Dear SPM:
I have some questions about setting up an event related design for
processing in SPM97. I have poured over the Buchel et al. article from
Neuron.
1) When jittering the ITI's was this mapped to particular intervals of 2.5,
3.0 or 3.5 TR's or was the interval continuous within the range of 2.5 -
3.5 TR's?
2) I noticed that even though you jittered the ITI's you still corrected
for slice timing differences. Is this correct?
3) When setting up the analysis in SPM one has to specify the event onsets
in terms of scans. I guess you figured this out in fractions of a scan. So
for the CS+ unpaired events in that paper from figure 1, the 2 onsets shown
would be specified as (counting the scans from the beginning of that
figure) approx
5.25 and 13.75 scans. Is this correct?
4) In terms of distributing the timing of the ITI relative to the scan
onset how carefully did you try to distribute the onsets relative to the
scans? By this I mean you had 26 CS+ unpaired events, did you try to
distribute the onsets of those 26 trials evenly over the TR? or did you
group onsets (6 at 1/4 into the TR, 7 at 1/2, 6 at 3/4 and 7 at even onset)
or something like that? This also has to do with question 1 regarding the
discrete vs. continuous possible onsets.
Thanks for any help,
Darren
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Darren R. Gitelman, M.D. E-mail: [log in to unmask]
Cognitive Neurology and Voice: (312) 908-9023
the Alzheimer's Disease Center Fax: (312) 908-8789
http://www.brain.nwu.edu
Northwestern Univ., 320 E. Superior St., Searle 11-470, Chicago, IL 60611
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