Dear Masha,
The sign is arbitrary in an ICA decomposition, and so simultaneously flipping the timecourse and spatial signs gives you exactly the same component. Therefore these two examples represent exactly the same component and there is nothing wrong at all.
All the best,
Mark
On 12 Apr 2013, at 21:11, Mahsa Shokouhi <[log in to unmask]> wrote:
> Hi everyone
>
> I've got strange results with melodic on brain-extracted, pre-processed BOLD data. I'm attaching the first component returned for both raw (no brain extraction) and brain-extracted data. The time course of the first component in the raw data exactly matches the paradigm we used. However, after applying the brain mask (using an in house matlab code) the time course seems to be inverted and red and blue regions are swapped (compared to non-brain extracted case). I'd appreciate any thoughts on what might have gone wrong.
>
> Thanks
> Mahsa
> <ICA1.jpg><ICA1_brainMasked.jpg>
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