Scaling Components


For each data-set, the component images are compared with a reference image like aggregate ICA image. The signs of the component images will be reversed accordingly. The image maps and time courses of components have arbitrary units after the back reconstruction step and is the motivation for adding scaling step in GIFT. Presently there are two scaling steps like Percent Signal Change and Z-scores.

Percent signal change : The procedure for scaling individual subject component images and time courses is given below:

Figure shows how calibration is done for a particular component:

Z-Scores : The component images and time courses are scaled to Z-scores. For each component, the time courses and spatial maps are divided with the their standard deviation. Figure below shows conversion to Z-scores: