Mental calculation in a prodigy is sustained by right prefrontal and medial temporal areas

Calculating prodigies are individuals who are exceptional at quickly and ac curately solving complex mental calculations. With positron emission tomogr aphy (PET), we investigated the neural bases of the cognitive abilities of an expert calculator and a group of non-experts, contrasting complex mental calculation to memory retrieval of arithmetic facts. We demonstrated that calculation expertise was not due to increased activity of processes that e xist in non-experts; rather, the expert and the non-experts used different brain areas for calculation. We found that the expert could switch between short-term effort-requiring storage strategies and highly efficient episodi c memory encoding and retrieval, a process that was sustained by right pref rontal and medial temporal areas.