PARIETAL LOBE: CHARACTERISTICS, ANATOMY, FUNCTIONS, DISEASES - GEOGRAFÍA - 2024

The parietal lobe is one of the four large lobes that make up the cerebral cortex of humans. It is located in the interior of the brain, just in the region where the parietal bone falls.

This region of the cerebral cortex is divided into two large structures. One referring to the left hemisphere and another referring to the right hemisphere. The two parietal lobes are practically symmetrical and have a similar function.

Parietal lobe

The parietal lobe of the brain stands out for its integration function, since it receives stimuli related to touch, heat, cold, pressure, pain and balance that come from multiple regions of the brain.

Injuries to the parietal lobe often cause anesthesia to the arm and leg on the handsome side. That is, if the parietal lobe of the right hemisphere of the brain is injured, anesthesia can be experienced in the left arm and leg of the body.

Likewise, when performing many other neuronal activities, parietal lobe lesions have also been related to alterations in the ability to read, perform mathematical calculations and other types of cognitive activities.

Characteristics of the parietal lobe

Posterior view of the parietal lobe

The parietal lobe is a region of the cerebral cortex that is located just behind the frontal lobe. In the lower part of this lobe the temporal lobe is located and behind this is the occipital lobe.

It is correctly distinguished from the frontal lobe since it is separated from it by a central groove. However, functionally, both lobes of the brain are closely related.

It occupies the middle and upper region of each of the cerebral hemispheres (the right and the left). Likewise, it borders the temporal lobe through the Silvio fissure.

On the other hand, it is separated from the last lobe of the cortex, the occipital lobe, through the external perpendicular fissure.

This region is characterized by containing a deep cleft, the interparietal cleft that with an ascending prolongation delimits three convolutions: the ascending parietal, the superior and the inferior.

Its main function is to receive and integrate the stimuli of the senses. This activity is carried out through the multiple connections that it establishes with different brain regions.

On the other hand, the parietal lobe is a brain structure that has been related to numerical knowledge, simple manipulation of objects, and spatial vision.

Features

Lateral view of the parietal lobe

The parietal lobe is a region of the cerebral cortex that is responsible for carrying out many different activities. This brain structure could participate in some way or another in most of the brain activities.

The different lobes of the cerebral cortex do not constitute autonomous structures that act separately, but rather are brain regions that are interconnected and work together in the development of most activities.

Despite this factor about the functioning of the parietal lobe, this structure of the cortex stands out for its participation in three main processes:

1. The integration and processing of sensory information that comes from different channels.
2. The processing of symbolic information, which includes processes related to language.
3. The processing of numerical information and, therefore, the development of mathematical activities.

Integration and processing of sensory information

The parietal lobe stands out mainly for having one of the largest association areas in the entire brain. That is, this structure is responsible for combining and integrating the information that comes from all areas of the body.

This fact makes it possible to organize the elements captured and developed by different brain structures and to constitute new information as a result of the integration of all the available data.

For this reason, the creation of abstract concepts occurs in part thanks to the parietal lobe, since this structure allows people to generate different ideas from the informational elements captured by different senses and elaborated by different brain structures.

For example, the parietal lobe participates in the development of the idea of ​​what a plant is thanks to the integration of information received by touch, smell, appearance or movement, as well as the participation of previously stored thoughts and beliefs. in memory of.

The parietal lobe not only participates in data integration processes about the world or external elements, but also carries out important activities on the information of how one relates to the world in real time.

That is, the parietal lobe is also responsible for integrating more abstract and complex information that includes both external sensory elements and internal sensory elements.

For example, the parietal lobe is responsible for unifying the data that comes from the muscles of the body, thanks to which the person is able to generate an idea about the physical position and the posture in which they are.

In short, the sensory integration function of the parietal lobe refers to the development of somesthetic processing. That is, it allows the development of the sensory capacity to recognize the sensations of the organism.

Processing of analytical information

The other great function of the parietal lobe is to work with symbols and arithmetic.

This activity is carried out in conjunction with the previous function. That is, the mathematical function arises from the analysis of what is sensory perceived.

In this sense, the parietal lobe is responsible for integrating all the informational elements and developing the imagination of a sequence of units with which, later, to work mathematically.

Processing of symbolic information

Finally, through the same mechanism as the one that allows the processing of analytical information, the parietal lobe allows the development of symbolic information.

In this case, the integration and processing of sensory information also plays a key role. From the conjunction of multiple types of informational data, the brain is able to initiate symbolic thinking.

