Lobes of the Brain

Lobes of the brain are sections in the brain. The human brain is considered the most complex organ in the body and is one of the main parts of the central nervous system. The largest and principal part of the brain is the cerebrum. The cerebrum is divided in half into roughly mirrored hemispheres, each of which is divided into sections based on the locations of major anatomical features. These sections, or lobes, of the brain are anatomically unique and responsible for different functions. However, brain lobes are not physically separate. They are physically connected by neural tissues or by neural nerve pathways, and, in this way, they function together to process and understand the stimuli transmitted through the nervous system. The lobes of the brain make possible various neurological functions that range from perceiving auditory and visual sensations—seeing and hearing—to reasoning and decision-making processes.

Background

The brain’s significance in thought and perception has not always been well understood. Ancient Roman physician Galen first proposed around 170 BCE that the brain contained four distinct cavities filled with fluid, or ventricles, that were responsible for thought, personality, and body function. It would be thousands of years before specific sections of the brain were understood in terms of the function and role they play in thought and personality.

A significant medical case in the nineteenth century allowed researchers some insight into brain functions. In 1848, a man named Phineas Gage was injured in a railway explosion. Although an iron rod went through his head and damaged his left frontal lobe, he survived the injury; however, his close friends and family noticed his personality had dramatically changed. Scientists were intrigued by observations of Gage made by his doctor, John Maryn Harlow. Damage to the frontal lobe area of Gage’s brain led to the conclusion that this lobe regulated a person’s personality characteristics. Further research led to the discovery of specific regions of the brain relating to certain functions, such as personality, sensation, and thinking ability.

Several decades later, physicians Paul Broca and Carl Wernicke were able to show through their studies that particular sections of the brain were responsible for speech. In the 1870s, Broca discovered that if a certain area of the brain was damaged, a person had difficulty speaking, even though the individual could process and understand language. In the 1890s Wernicke studied patients who were able to speak but not able to understand language. This led to his discovery of a small region that helps process auditory stimuli into comprehensible thoughts.

German physician Johann Cristian Reil discovered the insular cortex in 1809. Because this region is located deep within the brain and is difficult to access and study, it was not well understood for some time. By the late twentieth century, some experts considered it a separate lobe of the brain, and it became better understood by researchers as important in self-awareness and consciousness.

Overview

The outer tissue layer of folded gray matter is known as the cerebral cortex. The cerebral cortex is made up of layers of up to sixteen billion nerve cells that receive messages relating to stimuli collected from nerve cells throughout the body. The ridges and grooves, known as gyri and sulci, respectively, increase the surface area of the brain, which increases the number of neurons it can contain. The nerve cells in the cerebral cortex communicate with each other to interpret, process, and act on information from the nerve cells. The cerebral cortex gives humans unique cognitive abilities, such as language, imagination, higher-order thinking, memory, reasoning, problem-solving, and self-awareness.

One hemisphere of the brain, described as the dominant hemisphere, is associated with language and logic. Creativity, including imagination, resides in the non-dominant hemisphere. A person’s dominant hemisphere is usually the side opposite the dominant hand—for right-handed individuals, for example, the left hemisphere is usually dominant.

The left and right hemispheres are divided by a fissure and connected by the corpus callosum, which is a bundle of nerve fibers that allows the two sides to communicate with each other. These hemispheres are traditionally divided into four lobes: frontal, parietal, temporal, and occipital. However, many neurologists and scientists have also included two additional lobes located deeper in the cerebrum: the limbic lobe and the insular cortex. There has been some variation among experts as to the exact delineation of these lobes and the structures found within each lobe, especially where they are not clearly defined by anatomical landmarks.

Frontal Lobe

As the name suggests, the frontal lobe is located at the front of each cerebral hemisphere near the frontal bone in the skull. The frontal lobe is separated from the neighboring parietal lobe by the central sulcus, which is a fold in the brain tissues, and from the temporal lobe by the lateral sulcus, or Sylvian fissure, which is a large fold.

The anterior of the frontal lobe contains the prefrontal cortex, which provides the brain with executive control and memory. It assists with planning and decision-making, as well as providing a person with personality characteristics and processing of emotion. The posterior of the lobe contains the primary motor cortex. This area, along with the premotor area and the supplemental motor cortex, is responsible for coordinating and executing voluntary movement. The frontal lobe also contains the frontal eye fields to control certain eye movements, and the Broca’s area, which is the part of the brain that is responsible for speech production.

Parietal Lobe

Behind the frontal lobe and above the occipital lobe is the parietal lobe. It is in the middle part of the brain near the parietal bone and is separated from the occipital lobe by the parietooccipital sulcus. This part of the brain is divided into three regions, or lobules: the postcentral gyrus and the superior and inferior parietal lobules. The postcentral gyrus, also functionally known as the primary somatosensory cortex, regulates sensory information, which includes spatial relationships and navigation. It also interprets the sense of touch, including pain, temperature, and vibration. The superior parietal lobule is important in sensorimotor integration, and the inferior parietal lobule helps the brain with auditory and language functions.

Occipital Lobe

In the back of the brain, the smallest of the lobes, the occipital lobe, is located near the occipital bone. It is separated from the parietal lobe by the parietooccipital sulcus and the temporal lobe by the lateral parietotemporal line, which is an imaginary line rather than an anatomical landmark. It is known as the brain’s main visual processing center because it contains the visual cortex, which allows for visual perception. This area has specialized regions for understanding visual stimuli and processing spatial orientation and color. It allows visual memories to be formed, objects and faces to be recognized, and for the brain to match motor movement in response to visual stimuli.

Temporal Lobe

The temporal lobe is located on the side of each hemisphere of the brain corresponding to the temporal bone. This lobe is responsible for understanding auditory sensory input to create memories and understand language. Much of this processing is done in the primary auditory area, which is also known as the transverse gyri of Heschl, and the secondary auditory area. In the back of the temporal lobe on the dominant hemisphere of the brain is the Wernicke’s area, which helps people comprehend speech. Many neurological professionals also include the hippocampus in this region. This area enables people to learn new skills and is critical for long-term memory.

Limbic Lobe

The limbic lobe is an arc-shaped region found in the cerebrum at the middle of each hemisphere and around the corpus callosum, which connects the hemispheres. It may also be identified as a part of the temporal, parietal, and frontal lobes and not recognized as a separate region by all neurological professionals. It is responsible for modulating emotions as well as visceral and autonomic functions. It allows people to attach emotional significance to sensory information. Some people include the hippocampus in this lobe, instead of in the temporal lobe.

Insular Cortex

The insular cortex is found deep within the lateral sulcus, which is the fissure separating the temporal, parietal, and frontal lobes. It is covered by the opercula, which contains sections of the frontal, parietal, and temporal lobes. It is responsible for processing and integrating stimuli related to taste as well as visceral and pain sensations. It also provides vestibular functions and plays a role in consciousness. Although the role of the insular cortex is not well understood, it is thought by researchers to help regulate how self-awareness and emotions interact to create a personalized perception of reality.

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