Adolescents with Developmental Dyscalculia Do Not Have a Generalized Magnitude Deficit – Processing of Discrete and Continuous Magnitudes

Abstract

The link between number and space has been discussed in the literature for some time, resulting in the theory that number, space and time might be part of a generalized magnitude system. To date, several behavioral and neuroimaging findings support the notion of a generalized magnitude system, although contradictory results showing a partial overlap or separate magnitude systems are also found. The possible existence of a generalized magnitude processing area leads to the question how individuals with developmental dyscalculia (DD), known for deficits in numerical-arithmetical abilities, process magnitudes. By means of neuropsychological tests and functional magnetic resonance imaging (fMRI) we aimed to examine the relationship between number and space in typical and atypical development. Participants were 16 adolescents with DD (14.1 years) and 14 typically developing (TD) peers (13.8 years). In the fMRI paradigm participants had to perform discrete (arrays of dots) and continuous magnitude (angles) comparisons as well as a mental rotation task. In the neuropsychological tests, adolescents with dyscalculia performed significantly worse in numerical and complex visuo-spatial tasks. However, they showed similar results to TD peers when making discrete and continuous magnitude decisions during the neuropsychological tests and the fMRI paradigm. A conjunction analysis of the fMRI data revealed commonly activated higher order visual (inferior and middle occipital gyrus) and parietal (inferior and superior parietal lobe) magnitude areas for the discrete and continuous magnitude tasks. Moreover, no differences were found when contrasting both magnitude processing conditions, favoring the possibility of a generalized magnitude system. Group comparisons further revealed that dyscalculic subjects showed increased activation in domain general regions, whilst TD peers activate domain specific areas to a greater extent. In conclusion, our results point to the existence of a generalized magnitude system in the occipito-parietal stream in typical development. The detailed investigation of spatial and numerical magnitude abilities in DD reveals that the deficits in number processing and arithmetic cannot be explained with a general magnitude deficiency. Our results further indicate that multiple neuro-cognitive components might contribute to the explanation of DD.

Developmental Dyscalculia in Adults

“…In a similar vein, evidence from the developmental literature suggests that early in life, the processing of numerostiy, space and time are frequently intermixed in the natural environment of humans and animals alike (e. g., de Hevia, Izard, Coubart, Spelke, & Streri, 2014). Notably, recent brain imaging studies support the idea of overlapping neurofunctional circuits mediating such a generalized magnitude system (e. g., humans: Dormal, Dormal, Joassin, & Pesenti, 2012;McCaskey et al, 2017;Skagerlund, Karlsson, & Träf, 2016;animals: Tudusciuc & Nieder, 2009; but see Anobile et al, 2018;Kucian, McCaskey, von Aster & O'Gorman Tuura, 2018). For example, the fMRI study of Skagerlund and colleagues (2016) is among the irst that directly compared neurofunctional activation patterns across the three magnitude dimensions (i. e., number, time, line length) in healthy adults.…”

“…Most interestingly, and despite comparable response accuracies across groups, adults with DD displayed stronger frontal activations that were associated with quicker response latencies (a pattern which was not found in controls). Consequently, suggest that (right inferior and left superior) frontal activations in adults with DD might relect compensatory mechanisms in the presence of ineicient functioning in number-relevant parietal brain regions (for similar views in the developmental literature, see Kaufmann et al, 2011b;Kucian et al, 2006;McCaskey et al, 2017;Peters & De Smedt, 2018). With respect to brain structure, Cappelletti and Price (2014) conducted voxel-based-morphometry to investigate whether DD in adults might be accompanied by grey matter abnormalities.…”

“…Notably, affected children do not 'grow out' of DD. Rather, arithmetic diiculties tend to persist into adulthood if untreated (e. g., Ashkenazi & Henik, 2010;Cappelletti, Freeman & Butterworth, 2011;De Visscher, Noel, Pesenti & Dormal, 2018;Gliksman & Henik, 2018McCaskey, von Aster, O'Gorman Tuura & Kucian, 2017; for a detailed description of a single-case study of adult DD, see Kaufmann, Pixner & Göbel, 2011a). However, most research to date has focused on children with DD, neglecting the large number of adults sufering from DD.…”

The effect of self-regulation empowerment program training on neurocognitive and social skills in students with dyscalculia

“…Therefore, children with specific learning disorder are more vulnerable to behavioral and social problems given their frequent and continuing academic failures. Compared with typically developing children, they have a high level of behavioral (internalized and externalized problems) and socioemotional (deficiencies in the processing of social data, high levels of social exclusion, loneliness and weak interpersonal skills) problems [15]. Moreover, about 38% to 78% of the children with dyscalculia have social and communicative deficiencies [16].…”

Developmental Dyscalculia and Automatic Magnitudes Processing: Investigating Interference Effects between Area and Perimeter

“…In the past few years, the relationship between numbers and other magnitudes, such as space and time, has evoked a great deal of interest ( Walsh, 2003 ; Dehaene and Brannon, 2010 ; Gebuis and Reynvoet, 2012a ; Newcombe, 2014 ; Leibovich et al, 2016 ; McCaskey et al, 2017 ). Walsh (2003) was the first to suggest the existence of a common processing mechanism for time, space, and quantity, and he established a Theory of Magnitude (ATOM).…”