Temporal Brain Lobe

The temporal lobe is a particularly interesting part of our brain. Namely, this brain segment is present only in primates. Among all primates, humans have the biggest temporal lobes.

Scientists now know that 17% of the
cerebral cortex belongs to the temporal lobe. Most noteworthy, this lobe
contains auditory, vestibular, olfactory, linguistic, and visual functions.

In this article, we will elaborate on the position, structure, and functions of the temporal lobe. Also, we will talk about its role in the lexical-semantic processing of words, as well as lesions and their consequences.

Position and structure of the
temporal brain lobe

Like the frontal, parietal, and occipital lobes, the temporal lobe is also located on the surface of the brain (1). Under the temporal brain lobe, there is the so-called insula.

The temporal lobe occupies the underside of the hemisphere. From the frontal and parietal lobes, the temporal lobe is limited by the lateral sulcus. There are three convolutions on the upper side of the temporal lobe. Those are the upper, middle, and lower convolution.

The superior temporal gyrus is located between the sylvicus and the upper temporal sulcus, the middle - between the upper and lower temporal sulcus, the lower - between the lower temporal sulcus and the transverse cerebral fissure (1).

The lower surface of the temporal lobe contains the lower temporal gyrus, the lateral occipital-temporal gyrus, and the hippocampal gyrus.

A well-studied primary projection zone is the auditory cortex, which is located in the depth of the lateral groove (transverse temporal gyrus cortex). The temporal lobe projection cortex is also used to center the vestibular analyzer in the upper and middle temporal convolutions (1).

The area of the olfactory projection
is located in the hippocampal gyrus, especially in its front section (called
the hip). In addition to the fragrant projection zones, there are centers for
flavor recognition.

The hippocampal formation is positioned on the lobe’s medial side. Its segments include the subiculum, the parahippocampal gyrus, the hippocampus, white matter, and dentate gyrus.

Another anatomically important segment of the temporal lobe is the choroid fissure. It is located alongside the fimbria. Physically, it separates the optic tract and the temporal lobe. Also, it separates the midbrain and hypothalamus from the temporal lobe.

When it comes to the relation between the amygdala and the temporal lobe, we must emphasize that there are amygdala nuclei located on the temporal lobe medial aspect. This is very important, as the inputs from the olfactory bulb are sent to amygdala in this way. Likewise, it receives information from the association cortex in the same way. This is crucial for sensation modalities.

The Function of the Temporal Brain Lobe

Temporal brain lobes are responsible for listening, as well as converting sounds into pictures. They provide general speech perception and enable communication. The dominant temporal lobe of the brain allows you to fill in the words you hear, to find the necessary lexemes to express your thoughts.

Non-dominant lobe helps in recognizing intonation, as well as determining the expression of the human face. The front and middle temporal compartments are responsible for the odor. If odor recognition ability is lost in a mature or old age, it may signal the onset of Alzheimer's disease.

The importance of the function of
the temporal lobes can be understood if we understand that a damaged or lesion
on both temporal lobes may lead to a disability of absorbing the visual images.
The patient becomes too calm, and his/her sexuality and libido suffers as well.

Most noteworthy, the associative areas for multiple sensation modalities are found in the temporal brain lobe, alike they are located in the frontal and parietal lobes. These produce sensory information, motor response, and other information that requires new and previously stored experience. These actions combine learning, thought-making, affect and behavior.

Temporal lobes integrate auditory
stimuli, as well as sensory linguistic and visual information. Moreover, they
play a role in emotion control. Patients with damage to the right temporal lobe
usually lose the ability to recognize non-verbal auditory stimuli (e.g. music).

The left temporal lobe is mainly responsible for recognizing, memorizing, and forming speech. Patients with epileptogenic focus in the medial limbic-emotional part of the temporal lobe most often have complex partial seizures in the form of uncontrolled emotions, autonomic, cognitive, and emotional dysfunction.

Occasionally, such patients have personality changes characterized by a lack of sense of humor, philosophical religiosity, obsessiveness, and in men, libido may be diminished.

The function of the temporal lobe is related to the perception of auditory, taste, olfactory sensations, analysis and synthesis of speech sounds, memory mechanisms. The major functional center of the upper side of the temporal lobe is located in the superior temporal gyrus.

It also contains the auditory, or gnostic, the center of speech (the center of Wernicke). The temporal lobes play an important role in organizing complex mental processes, especially memory (2).

