Karl Wernicke (1848-1904)
The physiology of the brain was oriented during this period in the investigation of the functional location. Broca was one of the initiators, since he placed the center of articulated language on his foot in the third left frontal gyrus. A good number of experimental works followed as well as anatomo clinical observations that were establishing the areas of the cortex that govern the activities of the relationship life. In 1874 Wernicke described sensory aphasia.
Wernicke was born in Tarnowitz a small town in Upper Silesia (then part of Prussia), on May 15, 1848. His father worked as an administrator in a mining company. He completed his studies at the Gymnasiafrom Oppeln and Breslau. He studied medicine at the University of Breslau, which is located on the border with Poland. There he worked as an assistant to Heinrich Neumann (1814-1884) at the Allerheiligen Hospital. He earned a doctorate in 1870. During the Franco-German War (1870-1871) he was as assistant to the surgeon Fischer. Neumann provided Wernicke with a six-month stay in Vienna with Meynert to study anatomy. It is noted in the biographies that Wernicke felt great devotion to this doctor, one of the few he cited in his lectures and whose portrait was the only one that hung on the walls of the auditorium of the Wernicke clinic.
After his return to Breslau he published Der aphasische Symptomencomplex. Eine psychologische Studie auf anatomischer Basis(1874). On the subject of aphasia the neurologist Henry C. Bastian (1837-1915) anticipated proposing the existence of alterations in the field of understanding. He distinguished between aphasia and amnesia of language, two entities with different symptoms and different localization. To differentiate language alterations from those of writing and reading, he used diagrams that presented processing centers (the writing center, verbal auditory center, etc.). Wernicke established sensory aphasia as a clinical entity by placing the lesion in the posterior part of the temporal lobe (first left temporal gyrus), and whose main evidence was the loss of verbal or auditory comprehension.
Wernicke also formulated a general theory about aphasia that proposed the relationship between each of the components of language and a particular brain area. According to him, aphasia affected only language although certain associated symptoms could occur. The model allowed to predict the possible existence of pictures that had not been noticed and that depended on the area in which the lesion was found: central aphasias, if it was in any of the language centers; aphasias of conduction, if it did it along the connection routes between both centers. This associationist model was very successful among the researchers of the moment. Later, Lichtheim, based on Wernicke, developed a brain functioning scheme with three different centers for language with their corresponding connections:
The language model that Wernicke based on the reflex physiological arc served as a paradigm for all psychological processes and to develop a general theory of mental disorders. His disciples Liepmann and Lissauer, for example, applied this model to describe and also explain apraxia and agnosia.
Wernicke was at the Charité in Berlin, in the department of neurology and psychiatry, with Carl Westphal (1833-1890) between 1876 and 1878. He was a student of obsessive neuroses, especially agoraphobia, and one of those who introduced the patellar reflex as a neurological criterion. Wernicke later dedicated himself to private practice as a doctor of nerve diseases in Berlin. In 1885 he accepted an extraordinary professor position at the University of Breslau to succeed Neumann. From 1890 he was already an ordinary professor of psychiatry who was associated with the direction of the department of the mental illness hospital of the city. He had the opportunity to examine and observe many neurological and psychiatric cases. The city refused to build a building for a university psychiatric clinic, what put Wernicke in a violent situation, until he went on, in 1904, to the University of Halle as director of the psychiatric and neurological clinic. He did not reach a year as a director since, an accident, while riding his bicycle, led him to death at age 57 (June 15, 1905 in Dörrberg im Geratal), when he was preparing the second edition of his Fundamentals of Psychiatry .
As was usual then in psychiatry, Wernicke had been thoroughly trained in anatomy, under the influence of Theodor Meynert (1833-1893), as we have said. In 1872 Wernicke described the fissure that bears his name or fissure that sometimes limits the temporal and parietal lobes of the occipital lobe.
One of the central elements of his thinking was that mental illnesses could not be defined by their symptoms only, but that this symptom, or group of symptoms, had to respond to a structural, localizable, anatomical, encephalic alteration, and more precisely: cortical.
Between 1881 and 1883 he published the three volumes of his Lehrbuch der Gehirnkrankheiten (Treatise on Brain Diseases). This work includes a good number of original anatomical, pathological and clinical descriptions. In 1900, as a professor of psychiatry at Breslau, he published his Grundriss der Psychiatrie in Klinischen Vorlesungen (Compendium of Psychiatry in clinical classes). This work had profound repercussions in its time. Nissl (1860-1919) considered it very important, while Kraepelin called it “speculative anatomy.” Jaspers (1883-1969) also had his qualms about accepting it, but placed Wernicke next to Freud, as an example of opposite poles in the psychiatric theories of his time.
