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. 2015 Apr 8;35(14):5459–5470. doi: 10.1523/JNEUROSCI.4259-14.2015

Figure 3.

Figure 3.

Rich-club organization of MUA functional connectivity. A, Display of averaged functional connectivity during the first 4 weeks in vitro. For visualization purposes, connectivity at 28 DIV was thresholded with a high absolute weight threshold (median + 1.5 × SD); the same weight was used to threshold connectivity of all previous recording days. Depicted node size is proportional to the degree of average MUA connectivity; yellow nodes indicate the average rich-club at 28 DIV. B, Rich-club organization derived for MUA functional connectivity of a single MUA sequence. C, Normalized rich-club coefficients tend to decrease over development; depicted rich-club coefficients are averaged over a range of proportional thresholds (2–40% connection density). D, The nodes affiliated to the MUA rich-club varied across sequences; red circles indicate rich-club nodes derived from the maximal normalized rich-club coefficient. A rich-club consistency cutoff was used to define the average rich-club (yellow bars), and to separate stable rich-club nodes from nodes that were only occasionally classified as rich-club (black bars). E, Tracking back in time how connectivity strength of mature (average) rich-clubs developed, we found that hub nodes that end up in the mature rich-club were likely to form their strong connectivity early in development. F, To quantify differences in growth trajectories, logistic models were fitted to development of connectivity of nodes belonging to either the average rich-club or periphery. Members of the mature (average) rich-club demonstrated earlier and faster growth of connectivity than more peripheral nodes. G, Strongest average connectivity at 28 DIV also scaled with edge age, mirroring principles similar to what would be expected by a rich-get-richer network growth rule (H). H, Depicts normalized rich-club coefficients (averaged over k-levels) for all MUA graphs at 28 DIV and BA model networks, both at 10% connection density. I, Rich clubs of mature MUA graphs (28 DIV) also comprised nodes with significantly higher efficiency (E), betweenness centrality (B), participation coefficient (P), and higher within-module degree z-score (Z) than nodes of the periphery. B, H, and I show mean values ± SDs.