On 7/2/19 6:58 AM, Davide Nardo wrote:
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Dear Prof Greve,
I hope you don’t mind if I ask you another question.
I assume that for the same reason (i.e., FIR analysis), null events’ durations are multiple integers of the TR.
Actually, they are multiples of the dPSD
But what if one wants to jitter events?
It will just put random amounts of dPSD
Also, OptSeq does not accept --tnullmin and --tnullmax that are different from multiple integers of the TR.
Again, the dPSD
The problem with setting the dPSD to arbitrarily small values for an FIR analysis is that your statistical power drops by a factor of TR/dPSD
Best.
Davide
*From:*Davide Nardo *Sent:* 01 July 2019 18:38 *To:* 'Greve, Douglas N.,Ph.D.' DGREVE@mgh.harvard.edu *Subject:* RE: Question about OptSeq
Dear Prof Greve,
Thank you very much for your prompt and clear reply. It helps a lot!`
Best.
Davide
*From:*Greve, Douglas N.,Ph.D. <DGREVE@mgh.harvard.edu mailto:DGREVE@mgh.harvard.edu> *Sent:* 01 July 2019 15:07 *To:* Davide Nardo <Davide.Nardo@mrc-cbu.cam.ac.uk mailto:Davide.Nardo@mrc-cbu.cam.ac.uk>; Freesurfer support list <freesurfer@nmr.mgh.harvard.edu mailto:freesurfer@nmr.mgh.harvard.edu> *Subject:* Re: Question about OptSeq
No, there is not. optseq assumes you will be doing an FIR analysis (=finite impulse response = not assuming a shape to the hemodynamic response). In this analysis, this must be the relationship. If you assume a shape, then this relationship is not necessary. In your case, you can set the dPSD=1.
On 7/1/2019 7:19 AM, Davide Nardo wrote:
* External Email - Use Caution * Dear Prof Greve, I hope you don’t mind if I ask you a question about OptSeq. It looks like a constraint in using OptSeq is that any event duration must be an integer multiple of the dPSD, which in turn needs to be an integer multiple of the TR, and seemingly there is no exception to this rule. I am in a situation in which my TR = 2 sec, and my event duration = 3 sec, therefore I get an error message when running OptSeq. However, I am puzzled by this, as in my experience with fMRI an event duration does not necessarily need to be a multiple of the TR… Is there any way I can circumvent this requirement in OptSeq? Best. Davide Nardo -- Davide Nardo, PhD MRC Cognition and Brain Sciences Unit University of Cambridge 15 Chaucer Road Cambridge, CB2 7EF Davide.Nardo@mrc-cbu.cam.ac.uk <mailto:Davide.Nardo@mrc-cbu.cam.ac.uk>The information in this e-mail is intended only for the person to whom it is addressed. If you believe this e-mail was sent to you in error and the e-mail contains patient information, please contact the Partners Compliance HelpLine at http://www.partners.org/complianceline . If the e-mail was sent to you in error but does not contain patient information, please contact the sender and properly dispose of the e-mail.
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Greve, Douglas N.,Ph.D.