Over the last two decades a link between visuospatial working memory (VSWM) and arithmetic skills was postulated. During the basic stage of acquiring arithmetical understanding, children use a mental model for arithmetic that requires VSWM. Furthermore, it was suggested that numbers are represented on a mental number line, which also involves VSWM. These representations are believed to be the foundation blocks of mathematical processing. Interestingly, not only a cognitive link can be found between VSWM and math but also a common neuroanatomical basis. Specifically, in addition to its central role in number processing, the intraparietal sulcus (IPS) in the posterior parietal cortex, supports VSWM.Here, I propose to investigate the role of VSWM in typical and a-typical development of numerical cognition.In typically developing children I will test the influence of VSWM on the development of quantity representations on the mental number line and on high level arithmetic (strategy selection). Next, I will examine what are the neuro-cognitive mechanisms related to VSWM that underlie numerical processing, by testing college students during functional magnetic resonance imaging (fMRI) scan.In a-typical development I will study the role of VSWM in the etiology of developmental dyscalculia (DD) by testing the effect VSWM, on college students that suffer from DD. I will examine improvement in neuro-cognitive mechanism as a result of training using fMRI and behavioral parameters.The results from the present proposal will potentially affect multiple fields of study such as education and cognition. I hope that the results of the present study will give a new perspective on the building blocks of school arithmetic, offer effective intervention in the remediation of DD, and will provide schools with new practical tools and a theoretical perspective on arithmetic.