Abstract: Abstract: Mental calculation is complex cognitive procedure, which includes three tightly related processing stages: converting the stimulus into the appropriate internal codes, retrieving or calculating the answer, and producing the answer. Different numbers in different input formats are represented in different areas of the parietal lobe. The left intraparietal sulcus is mainly involved in arithmetic facts retrieval, moreover, and the left inferior frontal lobe is additionally involved in actual computation when mental arithmetic problems become more difficult. While the prefrontal cortex and the occipito-temporo-parietal regions are generally involved in mental arithmetic, predominant activation is typically found in the left hemisphere. It is also shown that approximate arithmetic, abacus mental calculation and mental calculation in a prodigy are more dependent on visual-spatial representation, involving the right prefrontal cortex and precuneus

Key words: mental calculation, abacus mental calculation, cognitive neuroscience