Role of the Medial Temporal Lobe in Lexical-semantic Word Processing

The importance of the temporal lobe in understanding the sensory stimulus is evident in its function of adding categorical features to the auditory and visual information.

The temporal lobe can be divided into several functional zones: zone for auditory and visual processing, zone responsible for the integration of these processes and emotion processing, and zone for spatial orientation and spatial memory.

On the lateral part of the temporal lobe, there are regions responsible for auditory functions and ventral visual flow. The medial temporal regions (which form part of the limbic cortex) include the amygdala, uncus, hippocampus with subiculum, entorhinal and perirhinal cortex, and fusiform wind.

Numerous studies that have used functional brain imaging have confirmed the role of the medial temporal lobe in lexical-semantic processing. To put it more precisely, this has been shown in tasks of determining the meaning of the terms, in a study by Vannucci from 2003 (3), as well as in naming, shown in a study by Sawrie from 2000 (4).

Moreover, it is shown in categorical fluency and lexical-meaning decision tasks. In conclusion, the lexical-semantic system comprises anterior temporal, posterior lateral, and ventral occipitotemporal regions, as well as the medial temporal lobe.

Psycholinguistic research shows that epileptic outbreaks can lead to neural communication dysfunction and damage to the semantic system due to decreased functional connectivity between language regions.

In different studies, due to the anatomical and functional specificity of the lesion, epilepsy of the medial temporal lobe was taken as a model of lexical-semantic deficits. Studies of language difficulties in temporal lobe epilepsy clearly confirm the connection of the temporal lobe to lexical-semantic processing.

A series of studies showed that patients with temporal lobe epilepsy perform worse in appointments, especially regarding their lexical-categorical categorical fluency, as well as the agreement of lexical-meaningful categories. Finally, they perform worse in the task of determining lexical-semantic characteristics.

Temporal Lobe Lesions

Lesions on the temporal lobes are responsible for hearing and perception disorders. Lesions of the temporal lobe also cause disorders in the perception of oral speech, dizziness, hallucinations and seizures, mental disorders and excessive irritation.

It is important to know what causes these lesions. First of all, the most common cause is a stroke. Secondly, brain tumors are responsible for many cases of temporal lobe lesions. Besides, various head injuries or traumas can lead to temporal lobe lesions.

Moreover, a surgical operation that is often undertaken in order to remove a brain tumor can sometimes cause a lesion in this region.

Similarly, brain infections often lead to lesions in different brain parts. If the temporal lobe is affected by an infection, such as the herpes simplex virus infection, this can leave lesions in this part of the brain.

Finally, various diseases and
conditions, including multiple sclerosis, can lead to temporal lobe damage.

Conclusion

The temporal lobe has many different functions for the whole and proper functioning of our organism. The temporal brain lobe is separated by the lateral furrow from the frontal and parietal lobes as well as from the occipital lobe.

Its key functions include roles in sound and language processing. Moreover, it is also used in functions that are related to memory and emotion management.

References

1. Kiernan JA. Anatomy of the temporal lobe. Epilepsy Res Treat. 2012;2012:176157. doi: 10.1155/2012/176157. Epub 2012 Mar 29. PMID: 22934160; PMCID: PMC3420617.  Found online at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3420617/
2. Jeneson A, Squire LR. Working memory, long-term memory, and medial temporal lobe function. Learn Mem. 2011 Dec 16;19(1):15-25. doi: 10.1101/lm.024018.111. PMID: 22180053; PMCID: PMC3246590.  Found online at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3246590/
3. Vannucci, M., Dietl, T., Pezer, N., Viggiano, M. P., Helmstaedter, C., Schaller, C., Elger, C. E., Grunwald, T. (2003). Hippocampal function and visual object processing in temporal lobe epilepsy. Neuroreport 14, 11, 1489–1492. Found online at: https://www.ncbi.nlm.nih.gov/pubmed/12960770
4. Sawrie, S. M., Martin, R. C., Gilliam, F. G., Faught, R. E., Maton, B., Hugg, J. W., Bush, N., Sinclair, K., Kuzniecky, R. I. (2000). Visual confrontation naming and hippocampal function: A neural network study using quantitative (1)H magnetic resonance spectroscopy. Brain 123, 4, 770–780. Found online at: https://www.ncbi.nlm.nih.gov/pubmed/10734008