Connectional architecture of the prefrontal cortex in the marmoset brain

The prefrontal cortex (PFC) has dramatically expanded in the primate lineage, but how it interacts with other brain regions is still only partially understood. We performed high-resolution connectomic mapping of the marmoset PFC and found two contrasting projection patterns in both the corticocortical and corticostriatal projections. One was the “focal” projection exemplified by submillimeter-scale axonal convergence in many cortical columns. The other was the “spread-type” projection, which was widely distributed across the cortex or striatum. Parcellation-free analyses revealed recapitulation of PFC gradients in these projections’ local and global distribution patterns. Simultaneous injection of a retrograde tracer further showed reciprocity of corticocortical projections. In mice, focal projections were primitive, underscoring the importance of the primate model in investigating the principles of PFC connectivity that are shared among primates including humans. Our data has been made freely accessible online and will be a valuable resource for basic and clinical neuroscience. ### Competing Interest Statement The authors have declared no competing interest.