[rfxplot-users] Using rfxplot with PPI

[James Jones-R. <jj...@co...>]

Hello all,

We are attempting to use rfxplot to quantify effect sizes of the PPI
results we have calculated, all within SPM8 on a Mac OS. We have calculated
PPI on seed voxels of interest, which generated a list of target voxels
whose timecourses significantly correlate with the seed voxels. We are then
feeding those target voxels (and the accordant SPM.mat file that the PPI
toolbox generated for each target voxel) into rfxplot in order to quantify
the effect size of that target voxel's correlation/connectivity with its
respective seed voxel.

I have two questions for you all. First, when one goes through the rfxplot
GUI, one has the option of choosing "beta" or "con" as the substrate for
the analysis. In our study, we had two sessions/runs. Choosing "beta" in
rfxplot leads to two lists of variables to analyze (an essentially
identical list for each session), whereas choosing the "contrast" option
only gives a single list of variables to select from.

Here's our issue. When we run the "beta" option, the ".gdata" results
variable includes two unique columns of data, with two different values for
each participant (one for each of their two sessions); however, when we run
the "contrast" option, the ".gdata" results variable only has a single
column and it is identical to the first of the two ".gdata" columns from
the "beta"-based analysis. Why is this?

Secondly, and more broadly, does anyone have experience using rfxplot to
quantify connectivity analyses from PPI, and if so, can you point to any
resources or literature we can review? Specifically, we'd like to know more
about how to confirm that the rfxplot results actually pertain to the
connectivity estimate between the seed voxels and the target voxels. There
does not seem to be a lot of information out there about combining these
toolboxes in this way, although it seems theoretically to be a sound way of
conducting the analyses.

Thank you very much for your time!

James
-- 
James Jones-Rounds
Laboratory Manager
Human Development EEG and Psychophysiology (HEP) Laboratory,
Department of Human Development,
--------------------------------------------
Cornell University | Ithaca, NY
607-255-9883
ee...@co...