Generality
The temporal lobe is one of the four great even and symmetrical areas in which the cerebral cortex of the human brain is ideally subdivided.
Protected by the temporal bone (which constitutes the latero-inferior portion of the cranial vault), the temporal lobe occupies, on each cerebral hemisphere, a position such as to coincide with the area of the head comprised between the temple, the ear and the portion immediately following the ear.
Including hippocampus, amygdala and Wernicke area, the temporal lobe plays a key role in understanding spoken and written language, in verbal memory, in the processes of perception, recognition and interpretation of sounds, in the interpretation of visual stimuli, in visual recognition of objects, in certain types of emotional reactions, and in long-term memory.
Brief anatomical review of the brain
The brain is, together with the spinal cord, one of the two fundamental components of the central nervous system .
Heavy about 1.4 kilograms and containing 100 trillion neurons (in the adult human being), the encephalon is a very complex structure, which can be divided into 4 large regions, which are: the brain proper (or telencephalus or , simply, brain ), the cerebellum, the diencephalon and the brainstem .
BRAIN PROPERLY SAID
The brain is the largest and most important region of the brain.
Its general anatomical shape requires the presence of:
- Two large specular hemispheres (the right cerebral hemisphere and the left cerebral hemisphere ), separated by a groove (the so-called interhemispheric groove ), and
- A corpus callosum, located at the base of the two aforementioned cerebral hemispheres.
On the surface, the brain has the so-called gray substance, which goes to make up a laminar layer called the cerebral cortex ; in the deeper layers (therefore below the surface), instead, it presents the so-called white substance .
What is the Temporal Lobe?
The temporal lobe is one of the four large areas (called lobes ), in which the cerebral cortex of each hemisphere of the human brain is ideally divided; to be precise, of the four lobes of the brain that form each cerebral hemisphere, the temporal lobe is the one with a latero-inferior seat .
The temporal lobe can be defined as an "even zone" of the telencephalon, where "even" means that it is present both on the right cerebral hemisphere ( right temporal lobe ) and on the left cerebral hemisphere ( left temporal lobe ).
What are the other lobes of the brain?
In addition to the temporal lobe, the frontal lobe, the parietal lobe and the occipital lobe are the framework of the cerebral lobes.
Of the cerebral cortex, the first constitutes the anterior area, the second the upper-lateral area and the third the posterior area.
Anatomy
Representing approximately 22% of the total cortical volume, the temporal lobe holds the primacy of the second largest lobe of each cerebral hemisphere, after the frontal lobe.
Located laterally both on the right cerebral hemisphere and on the left cerebral hemisphere, the temporal lobe is identifiable, in a human head, in the band between the temple (from which it derives the name "temporal"), the ear and the part immediately following the ear.
In the anatomy of the skull, the temporal lobe is the area of the brain that receives protection from the so-called temporal bone, that is the inferior bone-lower element of the cranial vault that forms the external auditory meatus and accommodates on the inner side the medium and internal structures of the ear .
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The temporal lobe is an even symmetrical area, where by symmetric we mean that it occupies the same position on the two cerebral hemispheres.
Localization in the cerebral hemisphere
Included in the so-called middle cranial fossa, the temporal lobe resides:
- At the back of the frontal lobe,
- Below the parietal lobe e
- Anterior to the occipital lobe.
If to divide it from the occipital lobe there is nothing particularly evident (therefore the passage from one lobe to the other is blurred), to separate it from the frontal lobe and from the parietal lobe there is a marked and deep cerebral groove, called lateral fissure of Silvio (or lateral fissure or sylvan fissure ). Reporting the boundary imposed by Silvio's lateral fissure is important, because the more traditional anatomical descriptions speak of the temporal lobe as the cerebral area located below the sylvian fissure.
Convolutions of the Temporal Lobe
In neurology, the term " convolution " refers to each section of a ridge-like cerebral cortex, between two of those typical depressions of varying depth, visible on the hemispheres of the brain and called grooves .
In the temporal lobe, the convolutions are altogether 5 and are called: superior temporal convolution, mean temporal convolution, inferior temporal convolution, fusiform convolution and para- hippocampal convolution .
Important zones of the Temporal Lobe
The temporal lobe extension area includes two very important nerve regions, which are the medial temporal lobe and the Wernicke area .
MEDIUM TEMPORAL LOBO
The medial temporal lobe is the innermost portion of the part of the cerebral cortex that constitutes the temporal lobe.
Being part of the so-called limbic system (a set of brain elements with a key role in emotional reactions, short-term memory, behavior, etc.), the medial temporal lobe is the seat of some very important brain structures and, in some ways, still the subject of neurological studies, such as the amygdala and the hippocampus.
WERNICKE AREA
Functionally related to the human being's ability to understand spoken and written language, the Wernicke area takes place in the posterior portion of the superior temporal convolution.
Temporal lobe blood supply
The inflow of oxygenated blood to the temporal lobe, a fundamental process to keep the latter alive, depends on two branches of the internal carotid artery - the so-called anterior corioid artery and middle cerebral artery - and the vertebrobasilar artery .
Venous drainage of the temporal lobe
The venous drainage of the temporal lobe - that is, that system of venous vessels that collects the blood transited through the temporal lobe tissues and is now deprived of oxygen - belongs to the superficial middle cerebral vein, as far as the most superficial portions of the cerebral area in question are concerned, and to the posterior chorioid vein, as regards the section known as the medial temporal lobe.
The superficial middle cerebral vein flows into Labbè's vein, which in turn flows into the transverse sinus .
