If you change the dPSD parameter to something else (e.g. 1) then it should give you NULL lengths that are not integer multiples of the TR.
Chris
________________________________________
From: SPM (Statistical Parametric Mapping) [[log in to unmask]] on behalf of John Gelburg [[log in to unmask]]
Sent: Tuesday, November 15, 2011 4:03 PM
To: [log in to unmask]
Subject: Re: [SPM] Trial onset is not aligned to TR start. Is it a problem?
Hi again,
The consensus from all the answers was that it is fine not to align event onset to the TR. However, the optseq2 imposes an event duration to be a multiple of TRs (http://surfer.nmr.mgh.harvard.edu/optseq/optseq2.help.txt).
Two my questions are:
1. (theoretical) If it's really not a problem, why optseq2 imposes such a restriction?
2. (practical) What other than optseq2 tool I can use generate design files to overcome this limitation?
Thanks a lot,
John
On Wed, Nov 9, 2011 at 9:22 AM, John Gelburg <[log in to unmask]<mailto:[log in to unmask]>> wrote:
Hi all,
Suppose, my trial duration is 4 seconds and the TR=2.5 seconds. How bad is it that some of my trials starts at the middle of a TR? Clearly, the SPM onset matrix can coop with it, but how bad it is from model estimation point of view?
Thanks,
John
|