The cerebellum (CB) and basal ganglia (BG) each have distinct functional subregions that are interconnected via disynaptic trans-thalamic pathways and interact with functionally connected cortical regions through discrete thalamic loops. Previous work shows functional connectivity between these phylogenetically ancient regions is topographically organized with high levels of interconnectedness (Hausman et al., 2019). It has been posited that this subcortical network provides the foundation from which cortical systems emerge, spanning cognitive, emotional, and motor domains, implying subcortical network measures are strongly related to cortical network measures (Bostan & Strick, 2018); however, it is currently unknown how differences in network measures within the subcortical network relates to differences within cortical networks. Here, rsfMRI data from 233 non-related, right-handed participants (Human Connectome Project-1200) were selected to test whether subcortical network interconnectedness predicted within-network interconnectedness in the cortex. 70 regions of interest comprising the CB-BG and canonical cortical resting-state networks (default mode, central executive, salience, motor, and emotional) were defined based on previous work. Network-level global efficiency (GE) in the CB-BG network positively predicted GE in all 5 cortical networks. When looking at network segregation, relationships were seen only when looking at the CB-BG network and cortical motor network. We also replicated previous findings showing a high degree of CB-BG interconnectedness in a large sample. This work has implications for understanding cortical network organization and cortical-subcortical interactions in healthy adults and may help in deciphering subcortical changes seen in disease states.
