You need to set up the psdwin to span the duration of a hemodynamic
response to your event as if it were presented in isolation. For a 3sec
event, you can probably use something like 24 sec (so min=0, max=24).
Since your TR=2, but your event duration is 3sec, I'd set dpsd=1 (so
that both the TR and the stimulus duration will be divided equally by
the dpsd). To control the first-order counter balance, use --focb 100.
This will cause optseq2 to compute the FOCB matrix fover 100 sequences,
and keep the one that is closest to the optimum.
doug
Linh Dang wrote:
Hi,
I have 2 questions.
1) How do I calculate psd min, max, and dpsd. Is there a formula for
calculating these values? I have 4 kinds of stimuli, stim duration =
3s, stim repetition = 25, TR =2 so:
optseq2 --ntp 180 --tr 2 --psdwin [?] --ev A 3 25 --ev B 3 25 --ev C
3 25 --ev D 3 25 --o 4types --tsearch 10 --nkeep 4
What should my psd min, max, and dpsd be?
2) My task is history-dependent. I would like to control the
probabilities that stimulus B follows A, C follows A, A follows D...
Is there a way for me to do that with optseq?
Thank you so much for your help.
Cheers,
Linh
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