This paper presents study that investigates brain activity (using ERP methodology) of male adolescents when solving short problems in algebra and geometry. The study design links mathematics education research with neuro-cognitive studies. We performed a comparative analysis of brain activity associated with the translation from visual to symbolic representations of mathematical objects in algebra and geometry. The findings demonstrate that electrical activity associated with the performance of geometrical tasks is stronger than that associated with solving algebraic tasks. Additionally, we found different scalp topography of the brain activity associated with algebraic and geometric tasks. Based on these results, we argue that problem solving in algebra and geometry are related to different patterns of brain activity. [For the complete proceedings, see ED597799.]