I have a question about the regressors produced by -stim_times_AM2 when used in combination with dmBLOCK. In creating the regressors, stim_times_AM2 subtracts the mean of the amplitudes to create the modulated regressor. This has the effect of creating an amplitude modulated regressor orthogonal to the original regressor. However, when combined with duration modulation (dmBLOCK) the regressors produced by stim_times_AM2 are not orthogonal. Should they be orthogonal?