I'm looking for some advice on troubleshooting data for potential issues that could be related no finding no activation in first level models (we have a significant behavioral effect that is pretty reliably associated with changes in activation compared to baseline). 

Our initial approach was to model the first-level with T/D derivatives, motion regressions, and outlier removal with the ART toolbox. We subsequently utilized a different masking approach setting the threshold to -inf and using an explicit whole brain mask to correct for possible inhomogeneity from out 32-channel coil (we found there were a number of voxels not included in the second level mask image). We've also attempted to remove the regressors of no interest. None of these strategies have lead to notable improvement. We're wondering if there may be some problems with our preprocessing approach.

Our data went through the following preprocessing pipeline: slice-time correction, realign, normalize, smooth (6 mm FWHM). We've additionally confirmed the accuracy of our SOT files. 

Are there any other avenues that would be worthy of pursuit?

Many thanks,

Drew