Thank you very much for your answer.I have no experience with gPPI, but I will try to use it. However, I was wondering whether is it also possible to run the analysis using standard PPI.I'm not sure if I understood it right. When you suggest not to model rest and let it be the implicit baseline, do you mean in the PPI connectivty analysis or in the first level activity GLM model?Thank you very much,Clara
Date: Mon, 13 Jun 2016 14:35:00 -0400
From: [log in to unmask]
Subject: Re: [SPM] PPI analysis with 3 conditions
To: [log in to unmask]Clara,I would recommend using the gPPI toolbox.I would also not model rest and let rest be the implicit baseline.Best Regards,Donald McLaren, PhDOn Mon, Jun 13, 2016 at 8:54 AM, clara garcia gorro <[log in to unmask]> wrote:Dear SPM experts,I have a question regarding standard PPI analysis. In have a motor tapping task in which I have 3 conditions: right hand, left hand and resting.I am interested in studying the connectivity of the putamen with the rest of the brain during the right hand condition compared to the rest condition.I initially ran the PPI analysis setting the right condition to 1 and the restng condition to -1. So, the PPI inteaction term looked like this:[1 1 -1; 2 1 1]where the first condition is rest, the second condition is right.However, I have been recently adviced to also include the resting condition in my PPI design too, setting left as a 0, in order to exclude the part of the BOLD response corresponding to the left hand condition.I have read is this paper:that standard PPI analysis is "potentially limited to simple experiments with only one or two conditions, respectively, or experiments that can be collapsed into two conditions for analysis".I was wondering if it is correct then to calculate my PPI interaction term like this:[1 1 -1; 2 1 1; 3 1 0]where the first condition is rest, the second condition is right and the third condition is left.Thank you very much in advance,Clara