Abstract
Dyscalculia is a learning disability affecting the acquisition of arithmetical skills in children with normal intelligence and age-appropriate education. Two hypotheses attempt to explain the main cause of dyscalculia. The first hypothesis suggests that a problem with the core mechanisms of perceiving (non-symbolic) quantities is the cause of dyscalculia (core deficit hypothesis), while the alternative hypothesis suggests that dyscalculics have problems only with the processing of numerical symbols (access deficit hypothesis). In the present study, the symbolic and non-symbolic numerosity processing of typically developing children and children with dyscalculia were examined with functional magnetic resonance imaging (fMRI). Control (n = 15, mean age: 11.26) and dyscalculia (n = 12, mean age: 11.25) groups were determined using a wide-scale screening process. Participants performed a quantity comparison paradigm in the fMRI with two number conditions (dot and symbol comparison) and two difficulty levels (0.5 and 0.7 ratio). The results showed that the bilateral intraparietal sulcus (IPS), left dorsolateral prefrontal cortex (DLPFC) and left fusiform gyrus (so-called “number form area”) were activated for number perception as well as bilateral occipital and supplementary motor areas. The task difficulty engaged bilateral insular cortex, anterior cingulate cortex, IPS, and DLPFC activation. The dyscalculia group showed more activation in the left orbitofrontal cortex, left medial prefrontal cortex, and right anterior cingulate cortex than the control group. The dyscalculia group showed left hippocampus activation specifically for the symbolic condition. Increased left hippocampal and left-lateralized frontal network activation suggest increased executive and memory-based compensation mechanisms during symbolic processing for dyscalculics. Overall, our findings support the access deficit hypothesis as a neural basis for dyscalculia.
Highlights
The ability to understand and manipulate numerosity is called “number sense” and is essential in perceiving our surroundings given that numbers are one of the most important features of modern life (Dehaene, 1997)
Participants were divided into groups according to their ages and the percentage distribution of each test was evaluated within the group to avoid the effect of age
Repeated-measures analysis of variance (ANOVA) was applied for the behavioral data analysis using SPSS v.23 software
Summary
The ability to understand and manipulate numerosity is called “number sense” and is essential in perceiving our surroundings given that numbers are one of the most important features of modern life (Dehaene, 1997). Various animal species and infants have basic number sense ability and there are shared characteristics of number sense in humans and animals that suggest a phylogenetic continuity (Dehaene, 2001). One of these common features across species is known as the “distance effect,” which is a difficulty in comparing two numbers as the numerical distance between these two numerosities decreases. The other shared characteristic is called the “size effect” which indicates that performance on comparing two numbers decreases with increasing number size (Moyer and Landeauer, 1967) These two effects could be considered as results of the “ratio effect.”. The ratio effect refers to that comparison difficulty depends on the ratio between the two quantities (Lyons et al, 2015; Hohol et al, 2020)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
