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Dear Karin,

In principle this is not a problem. Basically, the same rules apply for DCM as for a standard mass univariate GLM analysis: if you have enough trials to reliably find a difference using the GLM, then DCM will also be able to deal with this. Just as you generally wouldn't run a GLM modelling only 1 event (or block) the same holds for DCM.

Hanneke

On Tue, Apr 10, 2012 at 8:46 AM, Karin Lundengård <[log in to unmask]> wrote:
Dear SPM:ers,
I am going to use dcm on data from an experiment where the test persons are allowed to look at an image shown during several different  time spans. My question now relates to the fact that we have a higher number of instances when the image is shown during a short time than during a long time, so now I am wondering if this is a problem? Should I have an equal number of time points for each category och stimuli?
Yours,
Karin



--
Hanneke den Ouden, PhD

Center for Neural Science
New York University
4 Washington Place, room 873
New York NY 10003