Individual differences in the activity of executive function brain regions during number comparison.

Math skills require the integration of math-specific and domain-general skills, such as executive functions (EF). Neuroimaging studies consistently report intraparietal sulci activation during arithmetic tasks; however, activation of frontal brain regions associated with EF varies across studies. The discrepancies in brain regions associated with EF during math tasks may be due, in part, to variations amongst individuals and task demands. The current study examined neural activations associated with ratio effect in canonical math and EF regions in adolescents and subsequently examined how this activity was related to concurrently acquired behavioral measures of math ability and EF. Findings revealed differential relations between behavioral measures and neural ratio effects for symbolic (i.e., digits) vs. nonsymbolic (i.e., dot arrays) stimuli. The neural ratio effect during symbolic number comparison in the left inferior parietal lobe (IPL) and left inferior frontal junction (IFJ) correlated positively with an individual's calculation scores. Similarly, the neural ratio effect during nonsymbolic comparison in the right and left inferior parietal lobes correlated positively with an individual's math fluency. However, while a measure of an individual's inhibitory control positively correlated with the nonsymbolic neural ratio effect in the left IFJ, working memory positively correlated with the symbolic neural ratio effect in the left IPL, left IFJ, left precentral gyrus, and left posterior dorsolateral prefrontal cortex. These findings suggest that the format of numerical information influences the neural systems engaged and that engagement varies with individual differences in math abilities.