What is your command line? SHAHIN NASR wrote: > > Thanks Doug. > In my experiment, each trial (event) consists of 1 sec stimulus > presentation and 5 sec blank interval (TR=2). I have also added a > condition with just blank presentation which will be repeated as much > as other events. > > I have used optseq2 commands to generate the trial sequence. But I > faced two problem/questions: > > 1) Using this command, I expected to see a Null event (other than > my blank condition) with variable length (irrespective of TR) between > other trials. But to my surprise, length of the Null event was always > a multiplication of TR. Is that correct?
> 2) Also, for "psdmin psdmax" I wasn't sure if they are number of > TRs or number of seconds and what is a safe window length when my > stimuli are very simple visual objects (and no cognitive task). > > Once again, thanks for your help. > > > > On Fri, Dec 9, 2011 at 1:10 PM, Douglas N Greve > <gr...@nmr.mgh.harvard.edu <mailto:gr...@nmr.mgh.harvard.edu>> wrote: > > Hi Shahin, there are several ways to answer this question. If you > are going to analyze assuming a shape to the HRF, then the actual > delay between stimuli is technically not important (though 4s will > be good to avoid attenuation in the following stimulus). If you're > using an FIR model of the HRF (no assumed shape), then I usually > advise that you have, in total, as much time spent on fixation (or > whatever your null stimulus is) as you have for any other > stimulus. You can use optseq to compute the actual schedule. > doug > > > SHAHIN NASR wrote: > > Hi Surfers, > > It is my first experience with Event-related paradigms. In > my experiment, trials take minimum 6s (TR=2s). I wonder what > is the optimum variable delay between trials to be able to > analyze data without any confound. > > Regards > > -- > Shahin Nasr > > PhD in Cognitive Neuroscience > Martinos Imaging Center, MGH > Harvard Medical School > > > -- > Douglas N. Greve, Ph.D. > MGH-NMR Center > gr...@nmr.mgh.harvard.edu <mailto:gr...@nmr.mgh.harvard.edu> > Phone Number: 617-724-2358 <tel:617-724-2358> Fax: 617-726-7422 > <tel:617-726-7422> > > Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting > <http://surfer.nmr.mgh.harvard.edu/fswiki/BugReporting> > FileDrop: www.nmr.mgh.harvard.edu/facility/filedrop/index.html > <http://www.nmr.mgh.harvard.edu/facility/filedrop/index.html> > > > > 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. > > > > > -- > Shahin Nasr > > PhD in Cognitive Neuroscience > Martinos Imaging Center, MGH > Harvard Medical School > -- Douglas N. Greve, Ph.D. MGH-NMR Center gr...@nmr.mgh.harvard.edu Phone Number: 617-724-2358 Fax: 617-726-7422 Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting FileDrop: www.nmr.mgh.harvard.edu/facility/filedrop/index.html _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