He was the creator of terms and concepts that remain in force: fixation capacity, overvalued ideas, perplexity, delusions of explanation, native ideas, somatopsychic depersonalization, hallucinations, acute upper hemorrhagic polioencephalitis (Wernicke’s disease), mania with iracundia, presbyophenia as one of the forms of senile dementia (Wernicke syndrome), which reflect his deep sense of clinical observation and ability to extract the symptom, the sign, or the syndrome of a seemingly incomprehensible whole.
Despite his bad character, Wernicke was very patient and skilled in the search for signs and symptoms in his patients. Today we talk about “Wernicke reaction or sign”, to refer to the reaction observed in certain cases of hemianopia, in which the stimulation of the light projected on one side of the retina causes the contraction of the iris, while projected on The other side produces no reaction.
The Wernicke area is one of the main areas of the cerebral cortex responsible for understanding spoken and written language. It is considered the center of receptive language. Usually, but not always, it is found in the left hemisphere. This is true in 90% of right-handed people and in 70% of left-handed people.
Specifically, the Wernicke area encompasses the back of the left temporal lobe. However, the exact location and extent of this area has been a controversial issue among scientists.
Recent studies have shown that Wernicke’s area is activated in deaf people who communicate with sign language. This indicates that Wernicke’s area is not only used for spoken language, but for any language modality.
Its name is because it was discovered by the German neurologist Karl Wernicke in 1874. This scientist discovered this area while observing people who had damage to the back of the temporal lobe of the brain.
People who have damage in the Wernicke area may develop a condition called Wernicke’s aphasia. It is characterized by the inability to understand language, repeat words or phrases, despite having preserved the articulation of speech sounds.
Wernicke area discovery
Many of the scientists studying the brain come to conclusions thanks to the observation of patients with brain damage.
In this way, they examine patients who have suffered an injury or pathology that affects the brain, and compare them with healthy people.
In this context, the famous discovery made by Paul Broca is framed. In 1861, this neuroscientist studied the brain of a patient who could only emit the word “Tan.” Although I understood spoken language, I could only say that word.
Broca found that his patient had a lesion in the third frontal gyrus. Suggesting that this area was responsible for controlling speech.
In later studies he confirmed his hypotheses, taking the name of this part of the brain of “Broca’s area”. Broca’s studies gave a great boost to the study of the anatomical basis of language.
A short time later, Karl Wernicke made a similar discovery. He observed that his patients were not able to speak correctly. Although they pronounced well and retained a certain grammatical structure, the speech was meaningless and difficult to understand.
Apparently, what happened to these patients is that they couldn’t understand the language. And therefore, they could not have a smooth conversation.
Wernicke found lesions in the brain in the left hemisphere, but in the posterior part of the temporal lobe.
In 1874, he published a work on aphasia that some authors consider to be the first neurolinguistic theory. This scientist proposed that there is a “center for the auditory images of words”, which is located in the first temporal gyrus. This center allows us to understand the language we hear.
Wernicke described the first connectionist model of the neural bases of language. According to this perspective, language arises from the joint work of several language centers that are connected to each other.
Wernicke’s thesis argues that there are two anatomical locations for language. The first is the anterior area, which is located at the back of the frontal lobe (Broca’s area). This area contains “memories” of speech movements, thus controlling the production of language.
The second would be known as the Wernicke area, located in the posterior temporal lobe. In it would be the “images of the sounds”, that is, the one that deals with processing the words we hear and making sense of them.
Wernicke’s area is usually located in the left hemisphere, specifically in the temporal lobe.
It corresponds to Brodmann areas 21 and 22, covering the posterior area of the superior temporal gyrus. This area of our brain includes the auditory cortex and the lateral groove, that part where the temporal lobe and parietal converge.
However, its exact extent is unclear and there seems to be disagreement between authors. Sometimes the primary auditory cortex and other nearby areas are included. For example, the areas of Brodmann 39 and 40, located in the parietal lobe.
These areas have been associated with reading and semantic aspects of language.
Wernicke’s area is connected to another region of the brain called Broca’s area. This area is located in the lower part of the left hemisphere of the frontal lobe and controls the motor functions involved with speech production.
The difference between Broca’s area and Wernicke’s area is that the former is primarily responsible for planning speech production, while the latter receives the language and interprets it.
Broca’s area and Wernicke’s area are joined through a structure called an arcuate fascicle, which is a large bundle of nerve fibers.
Although recent studies have shown that these two areas are also connected by another structure called “Geschwind territory”. It is a kind of parallel path that circulates through the inferior parietal lobe.
These two areas, Broca’s and Wernicke’s, allow us to speak, interpret, process and understand spoken and written language.
Wernicke area and language models
Many authors have tried to explain how Wernicke’s area participates in language and connects with other structures.
The most prominent language models that describe the possible role of the Wernicke area are described below.
This was the first model of organization of the brain functions of language. It was proposed by Norman Geschwind from Wernicke’s studies.
