Greetings Freesurfers,
I am using optseq2 for the first time to generate a stimulus order for my trials and figure out the ideal ITI between trials. I have a few questions about how this works.
1. I tried specifying the PSD max as 18 seconds and minimum of 2 seconds. My ntp is 216 and my TR is set at 2 seconds. I have 9 events specified, each 14 seconds long with two repetitions of each. Here is the command I ran:
optseq2 --ntp 216 --tr 2 --psdwin 2 18 --ev ev1 14 2 --ev ev2 14 2 --ev ev3 14 2 --ev ev4 14 2 --ev ev5 14 2 --ev ev6 14 2 --ev ev7 14 2 --ev ev8 14 2 --ev ev9 14 2 --o test --nsearch 1000 --nkeep 100
In the par files that are generated, many of the NULL time durations are much longer than the PSD max I specified (i.e., I specified 18 seconds and some are as long as 58 seconds). Is this simply because the duration of my trials is so long that 18 seconds is not long enough of a max PSD? Does optseq2 just ignore my max PSD request if it is unrealistic?
2. Overall, I will have nine runs. While I realize that the mean ITI will remain the same in each par file, I want to minimize the duration of any single given ITI. As such, if I pseudorandomly select only 9 par files with the lowest maximum ITIs, is this acceptable? Is there some reason I would not want to do this?
3. If I wanted to change my TR from 2 seconds to 1.8 seconds, would it be acceptable to use the same trial order/ITI randomizations as I selected that were generated with a 2 second TR, or would I have to generate new ones? This is more a matter of whether I have to make new stimulus lists than running optseq2 again.
Many thanks, ~Sue Mosher
* * ** *** ***** ******** ************* Susan M. Mosher Program in Neuroscience Boston University 2 Cummington Street, Room 209F Boston, MA 02215-2425 smosher@bu.edu * * ** *** ***** ******** *************