Hi
On 30 Jun 2008, at 20:43, Christina Hugenschmidt wrote:
> Hi all,
>
> Thanks again for the helpful feedback on which program to run in
> order to
> transform fMRI data into power spectral data. I have run fslpspec
> successfully, and now have a couple of more questions:
>
> 1. What is the difference between running the fslfft and fslspec/
> fslpspec
> commands?
>
fslfft calculates spatial fft, fslpspec calculates the power spectral
density for each time series
> 2. When I run fslpspec, it outputs 60 brain volumes in a gz file. Do
> these
> 60 volumes represent different parts of the power spectrum? If so,
> how are
> they broken up? If not, what do they represent?
Yes, they contain the power at different frequencies. The first volume
represent frequencies that correspond to a single full cycle in he
length of the run and the last volume represents frequencies that
correspond to N/2 full cycles (where N is the number of original vols)
You can translate this from 'cycles' to frequencies' once you know
original TR, e.g.the Nyquist limit for your fmri data set is 1/(2*TR),
e.g. 0.1666... for a 3s TR - the final volume generated with fslpspec
corresponds to 0.1666... Hz
>
>
> 3. I am also curious about different options running the data. When
> I type
> in fslpspec it outputs <input> [options] [output]. I tried to get the
> command to run verbose by typing -v or -V after my input file, but
> both
> times it simply named the output file -v. How can I find out which
> options
> are available for this utility, and how should I enter them?
>
I think the only command line option is -m <maskname> which can be
used to explicitly specify a mask so that the power spectrum is only
claculated for voxel within this mask... not all that exciting ;)
> Thank you again for any help/suggestions you can offer. I appreciate
> the
> time and patience of the more experienced members on the list!
>
> Christina
hth
Christian
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