Topographic hub maps of the human structural neocortical network

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

Hub regions with betweenness centrality scores in the 80^th percentile displayed on inflated brain surfaces.

<p>The anatomical descriptions and lateralization patterns of the coloured hub regions are given in the bottom table. See also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0065511#pone.0065511.s002" target="_blank">Table S2</a>.</p

Node degree hub map.

<p>Average node degree pial (A) and inflated (B) surface hub map with a mean node degree of 102.57±19.78 (SD). The colour scale for the node degree values is shown at the right of subfigure (A). See also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0065511#pone.0065511.s001" target="_blank">Table S1</a>.</p

Scatter plot between node degree and cluster volume size.

<p>Scatter plot describing the relationship between node degree [mean 97.59±43.73(SD)] and cluster volume size as a fraction of the entire grey matter volume [median 0.099%, 0.016% (SD)] of a subset of 6,300 brain network nodes from all subjects. The correlation of the measures between all nodes is r_1259998 = .15.</p

Betweenness centrality hub map.

<p>Average betweenness centrality pial (A) and inflated (B) surface hub map with a mean betweenness centrality of 0.00124±0.00061 (SD). The colour scale for the betweenness centrality values is shown at the right of subfigure (A). See also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0065511#pone.0065511.s001" target="_blank">Table S1</a>.</p

Gender and hemispheric differences in small world indices.

<p>The differences between left and right hemispheric small-world indices are shown in boxplot (A). Boxplots grouped by gender are: (B) whole brain small world indices, (C) left and right hemispheric small world indices and (D) small world asymmetry indices. See also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0065511#pone.0065511.s003" target="_blank">Tables S3</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0065511#pone.0065511.s004" target="_blank">S4</a>. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0065511#pone-0065511-g005" target="_blank"><u>Figure 5</u></a><u> footnote:</u> *** and * indicate statistical significant differences with p_2-tailed<.001 and with p_2-tailed<.05. The degrees of freedom for the tests are A: df = 124, B-D: df = 61. Each boxplot shows the median (red line), the upper and lower quartile (blue rectangle), the smallest and largest observations (endpoints of the dashed line) and observations which should be considered as outliers (red pluses).</p