Figure 4.

Schematic presentation of coarse-graining procedure for brain-muscle network interactions. (Top left panel) Group-averaged Time Delay Stability (TDS) matrix representing interactions between different brain waves (δ, θ, α, σ, β, γ₁, γ₂) and the corresponding chin muscle tone EMG bands during wake (as shown in Figure 2A). Coarse-graining the TDS matrix is essential to assess the relative contribution of each brain wave or EMG frequency band in the network of brain-muscle interactions. (Top right panel) Coarse-grained matrix of brain-muscle interaction where each matrix element (horizontal red oval) shows the average coupling strength of a given EMG band with all brain waves derived from a particular EEG channel location. Coarse-graining the TDS matrix across brain waves provides information on the relative contribution of each muscle EMG band in the communication with different brain areas. (Bottom panel) Coarse-grained matrix of brain-muscle interaction where each matrix element (vertical red oval) shows the average coupling strength of a given brain wave from a given EEG channel with all EMG bands. This coarse-graining of the TDS matrix across EMG frequency bands quantifies the contribution of different brain waves and brain locations to the brain-locomotor cross-talk, identifying the main mediators of the brain-to-muscle interaction.