I am trying to run a linear mixed effects model similar to the 2*2*2 anova design. My DV is reaction time and fixed factors are time (pre vs. post:within-subject), condition (congruent vs. incongruent: within subject) and stimulation (vertex vs. DLPFC: between subject) My concerns are: a)I have very few participants: 7 in the vertex condition and 7 in the DLPFC condition. b)2 out of the 7 participants participated in both vertex and DLPFC condition. How do I compute a nested lmer model with reaction time as DV and time, condition and stimulation as factors? and how do i account for random intercepts and slopes with few number of participants? Thanks for all the help [[alternative HTML version deleted]]