Erik,

There doesn't seem to be anything wrong with your script, so it's likely the design matrix that is causing the issue. Upon review of your design matrix, I noticed high correlations between several of the PPI and task regressors. These can be traced back to a limited number of trials in each run for some conditions. If you have less than 10 events of a specific event type, then you should use the concatenated approach in gPPI to reduce the correlation between regressors. The reduction in correlation is due to an increase in the number of trials. To use the concatenated approach, set P.ConcatR=1.

Let me know if you still end up with odd values.

-Donald