The striatum serves as the major input nucleus for the basal ganglia (BG) and the principal neural interface between dopamine reward signals and cortico-basal ganglia-thalamo-cortical circuits. Information processing in the striatum is dependent on cell-type-specific circuits. In particular, Medium Spiny Neurons (MSNs), which account for the vast majority of all striatal neurons, are divided into two major cell types: D1- and D2- MSNs.1 D1-MSNs express dopamine receptor type 1 (DRD1) and form the “direct pathway” via monosynaptic projections to the basal ganglia output nuclei.2 D2-MSNs express dopamine receptor type 2 (DRD2) and form the “indirect pathway” via di-synaptic projections to the basal ganglia output nuclei.2 Activity in the direct and indirect pathways produces, broadly, opposing effects on thalamo-cortical projections. This cell-type-specific circuit model has been crucial to understanding the role of the striatum and BG in the control of movement and the mechanisms of Parkinson’s disease.3,4 However, the striatum and BG are involved in many behaviors besides the control of movement. For example, segregated neurochemical compartments in the dorsal striatum (DS) known as striosome (patch) and matrix are thought to
