You might find our brief technical report and the references
in that (particularly Kiebel et al 1999) to be useful in
explaining exactly what GRF does. The report is at:
Matthew Brett also has an excellent web page explaining GRF
and cluster-based inference at:
Hope these help.
All the best,
On 21 Dec 2004, at 00:07, Fornito, Alexander wrote:
> That worked -thanks!
> You're answer raised another issue for me. I'm still trying to
> understand how thresholding is achieved in FEAT. Let me see if I
> For voxel-based thresholding, is each voxel treated independently?
> Is the corrected p-value set by the user corrected according to GRF
> theory (eg., if I set the value to .05, the threshold is corresponds
> to a GRF corrected .05. In this case, is there any way of determining
> what the actual threshold is?
> For cluster-based thresholding, are the voxels smoothed according to
> the FWHM set in the pre-stats tab of the FEAT GUI? Thus, for eg., if
> the FWHM is 5mm then the stats are run on clusters of 5 or more
> contiguous voxels?
> What do the Z values and p values represent in cluster based
> thresholding, and are there any rules of thumb for determining what
> the appropriate values for these are?
> Once again, many thanks for your assistance,
> -----Original Message-----
> From: Andreas Bartsch [mailto:[log in to unmask]]
> Sent: Monday, December 20, 2004 8:01 PM
> To: [log in to unmask]
> Subject: [FSL] AW: [FSL] Timeseries in FSL view
> Hi Alex,
> ok - this one is easy:
> Load the 4D-file (e.g., filtered_func_data) into FSLView. The selected
> file appears in the lower box on the left. Once you have loaded the
> stats image (e.g., thresh_zstat1) you need to select the 4D-file in
> the box again to view the time series. I assume you had the stats
> image selected (which is 3D), so you could not access the time series
> of the 4D file.
> And yes - all clusters surviving the threshold are listed. But note
> that are always some stipulations involved in defining what is
> regarded as a cluster (which depend on the precise approach chosen).
> To define contiguous clusters, FEAT applies an initial Z-threshold you
> Best regards-
> -----Ursprüngliche Nachricht-----
> Von: Alex Fornito [mailto:[log in to unmask]]
> Gesendet: Mo 20.12.2004 03:39
> An: [log in to unmask]
> Betreff: [FSL] Timeseries in FSL view
> I'm having trouble accessing timeseries data in FSL view.
> I load the 4D image, and add the thresh_zstat image for the
> contrast of
> interest. The stat image gets overlaid on the 4D image, but I
> am uable o
> select "Timeseries" from the "View" menu. Am I missing
> Also, as an aside, in the report.html page, do the cluster
> lists obtaine
> by clicking on a contrast image represent an exhaustive list
> of all
> clusters that syurvived thresholding?
> Many thanks for your help,