PROJECT SUMMARY / ABSTRACT Numerical magnitude processing allows us to comprehend and compare quantities, in both symbolic and non-symbolic formats. This skill is thought to be critical for successful math learning, as evidenced by correlations between performance on numerical magnitude processing tasks and both concurrent and future math achievement. Magnitude processing has been reliably shown to recruit the brain’s frontoparietal network, including the intraparietal sulcus (IPS) and inferior frontal gyrus (IFG). Developmental dyscalculia, or math disability (MD), affects 6-14% of the population and is characterized by poor accuracy and fluency with arithmetic. Children with MD frequently show poor magnitude processing ability, as well as differences in frontoparietal brain activity when performing magnitude processing or arithmetic tasks. Despite prior research, the relationships between the brain regions that subserve magnitude processing and performance on specific math skills in children with MD are poorly understood. Further, to address the causal nature of any such relationships, it is necessary to characterize whether brain function during numerical magnitude processing changes following intervention (through tutoring in math), and if this brain function relates to the extent of the performance gains made in math skills following intervention. If poor magnitude processing is a cause of MD, then brain networks supporting this skill should be directly related to performance on specific math tasks. Furthermore, changes in brain function should accompany changes in these math tasks in response to the intervention. Where and whether these functional changes occur will be indicative of whether there is a role of the frontoparietal magnitude processing network in successful treatment. In the proposed study, I will investigate magnitude processing and its neural correlates (using fMRI) in children with MD, both cross-sectionally (Aim 1) and longitudinally in the context of an intervention (Aim 2). In Aim 1, I will assess whether activity and functional connectivity (FC) during a magnitude processing task correlate with performance on specific tests of math achievement. We expect to find correlations with math skills that rely on procedural computation (rather than verbally-mediated fact retrieval), due to its reliance on magnitude representations. In Aim 2, using data before and after math intervention, I will first investigate whether baseline (pre-intervention) activation/FC of frontoparietal regions (including IPS and IFG) predicts future gains in magnitude-reliant math subskills (2a). I will also assess pre-to-post activation/FC change in these magnitude processing regions (2b), and whether the degree of functional change correlates with degree of behavioral performance change (2c). Through these results, we will gain a better understanding of the relationship between magnitude processing in the brain and behavior, and furthermore whether c...