SPM Design Matrix


SPM design matrix contains information about the time courses and onsets for the regressors. Multiple regression and correlation sorting criteria in GIFT use SPM design matrix to sort components temporally. The SPM design matrix filename selected is in .mat format. Type load filename at the MATLAB command prompt to view the SPM structure. GIFT uses the following fields in SPM structure:
nscan
Refers to the number of scans. For multiple sessions, nscan should look be a row vector like [110 110 ... 110].
xX.X
Contains regressor time courses of dimension m by n where m is sum of scans over sessions and n (length of SPM.xX.name) is number of regressors.
xX.name
Contains the regressor names in a cell array. Number of regressors is equal to length of cell array.
xY.RT
Refers to the repetition time (TR).
xBF.UNITS
Refers to units in seconds or scans.
Sess
Contains information like onsets. Length of SPM.Sess is equal to the number of sessions (length of SPM.nscan).
How SPM structure should look like for one session and multiple sessions are discussed below:
One Session
SPM.nscan should be a number. Length of SPM.Sess structure should be one.
Multiple Sessions
SPM.nscan should be a row vector or a single number equal to the sum of SPM.nscan. Length of SPM.Sess should be equal to length of SPM.nscan.
Note: GIFT pulls session specific regressors only when the regressor names contain the session number like Sn(1) right_visual_hemisphere*bf(1) where 1 after Sn( refers to the session number.