Networks of brain-respiration interactions during different physiologic states.

<p>Brain areas are represented by Frontal (Fp1 and Fp2), Central (C3 and C4) and Occipital (O1 and O2) EEG channels. Network nodes with different colors represent seven frequency bands (<i>δ</i>, <i>θ</i>, <i>α</i>, <i>σ</i>, <i>β</i>, <i>γ</i>₁, <i>γ</i>₂) in the spectral power of each EEG channel. Network links between the respiration (purple hexagon) and EEG frequency nodes at different locations are determined based on the TDS measure (See Section <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0142143#sec003" target="_blank">Methods</a>), and links strength is illustrated by the line thickness. Shown are links with strength ≥3%TDS. Radar-charts centered in each hexagon represent the relative contribution of brain control from different brain areas to the strength of network links during different sleep stages. The length of each segment along each radius in the radar-charts represents TDS coupling strength between respiration and each frequency band at each EEG channel location. These segments are shown in the same color as the corresponding EEG frequency nodes. A pronounced stratification pattern is observed for the overall strength of network links—stronger links during W and LS (larger hexagons) and weaker links during REM and DS (smaller hexagons). Note the much weaker links (overall smaller hexagons) for all sleep stages in the brain-respiration network compared to other brain-organ networks, indicating much weaker coupling between the brain and respiration system as measured by %TDS. Similar to the brain-heart network (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0142143#pone.0142143.g013" target="_blank">Fig 13</a>), there are no links in the brain-respiration network during DS (all links <3%TDS).