Dear SpM members,
I'm new to SPM, particularly to Marsbar. Now I want to get % signal change for
each condition at specified ROI.
I used Marsbar-->Results
-->Estimate results
-->Import contrasts (selecting contrasts I'm interested in)
-->% signal change (a new window poped up, here I have some
questions).
In the window of "events NOT in event type", I could see the contrasts I
imported just now. I selected whatever I want--> Add to events in event
type-->give a name whatever I like-->Ok.
Then It asked me--> Duration (is this duration the same as the one I used in
specifying model? because the duration I used in defining model was not same
number due to delay of the program, eg. 32.4 32.3 32.5 32.4 32.4 32.5 32.3. And
the duration was different between contrasts and between subjects, so I had to
type the duration for each contrast and each subjects. Here I just used the
duration which was exactly same with the one for specifying model. Then in
Matlab, I got a message like below
sort-of % signal change
duration 32.4ms duration 32.3ms duration32.5ms duration32.4ms duration 32.4ms
duration32.5msduration 32.3ms
Region IPL_L 0.315
1. Is 0.315 the number I could consider it as percent signal change(31.5%)? If
so, I just need to use the method above to get the percent signal changes for
all of subjects,average them, then get the %signal changes for each condition,
correct?
2. Is the duration above I used correct? if not, how to determine the duration?
3. Here I used the contrasts I knew the duration, if I created a new event,
assuming I have two events uI and uC when I define model, now I want to create a
new event uI-uC, how could I know the duration if I want to get the percent
signal change for this event?
4. I also heard someone use raw timecourses to get %signal change. I got the raw
timecourses (based on the method mentioned in Marsbar FAQ) and save in
spreadsheet, but I don't know how to convert them to %signal change. Could
anyone help me out?
Thanks in advance!
Chunhong
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