Hi Paul,
1. Yes, those bandpassing parameters should be okay. You
are probably using a quadratic or possibly even cubic polort.
Note that using 0.01 instead would probably cost another 4 or
8 regressors.
2. I agree that it is a lot of regressors to lose, and you
are giving up fewer than most because 0.167 is a bigger
cutoff than most use. This is why I believe bandpassing
is too high a penalty to pay in general. There are more
efficient ways to remove likely noise.
But note that losing that many degrees of freedom is not
just a rationale, that is a real cost. You are projecting
out those high frequencies by modeling 46 regressors of no
interest. Running something like 3dBandpass would simply
hide such a fact, which is one of many reasons why we do
bandpassing via the linear regression, instead.
Essentially, bandpassing projects the data into a 99
(= 145-46) dimensional sub-space. It is like having 99
TRs left to model with. Modeling out another 12 for
motion, 3 for the polort and 50 for censoring would drop
it down to 34 remaining df to correlate with.
What is your motion censoring threshold?
- rick