Functional connectivity of the main math ROIs. a, Exemplar subject with simultaneous coverage of five regions activated during math, from earlier visual to the motor cortex. ITG, IPS, and mSFG showed strong math selectivity. Top time courses show averaged activity across trials for math and memory. Bottom plots show single trial activity ordered by RT (trial ends when subject presses the response button). Shaded error bars indicate the standard error of the mean across electrodes. b, The same exemplar subject: lagged correlation between the activated regions. The lines represent the pairwise correlation coefficient with preserved trial order subtracted from the average correlation from the distribution of 2,000 pairwise correlations generated by shuffling the trial order. The difference between correlation values from ordered and shuffled data informs how the regions are functionally connected at the single-trial level. Rightward peaks mean that correlations are delayed. c, Electrophysiological functional connectivity based on lagged correlation for each math-preferential/math-selective ROI with all the other regions, grouped using the temporal distance between them, calculated from the ROL analysis.