Hello Gang,
Sorry to come back AGAIN with a new question.
When thinking about it (it happens sometimes =)) I realize that maybe I should add a session effect to my model.
Since all the animals were scanned on the same day it may affect the result.
However, the session is strongly linked to "age" and I don't want to annihilate my findings by adding "session".
What are your thoughts?
In any case, out of interest could you please confirm the way to add this effect?

something like??? :

3dLME -prefix 3dLME_glt.nii.gz -jobs 20 -mask brainmask_nolr_func.nii.gz \
-model "Sexe*age*session" -qVars "age" -ranEff "~1+age" -num_glt 5 \
-gltLabel 1 "05MF" -gltCode 1 "Sexe : 0.5*M +0.5*F age :" \
-gltLabel 2 "1MF" -gltCode 2 "Sexe : 1*M -1*F age :" \
-gltLabel 3 "1MF" -gltCode 3 "Sexe : 1*M age :" \
-gltLabel 4 "1F" -gltCode 4 "Sexe : 1*F age :" \
-gltLabel 5 "1F" -gltCode 5 "Sexe : 0.5*M +0.5*F age : session :" \
-dataTable @disign_matrix.txt -resid resid.nii.gz

-gltLabel 5 would give me the full interaction?

Now (to see if I understood) suppose that i want to add another quantitative variable (e.g. weight) that on which I also want to see the effect I could do something like:

3dLME -prefix 3dLME_glt.nii.gz -jobs 20 -mask brainmask_nolr_func.nii.gz \
-model "Sexe*age*session" -qVars "age, weight" -ranEff "~1+age+weight" -num_glt 6 \
-gltLabel 1 "05MF" -gltCode 1 "Sexe : 0.5*M +0.5*F age :" \
-gltLabel 2 "1MF" -gltCode 2 "Sexe : 1*M -1*F age :" \
-gltLabel 3 "1MF" -gltCode 3 "Sexe : 1*M age :" \
-gltLabel 4 "1F" -gltCode 4 "Sexe : 1*F age :" \
-gltLabel 5 "1F" -gltCode 5 "Sexe : 0.5*M +0.5*F age : session :" \.
-gltLabel 6 "1F" -gltCode 5 "Sexe : 0.5*M +0.5*F age : session : weight :" \
-dataTable @disign_matrix.txt -resid resid.nii.gz

-gltLabel 6 would give me the full interaction?

is it correct?
Thank you!!