We repeated the DRD1, RXFP1, and CPNE4 FISH on regularly spaced pre- and peri-commissural coronal sections. We defined the regions of the VS by comparison of Nissl-stained sections with a high-resolution MRI and DTI Rhesus macaque brain atlas (Figures S6A and S6B)36,37 and we mapped all the nearby islands in two monkeys (Figures 6E and S5G-S5I). The CPNE4-positive islands appeared to correspond to the Islands of Calleja (ICj).38 This correspondence was verified by intense co-localization of CPNE4 and DRD1 in the cells of the major ICj, an easily identifiable landmark at the border between the NAc and the septal nuclei (Figure S6D). Previous studies have shown that cells in ICjs are granule cells.38 Likewise, the CPNE4-positive cells we examined were small and exhibited high packing density (Figures S6E and S6F). Thus, the cluster enriched with DRD1 and CPNE4 corresponded with granule cells in the ICjs. Outside of the ICjs, co-localization between DRD1 and CPNE4 was restricted to a dense cell layer at the ventral extreme of the OT, possibly corresponding to a portion of the anterior olfactory nucleus (AON) (Figures
