Hi all,
When I run selxavg-sess, I sometimes get the following error message at the beginning of the algorithm (right after I get the Residual Error Estimation):
ERROR: paradigm is ill-conditioned (1.17293e+07) Check your paradigm file for file for periodicities
My paradigm is fairly simple. It is a block-design, I use -gammafit, and there are 3 conditions that I present in 3 different orders across runs (e.g., in one run it might be 0 1 2 3 0 3 2 1 0). I always use the same paradigm-files, and this error message doesn't appear always.
In general I include the motion-correction parameters as covariates (flag -mcextreg in mkanalysis-sess.new). The problem is easily solved by not including the motion-correction parameters in the analysis. Can this error message be caused by a strong correlation between 2 of my mc-parameters ? What is the best solution in that case ? Maybe to compute a lower number of principal components whenever the problem occurs ?
Thank you for your help,
Hans P. Op de Beeck Kanwisher lab