Avian neuronal morphology reveals pallial adaptations in Pigeons (Columba livia)

Avian cognitive abilities rival those of primates. These capacities have been linked to high pallial neuronal density and prefrontal cortex-like dorsal ventricular ridge (DVR) circuitry. Although the DVR is now recognized as a pallial structure homologous to the mammalian cortex, its morphological basis remains unclear. Here, we combine Nissl staining, Golgi–Cox labeling, and 3D reconstruction to map neuronal morphology across five telencephalic regions in the Rock Pigeon (Columba livia). From 64 fully reconstructed neurons, we quantified dendritic field area, total dendritic length, branching architecture, and radial arbor organization. DVR neurons showed the largest dendritic fields and the highest branching complexity. Single-nucleus transcriptomic data further revealed that the Nidopallium Caudolaterale (NCL), the core DVR subregion, expresses a neuron-morphogenesis gene module whose activity correlates with dendritic field size. Together, these results identify a molecular and morphological signature of DVR neurons and highlight the computational significance of Nidopallium Caudolaterale. This work provides an integrated comparison of telencephalic neuronal morphology and gene expression in birds.