The Five Senses and Beyond: The Encyclopedia of Perception - Jennifer L. Hellier 2017

Parietal Lobe

The cerebrum is divided into four major divisions with the parietal lobe being located posterior to the frontal lobe, anterior to the occipital lobe, and superior to the temporal lobe. The parietal lobe is generally associated with integrating sensory information as well as spatial orientation. It has also been shown to be important for processing language and spirituality. Because there are two hemispheres of the brain, there are two parietal lobes present, both with the same functions.

Brain Cut-Out Hat Activity

The brain consists of the cerebral cortex and deep structures, such as the thalamus, hypothalamus, insula, and hippocampus. The main functions of the brain are to integrate and modulate both sensory and motor information as well as to produce cognition, higher reasoning, and thinking. The cerebral cortex is divided into two hemispheres with each containing the same lobes and deep structures. The four lobes and their general function are the frontal lobe, which produces higher reasoning and motor activities; the parietal lobe containing the somatosensory cortex—senses from the body, mainly touch, language processing, visual association cortices; the occipital lobe, which processes vision; and the temporal lobe, which stores memories, is the seat of many emotions, and is essential for language comprehension. The function of the thalamus is to modulate all sensory and motor function except for olfaction (the sense of smell). The hypothalamus is important for maintaining body temperature, while the insula plays a role in consciousness, emotion, maintaining homeostasis, perception, and self-awareness. Lastly, the hippocampus is necessary for building and storing memories.

Materials:

Scissors, white glue, tape, paper clips, card stock (preferably two different colors to represent the left and right hemispheres), and pencil or pen

Directions:

Print out the left brain hemisphere (see Appendix in this book) hat pattern on one color of the card stock, and repeat with the right brain hemisphere pattern on the other color of card stock. With a writing instrument, label the functions of each lobe and draw pictures pertaining to those functions. Note that the left hemisphere, in most humans, contains Broca’s area (forming sentences) and Wernicke’s area (understanding language), both necessary for language. When ready, cut out each hemisphere’s pattern. Then cut all of the solid lines that form the Vs along the edges of the brain. Pull the cut edge to the back side of the paper, making a flap to the dashed line. Glue these in place using the paper clips to hold them together until they dry. Next, place one hemisphere about an eighth of an inch or less underneath the other and tape together. Place on head, making sure the frontal lobe is in the front. Enjoy!

Riannon C. Atwater and Jennifer L. Hellier

Anatomical Divisions

The parietal lobe has three distinct anatomical boundaries. First, the central sulcus separates the parietal lobe anteriorly from the frontal lobe. The central sulcus is a prominent landmark in the mammalian brain as it is the longest, uninterrupted, “straight” groove on the lateral aspect of the cerebral hemisphere. Second, the parieto-occipital sulcus divides the posterior portion of the parietal lobe from the anterior portion of the occipital lobe. Lastly, the lateral or Sylvian fissure separates the ventral region of the parietal lobe from the dorsal region of the temporal lobe.

The parietal lobe is divided into anterior and posterior portions. The posterior parietal lobe can be further divided into the superior parietal lobule and the inferior parietal lobule. Within these regions, specific gyri have specific functions. Within the anterior parietal lobe, the narrow strip of brain tissue found just posterior to the central sulcus is called the postcentral gyrus and is the primary somatosensory cortex. Thus, the somatosensory cortex is the most anterior portion of the parietal lobe. Moving toward the occipital lobe, the somatosensory cortex and the posterior parietal lobe are separated by the postcentral sulcus. Lastly, the intraparietal sulcus divides the superior parietal lobule and the inferior parietal lobule.

Function

The postcentral gyrus is the somatosensory cortex with the function of integrating and processing all sensory information from the body’s surface and the underlying viscera. It is also important for the perception of the senses, particularly of touch, pain, and temperature. The somatosensory cortex is often referred to as Brodmann areas 3, 1, and 2. The number order for the somatosensory cortex may seem strange to the reader. This is because when German anatomist Korbinian Brodmann (1868—1918) first sectioned the brain, he did so at an oblique angle. The first area he studied was named Brodmann area 1. As he continued his research, he continued to number the regions based on the order in which he studied them.

The superior parietal lobule is a sensory association cortex, meaning it is used to integrate and process additional sensory information such as vision. Its integration of visual signals is used in spatial orientation of where the body is in space as well as compared to other items. This region is also known as Brodmann areas 5 and 7. The main function of Brodmann area 5 is being an association cortex to the somatosensory cortex, while the primary function of Brodmann area 7 is involved with spatial awareness. Most neuroanatomists consider this region as the dorsal stream of vision (the vision of “where” something is), while the ventral stream of vision (the vision of “what” or “how”) projects to the temporal lobe.

The inferior parietal lobule is a sensory association cortex that processes auditory information as well as language. It is also known as Brodmann areas 39 and 40. In most humans, the function of language is dispersed along the left hemisphere. Thus, the inferior parietal lobule, just around the posterior end of the lateral fissure, is called Wernicke’s area. This region is not only involved with understanding language but also the ability to read.

In addition to being association cortices, recent studies have shown that both the left and right parietal lobes (particularly the inferior parietal lobule) may be involved with a person’s understanding of spirituality or self-transcendence. Specifically, an imaging study revealed that the fronto-parieto-temporal network was activated when the person was describing spiritual experiences. This study suggests that there is a neurobiological basis for religious attitudes and behaviors in humans (Urgesi et al., 2010).

Diseases and Disorders

Damage to the parietal lobe can cause devastating consequences. Specifically, lesions to the right parietal lobe result in the loss of imagery, problems understanding visual relationships, and spatial neglect of the left side of the body. It is often caused by stroke and is characterized by the inability to attend to or interact with people or objects on the opposite side of the affected area. In severe cases, the person may act as if the left side of his or her body never existed. Damage to the left parietal lobe causes problems in understanding symbols—both written letters and mathematics—and language.

Jennifer L. Hellier

See also: Brain Anatomy; Brodmann Areas; Somatosensory Cortex; Somatosensory System; Visual System

Further Reading

Urgesi, Cosimo, Salvatore M. Aglioti, Miran Skrap, & Franco Fabbro. (2010). The spiritual brain: Selective cortical lesions modulate human self-transcendence. Neuron, 65(3), 309—319.

Van Vleet, Thomas M., & Joseph M. DeGutis. (2013). The nonspatial side of spatial neglect and related approaches to treatment. Progress in Brain Research, 207, 327—349.