Cytoarchitectonic, receptor distribution and functional connectivity analyses of the macaque frontal lobe

Based on quantitative cyto- and receptor architectonic analyses, we identified 35 prefrontal areas and introduced a novel subdivision of Walkers areas 10, 9, 8B and 46. Statistical analysis of receptor densities revealed regional differences in lateral and ventrolateral prefrontal cortex. Since structural and functional organization of subdivisions encompassing areas 46 and 12 demonstrated significant differences in the interareal levels of 2 receptors. Furthermore, multivariate analysis included receptor fingerprints of previously identified 16 motor areas in the same macaque brains, and revealed five clusters encompassing frontal lobe areas. Based on the functional connectivity analysis, clustered areas showed similar connectivity distribution pattern. In particular, rostrally located areas (in clusters 1-2) were characterized by bigger fingerprints, i.e., higher receptor densities, and stronger regional interconnections. Whereas, more caudal areas (in clusters 3-5) had smaller fingerprints, but showed a widespread connectivity pattern with distant cortical regions. Taken together, present study provides a comprehensive insight into the molecular structure underlying the functional organization of the cortex and, thus, reconcile discrepancies between the structural and functional hierarchical organization of the primate frontal lobe. Finally, our data are publicly available via the EBRAINS and BALSA repositories for the entire scientific community.