Sum Difference (Sum Diff) In simplest terms, I use Sum Difference when there is a strong differential in a group of frequencies between homologous sites and there are one or more frequency bands that show excessive activation. Training down the sum trains down the activity in both channels, training down difference reduces the asymmetry. You can also use a bipolar montage to achieve the same effect. The sum difference designs allow you to choose the bands that are most asymmetrical […]