Modulation of Adult Neuro- and Gliogenesis in the hyperpallium and mesopallium of pigeons (Columba livia f.d.)

In birds, adult neurogenesis is more widespread compared to mammals. It has been linked to spatial cognition and behavioral flexibility relying on networks involving the hippocampus. However, its significance in other brain regions remains poorly understood. To test whether environmental and behavioral experiences differentially affect neurogenesis beyond the hippocampus, we exposed adult pigeons (Columba livia f.d.) to different housing conditions and spatial-cognition related experiments after 5-bromo-deoxyuridine treatment to label active cell division. Pigeons received training in spatial-orientation tasks (operant chamber or homing) and were either housed permanently in a pigeon indoor loft or allowed to fly freely. Three months later, brains were collected and immunohistochemically processed to examine neuro- and gliogenesis in the meso- and hyperpallium, two regions relevant to sensory and associative processing with heterogeneous levels of adult cell generation. We show that training and housing conditions alter neurogenesis with refined regional effects. Training and outdoor experiences had a stimulating effect, though not consistently. Adult gliogenesis showed a different pattern, with lowest levels observed in loft pigeons that did not undergo training. The different experimental conditions also altered the anterior-posterior distribution of newborn cells in various ways, with deviations occurring primarily at posterior levels.Overall, the findings demonstrate that adult neuro- and gliogenesis represent a mechanism through which the brain integrates internal states and external experiences to dynamically adjust its functional organization.