According to this model, each of the characteristics of language such as perception, understanding, production, etc. They are managed by a specific area of the brain that communicates with others through a series of connections.
According to this model, language disorders arise due to damage in that network of connections between the different modules.
When the spoken word is heard, the auditory signal is first processed in the primary auditory cortex of the brain. Then it is sent to the Wernicke area. There, the structure of this signal (its sounds) is associated with the representation of the word stored in memory. Thus we managed to understand its meaning.
When a word is read aloud, something similar happens, although the information is initially perceived in the visual cortex. It is then transferred to the angular gyrus, and from there it travels to the Wernicke area.
Whether a word is heard or read aloud, the mental lexicon of Wernicke’s area recognizes it and interprets it according to the context.
So that the speech is given, this information is transmitted to the Broca area, which is responsible for controlling the pronunciation process. Next, the signals on the motor sequences are sent to the motor cortex that controls the muscles to be able to emit speech.
The Wernicke-Geschwind model is then based on the anatomical location of specific areas of the brain, which have different functions.
Although this model is very useful for explaining primary language disorders such as Broca’s aphasia or Wernicke’s aphasia, it does not explain other partial disorders.
In addition, part of the hypothesis that each of these areas are connected in series. That is, each previous step must be completed before moving on to the next, something that seems not to happen in all cases.
The American neurologist Marsel Mesulam proposed an alternative to the previous model. He defended the existence of a hierarchy of networks in which information is processed according to its complexity.
Thus, when simple language processes are performed, such as reciting the days of the week in order, the motor and premotor areas of the language are activated directly. However, when something that requires greater semantic and phonological analysis is expressed, other areas come into play.
Language would be the result of synchronized activity of broad neural networks. These are built by various cortical and subcortical regions, as well as by the roads that connect them.
It is not denied then that a localized lesion can generate a certain type of aphasia. What is denied is to attribute to a single area of the brain the loss of an entire linguistic function.
Damasio and Damasio Model
It is a model that works with interrelated systems. The first system is called “concept system” that allows the person to interact with their environment.
Anatomically it would be represented in the associative areas and in the motor areas, including the limbic system and the hippocampus.
Another system would be the “linguistic system” that is responsible for processing language, including phonemic representations and syntactic rules.
There would also be an “intermediate system” that would connect the previous systems. That is, the general concepts with their linguistic representations.
The main functions of the Wernicke area are related to reception processes and language comprehension.
Through several experiments using brain images, three zones have been found in the Wernicke area that are activated according to the function performed:
– One is activated when we pronounce words that we emit ourselves.
– The second responds to words spoken by another person, although it is also activated by remembering a list of different words.
– While, the third, it is related to the planning of speech production.
This shows that the general objective of Wernicke’s area is to represent the phonetic sequences (sounds). Whether we hear from other people, those we generate ourselves or those remembered by our memory.
When we read a book, we don’t store images of words in our memory, but rather, we remember words in the form of language.
This happens because what we perceive through our senses usually becomes language once processed. Subsequently, it is stored in memory with that “format”.
Wernicke’s area is the main area of the brain that interprets the language heard. The first way we learn language is through speech sounds. That explains its proximity and connection with the primary and secondary auditory areas of the temporal lobe.
In short, Wernicke’s area is responsible for the recognition, interpretation, compression and semantic processing of language. Whether spoken or written. In fact, this area also participates in both reading and writing.
Injuries in the Wernicke area
When there is an injury in Wernicke’s area, it is expected that certain alterations in the understanding of language are found.
The most typical consequence of damage in this area is Wernicke’s aphasia. It consists of difficulties in understanding what he hears, while the pronunciation of the phonemes is preserved.
Not understanding language, it is difficult for them to construct a discourse that has a coherent meaning. Although it articulates without problems the sounds of words.
More specifically, an injury in Wernicke’s area would cause:
– Problems to differentiate the phonemes of language (that is, the sounds of language). This directly causes speech to not be understood.
– Due to the difficulties in identifying the sounds of language, it is common for these patients to join words incoherently.
– Due to the above, they will not be able to evoke the graphic representations of the phonemes, having the writing altered.
However, there are authors who emphasize that in order for Wernicke’s aphasia to arise, more brain areas must be damaged. Specifically, adjacent areas. Since this is manifested by deficits that also encompass both understanding and part of the spoken, gestural and written expression.
Instead, they indicate that a lesion located in the Wernicke area would exclusively produce a disorder called “pure deafness for words.” It seems to affect only the reception of the language heard, so that these patients understand written language better.
In addition, they have preserved the identification of nonverbal sounds (such as a siren, a sneeze …) and writing.
It is important to note that there are other areas in the brain that have interpretive abilities. The patient can help them to recover their function. They consist of some areas of the temporal lobe and the angular gyrus of the opposite hemisphere.