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Dear AFNI users-

We are very pleased to announce that the new AFNI Message Board framework is up! Please join us at:

https://discuss.afni.nimh.nih.gov

Existing user accounts have been migrated, so returning users can login by requesting a password reset. New users can create accounts, as well, through a standard account creation process. Please note that these setup emails might initially go to spam folders (esp. for NIH users!), so please check those locations in the beginning.

The current Message Board discussion threads have been migrated to the new framework. The current Message Board will remain visible, but read-only, for a little while.

Sincerely, AFNI HQ

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Sharon R.S
June 06, 2006 10:05AM
Dear Afni Grandmasters!
I’m trying to find the optimal stimulus sequence of an event related paradigm with three different stimuli as indicated in the How to do 3.
However, I am struggling with the right RFSgen commands in order to adjust it to our experiment.
I want to optimize stimuli for the following design:
It is a mixed design (pure event related blocks with three occurring stimuli, which are separated with blocks of baseline periods).
Stimuli are presented for ½ a TR (TR=2 sec). There are however intrinsic in the design several restrictions, which have to be followed:
The randomized interstimulus interval has to range between 1-5 seconds. I would like to have a mean ISI duration of about 2 seconds. All of the three used stimuli have to occur equally balanced (1/3 per stimulus).

However, I have problems to choose the right options with RFSgen.
Using markov chain ignores the –nreps (20) and I get an unequal occurrence of my three stimuli, using random permuatatioln is not following my restrictions (range of ISI)…

Therefore, and since I am new to this field I would appreciate it much if you can give me any advice in order to precede my paradigm following these instructions.

RSFgen? ? \
?-?nt? 192 ? \
? -?num_stimts? 3?\
? -?nreps 1? 20?\
? -?nreps 2 20?\
? -?nreps 3? 20?\
?-?nblock 1? 2.0\
?-?nblock 2? 2.0\
?-?nblock 3? 2.0?\
? -?seed? 1234567?\
-?prefix RSF.stim?.100 >?&? /?dev/null
Thank You
Sharon

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Subject Author Posted

Finding optimal stimulus seq.

Sharon R.S June 06, 2006 10:05AM

Re: Finding optimal stimulus seq.

Gang Chen June 06, 2006 02:54PM