Temporal lobe: structure and functions

What functions does this important region of the brain perform?

The temporal lobe is one of the most important structures of the cerebral cortex, and therefore also one of the most studied in neuroscience. It is not possible to understand the functioning of the Central Nervous System without knowing at least a little about what the temporal lobes are.

Not only does it cover a large part of the surface of the brain, but it also allows to globally integrate a large part of the brain's globally integrates much of the sensory information that reaches us through the environment, and plays a very important role in the functioning of the central nervous system.It also plays a very important 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 pair of them in each brain), where they are located, and what functions they perform.

Location of the temporal lobe

Although the brain as a whole functions in a continuous interaction between the different brain areas, neuroscience studies show that many of the skills, 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 these is the temporal lobe, a brain region that is fundamental for such fundamental skills as speech and language. for such fundamental skills as speech or auditory perception, as well as 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 superior lateral area, by the Sylvian fissure, and is in close contact with the occipital lobe. It is also the lobe with the strongest connection with the limbic system (together with the orbitofrontal area), thus having a great influence on emotions and moods, as well as on memory.

It is necessary to take into account 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 alterations a part of a temporal lobe ceases to function, these functions may be totally or partially performed by its 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 very porous and to some extent fuzzy. They do not correspond exactly to physical boundaries of areas of the nervous system in charge of certain tasks, but it is a concept that helps to locate them in the brain.Rather, it is a concept that helps to locate them when mapping the brain.

Most relevant brain locations

Within the temporal lobe there are a great number of structures. This is because many interconnections from different parts of the brain coincide in this area of the cerebral cortex, some of which are not very similar to each other in terms of their functions. In fact, the concept of temporal lobe responds to much more anatomical than functional criteria, so it is natural that there are groups of nerve cells and small organs specialized in different tasks.

This causes the temporal lobe to incorporate groups of neurons responsible for performing many tasks, for example, integrating types of perceptual information coming from different senses. This is what makes it play an important role in language, a mental function in which sounds, letters, etc. are involved.

Some of the most relevant parts of the temporal lobe are the following. are the following.

1. Auditory cortex

The temporal lobe contains the primary, secondary and associative auditory cortex.. These areas of the brain are responsible for, in addition to perceiving sounds, coding, decoding and interpreting auditory information, being an indispensable element for survival and communication. In this last aspect, its participation in speech comprehension, which takes place in Wernicke's area, stands out.

2. Wernicke's area

Within the secondary auditory area of the dominant cerebral hemisphere, which is usually the left hemisphere for most of the population, Wernicke's area can be found. This area is the main area in charge of language comprehension, allowing verbal communication between individuals.allowing verbal communication between individuals. However, language production takes place in another area known as Broca's area, located in the frontal cortex.

3. Angular gyrus

This area is of special relevance, since it is the one that allows reading and writing.. It associates visual and auditory information, allowing to assign to each grapheme its corresponding phoneme and making it possible to produce a change in the type of data with which the brain works, from images to sounds with a symbolic component.

In people with lesions 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 gyrus participates in tactile recognition, as well as in language. Thanks to it we are able to recognize the relief of letters with our fingers and associate them with sounds.

5. Medial Temporal

This area, which includes the hippocampal region and several relevant cortexes, is involved in memory and recognitionprocessing information and helping to move from short-term memory to long-term memory. The left hemisphere is responsible for verbal information, while the right hemisphere stores visual patterns.

It is in this area of the temporal lobe where the first lesions appear in Alzheimer's disease, producing its initial symptoms.

6. Parieto-temporo-occipital association area

This is an association area responsible for integrating visual, auditory and somatic perception.. Among many other functions of great relevance, its participation in the perception and attention to space stands out, and its lesion may cause hemineglect.

7. Association area of the limbic system

This part of the temporal lobe is in charge of providing emotional information to perceptions, integrating emotion and perception.integrating emotion and perception. It also participates in memory and learning. Likewise, other research has shown that it is also involved in the regulation of sexual behavior and in the maintenance of emotional stability.

In short, 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 resulting from lesions in the temporal lobe

All the areas 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 infrequent that accidents, diseases and alterations accidents, diseases and alterations that may cause a malfunction of some of them are not infrequent. malfunction of some of them. Let us look at some typical disorders of the temporal lobe lesion.

1. Cortical deafness

This disorder involves the total loss of the auditory faculty, in spite of the fact that the sensory organs of the brain are functioning properly.This means that the sensory organs are functioning properly. That is to say, the auditory information reaches the perceptive organs, but it is not processed by the brain, so that the perception of sound is completely lost. This alteration is caused by the destruction of the primary and secondary auditory cortexes, or the nerve pathways that access them, in both hemispheres.

2. Hearing loss

As with deafness, this condition is caused by the destruction of the primary and secondary auditory cortex, with the difference that this destruction has only occurred in one hemisphere. this destruction has only occurred in one hemisphere..

Thus, hearing is completely lost in the ear opposite to the hemisphere in which the lesion occurred, but since the auditory cortexes of the other hemisphere are still functional, hearing is possible in the other ear.

Moreover, in some cases it is possible that over time a certain level of hearing is gained also through the ear that has been disabled, because neural plasticity allows parts of the brain to learn functions that were previously performed by others, and this can even occur by switching tasks from one hemisphere to the other.

3. Prosopagnosia

In cases of prosopagnosia, the affected person loses the ability to recognize faces, even those of loved ones. Recognition of persons must occur through other brain processing pathways.

This alteration is caused by bilateral lesion in the temporoccipital area..

4. Hemineglect

Caused by the affectation of the parieto-temporo-occipital association area, this disorder involves difficulty in orienting, acting or responding to stimuli occurring on the opposite side of the lesioned hemisphere.. Attention to that perceptual hemifield ceases, although the person himself can move in such a way that the stimuli he misses remain within reach of the functional perceptual field. It usually appears together with anosognosia, which is the ignorance of the existence of an alteration.

5. Aphasia

Aphasias are understood as language disorders due to a brain lesion.. The effects vary according to the location of the lesion, and when the lesion affects the temporal lobe there are certain characteristic symptoms.

Of the aphasias produced by a lesion in the temporal region, Wernicke's aphasia (produced by a lesion in the area of the same name, in which there is a loss or difficulty in verbal comprehension and repetition, which causes serious problems to the sufferer), anomic (loss or difficulty in finding the name of things, caused by lesions in temporo-parieto-occipital associative areas) or transcortical sensory (in which there are difficulties in comprehension but not in repetition, being the result of lesions in temporo-parieto-occipital associative areas).

If the connection of Wernicke's area with Broca's area, the arcuate fasciculus, is damaged, the so-called conduction aphasia will be produced, in which there is difficulty in repetition and a somewhat impaired comprehension, but good fluency is maintained.

6. Anterograde amnesia

This disorder the inability to record new material in memory.. That is to say, it is impossible for the patient to recover (either permanent or temporary disability) the declarative information of the activity performed after the lesion.

This alteration is produced by lesions in the medial temporal lobe, especially in the hippocampus. Lesions in the left hemisphere will affect verbal information, while in the right hemisphere the affectation will tend to be of other or non-verbal pathways.

7. Klüver-Bucy syndrome

This is a very common disorder in dementias, such as Alzheimer's disease.. This disorder is characterized by the presence of meekness, passivity, hyperorality, sustained attention difficulties, disappearance of fear and hypersexuality. It occurs in the presence of bilateral medial temporal lesions.