Columns of the avian CG/ICo as delineated by histochemistry and Fos induction in the territorial violet-eared waxbill and colonial zebra finch. Shown is a schematic rostro-caudal representation of Fos response in the avian CG and ICo following exposure to different social conditions (see legend at top). Abbreviations: AP, area pretectalis; Cb, cerebellum; CG, midbrain central gray; CT, commissura tectalis; CP, commissura posterior; DBC, decussatio brachiorum; DM, dorsomedial nucleus; ICo, nucleus intercollicularis; Is, nucleus interstitialis; OM, occipitomesencephalic tract; Ru, nucleus ruber; SPM, nucleus spiriformis medialis. See Fig. 1 for other abbreviations. Modified from Kingsbury et al. (2011).