“…The extent of the NCL is typically estimated based on an immunohistochemical staining method against tyrosine hydroxylase (TH), the rate-limiting enzyme in the production of dopamine ( Divac and Mogensen, 1985 ; Kröner and Güntürkün, 1999 ). These midbrain, dopaminergic afferents are denser within the NCL compared with neighboring nidopallial areas, which signifies another similarity to the PFC ( Divac and Mogensen, 1985 ; von Eugen et al, 2020 ; Kersten et al, 2022 ). Notably, the anti-TH method identifies a single portion of the pigeon caudal nidopallium, whereas it distinguishes three caudal nidopallial areas in the carrion crow and other songbirds (i.e., a dorsal, medial, and ventral NCL; von Eugen et al, 2020 ; Kersten et al, 2022 ).…”