Thanks a lot for your message. It definitely helped me because I really need optseq but I am not very confident with it. If I understand correctly, for 10 stim of 1.5 sec and a protocol with a TR of 4s, a correct optseq sequence would be like that: --ntp 15 --tr 4 --psdwin 0 18 1.5 (or 0.5) --ev ev1 1.5 10 -- etc..
dPSD or samplng interval should be a multiple of stimulus and PSDmin and max are set to correspond to haemodynamic response function (in this case I just multiplied the length of the stimulus by 12 to give enough time to accommodate the stim). Thanks you again for your help. Yours, Tamara
In message 462E641C.2000508@nmr.mgh.harvard.edu Doug Greve greve@nmr.mgh.harvard.edu writes:
The stim duration does not have to be a multiple of the TR. If has to be a mult of the dPSD, which you can set to 0.5sec.
Tamara Cristescu wrote:
Hello list, I am new to optseq2 and I would need some help with it. I have a very long experiment (many stimuli) and on top of that I have a long TR (4s) because I collect 60 coronal slices covering all the brain. My stimuli are quite short 1.5s or 2.5s but according to optseq the stimuli duration should be a multiple of TR. Therefore, the min stim duration I can use is 4s. I thought of modelling stimuli as having a duration of 4sec (1.5 stim and a 2.5 artificial "null" event which is different than the null event optseq estimates).
I have a couple of questions: 1 I would like to know whether is better to include psdwin when I estimate a sequence or leave it out and use the TR value instead?
You have to set psdwin.
2 Also, would a psdwin of 20s be enough for a 4 sec stimulus?
I'd probably go to 24.
3 My aim is to get a good sequence estimation with minimum time. I noticed that although I give a certain ntp, optseq estimates a sequence that may run longer.
It should not, though the last stimulus may extend behyond the last time point.
4 Is the previous version of optseq still available? I only found optseq2 on your website.
It should still be in the freesurfer distribution.
Thanks a lot for your help. Tamara
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