X	n by υ row mean-zero data matrix with n the number of time points in the experiment;
υ	total number of voxels in all slices;
G	specified n by p design matrix containing the time courses of all p factors hypothesized to modulate the BOLD signal, including the behavioral manip- ulations of the fMRI experiment;
β	P by υ matrix of parameters to be estimated;
ε	matrix of noise or residual errors typically assumed to be independent, zero-mean and Gaussian dis- tributed, i.e., N(0, σ2).