Degree distributions of the average network and individual networks.

<p>The distribution of the number of connections at each node, or degree, is plotted for each of the 194 subjects (blue), as well as for the average network (red). The Y-axis is the complimentary cumulative distribution (i.e., 1 minus the cumulative distribution function (CDF)). The average network has more low degree nodes than any of the other individual networks. The degree distribution of the average network, however, drops dramatically for degrees greater than 10, suggesting that there are fewer medium degree nodes.</p

The modular structure of the average network.

<p><i>a)</i> The modular structure of the average network, with each color indicating a distinct module. Note that the default mode network is split into two modules: <i>b)</i> anterior (medial frontal gyrus, green) and <i>c)</i> posterior (precuneus/posterior cingulate & inferior parietal lobes, red) modules. <i>d)</i> On the other hand, both anterior and posterior default mode regions appear consistent across subjects when analyzed using module-specific SI. <i>e)</i> Representative subjects from each of the four data sets confirm that both anterior and posterior portions of the DMN constitute one module at the individual level.</p

Selected modules from the average network.

<p>Shown here are the modules from the average network that correspond to the module-specific SI images shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0044428#pone-0044428-g002" target="_blank">Figures 2</a> & <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0044428#pone-0044428-g004" target="_blank">4</a>. The modules from the average network that correspond to the motor/ sensory cortices, the basal ganglia and the cerebellum were found to be similar with respect to their corresponding module-specific SI image. However, two distinctions were found in addition to those demonstrated in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0044428#pone-0044428-g005" target="_blank">Figure 5</a>. First, the average visual module includes only the area of the primary visual cortex. This is in contrast to the module-specific SI image for the visual cortex shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0044428#pone-0044428-g002" target="_blank">Figure 2</a>, which extends into secondary visual cortices. Second, the average network segregates the anterior from the posterior portions of the ventral and dorsal attention systems. In this case, the anterior portion consists of two modules, one for each of the bilateral dorsal lateral prefrontal cortices. Interestingly the posterior element of both ventral and dorsal attention systems (superior parietal lobules) is not separated into bilateral portions. It does, however, include secondary sensory cortices S2.</p

Comparison of network characteristics between the average network and individual networks.

<p>Comparison of network characteristics between the average network and individual networks.</p

Consistency of whole-brain functional modular organization across subjects.

<p>Global scaled inclusivity (SI) shows that several brain regions are consistently partitioned into the same modules across individuals. These areas include portions of the following cortices: visual, motor/sensory, precuneus/posterior cingulate, basal ganglia, and frontal.</p

A schematic of module-specific SI calculation.

<p>For a particular node of interest, the most representative subject with the highest SI is determined from subject-specific SI maps (a). Then the modular organization of the representative subject’s network is examined, and the module containing the node of interest is identified as the representative module. Next, modules with any overlap with the representative module are identified, and the corresponding SI values are calculated (b). A weighted sum of the overlapping modules is calculated with the SI values as weights, summing modules centered around the representative module. The resulting module-specific SI shows the consistency of the representative module across subjects.</p

A schematic of global SI calculation.

<p>Although the modular organization appears similar across subjects, modules slightly vary from subject to subject (a). Different colors denote nodes belonging to different modules. Among the subjects, one subject is chosen as the referent subject, and any overlap between that subject’s modules and any other modules from the other subjects are determined (b). This process results in maps of overlapping nodes between modules, along with SI values summarizing the fidelity of the overlaps. A weighted sum of the overlap maps, with the SI values as the weights, is calculated, yielding a subject-specific SI map (c). A weighted average of the subject-specific SI maps, with the Jaccard indices as weights, is then calculated, resulting in the global SI map summarizing the consistency of the modular organization across subjects at the nodal level (d).</p

Module-specific SI images of modules with limited consistency.

<p>Three resting state networks (RSNs) exhibited attenuated consistency across subjects, relative to those shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0044428#pone-0044428-g002" target="_blank">Figure 2</a>. Module-specific SI images are shown for the ventral attention network (superior parietal lobules, dorsal lateral prefrontal cortex and portions of the medial frontal gyrus, row 1), dorsal attention network (superior parietal lobules, intraparietal sulci, precentral and superior frontal gyri, row 2), and the cerebellum module (row 3).</p