Helping with Mediation Toolbox

[Rosalia Dacosta Aguayo]

Dear Dr. Wager,

My name is Rosalia. It is the first time I want to use mediation analysis with VBM data. I have been trying some analyses using BRAVO Toolbox but I am not satisfied with the results.

Anderson M Winkler told me (FSL list forum). I could give a try with your toolbox. I have been looking at your web page: http://wagerlab.colorado.edu/wiki/doku.php/help/mediation/m3_mediation_fmri_toolbox and I have seen that there are more possibilities of analysis and facilities in order to plot the results of the analysis.

My main objective here is to compare three groups regarding mediation analysis, not just one...as I have tried till now. The problem, is that I do not know how to do this kind of analysis neither with BRAVO nor your Toolbox. I am familiarized with X, Y, M and cov definitions...and the need of making a .txt file with the names of the images I want to analyze...but not sure how to cope when I want to see how mediation works in every group and if there are significant differences between groups regarding mediation analysis (direct paths (A and B, positive correlation or negative correlation, as well as AB indirect path as a product of A and B, with its sign depends on the signs of A and B).

By the other way, I have found that BRAVO has for now only implemented two-sided test...what if I have a hypothesis...it is estrange to find positive as well as negative AB results...although I have seen that the anatomical regions are described in the literature...so they have sense.

I would be very grateful if you could help me with the design of the model in order to accomplish the statistical mediation analysis I am interested and how to compare if mediation results for every group are statistically significant.

Hoping to hear news.....

Yours sincerely,

Rosalia

--

Rosalía Dacosta-Aguayo, Post-Doctoral Researcher.
Biomedicine, PhD
Clinical Neuropsychologist

Department of Neurosciences.
Group of Neurodegenerative Diseases
Gaixotasun Neuroendekapenezko Taldea
Neurozientziak Arloa

rosalia...@biodonostia.org
T. +34 943 006 128

IIS BIODONOSTIA - OSI DONOSTIALDEA
Pº Dr. Beguiristain s/n * 20014 Donostia-San Sebastián SPAIN * T.+34 943
006 012 * F. +34 943 006 250 * biodo...@biodonostia.org *
www.biodonostia.org