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Dear Donald, Thanks a lot for replying to my question. I didn't know that the gPPI toolbox could deal with parametric modulations. I will have a look at it! Best, Sebastian Am 10.10.2016 um 17:38 schrieb MCLAREN, Donald: > Sebastian, > > Please see inline responses below. > > > > Best Regards, > Donald McLaren, PhD > > > On Wed, Jul 27, 2016 at 3:17 PM, Sebastian Puschmann > <[log in to unmask] > <mailto:[log in to unmask]>> wrote: > > Dear list, > > normally a PPI analysis aims to investigate changes in functional > connectivity between a seed and other brain regions as function of > a psychological variable with discrete levels (like attention: > yes/no). I'm currently working on a data set in which I would like > to study changes in connectivity to a seed region as a function of > task performance measured in each trial. Therefore, I was > wondering whether it is possible to perform a "parametric" PPI, in > which the VOI time course of the seed region (here: right TPJ) is > modulated by the trial performance score? > > > Yes. This has been done in Humbert and McLaren for repeated swallows > using the gPPI toolbox. > > > I attached a figure showing an example of what I mean. It shows > the VOI time course in the right TPJ, the modulator, and the > resulting interaction. Here, the modualor is the mean-centered > performance score in task blocks (60 sec duration). It is set to > zero in phases not belonging to the task blocks. > > - Has such an approach ever been used? If so, could you provide me > with some references? > > > Yes. See above. > > - Would this be a "valid" way of analyzing my data? > > > Yes. > > - Are there other/better possibilities of performing such an > analysis? A DCM-like approach is not really possible, since I do > not have a strong anatomical hypothesis on a specific target > region. Instead, several target regions seem plausible. > > > Use the gPPI toolbox. > > > Thanks a lot! > Sebastian > > > -- Dr. Sebastian Puschmann Montreal Neurological Institute McGill University 3801 University St Montreal, QC Canada H3A2B4