Hello everyone,
I am very new to neuroimaging and spm, so I am glad there exists such a great platform to discuss problems!
I currently startet scanning and now I want to set up a batch for the 1st-level analyses. I am defining my contrasts right now and have a general question about the weights that I should use.
For example, if I want to look into the following contrast: negative_images>neutral_images and I have for both the negative and the neutral images separate regressors for those that were later remembered in a recall test or forgotten. I defined the regressors with the following weights:
negative_rem = 0.5
negative_forg = 0.5
neutral_rem = -0.5
neutral_forg = -0.5
zeros for the rest of my regressors
Does it matter whether I use 0.5 for both regressors of the negative images or could I just as easily use 1? Theoretically, for me this is the same, but I am not sure how spm will handle these regressor weights.
Thank you very much in advance, don't hesitate to ask for more information if necessary.
Best wishes,
Lisa
|