Nature Neuroscience, Published online: 08 June 2020; doi:10.1038/s41593-020-0641-7
Over 100 years ago, Ramon y Cajal hypothesized that two forces played a role in the evolution of mammalian brain connectivity: minimizing wiring costs and maximizing conductivity speed. Using diffusion MRI, Assaf et al. reconstructed the brain connectomes of 123 mammalian species. Their network analysis revealed that both connectivity and the wiring cost are conserved across mammals. They describe a conservation principle that maintains the overall connectivity: species with fewer interhemispheric connections exhibit better intrahemispheric connectivity.