Hippocampal connectivity patterns echo macroscale cortical evolution in the primate brain

COEX 

While the hippocampus is key for uniquely human cognitive abilities, it is also a phylogenetically old cortex and paradoxically considered evolutionarily preserved. Here, we introduce a comparative framework to quantify the preservation and reconfiguration of hippocampal organisation in primate evolution, by analysing the hippocampus as an unfolded cortical surface that is geometrically matched across species. Our findings revealed an overall conservation of hippocampal macro- and micro-structure, showing anterior-posterior and, perpendicularly, subfield-related organisational axes in both humans and macaques. However, while functional organisation in both species also followed an anterior-posterior axis, the latter showed a marked evolutionary reconfiguration, which mirrors a rudimentary integration of the default-mode-network in non-human primates. Our findings suggest that microstructurally preserved regions like the hippocampus may still undergo functional reconfiguration in primate evolution, due to their embedding in heteromodal association networks.