Songbird vocal circuits, despite residing in a structure not found in mammals, contain neurons with gene expression profiles remarkably similar to those in the mammalian neocortex. However, these neurons are organized differently and show greater regulatory gene expression similarity to neurons in the mammalian ventral pallium, suggesting a distinct evolutionary origin but convergent evolution of functional cell types.

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This study provides a valuable resource for understanding the cellular diversity and evolutionary origins of songbird vocal circuits. The use of single-cell RNA sequencing allows for a detailed comparison of cell types across species and provides insights into potential homologies and differences between avian and mammalian brains. The findings are significant and well-supported by the data, though the limited generalizability to other species and behaviors and the need for functional validation constitute minor limitations.