The nucleus accumbens (NAc) contains multiple subpopulations of medium spiny neurons (MSNs): one subpopulation expresses D1-type dopamine receptors, another expresses D2-type receptors, and a third expresses both. The relative roles in NAc of D1 neurons versus D2 neurons in appetitive motivation were assessed here. Specifically, we asked whether D1-Cre mice or D2-Cre mice would instrumentally seek optogenetic self-stimulation of those respective subpopulations in NAc, or instead avoid NAc laser stimulation. and Some statistical forms have been exported from SPSS for the purposes of accessibility to viewers. Please see the "readme" text for descriptions of each individual excel file.