as grey matter[1]. The cortex is grey because nerves in this area lack the insulation (myelin) that makes most other parts of the brain appear to be white[2]. Image: Layers and cells of the cerebral cortex [3] Show The cerebral cortex
The main difference between cerebrum and cerebral cortex
Structure[edit | edit source]The outer layer of the cerebral hemisphere is termed the cerebral cortex. This is inter-connected via pathways that run sub-cortically. It is these connections as well as the connections from the cerebral cortex to the brainstem, spinal cord and nuclei deep within the cerebral hemisphere that form the white matter of the cerebral hemisphere. The deep nuclei include structures such as the basal ganglia and the thalamus. The main difference between cerebrum and cerebral cortex is that cerebrum is the largest part of the brain whereas cerebral cortex is the outer layer of the cerebrum. The cerebrum comprises two cerebral hemispheres. The cerebral cortex is made up of gray matter that covers the internal white matter.[5] The cerebrum consists of two cerebral hemispheres, the right and left hemisphere are connected by the corpus callosum which facilitates communication between both sides of the brain, with each hemisphere in the main connection to the contralateral side of the body. The hemispheres are divided into four lobes; Neocortex[edit | edit source]The phylogenetically most recent part of the cerebral cortex, the neocortex, has six horizontal layers (the more ancient part of the cerebral cortex, the hippocampus, has at most three cellular layers). Neurons in various layers connect vertically to form small microcircuits, called 'columns'.
Image: Cerebral cortex. To the left, the groups of cells; to the right, the systems of fibers. Quite to the left of the figure a sensory nerve fiber is shown. Cell body layers are labeled on the left, and fiber layers are labeled on the right. Allocortex[edit | edit source]The allocortex (also known as heterogenetic cortex) is a part of the cerebral cortex characterized by fewer cell layers than the neocortex (i.e. fewer than six). More ancient phylogenetically than the mammals, evolved to handle olfaction and the memory of smells. The specific regions of the brain normally described as part of the allocortex are:
2. Paleocortex (3 three to five layers) The cellular organization of the old cortex is different from the six-layer structure mentioned above. Unable to form so many complex micro circuits. Function[edit | edit source]The cerebral cortex is involved in several functions of the body including:
The cerebral cortex contains:
2. Motor areas: including the primary motor cortex and the premotor cortex, regulate voluntary movement[2]. Why Wrinkles are Good![edit | edit source]Over time, the human cortex undergoes a process of corticalization, or wrinkling of the cortex. This process is due to the vast knowledge that the human brain accumulates over time. Therefore, the more wrinkly your brain, the smarter and more intelligent you are![8] References[edit | edit source]
Learning Objectives
The four lobes of the brain are the frontal, parietal, temporal, and occipital lobes (Figure 2). The frontal lobe is located in the forward part of the brain, extending back to a fissure known as the central sulcus. The frontal lobe is involved in reasoning, motor control, emotion, and language. It contains the motor cortex, which is involved in planning and coordinating movement; the prefrontal cortex, which is responsible for higher-level cognitive functioning; and Broca’s area, which is essential for language production. People who suffer damage to Broca’s area have great difficulty producing language of any form. For example, Padma was an electrical engineer who was socially active and a caring, involved mother. About twenty years ago, she was in a car accident and suffered damage to her Broca’s area. She completely lost the ability to speak and form any kind of meaningful language. There is nothing wrong with her mouth or her vocal cords, but she is unable to produce words. She can follow directions but can’t respond verbally, and she can read but no longer write. She can do routine tasks like running to the market to buy milk, but she could not communicate verbally if a situation called for it. Probably the most famous case of frontal lobe damage is that of a man by the name of Phineas Gage. On September 13, 1848, Gage (age 25) was working as a railroad foreman in Vermont. He and his crew were using an iron rod to tamp explosives down into a blasting hole to remove rock along the railway’s path. Unfortunately, the iron rod created a spark and caused the rod to explode out of the blasting hole, into Gage’s face, and through his skull (Figure 3). Although lying in a pool of his blood with brain matter emerging from his head, Gage was conscious and able to get up, walk, and speak. But in the months following his accident, people noticed that his personality had changed. Many of his friends described him as no longer being himself. Before the accident, it was said that Gage was a well-mannered, soft-spoken man, but he began to behave in odd and inappropriate ways after the accident. Such changes in personality would be consistent with loss of impulse control—a frontal lobe function. Beyond the damage to the frontal lobe itself, subsequent investigations into the rod’s path also identified probable damage to pathways between the frontal lobe and other brain structures, including the limbic system. With connections between the planning functions of the frontal lobe and the emotional processes of the limbic system severed, Gage had difficulty controlling his emotional impulses. However, there is some evidence suggesting that the dramatic changes in Gage’s personality were exaggerated and embellished. Gage’s case occurred amid a 19th century debate over localization—regarding whether certain areas of the brain are associated with particular functions. On the basis of extremely limited information about Gage, the extent of his injury, and his life before and after the accident, scientists tended to find support for their own views, on whichever side of the debate they fell (Macmillan, 1999).
Watch this clip about Phineas Gage to learn more about his accident and injury. You can view the transcript for “Phineas Gage (LEGO Stop-Motion Video)” (opens in new window). One particularly fascinating area in the frontal lobe is called the “primary motor cortex”. This strip running along the side of the brain is in charge of voluntary movements like waving goodbye, wiggling your eyebrows, and kissing. It is an excellent example of the way that the various regions of the brain are highly specialized. Interestingly, each of our various body parts has a unique portion of the primary motor cortex devoted to it. Each individual finger has about as much dedicated brain space as your entire leg. Your lips, in turn, require about as much dedicated brain processing as all of your fingers and your hand combined! Because the cerebral cortex in general, and the frontal lobe in particular, are associated with such sophisticated functions as planning and being self-aware they are often thought of as a higher, less primal portion of the brain. Indeed, other animals such as rats and kangaroos while they do have frontal regions of their brain do not have the same level of development in the cerebral cortices. The closer an animal is to humans on the evolutionary tree—think chimpanzees and gorillas, the more developed is this portion of their brain. The brain’s parietal lobe is located immediately behind the frontal lobe, and is involved in processing information from the body’s senses. It contains the somatosensory cortex, which is essential for processing sensory information from across the body, such as touch, temperature, and pain. The somatosensory cortex is organized topographically, which means that spatial relationships that exist in the body are generally maintained on the surface of the somatosensory cortex. For example, the portion of the cortex that processes sensory information from the hand is adjacent to the portion that processes information from the wrist. The temporal lobe is located on the side of the head (temporal means “near the temples”), and is associated with hearing, memory, emotion, and some aspects of language. The auditory cortex, the main area responsible for processing auditory information, is located within the temporal lobe. Wernicke’s area, important for speech comprehension, is also located here. Whereas individuals with damage to Broca’s area have difficulty producing language, those with damage to Wernicke’s area can produce sensible language, but they are unable to understand it. The occipital lobe is located at the very back of the brain, and contains the primary visual cortex, which is responsible for interpreting incoming visual information. The occipital cortex is organized retinotopically, which means there is a close relationship between the position of an object in a person’s visual field and the position of that object’s representation on the cortex. You will learn much more about how visual information is processed in the occipital lobe when you study sensation and perception.
Consider the following advice from Joseph LeDoux, a professor of neuroscience and psychology at New York University, as you learn about the specific parts of the brain:
auditory cortex: strip of cortex in the temporal lobe that is responsible for processing auditory information Did you have an idea for improving this content? We’d love your input. Improve this pageLearn More |