model1 <- lme(categorical_FOD_FODs~Condition_FODs*Gender_FODs,random=~1|ID/Ch,na.action=na.omit, method = "ML", data=long1.RSPL,control = lmeControl(opt = "optim"))

model1 fits a mixed effects model with the categorical_FOD_FODs as the dependent variable and Condition_FODs and Genders_FODs as fixed effects. Random intercepts were fitted at the level of the Participant and the 
Variable (Ch)