Anatomy

Anterior view of the parietal lobe

The parietal lobe, or rather the parietal lobes (one in the right hemisphere of the brain and one in the left hemisphere), are structures that provide the cortical mechanisms that perceive somatosensory stimuli.

This structure is characterized by being connected with many other brain regions that send it stimuli of different kinds. When stimuli reach the parietal lobe, it is responsible for integrating them with memory and past experiences, as well as with other afferent sensory perceptions.

This functioning of the parietal lobe allows to generate the recognition of the somatic and extra-corporal events of the person. Likewise, the activity of the parietal lobe contributes to functions such as attention and the development of «mental maps»

Anatomically it is divided into three large areas: the primary somatosensory area, the sensory area and the sensory associative area.

Primary somatosensory area

Areas 3, 1, 2

The primary somatosensory area (or area 3-1-2) is a region that is located immediately after the Rolando fissure, that is, the region of the parietal lobe that borders the frontal lobe.

It is part of the ascending parietal gyrus and is characterized by receiving information from the thalamic nuclei on the opposite side of the body. It has an organized somatotopic pattern called the sensory homunculus.

The sensitive homunculus is a functioning pattern that is proportional to the sensations it encodes. That is, the primary somatosensory area contains multiple regions and each of them is responsible for developing certain sensations.

Depending on the sensory intensity of each of the sensations, the specific region of the somatosensory area will be larger or smaller. For example, the hand has a large sensory region within the primary somatosensory area, since a large number of sensory receptors are found in this region of the body.

The sensory information that comes from the muscles and joints of the body, which is important for the proprioception of the limbs, is projected in area 3a of the primary somatosensory area.

The main function of area 1 of this region of the parietal lobe is to process the information that comes from the skin (area 3b), while area two is responsible for combining the information that comes from areas 3 and 1.

On the other hand, area 1 of the parietal lobe is responsible for projecting to other areas of the same lobe (5 and 7). These are secondary areas that facilitate learning, build body image and plan movements in extra-personal space.

The primary somesthetic area is called the somatomotor cortex since the majority of its stimulations (80%) produce sensitive responses, while the minority (20%) generate motor responses.

Finally, it should be noted that this area of ​​the pariteal lobe contains the critical properties that allow the development of recognition of the leather regions in space.

Likewise, the qualities of this area make it possible to identify the position of the stimuli, discriminate the differences in weight of the raised objects, discriminate the different sensory stimuli and abstract the nature of the objects through their tactile qualities.

Secondary area

Lateral surface of the left cerebral hemisphere. Source: Henry Vandyke Carter

The secondary area (or area 40) is a region of the parietal lobe that is primarily responsible for transmitting and integrating detailed aspects of sensory information.

In fact, injury to this area of ​​the parietal lobe often causes a bilateral loss of the fine and subtle aspects of sensation. On the other hand, the secondary area is responsible for developing the body scheme.

Finally, awareness of various sensory modalities can enter the mental sphere through subcortical centers and the cortex of the postcentral gyrus or area 40.

Sensory associative area

Finally, the sensory associative area is formed by areas 5 and 7 of the parietal lobe. This region is located in the superior parietal gyrus of the lobe.

The sensory associative area is responsible for programming the body's motor activities. Specifically, it plays a fundamental role in the development of activities related to the projection of the arm towards a visual target and in manual manipulation actions.

The associative sensory area develops a spatial reference system that is used to drive body movements in combination with visual and somatosensory sensations.

Likewise, these regions of the parietal lobe are characterized by actively participating in the development of the body scheme.

Lesions in the parietal lobe

The parietal lobe is a brain structure that is primarily responsible for integrating and receiving sensory information, as well as generating thought processes from the data received.

Lesions in this brain structure usually generate conditions related to the functioning of the perceptual senses and the development of cognitive activities.

The symptoms that originate differ markedly depending on whether the parietal lobe of the right hemisphere of the brain is damaged or the parietal lobe of the left hemisphere is damaged.

Lesions in the left hemisphere

Lesions in the angular gyrus of the left hemisphere can cause a pathology known as Gerstmann syndrome.

This syndrome is usually caused by lesions in the posterior perital cortex (areas 7 and 40) and its main symptoms are the inability to name and locate parts of the body.

Right hemisphere injuries

Lesions in the right parietal lobe generate contralateral negligence, they are usually associated with anosognosia (lack of awareness of the disease), anosodiaphoria (indifference to the disease) and hemiasomatognosia (feeling of not belonging to the body itself).

Likewise, lesions in this region of the parietal lobe usually produce ideomotor apraxia (inability to carry out a motor act under verbal command), idetatory apraxia (inability to handle objects), somatoespatial dyspraxia or pain asymbolism.

References

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