Wernicke’s Area

Summary

The area of the associative auditory cortex is called Wernicke's area. Simply put, this brain segment is responsible for understanding speech. As we will elaborate on brain centers for speech, words, and language in this article, it is important to emphasize the difference between Broca's area and Wernicke's area.

Broca's speech area is in charge of grammatical details and the correct order of words that makes the speech fluent. Damage to this zone leads to disorders of speech in terms of fluency. There are also difficulties in using prepositions, adverbs, and conjunctions.

On the other hand, in 1874, German anatomist Carl Wernicke (1848–1905) found that patients with problems with language comprehension had a part of the left hemisphere of the brain-damaged. This area was named the Wernicke's area or region. We can say that Wernicke's area processes the meanings of sounds (1). This zone adds meaning and understanding of the words that we hear.

In this article, we will talk about its anatomical position, relation to other areas, its structure, and its function. Finally, we will provide information on the damage of the Wernicke's Area, its consequences, and possible treatments.

The Discovery of the Wernicke Area

In the 19^th century, neuroscientists were trying to discover and localize functions and abilities in our brain and relate them to their responsible centers. One of the areas of their interest was language production, processing, and understanding. 

Paul Broca was one of the pioneers when it comes to language centers research. In the early 1870s, he made a remarkable discovery. Namely, he identified the brain region responsible for language production.

Paul Broca also made research on patients with problems in producing language, especially in cases when they do understand the language but cannot speak. Broca found that lesions in a specific part of the frontal lobe lead to that very disorder. It is this brain area that we today know as the Broca's area.

The other key neuroscientist of the 19^th century is German neurologist, Carl Wernicke, as mentioned in the introduction. This neurologist was interested in patients with a similar, yet so different problem.

Wernicke’s patients were able to speak but their speech was meaningless. In addition, they were not able to understand, i.e. comprehend language. Wernicke was devoted to examining the brains of these patients. He found lesions in an area located between the temporal, parietal, and occipital lobes, we today know as the Wernicke’s area (2).

It was proven that this brain region is responsible for language comprehension and the production of meaningful speech.

Position and Structure of the
Wernicke’s Area

This brain segment is positioned in the left temporal lobe. Although the position of Wernicke is sometimes visually depicted as being in the left hemisphere of the brain, particularly in the vicinity of the lateral sulcus – a large, prominent brain groove, the exact location of the Wernicke’s Area is still not agreed upon by the scientists.

Therefore, when it comes to its anatomical position, we can say that the Wernicke’s area is generally described as positioned in the back segment of the temporal lobe, even though we must emphasize that its exact location may vary. Furthermore, this zone is most commonly found in the left hemisphere of the brain, but this can also vary.

It is connected to the Broca’s area via a dense bundle of nerve fibers called the arcute fasciculus. Superiorly, the Wernicke's area is related to and bound by the angular gyrus. This brain segment found in the parietal lobe is responsible for memory operations, number processing, reasoning, and it also plays a role in language processing. 

The process of forming and understanding speech

In order to understand the function of the Wernicke area better, we will introduce you to the process of forming, production, and understanding speech. Namely, speech and language production and comprehension are very complex processes. As expected, they rely on several brain segments.

The main three areas scientists identified up to now include the Broca’s area, the Wernicke's area, and the angular gyrus. As already described in the position and structure section, the Wernicke's area has a strong connection to the Broca's area. These two zones are linked via a group of arcuate fasculicus. These are bundles of the nerve fiber.

When it comes to the functions,
shortly, we can say that the Wernicke's area is responsible for language
understanding/comprehension, the Broca's area is responsible for producing
speech, i.e. communicating our thoughts, while the angular gyrus, is
responsible for using sensory information as an important part of language
comprehension.

The Function of the Wernicke's Area

As already stated, the key function of the Wernicke’s Area is understanding speech. It processes the meanings of sounds. However, research done in recent years has shown that there are more than two speech areas in the dominant cerebral hemisphere.

