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]> 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