Dear Nicolo,
It is possible that your activation does not quite pass this
threshold but that the console analysis showed a much
more liberally thresholded version of the results. To see
if you also have similar activation, just below significance,
load the zstat1.nii.gz file from the stats subdirectory (inside
the feat directory) into FSLView to look at the unthresholded
statistics. This should give you a feeling for whether the
analysis is showing you similar things, but the statistics are
just a little weak, or whether something is very different and
you can't detect things that were shown on the console, which
is probably indicative of a bigger error in setting up the
analysis.
It is not worth turning to FLOBS at this stage, and I would
only consider it if you activations are close to statistical
significance and you have an expectation that the HRF
in your group might be reasonably different from the standard
population. With a 10s on and 10s off design (which is quite
quick), the details of the HRF are largely washed out.
It may also be worthwhile running ICA to see if there are
any major artefacts in your data that you could clean up
with ICA-based denoising. But first look at your
unthresholded stats.
Hope this helps.
All the best,
Mark
On 21 Jan 2011, at 15:48, Nicoḷ Cardobi wrote:
> Thanks for the very quick reply.
>
> I change the convolution to gamma (I think that's the default setting of convolution with square basic shape wave), and I set the other parameters as you kindly advised, however I still not obtain a decent activation map.
>
> I post here a zmap thresholded with cluster correction (z threshold = 2.3 and p < 0.05)
>
> [URL=http://img200.imageshack.us/i/renderedthreshzstat1.png/][IMG]http://img200.imageshack.us/img200/8932/renderedthreshzstat1.png[/IMG][/URL]
>
> I add also a time series plot, witch may reveal the problem:
>
> [URL=http://img806.imageshack.us/i/tsplotzstat1.png/][IMG]http://img806.imageshack.us/img806/2495/tsplotzstat1.png[/IMG][/URL]
>
> The full mode fit and the cope one seems to be very different by the data. Is this the problem? Do I have to use the FLOBS in order to create an optimal basis set that fits better to the data?
>
> Best regards.
>
> P.s.: the z-threshold set in Misc tab has any relationship between the z-threshold set in the cluster thresholding? The default setting is 5.3 and changing it produces a modification in the design efficiency.
>
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