Moreover, the entire group of areas decodes the structure of difficult sentences, the second one decodes the structure of easy, simple sentences, and the third group of areas is responsible for the meaning of the words. These processes happen whether we talk or listen.

These regions are positioned in the Broca’s and the Wernicke’s areas, as well as the anterior portion of the temporal lobe. Furthermore, they are located in several parts of the anterior lobe, as well as the inferior parietal lobe. Remarkably, according to what we know today, the occipital lobe is not involved in speech processing at all.

Damage of the Wernicke’s Area

Aphasia is the loss or disruption of language skills that were already previously acquired and functional. Aphasia is a condition usually caused by a brain injury. Injuries to the brain especially occur as a result of a stroke, but can also occur as a result of physical injuries, tumors, dementias, infectious brain diseases, etc.

In more medical terms, speech
disorders resulting from damage to the corresponding speech centers in the
dominant cerebral hemisphere of the cerebral cortex and their subcortical
connections are called aphasia or, if the impairment is incomplete, dysphasia.

Depending on the part of the brain
that is affected by the injury, a patient with aphasia partially or completely
loses one or more linguistic abilities. Language skills include the production
of spontaneous speech, speech comprehension, the ability to name items,
repetition, reading, and writing.

Aphasia can also be accompanied by cognitive function impairment(s), such as loss of attention, memory problems, and thinking disorders. In addition to the spoken languages, sign language functions can also be damaged by aphasia. Sign languages also represent structured linguistic systems and have a phonological, morphological, and syntactic level.

Consequently, aphasia causes similar problems to those who use the sign language as to those who use the spoken language. Depending on the part of the brain that is injured and the language abilities that are impaired, there are several basic types of aphasia. First of all, the damage of the temporal lobe in the dominant hemisphere is characterized by a type of aphasia interesting for us, in this article.

It is the Wernicke's aphasia. Sensory aphasia results from damage in the Wernicke's arena in the temporal lobe of the left cerebral hemisphere brain. A patient with sensory aphasia can speak but the words are meaningless and incomprehensible. The patient understands neither his own nor the speech of others. That's why he or she cannot be aware of his/her own mistakes.

This condition is usually easily
recognized as the patient makes meaningless speech sounds. This is also called
receptive aphasia. Namely, the sounds do not make any sense. In addition, the
patient makes sentences, even long ones, but they don’t have proper meanings.
As the patient himself cannot understand speech, he/she is not aware of the
mistakes. That’s why these patients’ speech is called “word salad”.

Appropriate exercises and methods that do not differ much from those used when teaching young children to express themselves can result in restoring the lost speech ability. These methods either restore the function of the Wernicke's area or help develop a new network of cells to perform the function of the damaged zone. This brain trait is called plasticity. In other words, our brain is capable of repair and regrowth (3).

Conclusion

The Wernicke area is anatomically positioned in the left brain hemisphere. More precisely, it is located in the back (posterior) third of the upper temporal convolution. It is located near the auditory cortex. Its key function includes speech comprehension. Therefore, the Wernicke area is a unique language comprehension and receptive language center.

Its damage results in a condition
called Wernicke aphasia. The patient does not lose the fluency of speaking, but
the speech becomes meaningless. The patient also loses the ability to
understand speech. This condition usually results from a stroke, a tumor, or a
physical injury that affected the Wernicke area.

References

1. Javed K, Wroten M. Neuroanatomy, Wernicke Area. [Updated 2019 Jan 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan. Found online at: https://www.ncbi.nlm.nih.gov/books/NBK533001/
2. DeWitt I, Rauschecker JP. Wernicke's area revisited: parallel streams and word processing. Brain Lang. 2013 Nov;127(2):181-91. doi: 10.1016/j.bandl.2013.09.014. PMID: 24404576; PMCID: PMC4098851.  Found online at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4098851/
3. 3. Binder JR. The Wernicke area: Modern evidence and a reinterpretation. Neurology. 2015 Dec 15;85(24):2170-5. Found online at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4691684/