Brain activity during arithmetic in symbolic and non-symbolic formats in 9-12 year old children.

People process numbers in different formats, such as dot arrays (non-symbolic), Arabic digits and number words (symbolic), and use these representations when performing arithmetic calculations. It remains, however, unclear if and how these various presentation formats affect brain activity during arithmetic. We conducted an fMRI study in 23 typically developing children aged 9-12. The children were asked to subtract numbers up to 10 and had to compare the result to a reference number. Numbers were presented in non-symbolic (dot arrays), as well as symbolic formats (Arabic digits and number words). Our findings suggest that similar brain networks are recruited during arithmetic with different symbolic formats, i.e. Arabic digits and number words. On the other hand, there are clear differences between calculating with symbolic and non-symbolic formats. Specifically, calculating in symbolic formats showed increased activity in angular and supramarginal gyri, whereas arithmetic in the non-symbolic format showed increased activity in middle occipital and superior parietal lobes, as well as in superior frontal gyrus and insula. These differences in brain activity might be explained by differences in the strategies used to solve these arithmetic problems.