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 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 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.
