I am new to optseq2 so I really need advices to my
questions. We have an experiment of 2 factors with 36 trials for each
factor, and another 24 null trials. So in total we have 96 trials. We
also have 3 random jitters which make our trials could last for either
4.6, 5 or 5.4 seconds. The total session time is thus 480 seconds.
Since our TR is 2 seconds, the ntp = 240.
My questions are:
(1) How can I set the psdwin? My intuition is that dPSD
should be divided by both TR and trial duration. That means we can only
have a dPSD = 0.2. Would that be too small? I observed that by doing
this the largest psdmax is only 2 seconds.
That is not too small, but if you are going to analyze your data with
an FIR model, then it will kill your power. If you are going to assume
a shape (eg, gamma function or diff of gammas), then it is fine.
(2) What should I do if I want to break the session into two
parts? The previous optseq version seems to allow one specify the runs
for each sesssion. But I did not find this option in optseq2. Can I
just use half the trials to get two sequences and use them for the two
parts?
Yes, spec --nkeep 2
doug
Thanks! Your suggestion is appreciated.
Hongchuan
2008-11-03
Hongchuan Zhang, Ph.D.
Postdoctoral Research Associate
Developmental Cognitive Neuroscience Laboratory
Northwestern University
2240 North Campus Drive
Frances Searle Building, Room 2-356
Evanston, Illinois, 60208
phone: (847)467-1549
e-mail: hongchuan-zhang at
northwestern.edu
--
Douglas N. Greve, Ph.D.
MGH-NMR Center
greve@nmr.mgh.harvard.edu
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Fax: 617-726-7422
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