(a) Event-related fMRI design of arithmetic problem solving task. (b) Sagittal slice of predefined region of interest (ROI) in the hippocampus used for the inter-problem pattern stability analysis. (c) 26 × 26 correlation matrix representing trial-by-trial brain activation pattern stability in the hippocampus during addition problem solving. (d-e) Inter-problem pattern stability in the left and right hippocampus for problems correctly solved by children at T1 and T2, adolescents, and adults. (f-g) Results of whole-brain analysis showing hippocampal regions that showed significant increases in inter-problem multivoxel pattern stability from childhood through adolescence into adulthood. Note that only correctly performed trials (problems) from each participant's event-related fMRI data were used in the analysis. Notes: a.u., arbitrary units; * P<0.05; **, P<0.01; L, left; R, right.