Hi Markus
> dear spmer.
> a few weeks ago there was a question about a paradigm with scan pauses. i
> could not find any reply to this (neither could i find something in the
> archives). i have to ask almost the same question due to a paradigm, which
> needs scan pauses (due to the noise of the scanner).
> we explored the following paradigm:
> 60 scans baseline - 5 min pause with sensoric testing- 108 scans
> stimulation - 15 min pause with sensoric testing - 60 scans - 15 min pause
> with sensoric testing - 60 scans.
> we want to answer the BOLD-signal changes after the stimulation over a tine
> period of 50 minutes.
> now we have to face the problem of the interruption of the time series.
> here my questions:
>
ok I'll try - no warranties ...
> 1. is it absolutely impossible to conduct a paradigm with scanning pause
> (and why)?
>
I don't think so ... :-\
> 2. is there a time limit of the pause which would be tolerable?
>
well the time your subjects can stay in
> 3. is there any method, how we can test, whether the pause is really a
> problem or not (and not just theoretical)?
>
can help on this one
> 4. can we do something to solve this problem (like correction for global
> changes)?
>
yep - the global scaling should do the trick - or you can correct for
globals using another method see e.g. NeuroImage 22 p360 the paper by
Macey et al.
> 5. if we have to regard the 4 blocks as individual sessions, is it possible
> to use the first session (baseline) as the baseline condition and contrast
> all the other sessions with it?
> i would appreciate any commend about this very much (and even more, if it
> is not to technical).
>
well once it is corrected for globals it should be ok. Note that a nice
a way to look at the effect of learning is to use time as parametric
regressor .. I don't remember exactly how but for sure you'll find
details in paper from Henson et al.
Hope this helps (a bit)
cyril
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