Parietal Lobe: Function, Location and Structure

Neuroscientists have long divided the brain into four distinct lobes. Originally this division was based solely on the location of the lobes within the skull, but we now know that each lobe carries out a number of highly specialized functions. The parietal lobe is located just under the parietal bone of the skull. This important brain lobe helps integrate sensory input and process language.

Where is the Parietal Lobe Located?

The brain is divided into a number of regions, but the area most humans refer to when they discuss the brain is the cerebral cortex, or cerebrum. This evolutionarily new region of the brain is present in all mammals, and is what allows complex thoughts rather than just automatic and unconscious processes.

Neuroscientists divide the cerebrum into four distinct lobes: parietal, frontal, temporal, and occipital. Because the brain is also divided into right and left hemispheres, each lobe has two separate regions. Thus the parietal lobe can be further divided into the left and right parietal lobes.

The parietal lobe rests near the top and center of the cerebral cortex, just behind the frontal lobe and above the occipital and temporal lobes. The parieto-occipito sulcus separates it from the frontal lobe, while the lateral sulcus—sometimes referred to as the Sylvian fissure—separates it from the temporal lobe. The parietal lobe's two hemispheres are divided by the medial longitudinal fissure.

What is the Function of the Parietal Lobe?

The parietal lobe is vital for sensory perception and integration, including the management of taste, hearing, sight, touch, and smell. It is home to the brain's primary sensory area, a region where the brain interprets input from other areas of the body. Research suggests that, the more sensory input a region of the body provides, the more surface area of the parietal lobe is dedicated to that area. For example, the fingers and hands are a primary site for sensory data, so much of the parietal lobe is dedicated to receiving and processing their input.

Some of the other functions of the parietal lobe include:

• Distinguishing between two points, even without visual input.
• Localizing touch: When you touch any object with any part of your body, your parietal lobe enables you to feel the sensation at the site of the touch and not, say, in your brain or all over your body.
• Integrating sensory information from most regions of the body.
• Visuospatial navigation and reasoning: When you read a map, follow directions, or prevent yourself from tripping over an unexpected obstacle, your parietal lobe is involved. The parietal lobe is also vital for proprioception—the ability to determine where your body is in space, including in relationship to itself. For instance, touching your finger to your nose without the assistance of a mirror is a function of the parietal lobe.
• Some visual functions, in conjunction with the occipital lobe.
• Assessing numerical relationships, including the number of objects you see.
• Assessing size, shape, and orientation in space of both visible stimuli and objects you remember encountering.
• Mapping the visual world: a number of recent studies suggest that specific regions in the parietal lobe serve as maps to the visual world.
• Coordinating hand, arm, and eye motions.
• Processing language.
• Coordinating attention.

Like all other regions of the brain, the parietal lobe is not fully understood. Researchers are consistently making new findings about how this brain region works, and it is unlikely that we have identified all of its functions.

What Are Some Important Structures in the Parietal Lobe?

In addition to being divided into left and right hemispheres, the parietal lobe has a number of distinct structures, each with its own unique contribution to brain functioning. Those structures include:

• Postcentral gyrus: This region is the brain's primary somatosensory cortex, and maps sensory information onto what is known as a sensory homonculus. Some researchers also refer to this region as Brodmann area 3.
• Posterior parietal cortex: This region is thought to play a vital role in coordinating movement and spatial reasoning. It also plays a role in attention, particularly attention driven by new stimuli, such as when an animal jumps into the road while you are driving. 
• Superior parietal lobule: This region helps you determine your own orientation in space, as well as the orientation of other objects. It also receives significant input from the hand, suggesting that it helps coordinate fine motor skills and sensory input from the hands. 
• Inferior parietal lobule: Sometimes called Gerschwind's territory, this region aids in assessing facial expressions for emotional content. Some research suggests it plays a role in other functions, including language processing, basic mathematical operations, and even body image. It contains a number of sub-regions, including the angular and supramarginal gyrus. 

How Does the Parietal Lobe Interact With Other Areas of the Body?

It is a myth that any single brain region controls any function. Rather, each region of the brain works in conjunction with the body. Without the environment, the brain could do little or nothing, and the parietal lobe is no exception. Its role in sensory processing means that the parietal lobe depends on a cascade of sensory input from all over the body, including the eyes, hands, tongue, and skin. These disparate regions cannot function without the input of the parietal lobe, which assigns meaning to the sensory input you encounter each day.

The parietal lobe also sends signals to and receives signals from other brain regions, most notably the occipital lobe. The occipital lobe aids the parietal lobe in visual perception and processing, as well as spatial navigation and reasoning.

Though each brain region has a specific set of functions, many of these functions are interchangeable and cross brain regions. Every brain region, for instance, is vital for language processing. Some research has also found that, when there is damage to one region of the brain, nearby regions may compensate, particularly if an injured person receives immediate and comprehensive occupational and physical therapy.

How Does Damage to the Parietal Lobe Affect Functioning?

Because of the parietal lobe's role in sensory integration, spatial reasoning, and language skills, damage to the parietal lobe can have a broad range of consequences. The specific prognosis depends in large part on the location of the injury, the severity of the injury, and whether the injury can be treated. For instance, a lesion pressing on the parietal lobe will have a better prognosis with improved functioning if the lesion can be removed.

Quality medical care is incredibly important, particularly when that care includes comprehensive physical, occupational, and speech therapy. Appropriate treatment can help your brain learn to work around the injuries, and may even aid other brain regions to compensate for those injuries. Your age, nutritional status, overall health at the time of the injury, and commitment to a healthy lifestyle are also important. A healthy person who continues exercising and trying novel strategies is much more likely to recover than someone with ongoing cardiovascular problems who is unwilling to try new strategies or embrace lifestyle remedies.

Three specific syndromes are especially common in people with parietal lobe damage:

• Right parietal lobe damage can impede your ability to care for your body because it undermines your ability to notice or care for at least one side of the body. This phenomenon is known as contralateral neglect. People with damage to the right parietal lobe may also be unable to make or draw things.
• Gerstmann's syndrome is a cluster of symptoms resulting from damage to the left parietal lobe. People with Gerstmann's syndrome often struggle with writing, arithmetic, language, and the ability to perceive objects, though the degree and extent of damage varies from person to person and injury to injury.
• Damage that crosses both parietal lobes leads to a condition called Balint's syndrome, which impedes motor skills and visual attention. People with Balint's syndrome may not be able to voluntarily direct their eyes. They struggle to integrate the components of a visual scene, and may be unable reaching for or manipulating an object without looking at it.
  

Sources:

• Parietal Lobes. Neuro Skills. Accessed May 11, 2020. Learn More.
• About Brain Injury: A Guide to Brain Anatomy. Brain Injury Minnesota. Accessed May 11, 2020. Learn More.