Temporal lobe: structure and functions
Jul 16, 2021
The temporal lobe It is one of the most important structures of the cerebral cortex, and therefore also one of the most studied in neuroscience. You cannot understand the workings of the Central Nervous System without knowing even a little about what the temporal lobes are.
It not only covers a good part of the surface of the brain: it also allows global integration of a good part of the sensory information that comes to us through the environment, and has a very relevant role in processing the contents of vision and hearing, as well as language in general.
In this article we will see what are the characteristics of the temporal lobes (as there are a couple of them in each brain), where they are located, and what functions they carry out.
Location of the temporal lobe
Although the whole of the brain functions in a continuous interaction between the different brain areas, the studies carried out from the neurosciences reflect that many of the aptitudes, abilities, capacities and functions of the nervous system are especially linked to certain regions.
In this sense, the human cerebral cortex has traditionally been divided into five sections, called lobes of the brain. One of them is the temporal lobe, a fundamental brain region for skills as fundamental as speech or auditory perception, in addition to being closely linked to affectivity, memory and recognition.
The temporal lobe is located on the lower side of the brain, approximately at the level of the ears. This region is anatomically separated from the parietal lobe, which corresponds to the upper lateral zone, by the Silvio fissure, and is in close contact with the occipital lobe. It is also the lobe with the greatest connection to the limbic system (together with the orbital-frontal area), thus having a great influence on emotions and moods, as well as memory.
It is necessary to note that there are actually two temporal lobes, one in each Cerebral hemisphere. This consideration is relevant, since some of the functions of this lobe are located in most people in a specific hemisphere. However, when due to neurological disorders a part of a temporal lobe ceases to function, these functions can be carried out totally or partially by their counterpart in the opposite hemisphere.
On the other hand, the boundaries of the temporal lobe, like those of any other part of the brain, are highly porous and to some extent diffuse. They do not correspond exactly to the physical limits of areas of the nervous system in charge of certain tasks, but it is a concept that helps to locate when mapping the brain.
Most relevant brain locations
Within the temporal lobe there are a large number of structures. This is so because in this area of the cerebral cortex, many interconnections from different parts of the brain, some of which are not very similar to each other in terms of their functions. In reality, the concept of the temporal lobe responds to criteria much more anatomical than functional, in a way that it is natural that there are groups of nerve cells and small organs specialized in tasks different.
This makes the temporal lobe incorporate groups of neurons in charge of performing many tasks, for example, integrating types of perceptual information that comes from different senses. This is what makes it have an important role in language, mental function in which they have to see sounds, letters, etc.
Some of the most relevant parts of the temporal lobe are as follows.
1. Auditory cortex
In the temporal lobe are the primary, secondary and associative auditory cortices. These areas of the brain are responsible for, in addition to perceiving sounds, carrying out coding, decoding and interpretation of auditory information, being an essential element for survival and the communication. In this last aspect, his participation in speech comprehension stands out, which occurs in Wernicke's area.
2. Wernicke area
Within the secondary auditory area of the dominant cerebral hemisphere, this being generally the left for the majority of the population, Wernicke's area can be found. This area is the main person in charge of understanding the language, allowing verbal communication between individuals. However, language production occurs in another area known as Broca's area, located in the frontal cortex.
3. Angular twist
This area is of special relevance, because it is the one that allows literacy. In it, visual information is associated with auditory information, allowing each grapheme to be assigned its corresponding phoneme and making there may be a change in the type of data that the brain works with, from images to sounds with a component symbolic.
In people with injuries in this area, reading is usually affected, being very slow or non-existent.
4. Supramarginal gyrus
It is part of the tertiary sensitive area. This twist participates in tactile recognition, in addition to participating in language. Thanks to it, we are able to recognize the relief of letters using our fingers and associate them with sounds.
5. Medial temporal
This area, which encompasses the hippocampal region and several relevant cortices, participates in memory and recognition, processing information and helping to move from short-term memory to long-term memory. The left hemisphere is responsible for verbal information, while visual patterns are stored in the right.
