I'm setting up the multi-condition '.mat' file for a large project. The tests have 'correct' and 'incorrect' behavioral results. So I need to set the conditions according to them. But some controls had perfect trials without a single mistake. Now, the dilemma is that SPM8 doesn't accept blank vectors [] as onset or duration. If I simply dump the 'incorrect' blocks, it will mess up the contrast manager pipeline for ~100 subjects. I don't want to change the dimensions of the design matrix. 

  Can I set up a null condition in SPM8? If not, can I use Onset at 0 sec, duration = 0, to minimize the impact of these useless conditions to the GLM regression? Or if there's better choice.

Thank you very much!  
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Kai Zhang

Poston Lab, Stanford University

Palo Alto, CA 94304