THE EVOLUTION OF SPATIAL NAVIGATION AT SINGLE-CELL RESOLUTION

Spatial navigation is a fundamental cognitive function, and the entorhinal cortex (EC), as part of the hippocampal formation, plays a central role in spatial processing. While the EC is structurally conserved across mammals, differences in navigational strategies suggest species-specific molecular specializations. Here, we present a single-cell transcriptomic atlas of the EC across four mammals: human, baboon, mouse, and fruit bat. Excitatory neurons largely grouped by cortical layer, though species-specific expression patterns altered canonical markers, resulting in mixed-layer subtypes. In fruit bats, we identified unique superficial-layer subtypes, potentially reflecting adaptations to 3D navigation. Inhibitory neurons were highly conserved, yet primates showed an expansion of CGE-derived Vip subtype. To link molecular identity with circuit-level architecture, DTI revealed species-specific connectivity patterns in the MEC of baboons and fruit bats. Our atlas demonstrates that cross-species single-cell analysis is feasible even without high-quality reference genomes and provides a valuable resource for exploring the molecular foundations of spatial navigation across mammals.