Hi all,
After reading posts on here which advise using optseq to aid fMRI design and recent advice I've received on here too (thanks Jesper! FSL list msg: 053580, 2013-06-05, 21:36, 29, length of ISI?), I am using optseq2 to help calculate stimulus order and timing. I've read the help in some detail but am still a little unclear on some of the appropriate values to input and indeed what values I am aiming for in the output. It'd be great if anyone who has used it can help out...
Briefly, my study is a simple food cue reactivity study in which three different types of pictures (50 each) are presented for 3s each, in pseudo-random sequence. I now intend to include null events to optimise the spacing of the events to detect a difference between conditions, but also to provide a baseline for a 'sanity check' just in case.
I am uncertain as to the value of psdwin and associated variables (PSD, min, max dPSD) - should I include a post-stimulus delay or should that be set to 0 as in most examples? Also what is the recommended psdwinMAX value for events of 3s? 12 or as much as 18 seconds to capture the whole haemodynamic response? T
Also I am not certain how to judge the resulting output. I understand I should maximise 'efficiency' but I can't find any advice as to what is a 'good' value of efficiency to aim for. Any advice here? Also should I be judging the sequence on any other values?
So I have inputted the following and got a value of 2.586 for efficiency for the best sequence. Is this reasonable/sufficient?
optseq2 --ntp 200 --tr 3 ---psdwin 0 12 3 --ev ev1 3 50 --ev ev2 3 50 --ev ev3 3 50 --nkeep 3 --o test6 --nsearch 10000
Many thanks in advance,
Ella
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