afni.nimh.nih.gov

I suggest using 3dLMEr with something like

3dLMEr -model “Session*Velocity*Pleasantness*Oxytocin+Movement+(Oxytocin|subject)+(Pleasantness|subject)”

If you're interested in comparing Session and Velocity levels, centering within each Session and Velocity may be important for Pleasantness and Oxytocin.

Gang