Cortico-subcortical converging organization at rest.

Local segregation and global integration are the fundamnetal organizational principles of human brain. It is unknown how subcortex configures itself with respect to the segregation and integration dynamics at rest. Using resting state functional MRI data of 92 healthy adult participants, we revealed three non-overlapping segregated communities in subcortex, confining anatomically to thalamus, basal ganglia, and subcortical limbic structures, termed as subcortical networks. Further using network science, we analysed the topology of subcortex and found about 80% of subcortical regions acting as hubs, connecting with other cortical as well as subcortical communities. Next, using statistical modelling, we determined the role of subcortex (both at region-level and network-level) in cortical information integration and found multiple, widespread cortical regions (networks) converging onto individual subcortical regions (networks) (a many-to-one mapping). Individual subcortical networks showed varied extent of convergence, broadly from primary and association networks in cortex. We found functional diversity of cortex to be the major driving factor behind cortical convergence within subcortex and that the absence of subcortical regions significantly impacted the information transmission efficiency within the cortico-subcortical converging organization. Overall, our results provide insights into the subcortical organization at rest and underscore the subcortical contributions in shaping the large-scale brain dynamics.