Hi all,
I want to understand basic thing about spm. What is really more important to spm the active or task volumes or the specification of a condition.
For example, I have a block design and then defined it as event by randomly selecting a number of trials among the active and rest blocks. I get ~ same activations using the exact same volumes but changing the condition from ~ 1000 onset to 100 onsets. The reason why I did that was because I did an experiment to see the linear effects of using parameters as a mixed block design. The result was not similar to what other did. Then I found that it is better to design an experiment such this as an event design. Since I did not have a new experiment, I thought I can play with what I have. In terms of the linearity, I got really nice result as what I want. I just want to understand how and why although I used the same volumes. Does spm ignore the other activations that I do not defined? Can you comment please ?
Thanks
AS
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