Figure 12.

Characteristic profiles of network links strength representing interactions between integrated brain activity at cortical areas and individual chin-EMG frequency bands. Group-averaged links strength is obtained using the TDS method (Materials and Methods section 2.3), where each link represents the interaction of brain activity from a given cortical area (averaged over all brain waves derived from the EEG channel located at this cortical area) and each muscle tone rhythm (frequency band) derived from the chin EMG signal. Links are grouped by brain cortical areas in both left and right hemisphere (Frontal Fp1 and Fp2, Central C3 and C4, Occipital O1 and O2; marked on top of the panels), and are ordered from low- to high-frequency chin EMG bands. Bars indicate the strength of links shown on the network maps in Figure 11. The displayed profiles provide detailed information on the interaction between averaged cortical activity at a given EEG channel location with each individual chin EMG frequency band. Error bars represent the standard error; horizontal green lines mark a threshold %TDS = 2.3% based on a surrogate test (section Method 2.4) above which network interactions are physiologically significant with >97% confidence level. A characteristic profile of links strength is associated with each physiological state (sleep stage)—uniform distribution of links strength across EMG bands for all cortical brain areas during wake, and dominance of low-frequency chin EMG δ and θ bands during REM, light and deep sleep (pair-wise MW tests comparing links mediated by δ and θ EMG bands vs. any other links between EMG bands and a given cortical area show statistically significant difference with p ≤ 0.05). Links strength profiles show clear symmetry between left and right hemisphere (pair-wise MW tests p ≥ 0.65) with a gradual decline in links strength from the Frontal to Central and Occipital areas.