The use of language is one of the main capacities of human beings . Mastering it more or less influences how we relate to other people, how we see ourselves and even how we think.
Perhaps that is why there is a strand of neuropsychology very interested in language disorders, among which the best known are dyslexia and aphasia. However, there are also some others, such as alexia and agraphia .
What is alexia?
Put very simply, alexia is a loss of the ability to read correctly that is due to an injury to the brain . Therefore, the term alexia refers to a range of reading disorders that are caused by brain damage.
Alexia differs from dyslexia in that in the latter, reading problems appear without any identifying injury marks in the neural tissue of the brain regions associated with language. If in alexia the disorder appears due to acquired damage, in dyslexia the explanation has more to do with the way the brain develops during childhood, with a genetic component and with a dynamic of learning that gives problems. This explains why dyslexia is also known as acquired dyslexia.
In addition, as with all language disorders, alexia can occur in milder forms and in more severe forms in which the person is totally unable to read.
What is agraphia?
Agraphia is the inability to write correctly whose cause is also a brain injury .
Usually, agraphia appears in conjunction with other language disorders (especially with aphasias and alexias). Therefore, cases of pure agraphia in which the only language-related difficulty affects writing and no other ability are very rare.
Types of Alexia
As the concept of alexia is very broad, many subcategories are used in neuropsychology and psycholinguistics to differentiate the ways in which this disorder can occur and make it easier to intervene on a case-by-case basis (as well as allowing research to be carried out in which different lesions produce different effects).
1. Alexia without agraphy, or pure alexia
As its name indicates, pure alexia serves to identify cases in which there is only an inability to read, but not to write . People who experience it see the letters as if they were simple drawings, and are not able to translate these visual signals into phonemes. Therefore, and although it may seem strange, in the cases in which alexia is diagnosed without agraphia the affected person is unable to understand what he or she has written.
This is the least common type of alexia, since for it to occur the lesions have to affect both lobes of the brain and make it impossible for visual information collected from both eyes to pass to the left side of the brain to be processed by the language areas, while those involved in the production of written language remain intact and connected to each other.
2. Alexia with agraphy, or central
People who experience dyslexia with agraphia have serious problems with both reading and writing .
This type of alexia is also known as angular alexia , because it affects an area of the brain called the angular gyrus. In angular gyrus, which is located in the lower part of the parietal lobe (usually on the left side of the brain), it is responsible, among other things, for converting letters into sounds and vice versa. An injury that destroys this area or isolates it from the rest of the cortex is therefore very likely to produce agraphic alexia.
3. Alexia anterior, or front
Unlike the other two types of alexia, in which the injury occurs in areas of the brain near the back of the head, anterior alexia is caused by an injury that mainly affects the frontal lobe, in the area near the left temple. It is an alexia associated with Broca’s aphasia, although when speaking of frontal alexia, reading problems are usually more serious than those related to other language functions.
In patients with milder symptoms of this type of alexia, the main difficulties are related to problems in understanding the syntactic relationships between the words that are read. When the alexia is more severe, they cannot identify words that are spelled for them, nor name the letters in a short sentence. However, one thing that distinguishes frontal alexia from the other two categories is that it is easier to read familiar words.
How can alexia be treated?
Alesias are always caused by injuries to the brain, and therefore any treatment initiative must be supervised by specialists whose field is related to neurology and who can provide a personalized service.
- Junqué, C. and Barroso, J. (Coords.) (2009). Manual of Neuropsychology. Madrid: Síntesis.
- Moore, M. M., Brendel, P. C., Fiez, J. A. (2014). Reading faces: Investigating the use of a novel face-based orthography in acquired alexia.Brain and Language, 129, pp.7 – 13.
- Pflugshaupt, T., Gutbrod, K., Wurtz, P., Von Wartburg, R., Nyffeler, T., De Haan, B., Karnath, H., Mueri, R. M. (2009).About the Role of Visual Field Defects in Pure Alexia. Brain, 132(7), pp. 1907 – 1917.