One of the reasons why neuropsychology is interesting is that it allows us to verify to what extent mental processes that appear to be a single thing are, in reality, the result of many different mechanisms that act at the same time in the human brain. Prosopagnosia, for example, is proof that a person with the ability to see perfectly may become unable to recognize human faces.
Although the sight of something that should be familiar and its recognition seem to have to go hand in hand, an injury to certain areas of the brain can cause that illusion to fade, by canceling one of these mechanisms and causing the other to continue functioning. without counting on him.
But this does not only occur with the basic mental processes related to perception, but also extends to those more related to the most abstract thinking. Aphasias, for example, are an example of how certain facets of language use and masteryand not others, can be altered by certain lesions in the brain.
Aphasias are a group of language disorders caused by brain damage. Unlike what happens with other types of language disorders, such as alexia, an aphasia affects both spoken and written language.
A person with aphasia has an altered ability to use language itself, both in understanding and producing it, although they do not have any perceptual or motor problem that could prevent them from hearing or seeing well or moving their mouth muscles to speak. .
What causes aphasia?
The variety of brain lesions that can trigger the appearance of aphasia (or several types of aphasia at the same time) are very varied, because The network of neurons that play a role in the production or understanding of language is widely distributed.
Aphasias are generally considered to occur when a lesion interrupts the flow of information through which we move from images and thoughts to linguistic symbols organized following the structure of language (in a way similar to when we notice that we have a word “on the tip of the tongue”) or when this brain damage prevents the words heard or read from being transformed into images and thoughts.
However, this is still a matter of debate, since It is not clear to what extent our brain distinguishes between thoughts formulated as part of language and thoughts that exist independently of the languages were mastered.. On the other hand, the concept “aphasia” is quite abstract. What many patients with language disorders present are, rather, types of aphasia.
Types of aphasias
From a practical point of view, it is not as useful to talk about the causes of aphasia in general as it is to talk about the different types of aphasia, since This allows us to know what is happening to each individual patient.. Furthermore, the existence of these different types of aphasias allows us to see that language is actually a puzzle of different mental processes that we would not normally think of considering separately.
Next you can read what these types of aphasias are.
Broca’s aphasia
People with Broca’s aphasia have more difficulties producing language than understanding it. They have a hard time writing and speaking, they take a long time choosing the words they want to say and they also have problems pronouncing and modulate the tone of voice. The symptoms of this type of aphasia can be detected even by someone who does not understand the patient’s language.
Although they have less difficulty understanding text or oral language compared to their ability to speak and write, people with Broca’s aphasia They will be unable to literally repeat the phrases or words they hearregardless of whether they understand them or not.
An example of a fictional character who presents symptoms similar to the classic picture of Broca’s aphasia is Hodor, from the series Game of Thrones and the A Song of Ice and Fire books: although he seems to understand what is said to him, his ability to speak is almost completely nullified.
Wernicke’s aphasia
Unlike what happens in the previous type of aphasia, in Wernicke’s speech is fluent and it is not difficult to speak at a normal pace or even very quickly, maintaining correct pronunciation and intonation.
However, in general the phrases or words produced by a person with Wernicke’s aphasia are not well constructed, since words are often replaced by others belonging to the same semantic field (for example, replacing “oven” with “washing machine”). some phonemes are changed for others (changing “gato” for “gado”) or sentences are constructed with major syntactic errors in which nothing can be understood because there is no adequate structure and verbs have been replaced by adverbs, nouns by articles. , etc.
Besides, In this type of aphasia, the understanding of oral and written language is quite altered.as well as the ability to repeat words.
conduction aphasia
If in Broca’s and Wernicke’s aphasias the lesion affects the areas related, respectively, to the production of language and the organization of language to form units with meaning, in conduction aphasia the brain damage affects the networks of neurons that They connect these two nuclei of the brain to each other.
That is why a patient with this type of aphasia will have fluent speech and his ability to understand language will remain in a relatively good state, but You will not be able to literally repeat the words or phrases that you hear and see writtensince in order to do this the circuits must be intact that lead from the part of the brain in which the word or phrase is recognized as a meaningful whole to the part in which this information is “translated” into speech instructions. or writing.
Furthermore, in this type of aphasia the sentences produced also tend to present inappropriate substitutions of phonemes and words.
global aphasia
Another type of aphasia is global aphasia. It consists of a generalized language impairment that severely affects both language production and comprehension. Generally, people with this syndrome cannot repeat words or phrases either, and in some cases they will only be able to say one or a few syllables or words that they will repeat regardless of the context.
Transcortical aphasias
The transcortical aphasias They are characterized by maintaining the ability to repeat phrases and words preserved, something that did not occur in the four previous types of aphasias.
Transcortical motor aphasia
In this syndrome, symptoms similar to those of Broca’s aphasia occur, with non-fluent speech and the ability to understand language more preserved, but adding the possibility of repeating the sentences they hear or read, no matter how long they may be. That is, someone with transcortical motor aphasia is not able to speak spontaneously, but they can repeat anything.
It looks like a version of Wernicke’s aphasia in which you can repeat what you hear, but not what you read. Besides, Sometimes all types of syllables or words that have been heard are involuntarily repeateda phenomenon known as echolalia.
Mixed transcortical aphasia
This type of aphasia is similar to a mild version of global aphasia in which the ability to repeat is preserved, even if what is said is not understood. Among the typical symptoms of this type of language alteration, echolalia is also common.
anomic aphasia
Unlike what happens with the rest of the types of aphasias, in anomic aphasia both language production and comprehension may be nearly normal, and Its main symptom is anomiathat is, the difficulty in finding the right words to say something. People with anomic aphasia tend to use a lot of generic terms such as “thing”, “that”, etc.
From time to time these difficulties lead them to use circumlocutions, to try to explain themselves again using alternative phrases or lengthening what is being said to try to accumulate details and clues about what they want to say.
Language is more complicated than it seems
It is not always easy to know how to identify the types of aphasias that some patients present, since Symptoms can vary greatly and be more or less severebut in all of them (except the global one) it is clear that behind the use of language there are many parts of the brain more or less specialized in a task and coordinating with each other so that everything works as it should.
Therefore, certain capabilities may be lost while others, closely related to the first, are preserved.
