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Thanks Donald for your advice. Hope someone who knows the task or the cognitive aspects of response inhibition and how well to model it in the context of PPI analyses will read this message! Yann On 29 Apr 2014, at 1:02 am, MCLAREN, Donald <[log in to unmask]> wrote: > > I did not mean to use gPPI to evaluate brain activation, it was just a more general question regarding basic analyses. But I guess I can go with 'NoGo’ (>implicit baseline / >0) for brain activation, it is fine, right? > > Yes. > > Regarding functional connectivity, it seems therefore relevant to just use the NoGo (>0) PPI contrast to evaluate functional connectivity for this particular condition (response inhibition), right? > > Yes. However, whether this contrast represents response inhibition is a cognitive question and should be directed to researchers who understand the cognitive aspects of response inhibition better than I do. > > > Thanks again. > > Cheers, > > Yann > > > On 24 Apr 2014, at 12:11 pm, MCLAREN, Donald <[log in to unmask]> wrote: > >> Yann, >> >> gPPI should only be used for looking at the connectivity of task data, not brain activation. >> >> As for the contrast you want to use, that is more of a psychological construct question than an analysis question and others who have more experience with your task can answer. >> >> With gPPI, you can either compare conditions (e.g. Nogo>Congruent) or compare conditions against baseline (e.g. Nogo>0). >> >> The former would reveal regions where the connectivity is more positive/less negative than the congruent condition. The second contrast would reveal regions where the Nogo connectivity is greater than the connectivity at baseline. >> >> Hope this helps. >> >> >> Best Regards, Donald McLaren >> ================= >> D.G. McLaren, Ph.D. >> Research Fellow, Department of Neurology, Massachusetts General Hospital and >> Harvard Medical School >> Postdoctoral Research Fellow, GRECC, Bedford VA >> Website: http://www.martinos.org/~mclaren >> Office: (773) 406-2464 >> ===================== >> This e-mail contains CONFIDENTIAL INFORMATION which may contain PROTECTED >> HEALTHCARE INFORMATION and may also be LEGALLY PRIVILEGED and which is >> intended only for the use of the individual or entity named above. If the >> reader of the e-mail is not the intended recipient or the employee or agent >> responsible for delivering it to the intended recipient, you are hereby >> notified that you are in possession of confidential and privileged >> information. Any unauthorized use, disclosure, copying or the taking of any >> action in reliance on the contents of this information is strictly >> prohibited and may be unlawful. If you have received this e-mail >> unintentionally, please immediately notify the sender via telephone at (773) >> 406-2464 or email. >> >> >> On Wed, Apr 23, 2014 at 6:16 PM, Yann Quidé <[log in to unmask]> wrote: >> Dear Donald and others, >> >> I am using gPPI with an event-related design (modified Flanker task, including ‘Congruent’, ‘Incongruent’, NoGo’, and ’Neutral’ conditions), and was wondering how to build the final PPI contrast for the 'Nogo’ condition? I am also wondering what will be the best option to analyse brain activation for this condition. >> Does it need to be contrasted with say the ‘Congruent’ condition, or can if I leave it alone, will it be contrasted against the implicit baseline? Or am I totally wrong, and there is a 3rd option? Depending of the paper I read I can find both option for brain activation analyses. >> >> Thanks for your help. >> >> Best, >> >> Yann >> > >