Imagine for a moment that you can not understand numbers and calculations as simple as 2 or 2 + 2. This alteration of the mathematical skills, known as acalculia, was described by the neurologist Salomon Henschen in 1925 and to this day it astonishes the world of science.
What if we told you that an area of your brain is responsible for mathematical calculations? It would be something like an integrated calculator, right? In this sense, acalculia is a deficit that directly affects the ability to calculate due to an acquired brain damage.
The different types of acalculia
The acalculias are divided into two large groups according to the altered capacities and the damaged areas. In general, the affected hemisphere is the left hemisphere, in charge of logical reasoning. Likewise, the classification of acalculias will depend both on the area of the affected left hemisphere and on the degree to which the abilities are altered.
Primary acalculia is a defect in calculus skills not linked to other disorders. Patients lose the ability to understand the numerical concepts and therefore combine them.
The main failures are seen in the execution of operations and in more abstract issues, such as the use and interpretation of signs. The lesions are associated with the frontal lobe of the left hemisphere. This lobe is considered the conductor in our brain, so its alteration entails an inability to alternate mathematical concepts. Then we can differentiate two clear symptoms of primary acalculia:
- Anarimetics Impossibility to perform arithmetic calculations.
- Asyntactic Loss of the computational sense.
The secondary acalculia consists in the alteration of the mathematical abilities in association with other neuropsychological disorders. Then the secondary acalculia can be derived from a linguistic, spatial deficit and executive functions in general. In summary, we can group them in the following categories:
- Aphasic acalculia. The defects in the calculation come from linguistic alterations. The inability to understand and code the numeric language results in an inability to operate with it.
- Alkalic acalculia. Mainly linked to the problems of reading and recognition of the numerical symbols. The patient can not understand through reading.
- Aggregate acalculia. Agraphy is the inability to communicate and express oneself through writing. This disorder does not come from the inability to execute the movement, but from the incomprehension of the act of writing on a symbolic level. Consequently, the patient is unable to write numbers.
- Frontal acalculia. Perhaps the most common among the acalculias. It is closely linked with attentional disorders. These patients tend to persevere, which consists in repeating the errors systematically. This condition is caused by the inability to identify errors and propose new strategies for solution.
- Semantic acalculia. It is a difficulty in handling the concepts of relationship. A clear example would be the inability to associate mathematical problems with the operations necessary for their solution.
- Spatial acalculia. It would be a consequence of an injury in the right hemisphere. The difficulty in performing arithmetic calculations is associated with problems in spatial processing.
How is a primary acalculia diagnosed?
The most important thing is to observe that the symptoms are expressed both orally and in writing. Primary acalculia consists of a loss of the numerical concept, which can sometimes be confused with different aphasic symptoms. It is necessary to verify that the deficit is due to the loss of the concept and not to a failure in the verbal comprehension of the slogans.
Why do patients with frontal lesions fail in numerical tasks?
First, the resolution of numerical tasks requires a plan in which different mathematical concepts are integrated. To solve a sum, for example, it is necessary to understand the concept of additivity. Second, most mathematical problems require abstract reasoning. The lack of inhibition in syndromes of a frontal lesion makes this process difficult when concentration fails.
As we mentioned earlier, the frontal lobe is the director of the cerebral orchestra; if this presents faults, it will be more complicated to arrange the information in a way that favors the resolution of the problem.
Acalculia and other conditions
Acalculia can be seen in aphasic subjects as long as their linguistic abilities are affected. In Broca’s aphasia, for example, the deficit manifests itself in the syntax applied to the calculation. In the aléxic acalculia, on the other hand, the deficit is correlated with reading difficulties.
A more explanatory example is the pure alexia, where the difficulties for the verbal and literal interpretation of the written language are evidenced in the erroneous interpretation of numbers, magnitudes and hierarchies.
Other ways to detect acalculia
In agraphy, acalculia can appear related to the inability to write quantities. Thus, the type of acalculia will depend on the type of agraphy.
In Wernicke’s aphasia, for example, the patient has errors in copying numbers to dictation. To overcome this deficit of verbal comprehension, these patients usually invent the numbers and assign them an order of their own.
The approach to acalculia
The main thing is to understand that it is a disorder very different from dyscalculia, which consists of a problem of development and learning, and therefore requires other strategies in the intervention. For its part, the diagnosis of acalculias is usually in the hands of neuropsychologists, who use various tests. In these, the person has to perform mental arithmetic, written operations, successive operations, interpretation of arithmetic signs and alignment of numbers in columns.
The treatment of primary acalculia will depend on the type of injury and its severity. Since the lost nervous tissue can not be recovered, rehabilitation usually focuses on one objective: to teach new strategies based on neuroplasticity.
Although the recovery will never be total, tools that improve the adaptation of the person must be granted. On the other hand, the treatment of secondary acalculias will vary according to the associated disorder. The advancement of technology provides computer tools and applications that are a hope for patients.