Figure 1.

(A) PICA of fMRI data. X represents a space-time matrix having in its M column the N dimension time series, the columns of mixing matrix A are the time courses, and the rows of matrix S are the independent components. Matrix A is a rectangular matrix and the number of components K is less than the size N of data. (B) Schematic representation of the method applied to matrix S. Steps 1 and 4 operate on the row of matrix S (setting some ICs to 0), steps 2 and 3 on the elements (setting some voxels to 0).