Abstract
Hubs within the neocortical structural network determined by graph theoretical analysis play a crucial role in brain function. We mapped neocortical hubs topographically, using a sample population of 63 young adults. Subjects were imaged with high resolution structural and diffusion weighted magnetic resonance imaging techniques. Multiple network configurations were then constructed per subject, using random parcellations to define the nodes and using fibre tractography to determine the connectivity between the nodes. The networks were analysed with graph theoretical measures. Our results give reference maps of hub distribution measured with betweenness centrality and node degree. The loci of the hubs correspond with key areas from known overlapping cognitive networks. Several hubs were asymmetrically organized across hemispheres. Furthermore, females have hubs with higher betweenness centrality and males have hubs with higher node degree. Female networks have higher small-world indices.
Highlights
Recent studies have investigated the human connectome with graph theory by dividing the neocortex into 100–1000 parcels and examining the anatomical connections derived from diffusion weighted magnetic resonance imaging (DW-MRI or DWI) techniques [1,2,3,4,5,6]
How Hub Regions were Defined By comparing the node degree and the betweenness centrality maps we observed that in the human brain hub regions are more pronounced in the betweenness centrality map
The distribution of betweenness centrality values for individuals appear to follow a power law with a long tail whereas node degree values appear normally distributed skewed to the right with a longer tail
Summary
Recent studies have investigated the human connectome with graph theory by dividing the neocortex into 100–1000 parcels and examining the anatomical connections derived from diffusion weighted magnetic resonance imaging (DW-MRI or DWI) techniques [1,2,3,4,5,6]. At the same time lesion studies have identified critical brain regions related to important neurocognitive networks [9,10,11]. These critical regions should be considered as candidate hubs, as they are located in highly connected association cortices. Besides the default network, other important neurocognitive networks should contain hubs that would be detectable by means of graph theoretical analysis To test this hypothesis we extend previous work with a detailed map of the neocortex which displays the distribution of its hubs. This approach was chosen, because the smallworldness measure describes global network properties and because the human brain has a small-world topology [7,17]
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