Computational analysis of functional connectivity between areas of primatecerebral cortex

Recent analyses of association fibre networks in the primate cerebral corte x have revealed a small number of densely intra-connected and hierarchicall y organized structural systems. Corresponding analyses of data on functiona l connectivity are required to establish the significance of these structur al systems. We therefore built up a relational database by systematically c ollating published data on the spread of activity after strychnine-induced disinhibition in the macaque cerebral cortex in vivo. After mapping these d ata to two different parcellation schemes, we used three independent method s of analysis which demonstrate that the cortical network of functional int eractions is not homogeneous, but shows a clear segregation into functional assemblies of mutually interacting areas. The assemblies suggest a princip al division of the cortex into visual, somatomotor and orbito-temporo-insul ar systems, while motor and somatosensory areas are inseparably interrelate d. These results are largely compatible with corresponding analyses of stru ctural data of mammalian cerebral cortex, and deliver the first functional evidence for 'small-world' architecture of primate cerebral cortex.