Dear Jason
The same question has come up before in the context of DCM, and unfortunately, there isn't a staightforward answer to it.
If you have a very robust task / look at connectivity between very robustly coupled regions a few blocks / scans may be sufficient to get clear results.
The weaker and/or more variable your connectivity, the more scans you need to get a robust estimation at the first (individual) level.
From the above it, however, also follows, that you can (partially) offset a low number of scans with a high number of subjects. Basically, having a limited number of scans will result in more noise in your first-level estimates. So in order to get robust group-level effects, you need more subjects. When assessing a similar sample-size, your statistics will become less significant with a lower number of volumes.
Best reagrds
Simon
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Von: SPM (Statistical Parametric Mapping) [[log in to unmask]]" im Auftrag von "Jason Smucny [[log in to unmask]]
Gesendet: Donnerstag, 10. Mai 2012 01:23
An: [log in to unmask]
Betreff: [SPM] Minimum volumes for CONN functional connectivity?
Hello SPM Community,
I am attempting to do a connectivity analysis using CONN 13 with the "sparse" option. I was wondering, what are the minimum number of volumes required to do an effective analysis? I only have 12 or so volumes per condition; do I need to collapse across all conditions, or can I analyze connectivity between conditions? Thank you
Jason Smucny
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