a, b, Representative coronal sections of HC (a) and LC (b) P1 vole hemispheres hybridized to Id2. Note the lateral shift in layer II/III Id2 expression in LC voles (arrow, b) compared to HC voles (arrow, a). c, Line drawing of the anatomical level (using Paxinos et al., 2007 as a guide) in which a static electronically-drawn region of interest (ROI) was placed on sections of binary-converted ISH experiments to quantify levels of mRNA expression. d, LC brains display an increase in Id2 transcript densities compared to HC in the ROI defined in (c) (***p=0.008, Student’s t). Bars represent group means ± SEM. ISH images and line drawing oriented dorsal (D) up, lateral (L) right. Scale bar = 1,000 μm.