Hi,
I conducted an fMRI experiment to investigate auditory spatial working memory.
To avoid confounds of scanner noise I used a sparse temporal sampling approach.
Now I have difficulties setting up the design matrix. Consulting the list archives left
me confused.
My acquisition time for 35 slices was 4s and the interscan interval (TR) amounted to
14s. The auditory stimulation was moved within this 14s-time frame, which varied the
delay between the end of the stimulation and the onset of the MR acquisition (2-8s) and
therefore also the delay between the MR acquisition and the next auditory stimulation.
This was done to get some information about the timing of brain activity.
I now have problems with the design matrix. In the archives it said that I should use TA as
TR (what makes sense), not to convolve with the hrf but 'use a FIR model with only a single bin
and a basis set that is as long as your TR'. How do I manage to have only one bin?
And isn't it possible to use the HRF but account for the delay between stimulation and the scanning
as well as for the in-built physiological delay in the HRF by specifying my model in seconds
and to predate my onsets so that my scan actually more or less starts at the peak of the HRF?
Thank you very much in advance for any comments! I appreciate them!
Best, Susanne Leiberg
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Dipl.-Psych. Susanne Leiberg
Institute of Medical Psychology and Behavioral Neurobiology
MEG-Center
Otfried-Müller-Str. 47
72076 Tübingen
Phone: + 49-7071-2987716
Fax: + 49-7071-295706
Email: [log in to unmask]
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