From Electric brain stimulation improves maths performance:
"The research looked at influencing newly-learned (rather than existing) mathematical abilities: volunteers were asked to learn new symbols, demonstrate that they had learned them, and then apply this knowledge to solving puzzles involving these symbols. Electrical stimulation was applied at the point when they were learning the symbols. The new research shows that right to left stimulation of the parietal lobe enhances the ability of volunteers to retain and apply this new knowledge to problems for at least six months. Previous work by the team showed that a similar induced impairment effect was short-lived."
Link to the abstract and the paper Modulating Neuronal Activity Produces Specific and Long-Lasting Changes in Numerical Competence.