The cerebrum is the largest part of the brain and divided into left and right hemispheres separated by a deep groove. Each side of the cerebral hemisphere controls the opposite side of the body. As a whole, the cerebrum is responsible for:
- Initiating and coordinating movement
- Thinking, reasoning, problem-solving
- Emotions and learning
- Speech, vision, hearing, touch
The cerebrum contains grey matter and billions of unmyelinated neurons (brain cells) called the cerebral cortex. Deeper parts of the cerebrum contain white matter, which is the collection of myelinated nerve fibers that connect different regions of the central nervous system (CNS) and spinal cord. Myelin sheath insulates and covers the neurons intermittently, helping to speed up nerve signals.
The cerebral cortex that is present superficially to the cerebrum is arranged in a folded manner and is only 2-4 millimeters thick. The folds on the cerebral cortex are called gyri, which are divided by grooves. The smaller grooves are called sulci and larger groves are called fissures. The fold of the sulci conceals about 66% of the brain's surface, with a total surface area of approximately 16 square feet. The cerebral cortex folds are the reason for the distinctive look of the brain.
4 major lobes of the cerebrum and their functions
The cerebrum is divided into four major lobes, each lobe with two halves, right and left. All four right halves come into the right hemisphere of the cerebrum and all four left halves come into the left hemisphere.
- Frontal lobe: Frontal lobe is located near the front, and it is the larger lobe that constitutes 2/3 of the human brain. The frontal lobe is present beneath the frontal skull bones, corresponding to the forehead. The two halves of the frontal lobes are called the left and right frontal cortex. It plays an important role in memory, social protocols, concentration, motivation, and a variety of other functions.
- Parietal lobe: Parietal lobe is located behind the frontal lobe and above the temporal lobe, toward the upper area of the skull. The two parietal lobes are separated by the central sulcus. Temporal and parietal lobes are separated by the lateral sulcus, also called Sylvian fissure. The parietal lobe is a primary sensory area that interprets higher functions. It can perceive sensory information from outside the body, such as touch, pressure, pain, taste, and temperature. It helps the brain understand symbols, written and spoken linguistic issues, mathematical problems, codes, and riddles.
- Temporal lobe: Temporal lobe is located behind and close to the ear within the skull and is primarily responsible for the formation and preservation of both conscious and long-term memory. It helps the brain identify objects, recognize language, and plays an important role in visual and auditory processing. Disorder in the temporal lobe can lead to seizures.
- Occipital lobe: Occipital lobe is in the backside of the upper brain below the occipital bone of the skull, behind the parietal and temporal lobes, and above the cerebellum. The central cerebral fissure divides the two occipital lobes, and a membrane called tentorium cerebelli separates it from the cerebellum. The occipital lobe is identified by the folds sulci and gyri. The occipital lobe is divided into four parts, each of which is responsible for a separate set of visual functions. Damage to the occipital lobe may lead to problems with vision.
4 major areas of the cerebrum and their functions
- Broca’s area: By translating thoughts into language, this area helps with speech development. Damage to this region can impair your ability to talk, interpret language, or generate coherent speech.
- Wernicke’s area: Wernicke’s region is responsible for processing words to give meaning to speech and writing.
- Limbic system: The temporal lobe is an important component of the limbic system, which is responsible for learning, emotions (love, envy, etc.) and memory. It helps form conscious long-term memory. Due to the presence of the limbic system, the temporal lobe contributes to a variety of autonomic states and physiological processes, such as sexual arousal, anxiety levels, and hunger.
- Primary visual cortex: Brodmann area 17, V1, or primary visual cortex interprets and transfers information received from the retina, such as shape, motion, location, and color of objects in the visual field. Ventral and dorsal streams are two different pathways through which the stimulus of the primary visual cortex works.
What disorders are caused by damage to the cerebrum?
The cerebrum can be damaged in many ways, causing disruption in its normal functions.
- Acquired brain injury is an injury at the cellular level caused by stroke or toxic substances (dementia, Alzheimer’s).
- Neurological illness and traumatic brain injury caused by external force, such as a car accident or physical violence, damages the skull, which eventually damages the brain.
Both hemispheres of the cerebrum are anatomically and functionally connected. Depending on the part of the brain affected, some symptoms are more prominent than others.
Damage to the right hemisphere of the cerebrum
- Sensory impairment with left-sided weakness or paralysis
- Denial of paralysis or disability, or a lack of understanding of the difficulties caused by stroke (left neglect)
- Spatial issues with depth perception or directions, such as up and down or front and back
- Memory issues
- Other nonspecific changes in behavior, such as a lack of care, impulsivity, inappropriateness, and sadness
Damage to the left hemisphere of the cerebrum
- Sensory impairment and right-sided weakness or paralysis
- Problems with speech and language comprehension (aphasia)
- Visual issues, such as an inability to view the right visual field of each eye
- Impaired capacity to do math or organize, reason, and analyze information
- Behavioral alterations depression, cautiousness, and hesitation
- Impaired reading, writing, and learning abilities
- Memory issues
Science Direct. Cerebrum. https://www.sciencedirect.com/topics/neuroscience/cerebrum
Kids Health. Your Brain & Nervous System. https://kidshealth.org/en/kids/brain.html
Boeree GC. The Cerebrum. http://webspace.ship.edu/cgboer/genpsycerebrum.HTML
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Left Brain vs. Right Brain
Are left brain vs. right brain theories myth or fact? They actually are a little of both! Scientists and researchers have tried to answer this question since the 1800s. In the 1960s, neuroscientist Roger Sperry began to research the right brain vs. left brain theory. In 1981, together with neuroscientist Torsten Wiesel, he won the won the Nobel Prize for his "split-brain" theory. In the split-brain theory, the left and right sides of the brain are connected by the corpus callosum (where place each side of the brain meets and sends signals and communicates with other), and that both the left and right sides of the brain have specific functions.
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REFERENCE: Corballis, MC. "Left Brain, Right Brain: Facts and Fantasies." PLoS Biol. 2014 Jan; 12(1): e1001767.
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