6 Major Parts of the Brain and How they Work
6 Major Parts of the Brain and What They Do
I always like to say that teachers are brain changers. They work every day to change their students’ brains. If that is the case then it would be logical to conclude that the more teachers knows about the brain, the better equipped they will be to change their students’ brains. This post looks at six parts of the brain and what they do.
1. Lobes of the Brain
Although the minor wrinkles are unique in each brain, several major wrinkles and folds are common to all brains. These folds form a set of four lobes in each hemisphere. Each lobe tends to specialize for certain functions.
Frontal Lobes. At the front of the brain are the frontal lobes, and the part lying just behind the forehead is called the prefrontal cortex. Often called the executive control center, these lobes deal with planning and thinking. They comprise the rational and executive control center of the brain, monitoring higher-order thinking, directing problem solving, and regulating the excesses of the emotional system. The frontal lobe also contains our self-will area—what some might call our personality. Trauma to the frontal lobe can cause dramatic—and sometimes permanent—behavior and personality changes. Because most of the working memory is located here, it is the area where focus occurs (Geday & Gjedde, 2009; Smith & Jonides, 1999). The frontal lobe matures slowly. MRI studies of post-adolescents reveal that the frontal lobe continues to mature into early adulthood. Thus, the capability of the frontal lobe to control the excesses of the emotional system is not fully operational during adolescence ( Dosenbach et al., 2010; Goldberg, 2001). This is one important reason why adolescents are more likely than adults to submit to their emotions and resort to high-risk behavior.
Temporal Lobes. Above the ears rest the temporal lobes, which deal with sound, music, face and object recognition, and some parts of long-term memory. They also house the speech centers, although this is usually on the left side only.
Occipital Lobes. At the back are the paired occipital lobes, which are used almost exclusively for visual processing.
Parietal Lobes. Near the top are the parietal lobes, which deal mainly with spatial orientation, calculation, and certain types of recognition.
2. Motor Cortex and Somatosensory Cortex
Between the parietal and frontal lobes are two bands across the top of the brain from ear to ear. The band closer to the front is the motor cortex. This strip controls body movement and, as we will learn later, works with the cerebellum to coordinate the learning of motor skills. Just behind the motor cortex, at the beginning of the parietal lobe, is the somatosensory cortex, which processes touch signals received from various parts of the body.
3. Brain Stem
The brain stem is the oldest and deepest area of the brain. It is often referred to as the reptilian brain because it resembles the entire brain of a reptile. Of the 12 body nerves that go to the brain, 11 end in the brain stem (the olfactory nerve—for smell—goes directly to the limbic system, an evolutionary artifact). Here is where vital body functions, such as heartbeat, respiration, body tem¬perature, and digestion, are monitored and controlled. The brain stem also houses the reticular activating system (RAS), responsible for the brain’s alertness.
4. The Limbic System
Nestled above the brain stem and below the cerebrum lies a collection of structures commonly referred to as the limbic system and sometimes called the old mammalian brain. Many researchers now caution that viewing the limbic system as a separate functional entity is outdated because all of its components interact with many other areas of the brain.
Most of the structures in the limbic system are duplicated in each hemisphere of the brain. These structures carry out a number of different functions including the generation of emotions and processing emotional memories. Its placement between the cerebrum and the brain stem permits the interplay of emotion and reason.
Four parts of the limbic system are important to learning and memory. They include the following:
The Thalamus. All incoming sensory information (except smell) goes first to the thalamus (Greek for “inner chamber”). From here it is directed to other parts of the brain for additional processing. The cerebrum and the cerebellum also send signals to the thalamus, thus involving it in many cognitive activities, including memory.
The Hypothalamus. Nestled just below the thalamus is the hypothalamus. While the thalamus monitors information coming in from the outside, the hypothalamus monitors the internal systems to maintain the normal state of the body (called homeostasis). By controlling the release of a variety of hormones, it moderates numerous body functions, including sleep, body temperature, food intake, and liquid intake. If body systems slip out of balance, it is difficult for the individual to concentrate on cognitive processing of curriculum material.
The Hippocampus. Located near the base of the limbic area is the hippocampus (the Greek word for “sea horse,” because of its shape). It plays a major role in consolidating learning and in converting information from working memory via electrical signals to the long-term storage regions, a process that may take days to months. It constantly checks information relayed to working memory and com-pares it to stored experiences. This process is essential for the creation of meaning.
Its role was first revealed by patients whose hippocampus was damaged or removed because of disease. These patients could remember everything that happened before the operation, but not afterward. If they were introduced to you today, you would be a stranger to them tomorrow. Because they can remember information for only a few minutes, they can read the same article repeatedly and believe on each occasion that it is the first time they have read it. Brain scans have confirmed the role of the hippocampus in permanent memory storage. Alzheimer’s disease progressively destroys neurons in the hippocampus, resulting in memory loss.