It is in this area of the temporal lobe where the first Alzheimer's lesions appear, producing its initial symptoms.
6. Parieto-temporo-occipital association area
It is an area of association that is responsible for integrating visual, auditory and somatic perception. Among many other functions of great relevance, his participation in the perception and attention to space stands out, and the suffering of hemineglect can cause his injury.
7. Limbic system association area
This part of the temporal lobe is responsible for providing emotional information to perceptions, integrating emotion and perception. It also participates in memory and learning. Likewise, other research has shown that it also has to do with the regulation of sexual behavior and the maintenance of emotional stability.
Ultimately, this part of the temporal lobe integrates mental processes linked to emotions and allows our experiences to leave a mark on us that goes beyond what we can explain with words.
Disorders derived from temporal injuries
All the areas that we have seen are of great importance for the correct functioning of the human organism in general and of the temporal lobes in particular.
However, it is not uncommon for accidents, illnesses and disturbances to occur that can lead to malfunctions of some of them. Let's look at some typical disorders of the temporal bone injury.
1. Cortical deafness
This disorder involves the total loss of hearing ability, despite the fact that the sensory organs function properly. That is, the auditory information reaches the perceptual organs, but it is not processed by the brain, thereby losing the perception of sound completely. This alteration is produced by the destruction of the primary and secondary auditory cortices, or the nerve pathways that access them, from both hemispheres.
As with deafness, this affectation is produced by the destruction of the primary and secondary auditory cortex, with the difference that this destruction has only occurred in one hemisphere.
In this way, hearing is completely lost in the ear opposite the hemisphere in which the injury has occurred, but since the auditory cortices of the other hemisphere are still functional, hearing is possible through the other hearing.
In addition, in some cases it is possible that with the passage of time a certain level of hearing may also be gained by the ear that has been disabled, due to the fact that the Neuronal plasticity it allows parts of the brain to learn functions that were previously performed by others, and this can happen even by passing tasks from one hemisphere to the other.
In cases of prosopagnosia, the affected person loses the ability to recognize faces, even those of their loved ones. The recognition of people has to occur through other processing pathways of the brain.
This alteration is caused by a bilateral lesion in the temporoccipital area..
Caused by the involvement of the parieto-temporo-occipital association area, This disorder involves difficulty in orienting, acting or responding to stimuli that occur on the opposite side of the injured hemisphere. Attention to this perceptual hemifield ceases, although the person himself can move so that the lost stimuli remain within the reach of the functional perceptual field. It usually appears together with anosognosia, which is the ignorance of the existence of an alteration.
They are understood as aphasia the language disorders due to brain injury. The effects vary according to the location of the injury, and when it affects the temporal lobe there are certain characteristic symptoms.
Of the aphasias that are produced by a lesion in the temporal bone, Wernicke's aphasia (produced by a lesion in the area of the same name, in that there is a loss or difficulty in verbal comprehension and repetition, which causes serious problems for the person who suffers), the anomic (loss or difficulty in finding the name of things, produced by lesions in associative temporo-parieto-occipital areas) or the sensory transcortical (in which there are difficulties in understanding but not in repetition, being the product of lesions in associative areas temporo-parieto-occipital).
If the connection of Wernicke's area with Broca's area, the arcuate fasciculus, is injured, the so-called aphasia of driving, in which the difficulty in repetition and a somewhat altered comprehension stand out, but a good fluency is maintained.
6. Anterograde amnesia
This disorder implies the inability to store new material in memory. That is, it is impossible for the patient to recover (whether permanent or temporary disability) the declarative information of the activity carried out after the injury.
This alteration is produced by injury to the medial temporal lobe, especially in the hippocampus. Injuries in the left hemisphere will affect verbal information, while in the right the affectation will tend to be nonverbal or other ways.
7. Klüver-Bucy syndrome
It is a very common disorder in dementias, such as Alzheimer's. This affectation is characterized by the presence of meekness, passivity, hyperality, difficulties in sustained attention, disappearance of fear and hypersexuality. It occurs in bilateral medial temporal injuries.
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