Dear Jamie,
> I am comparing signal strength in sparse versus continuous acquisition in animals. I have some sessions of sparse and some sessions of continuous for 2 subjects.
> Because I cannot do a group study, I am wondering if there is any way, at the first-level analysis, of including the sparse data and the continuous data in the same statistical model?
> I assume that analyzing continuous and sparse separately and then comparing con images from one type of scan and the other type won't work because the scaling applied will be different?
>
> I would like to be able to do more than just do an eyeball comparison of activation extents or t-values, but I don't know how I can statistically compare the two types of scanning protocols within a single subject.
Yes, this is a bit of a tricky issue! You cannot combine the two
types of sequences in the same first-level model because the timing of
the scans differ, and I'm not aware of a way to encourage SPM (or any
other program) to gracefully deal with this. However, I do think you
can get some useful information out of comparing the parameter
estimates for the two models. This is the approach we took in a paper
comparing scanning sequences (including a sparse one) for a sentence
comprehension task:
Peelle JE, Eason RJ, Schmitter S, Schwarzbauer C, Davis MH (2010)
Evaluating an acoustically quiet EPI sequence for use in fMRI studies
of speech and auditory processing. NeuroImage, 52, 1410–1419.
doi:10.1016/j.neuroimage.2010.05.015
It will probably be helpful to think about what brain regions you are
most interested in for this comparison, because we (and others) have
found that the effect of sequence is different depending on where you
look—another bit that makes this less than straightforward.
Good luck!
Best regards,
Jonathan
--
Dr. Jonathan Peelle
Department of Neurology
University of Pennsylvania
3 West Gates
3400 Spruce Street
Philadelphia, PA 19104
USA
http://jonathanpeelle.net/
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