g., degree versus participation

coefficient) denote hub-like roles in cognition, as discussed below. A challenging topic is how to characterize the functional role of selleck products hubs. One approach might be to study the various systems involved with a hub. However, the functions performed by systems are often unclear. For example, what functions are performed by the default mode system or cingulo-opercular systems? There are many ideas, but there is little consensus. Another approach is to examine the proposed functions of individual hub regions. However, the brain is everywhere “integrative” in some sense, and the “functions” of much of human cortex are contested or unknown. Defensible conclusions about hub-like processing seem unlikely to emerge from this approach. Another approach would be to study the hodology CAL-101 solubility dmso of hub regions and to infer the function and importance of a hub from the physical projections it sends and receives. This approach may prove quite fruitful. However, it also has important limitations. First, because detailed anatomical information is mainly available in nonhuman primates, inferences in humans would depend on the similarity between human and nonhuman primate anatomy (and function). Our hub regions and degree-based hubs largely avoid unimodal sensory or motor cortex, making such inferences tenuous. Second,

the relationship between the structural and functional properties of a network is not simple or clear. For example, it is not obvious that hubs in a structural network should correspond to a degree-based hub in a functional network, or even a hub of the sort we are advocating (Honey et al., 2009). There is no

doubt that anatomical connections, chemoarchitecture, and cytoarchitecture will eventually inform our understanding of hub location and function, but they may not be the most fruitful starting point for creating functional descriptions of hubs at present. We suggest a lesion-based approach to characterizing hub function. Hubs are interesting because they are single nodes that exert disproportionate influence over network structure and dynamics due to of the number and placement of their edges. As such, their elimination can produce profound Liothyronine Sodium effects in a network (Albert et al., 2000, Jeong et al., 2000 and Jeong et al., 2001). Our observations lead to several predictions in the brain. The removal of a provincial hub should produce effects mainly within a single community, with limited impact on global network function. The removal of the sort of hubs identified in this report should produce effects within multiple communities, producing more global effects in the network. The removal of nonhub nodes should minimally alter community and global network function. These predictions can be tested by studying spontaneous activity, evoked activity, and behavior in the context of transient or permanent inactivation of nodes.