The posterior corioid vein, on the other hand, joins the internal cerebral vein, which, becoming the so-called large cerebral vein (or vein of Galen ), flows into the straight sinus .
Function
The temporal lobe participates in very important functions, such as:
- The perception of sounds, their recognition and their interpretation .
All these functions related to sounds belong specifically to the superior temporal convolution, which communicates with the cochlea (one of the fundamental components of the inner ear).
In everyday life: these are functions that allow human beings to perceive and give meaning to sounds, and to recognize a sound already heard in the past.
- The interpretation of visual stimuli and the recognition of objects, through the construction of a visual memory .
These abilities of the temporal lobe depend, in particular, on the fusiform convolution and the paraippocampal convolution.
In everyday life: these are skills that allow human beings to recognize faces, body language, everyday objects, etc.
- Understanding of spoken language and written language, and verbal naming and memory .
As already mentioned, these functions belong to the Wernicke area.
In everyday life: these functions allow human beings to name objects, understand which object or person the name refers to, remember verbal exchanges and understand the language used by others.
- Long-term memory and the control of seemingly unconscious reactions, such as hunger, thirst, emotions, etc.
These functions of the temporal lobe are characterized by the structures of the medial temporal lobe (limbic system), primarily the hippocampus and secondly the amygdala.
In everyday life: these functions allow human beings to preserve memories.
The Temporal Lobe is not an autonomous organ
Just like all other cerebral lobes, the temporal lobe is a nervous structure whose functioning is strictly dependent on the interaction with the other encephalic components (including the other lobes of the brain); this means that it is not an autonomous organ, but one of the various components of that complex "machine" called encephalon.
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The correct functioning of an area of the brain also depends on the correct functioning of the other brain regions with which the aforementioned area is related.
Therefore, it is possible for the temporal lobe to malfunction due to the malfunction of a brain area connected to it.
diseases
Like any other region of the brain, the temporal lobe can develop a more or less extensive lesion, in the moment in which it undergoes a trauma or is the object of stroke (ie the phenomenon of interruption of the blood supply to a brain area, followed by necrosis of the latter due to lack of oxygen).
In addition, some medical conditions are related to the temporal lobe, such as frontotemporal dementia, temporal lobe epilepsy and schizophrenia .
Temporal Lobe Injury
Premise: for reasons that are still unclear, in every human brain there is a dominant cerebral hemisphere on the other. This dominance implies, for the dominant hemisphere, a sort of functional specialization, which the non-dominant hemisphere, although equal, does not possess and is generally unable to imitate.
In most people, the dominant cerebral hemisphere is the left.
Temporal lobe injury has different consequences depending on:
- The affected cerebral hemisphere . The lesion of the temporal lobe of the dominant hemisphere produces different effects of the temporal lobe lesion of the non-dominant hemisphere;
- The precise location of the damage . The lesion of a certain temporal lobe zone involves problems different from the lesion of a temporal lobe zone different from the previous one; likewise, total temporal lobe injury produces problems other than partial injury.
UNILATERAL INJURY OF THE DOMINANT TEMPORAL LOBO
The possible consequences of an injury to the dominant temporal lobe are:
- Receptive aphasia (or Wernicke's aphasia ): the patient develops problems in the production and understanding of language;
- Acquired dyslexia (or alessia ): the patient partially or totally loses the ability to read;
- Agraphia and acalculia : the patient loses the ability to write (agraphia) and perform calculations (acalculia);
- Verbal-auditory agnosia : the patient is incapable of recognizing sounds or noises and finds problems in understanding the language heard;
- Nominal dysphasia : the patient loses the ability to identify objects with a name.
UNILATERAL INJURY OF THE NON-DOMINANT TEMPORAL LOBO
The possible consequences of a lesion against the non-dominant temporal lobe are less serious than the previously analyzed case and consist of:
- Quadrantonopsia : the patient suffers the loss of a quarter of the visual field;
- Alterations of non-verbal memory : the patient loses part of the ability to store in the mind noises, sounds, faces, figures, smells, tastes etc .;
- Prosopagnosia : the patient is incapable of recognizing the faces of known people and sometimes even his own face. This disorder can be considered a special case of the previous point (alterations of non-verbal memory).
LESION OF BOTH TEMPORAL LOBES
To the consequences of the dominant and non-dominant unilateral lesions, the lesion of both temporal lobes can add further problems, such as: deafness, apathy, deep memory and learning deficits, and / or a medical condition known as Klüver-Bucy syndrome .
Frontotemporal dementia
Belonging to the great category of dementias, frontotemporal dementia is a neurodegenerative disorder of the brain, which appears due to the progressive deterioration of neurons (nerve cells) located in the frontal lobes and in the temporal lobes of the brain.
Those suffering from frontotemporal dementia develop behavioral and language problems, inability to think, memory impairment (amnesia), balance disorders and reduced control of some body muscles.
Epilepsy of the Temporal Lobe
Temporal lobe epilepsy is a neurological condition that combines the periodic occurrence of epileptic seizures with visual, olfactory, auditory, taste sensory hallucinations, etc. and to memory problems.
Schizophrenia
Schizophrenia is a serious form of chronic psychosis, which causes auditory hallucinations, delusions, changes in affectivity, bizarre behavior and problems affecting the capacity for thought and language.
According to the most reliable scientific studies, this psychiatric illness would be related to the temporal lobe from the dependence on the latter of one of the most common symptoms: auditory hallucinations.
