Structural and functional brain anatomy in children with developmental dyscalculia: what counts?

Calculation ability represents an extremely complex cognitive process. It has been understood to be associated with and depend upon multifactor abilities, including verbal, spatial, memory, and executive functions (Ardila et al., 1998). The complexity of numerical processing may refer to the difficulties investigating its disorder: Developmental Dyscalculia (DD). The underlying deficits, which cause DD, remain unanswered but various factors have been proposed. These can be classified into two models: Domain general or domain specific factors. An involvement of domain specificity in the development of DD results from infant and non-human primate studies (McCrink and Wynn, 2004; Nieder, 2005). It has been argued that the core aspect of numerical cognition is an innate “number sense”, which is a short-hand term for our ability to quickly understand, approximate and manipulate numerical quantities (Dehaene, 1997). The core deficit hypothesis proposes that an impaired system leads to deficits in number sense what is the cause of a least some types of DD. This ‘number sense’ is located in the parietal lobe and therefore, children with DD should exhibit a dysfunction of this region. On the other hand, domain general factors, as attention or working memory, which stand for an involvement of the executive system in calculation, are not in the focus of investigations about the underlying deficits of DD. The main goal of this thesis was to evaluate the neural network of children with DD in respect of a domain general approach. In Study A, entitled “Optimized Voxel Based Morphometry in Children with Developmental Dyscalculia” we investigated dyscalculic children compared to control children by use of voxel-based morphometry. This method reveals anatomical differences between groups and is independent of cognitive functions. Results show decreased grey matter volume in the right IPS. If it is assumed that the right IPS exclusively serves as a region that represents a core analog representation of number this finding would contribute to the domain specific hypotheses, described above. But there were additional clusters at the bilateral middle frontal gyrus, the left inferior 5 frontal gyrus and bilateral anterior cingulum which refer to possible domain general impairments of the attentional and the working memory system, which might have a negative effect on the acquisition of number representation and number processing capacities. In Study B, entitled “Dysfunctional Neural Network of Spatial Working Memory Contributes to Developmental Dyscalculia” special interest has been addressed to neural functions of a domain general factor, spatial working memory. Functional magnetic resonance imaging (fMRI) was used to examine children with and without DD with a spatial working memory paradigm. We found reduced activation in working memory relevant brain areas, such as the right IPS, the right inferior frontal lobe and in the right insula in children with DD when compared to control group. Decreased activation in the right IPS of children with DD during a spatial working memory task may indicate that more domain general factors such as working memory influence the acquisition of arithmetic competencies and the development of a mental number line. Therefore, our data support the general domain hypothesis and we conclude, that poor spatial working memory capacity in DD influences the formation of a core understanding of numerical information and the development of a ‘mental number line’. Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-51689 Dissertation Originally published at: Rotzer, S. Structural and functional brain anatomy in children with developmental dyscalculia: what counts? 2011, University of Zurich, Faculty of Arts.