Networks of physiologic interactions among key organ systems during different physiologic states.

<p>Interactions among organ systems are represented by weighted undirected graphs, where links reflect the strength of dynamic coupling as measured by % TDS (Section <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0142143#sec003" target="_blank">Methods</a>). Darker and thicker links between organ systems correspond to stronger interaction with higher %TDS. The size of each organ node in the network is proportional to the strength of the overall brain-organ interaction as measured by the summation of the TDS links strength for all frequency bands and EEG channel locations. Hexagons representing individual organs in the networks are obtained in the same way as in Figs <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0142143#pone.0142143.g007" target="_blank">7</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0142143#pone.0142143.g009" target="_blank">9</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0142143#pone.0142143.g011" target="_blank">11</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0142143#pone.0142143.g013" target="_blank">13</a>, and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0142143#pone.0142143.g015" target="_blank">15</a>; and are normalized to the same size. Color bar represents different physiologically relevant frequency bands in the EEG spectral power and is used in the radar-charts for the brain-organ interactions shown in each hexagon. The color of each organ node as well as the edge color of the organ hexagon corresponds to the dominant frequency band in the coupling of the organ system with the brain. Notably, larger organ nodes representing stronger brain-organ interactions are consistently connected by stronger organ-organ links (thicker and darker lines). A pronounced re-organization in the configuration of network links strength is observed with transitions from one sleep stage to another, demonstrating a clear association between network structure and physiologic function.