Recent studies of brain-damaged patients have revealed that although the hippocampus plays an important role in the recall of facts, objects, and places, it does not seem to play much of a role in the recall of long-term personal memories (Lieberman, 2005). One surprising revelation in recent years is that the hippocampus has the capability to produce new neurons—a process called neurogenesis—into adulthood (Balu & Lucki, 2009). Furthermore, there is research evidence that this form of neurogenesis has a significant impact on learning and memory (Deng, Aimone, & Gage, 2010; Neves, Cooke, & Bliss, 2008). Studies also reveal that neurogenesis can be strengthened by diet (Kitamura, Mishina, & Sugiyama, 2006) and exercise (Pereira et al., 2007) and weakened by prolonged sleep loss (Meerlo, Mistlberger, Jacobs, Heller, & McGinty, 2009).
The Amygdala. Attached to the end of the hippocampus is the amygdala (Greek for “almond”). This structure plays an important role in emotions, especially fear. It regulates the individual’s interactions with the environment that can affect survival, such as whether to attack, escape, mate, or eat.
Because of its proximity to the hippocampus and its activity on PET scans, researchers believe that the amygdala encodes an emotional message, if one is present, whenever a memory is tagged for long-term storage. It is not known at this time whether the emotional memories themselves are actually stored in the amygdala. One possibility is that the emotional component of a memory is stored in the amygdala while other cognitive components (names, dates, etc.) are stored elsewhere (Squire & Kandel, 1999). The emotional component is recalled whenever the memory is recalled. This explains why people recalling a strong emotional memory will often experience those emotions again. The interactions between the amygdala and the hippocampus ensure that we remember for a long time those events that are important and emotional.
Teachers, of course, hope that their students will permanently remember what was taught. Therefore, it is intriguing to realize that the two structures in the brain mainly responsible for long-term remembering are located in the emotional area of the brain.
A soft, jellylike mass, the cerebrum is the largest area, representing nearly 80 percent of the brain by weight. Its surface is pale gray, wrinkled, and marked by deep furrows called fissures and shallow ones called sulci (singular, sulcus). Raised folds are called gyri (singular, gyrus). One large sulcus runs from front to back and divides the cerebrum into two halves, called the cerebral hemispheres. For some still unexplained reason, the nerves from the left side of the body cross over to the right hemisphere, and those from the right side of the body cross to the left hemisphere. The two hemispheres are connected by a thick cable of more than 200 million nerve fibers called the corpus callosum (Latin for “large body”). The hemispheres use this bridge to communicate with each other and coordinate activities.
The hemispheres are covered by a thin but tough laminated cortex (meaning “tree bark”), rich in cells, that is about one tenth of an inch thick and, because of its folds, has a surface area of about two square feet. That is about the size of a large dinner napkin. The cortex is composed of six layers of cells meshed in about 10,000 miles of connecting fibers per cubic inch! Here is where most of the action takes place. Thinking, memory, speech, and muscular movement are controlled by areas in the cerebrum. The cortex is often referred to as the brain’s gray matter.
The neurons in the thin cortex form columns whose branches extend through the cortical layer into a dense web below known as the white matter. Here, neurons connect with each other to form vast arrays of neural networks that carry out specific functions.
The cerebellum (Latin for “little brain”) is a two-hemisphere structure located just below the rear part of the cerebrum, right behind the brain stem. Representing about 11 percent of the brain’s weight, it is a deeply folded and highly organized structure containing more neurons than all of the rest of the brain put together. The surface area of the entire cerebellum is about the same as that of one of the cerebral hemispheres.
This area coordinates movement. Because the cerebellum monitors impulses from nerve endings in the muscles, it is important in the performance and timing of complex motor tasks. It modifies and coordinates commands to swing a golf club, smooth a dancer’s footsteps, and allow a hand to bring a cup to the lips without spilling its contents. The cerebellum may also store the memory of automated movements, such as touch-typing and tying a shoelace. Through such automation, performance can be improved as the sequences of movements can be made with greater speed, greater accuracy, and less effort. The cerebellum also is known to be involved in the mental rehearsal of motor tasks, which also can improve performance and make it more skilled. A person whose cerebellum is damaged slows down and simplifies movement, and would have difficulty with finely tuned motion, such as catching a ball or completing a handshake.
Recent studies indicate that the role of the cerebellum has been underestimated. Researchers now believe that it also acts as a support structure in cognitive processing by coordinating and fine-tuning our thoughts, emotions, senses (especially touch), and memories. Because the cerebellum is connected also to regions of the brain that perform mental and sensory tasks, it can perform these skills automatically, without conscious attention to detail. This allows the conscious part of the brain the freedom to attend to other mental activities, thus enlarging its cognitive scope. Such enlargement of human capabilities is attributable in no small part to the cerebellum and its contribution to the automation of numerous mental activities.