Hi
> Hello all,
>
> I've got two (and a half) questions about fsl_regfilt.
>
> 1) When regressing out part of a design matrix, does it matter
> whether this design matrix consists only of all possible noise time
> courses, or whether it also includes the events of interest? To be
> more specific, I want to filter motion related and created a noise
> only design matrix that I used for filtering. However, in my study,
> motion is correlated with the events of interest. When including the
> noise regressors in the design for a feat analysis the influence of
> the noise gets nicely reduced, giving more pronounced activation
> patches. However, I am concerned that my noise only model would
> reduce effects, when always full model will be fitted with
> fsl_regfilt. So, does fsl_regfilt fit only the selected regressors,
> or will the full modell be fitted befor the selected regressors are
> filtered out?
No, what happens is this:
-you specify a full design matrix (X, say)and using -f) the set of
regressors you would want to be removed. This effectively partitions
the matrix X into a signal and a noise part. fsl_regfilt then projects
the data onto all of X to generate parameter estimate maps S. Using
the information provided with the -f option these maps are then also
sub-divided into noise maps and signal maps. The filtered data is
data - X_{noise} * S_{noise}
i.e. the new data is obtained by regressing the full model and then
removing the noise terms.
> 2) In the FAQ melodic is suggested for filtering noise related ICs,
> but the melodic webpage links to a page, where fsl_regfilt is used.
> Are this two options of doing exactly the same thing, or is there a
> difference? If they are different, what is the recommended method?
>
fsl_regfilt exists because melodic ended up being loaded with too much
different functionality - the filtering will at some point be entirely
removed from melodic and fsl_regfilt will be the only tool provided
for this purpose.
>
> .5) After filtering the data, There is no motion visible when using
> the movie loop with fslview. I am pretty impressed by this effect,
> since I have data dominated by artefacts. Is fsl_regfilt really that
> effective or is this just a bug in fslview causing only one volume
> being displayed?
>
not sure what's going on - maybe it is that good ;) If you upload the
data we can have a look.
cheers
christian
>
> Thanks for your help,
> wolf
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