Multidimensional visual feature encoding and functional organization in the pigeon entopallium.

Understanding how birds perceive and recognize visual objects remains a fundamental question in neuroscience. The entopallium, a key node in the avian tectofugal pathway, has long been implicated in complex visual processing, yet its internal functional architecture remains incompletely understood. In this study, neuronal activity in the pigeon entopallium was systematically mapped using controlled visual stimuli that independently varied in color, shape, and motion. Recordings revealed marked hue selectivity that remained invariant across luminance levels, pronounced orientation tuning in response to shape stimuli, and robust direction selectivity for moving stimuli. Spatial mapping further revealed distinct functional segregation, with color-selective neurons localized anteroventrally, shape-selective neurons dorsally, and motion-selective neurons posteriorly. At the same time, partial overlap among these response classes was observed, with a subset of neurons exhibiting joint tuning across stimulus dimensions, suggesting an organizational scheme characterized by regional specialization and partial cross-feature integration. Notably, entopallium neurons exhibited a moderate level of visual feature integration and shared important functional properties with early to intermediate stages of mammalian visual processing. Together, these findings establish the entopallium as a major site for multidimensional visual analysis in birds and provide evidence for convergent principles underlying the evolution of complex visual systems across vertebrates.