Dear SPMers,
I have a group of 7 subjects (rats) and I would like to perform a group
analysis (mixed effects).
I have done the 1st level analysis (fixed effects) for each subject and
I have two con_001 and con_002 images, wich are respectively the
contrast image for a positive effect (activation) and for a negative
effect (deactivation) of one condition (current stimulation) .
Then, I have done a one-sample-t-test : I feed all the con_001 of each
subject into the 2nd level analysis , then I entered a T contrast [1]
and SPM displayed the thresholded T-statistic image. But when I entered
a F contrast [1], I have got this error:
"
??? Inf computed by model function, fitting cannot continue.
Try using or tightening upper and lower bounds on coefficients.
"
Based on the procedure described in SPM8 manuel concerning the "face
group data", It is mentionned that I have to enter a F contrast.
I am confused by this and I have some questions:
(1) which contrast should I enter, F or T contrast? and what is the
differenece between them?
(2) Is the one-sample-t-test, the appropriate one to run mixed effects
analysis?
(3) Do I have to run two separate "one-sample-t-test" for
positive(activation) and negative-deactivation) effects?
Thank you for your help.
Best regards,
Salem
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