Just enter "seconds" for Units for Design, and enter the event onsets. It doesn't matter if your ITI and TR aren't identical.
Although you say it's a block design; so it really isn't a problem.
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From: SPM (Statistical Parametric Mapping) [[log in to unmask]] On Behalf Of Reem Jan [[log in to unmask]]
Sent: Sunday, February 28, 2010 7:30 PM
To: [log in to unmask]
Subject: [SPM] Wrong fMRI design - can anything be salvaged?
Dear SPMers
I am a new-ish PhD student who is fairly new to fMRI and SPM. I use the Stroop paradigm as a cognitive task during fMRI and both my fMRI protocol and Stroop paradigm (on E-Prime) were designed and running before I joined the project. After having analysed my data using SPM8 and the activations did not look typical, I looked into my E-Prime Stroop design and found out that the trials were on for 2.5 seconds whilst the TR on the MRI scanners was 3.0 seconds, which causes an accumulative shift.. I wonder if anyone can suggest anything that can be done to salvage the data or do anything about it.
We use a 1.5T scanner. My parameters are as follows:
FOV 192mm, 64 x 64 matrix, TR 3000ms, TE 50ms, 35slices, thickness 4mm, 0mm gap, Flip angle 90, 122 measurements (although only 118 volumes are recorded and used).
The Stroop paradigm I use is a blocked design with 3 conditions.
Your advice and suggestions are much appreciated.
Kind regards
Reem Jan
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