Network Centrality in the Human Functional Connectome

Abstract

The network architecture of functional connectivity within the human brain connectome is poorly understood at the voxel level. Here, using resting state functional magnetic resonance imaging data from 1003 healthy adults, we investigate a broad array of network centrality measures to provide novel insights into connectivity within the whole-brain functional network (i.e., the functional connectome). We first assemble and visualize the voxel-wise (4 mm) functional connectome as a functional network. We then demonstrate that each centrality measure captures different aspects of connectivity, highlighting the importance of considering both global and local connectivity properties of the functional connectome. Beyond "detecting functional hubs," we treat centrality as measures of functional connectivity within the brain connectome and demonstrate their reliability and phenotypic correlates (i.e., age and sex). Specifically, our analyses reveal age-related decreases in degree centrality, but not eigenvector centrality, within precuneus and posterior cingulate regions. This implies that while local or (direct) connectivity decreases with age, connections with hub-like regions within the brain remain stable with age at a global level. In sum, these findings demonstrate the nonredundancy of various centrality measures and raise questions regarding their underlying physiological mechanisms that may be relevant to the study of neurodegenerative and psychiatric disorders.

Coupling of functional connectivity and regional cerebral blood flow reveals a physiological basis for network hubs of the human brain

“…During rest, we found that functional hubs were located primarily in the DMN and visual areas, which was approximately in accordance with previous functional (7,8,24) and structural network studies (5, 6). These hub regions largely overlapped with the brain regions that have high rCBF during rest as observed in previous PET (9) and ASL (25) studies.…”

Network measures predict neuropsychological outcome after brain injury

“…For example, Hagmann et al (5) reported that the posterior midline is the "core" of structural brain networks, and Buckner et al (6) reported that "cortical hubs" are found in the precuneus/posterior cingulate (pCC) and elsewhere in the default mode network (DMN). Several other studies have found that regions of the DMN, especially the pCC, have high ratings on related measures of network importance (7)(8)(9) (Fig. S1).…”

Increased thalamic centrality and putamen–thalamic connectivity in patients with parkinsonian resting tremor

“…We also calculated the same measures for bilateral cerebella and bilateral primary motor cortices as an investigation of nodal specificity because these regions are also involved in the CRB‐THA‐MC loop. Specifically, four commonly used centrality metrics for the above regions were calculated: degree centrality, betweenness centrality, within‐module degree, and participation coefficient (Buckner et al., 2009; Bullmore & Bassett, 2011; He et al., 2009; van den Heuvel & Sporns, 2013; Meunier, Achard, Morcom, & Bullmore, 2009; Power, Schlaggar, Lessov‐Schlaggar, & Petersen, 2013; Rubinov & Sporns, 2010; Zuo et al., 2012). The first two measures assess the importance of a given node from a more global perspective, and the last two probe the nodal centrality at a more modular level, thereby providing complementary information for a detailed description of a node's role in a complex network.…”

“…In the following section, we briefly summarize the concepts and computations of these centrality measures. For more details, see related studies described previously (Bullmore & Bassett, 2011; van den Heuvel & Sporns, 2013; Power et al., 2013; Rubinov & Sporns, 2010; Zuo et al., 2012). …”