Researchers decipher the brain aspects of developmental dyscalculia and deficits in basic numerical skills
By Avishai Henik and Orly Rubinstein
A learning disability is a neurodevelopmental disorder that limits the ability of children and adults to acquire various cognitive skills. Such limitations are manifested in different ways: as specific difficulties in acquiring written and spoken language, acquiring invoicing skills, attention disorders, and the like. The learning disability makes it difficult for the children (or the adults) to function at different levels of the education systems. These are developmental disorders, since they appear at a young age and are also found in adults who have not been properly treated.
One of the learning disabilities is developmental dyscalculia - a difficulty with arithmetic that is reflected in the failure to perform various invoicing tasks, including arithmetic operations (subtraction, multiplication, etc.), solving invoicing problems, and invoicing thinking. Even before entering school and before formal studies in mathematics have begun, these children will have difficulty with tasks such as counting objects and comparing numbers or quantities. Children and adults who suffer from this deficiency may have difficulty in everyday circumstances, such as checking the surplus they get when buying in a store. For these children, math classes at school are a source of great anxiety, since they are required to invest enormous effort to understand things that other children in the class have no difficulty with. The American Psychiatric Association defines such a child as having very low scores on standardized math tests relative to the scores expected based on the child's chronological age, education and intelligence. One of the accepted definitions is that the child's math knowledge level is two grades below the chronological age when the intelligence is at least average and the defect is not due to difficulties in education or other difficulties (for example, reading problems). The phenomenon encompasses between 3% and 8% of the child population. That is, the frequency of the phenomenon is not lower than that of developmental dyslexia - a learning disability in reading. However, while the study of developmental dyslexia has made real progress, the study of dyscalculia is lacking - despite the importance of arithmetic skills, which even predict employment and wages better than reading skills.
In recent years, quite a few researchers in the field of cognitive neuroscience have turned to studying the mental processes involved in processing numerical information. Since these scientists are interested in the connection between brain and behavior, studies have been conducted not only in the behavioral aspect but also in the brain aspects of this disability.
Some researchers followed the development of relatively high school skills, for example addition and multiplication and focused on general cognitive functions, such as a limited range of working memory (short-term memory), attention deficits, visual-spatial dysfunction, or a defect in retrieving information from memory (e.g. , retrieving invoice facts like 2X4=8 from memory). Other studies have emphasized the importance of basic numerical skills (eg division, differentiating between quantities). Studies done in our laboratory show basic difficulties in processing numbers among those with developmental dyscalculia. For example, difficulty relating digits (for example the symbol "3") to quantities (for example ···).
Numerals are symbols that indicate size, quantity or ordinal position. In people without developmental dyscalculia there is an automatic connection between digits and sizes and quantities (for example, 8 represents a larger quantity than 4). When a digit is presented, the associations to corresponding amounts and sizes immediately arise. In people characterized by developmental dyscalculia, this connection is weak and not automatic. More than that, the difficulty is specific to the numerical symbol system. It is not a general difficulty in making a connection between symbols and their representations. For example, there is no difficulty in linking letters to the sounds they represent.
Additional research reinforces this direction and points to additional basic difficulties such as a share. Imagine that you are presented with several items and you are asked to name them as quickly as possible. The speed of your response will depend on the number of items; As the number of items increases, the response time will increase. This rule has one caveat: when the number of items is 4 or less - the response time does not change and remains constant. We perceive this number of items automatically, at once, like we perceive colors and smells. This phenomenon is called subitizing. Our impression is that the subitizing range of children suffering from developmental dyscalculia is smaller than the accepted range.
What is the brain aspect of the injury? Numerical information processing involves the parietal lobes and in a special way the intraparietal sulcus (IPS). It is a deep and winding groove in the cerebral cortex about 500 mm long. In recent years, evidence has accumulated that this area (IPS) plays an important role in developmental dyscalculia. The IPS is found to be damaged (fewer neurons, or a shorter and less deep groove) in populations suffering from math difficulties. We recently found that acquired brain damage (as a result of a stroke, or temporary damage) in the IPS is accompanied by a pattern similar to the pattern shown by a population diagnosed with developmental dyscalculia.
The impression is that basic-unique defects involving unique brain areas are at the base of developmental dyscalculia. However, it is clear that we still have a long way to go. Also, although there is evidence of a family context of developmental dyscalculia, the genetic factors involved are still unclear. Expanding and deepening the research in the coming years will deepen the understanding of the phenomenon, improve its diagnosis, enable its advancement, and point to possible treatment directions.
Cognitive neuroscience is a relatively new field that deals with functions such as learning, perception, attention, language, memory, emotions and other cognitive functions that are included under the heading of higher mental functions. This science involves different fields of science such as neurology, physiology, psychiatry, psychology, linguistics. The purpose of the field is to understand higher cognitive functions and to understand their brain context. Cognitive neuroscience has advanced greatly due to the development of non-invasive methods for imaging brain functions (for example, functional brain imaging - fMRI).
