Hi SPM Users,
I am interested in contrasting fMRI effects between sessions and wanted your thoughts on my 1st and 2nd level setup.
My participants have undergone four conditions, related to different types of brain stimulation with TMS in the scanner. Each condition was run as a separate scan session.
At the 1st level, in each condition I create a regressor modelling the onsets of each stimulation pulse. I then create a con image for this stimulation regressor, for each session, which then gets passed to the second level.
I am ultimately interested in contrasting con images for the stimulation regressors obtained in different sessions. So, for the 2nd level, I run a full factorial analysis with Name = Conditions, Levels = 4 (i.e., condition 1, 2, 3, and 4), and Independence = No. Each cell in the design thus contains the con images for the stimulation regressor of each session.
I then contrast these cells at the 2nd level to obtain the difference map.
Is this the best way to setup the model, or should I be generating the between-session contrasts at the first level? If so, how?
Thank you.
With Kind Regards,
Thapa
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