Hi Christian
Thanks for your information. I can see the activation in the first
thresholded IC map under the alternative hypothesis is weak (seems no
activation), however it can show reasonable activation pattern in the
second thresholded IC map under the null hypothesis. But when I interpret
these thresholded IC maps, for instance, looking at the second thresholded
IC map, is there any cautions for the interpretation (is it the same
interpretation with the first thresholded IC map)? The weak activation
shown in the first thresholded IC map, is it resulted by setting the
threshold level (p = 0.95) too high?
Cheers
Angel
On Fri, 4 Jan 2008 20:50:27 +0000, Christian F. Beckmann
<[log in to unmask]> wrote:
>Hi,
>
>this happens in cases where the mixture-model based inference step
>detects that there is only a single Gaussian distribution present
>(i.e. the histogram of the IC does not have fat tails). In this case
>both thresholding under the alternative hyp and under the null hyp
>becomes valid and melodic generates the latter at a p<0.05 level in
>addition to the normal alternative hyp test. There are different
>possible ways why this might happen, e.g. SNR is very low or the
>mixture model simply failed to find a good estimate - you can check
>what's going on by having a look at the mixture-model fit (click on
>the thresholded map and you'll see the mm report page)
>hth
>Christian
>
>
>
>
>
>On 4 Jan 2008, at 15:00, Angel Wong wrote:
>
>> Dear FSL users I have performed a model-free group analysis using
>> multi-subject tensor ICA. The components can be generated properly.
>> But when I looked at the results, I found some components contain 2
>> thresholded IC maps. One is entitled as 'thresholded IC map
>> alternative hypothesis test at p>0.95', another is entitled as
>> 'thresholded IC map (2) 2-sided null hypothesis test at 0.05'. I
>> would like to ask: 1) Why there are two thresholded IC maps
>> generated for some of the components? 2) What is the difference
>> between the two thresholded IC maps and their significance? Many
>> thanks Angel
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