AICHA is a whole-brain population-level atlas of homotopic regions of the resting brain. This atlas was created at the basis of BOLD fMRI resting-state functional connectivity of 282 subjects. Homotopic regions were mapped with the same color. Only 6 color were used for the color mapping, regions sharing a border were mapped with different colors, accordingly to the 3-Dimensionnal version of the “4 color map theorem”.