Hi Sam,
> But resting-state sequences normally have a fixed scanning duration, and
> this is the same for every subject.
We can't assume any sort of similarity in the BOLD time series across subjects
in resting state fMRI, and tensor-ICA does not work well in this
scenario. So the
recommended approach is temporal concatenation.
> And what if I want to use fsl_regfilt denoising, which requires the single-session
> ICA approach? Is this not possible with resting-state data?
Yes it is possible - you can perform single-subject ICA-based denoising as a
separate preprocessing step for each subject prior to running your group ICA.
> But why should we assume that the temporal response is consistent between
> sessions/subjects in task fmri? Some subjects might have had longer scanning
> times or they might engage the task very differently.
You won't be able to use melodic for group ICA at all if your subjects
have a different
number of time points. And I would argue that for most simple
experimental stimuli,
you should be able to assume some sort of correspondence of activity
across subjects
in the regions of the brain that were involved. Obviously this will
not hold for more
complicated stimuli, or stimuli with timings that vary across
subjects, for which you
should stick with temporal concatenation.
Cheers,
Paul
On 05/03/2019, Sam W. <[log in to unmask]> wrote:
> Hi,
>
> Can someone please explain to me why we need to select "Multi-session
> temporal concatenation" for resting-state data? In the Melodic help webpage
> it says that we should use this approach if we "can not assume that the
> associated temporal response is consistent between sessions/subjects." But
> resting-state sequences normally have a fixed scanning duration, and this is
> the same for every subject. And what if I want to use fsl_regfilt denoising,
> which requires the single-session ICA approach? Is this not possible with
> resting-state data?
> For the "Multi-session Tensor-ICA" approach the webpage says "It is
> recommended to use this approach for data where the stimulus paradigm is
> consistent between session/subjects.". But why should we assume that the
> temporal response is consistent between sessions/subjects in task fmri? Some
> subjects might have had longer scanning times or they might engage the task
> very differently.
>
> Thank you for your help
> Sam
>
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