The neural mechanisms underlying individual differences in arithmetic fact learning.

A major building block for the successful development of mathematical competencies is the ability to acquire and retrieve arithmetic facts such as the multiplication table. There are large individual differences in this ability, and individuals with mathematical learning disorders or dyscalculia display deficits in this ability. However, the mechanisms underlying these individual differences are poorly understood. Recently, a new hypothesis has been proposed: the sensitivity to interference (STI) in memory hypothesis. When we are learning arithmetic facts at school, the storage of these facts in memory depends on the overlap between a new problem and the problems that are already stored: the more overlap (or interference), the more difficult it will be to memorize the new problem. Moreover, the higher the individuals STI, the more difficulties he or she will have in learning these arithmetic facts. This project aims to investigate what mechanisms underlie the STI effect by combining behavioral data with data on brain activity, using the complementary expertise of the project partners in Leuven and Graz. We propose four work packages (6 studies) in which we investigate competence-related differences in the STI effect in children (with and without dyscalculia) and adults, the development of this effect in a training study in adults and a longitudinal study in children, and its malleability by influencing adults brain activity via non-invasive brain stimulation.

A major building block for the successful development of mathematical competencies is the ability to acquire and retrieve arithmetic facts such as the multiplication table. Previous research has shown large individual differences in this ability; especially individuals with mathematical learning difficulties display poor performances. Recently, a new hypothesis has been proposed to explain this phenomenon: the sensitivity to interference (STI) in memory hypothesis. When we learn arithmetic facts at school, the storage of these facts in memory depends on the similarity between a new problem and the problems that are already stored. The more similar (or interfering) these problems, the more difficult it will be to memorize the new problem. In addition, individuals with a high STI show more difficulties to learn these interfering arithmetic facts. Despite this knowledge, it was unknown how the STI effect emerges in the human brain and how differences in the STI effect can be explained by brain functions. This joint research project (Belgium-Austria) investigated the brain mechanisms of the STI effect by combining behavioral and neuroimaging data such as functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). Using the complementary expertise of project partners at the University of Graz and the KU Leuven, 11 studies on the brain mechanisms associated with individual differences in arithmetic and mathematical learning were conducted. In these studies, we identified specific brain markers associated with differences in the STI effect in adults (i.e., the left inferior frontal gyrus) and the relevance of the semantic control network (including the aforementioned region) to resolve interference in arithmetic fact retrieval. However, in a specifically designed one-week arithmetic training study we were not able to find conclusive evidence that the STI can be reduced in adults with poor arithmetic skills. In children, the behavioral STI effect could be corroborated, but no neural correlates of this effect could be revealed. In the additional studies, further insights into the neuroanatomical correlates of individual differences in arithmetic and mathematical competencies in children and adults could be achieved. These findings have substantially advanced our understanding of how the brain computes arithmetical problems and what role STI plays for individual differences in arithmetic competencies.