Figure 7. Hyperbrain (between-brains) coherence maps for J1 and J2 in the theta and alpha frequency bands and for the four difficulty levels (3, 4, 5 and 6 juggled balls).

The maps are normalized after thresholding to enhance the differences across the retained functional connections. Each coherence map is composed of four quadrants: the upper left and lower right quadrants correspond to the individual coherence maps of J1 and J2, respectively. The upper right and lower left quadrants are the hyperbrain coherence maps between J1 and J2. These maps are specular and display the same type of information, as the upper right map is calculated as J1 vs. J2, whereas the lower left map is calculated as J2 vs. J1. In each quadrant (or individual/hyperbrain coherence map), the electrodes are grouped according to the cortical areas (frontal, central, parietal and occipital), and are listed in the following order from top to bottom and from left to right: “fr” includes the frontal electrodes Fp1, Fpz, Fp2, F7, F3, Fz, F4, F8; “ce” includes the central electrodes FC5, FC1, FC2, FC6, T7, C3, Cz, C4, T8; “pa” includes the parietal electrodes CP5, CP1, CP2, CP6, P7, P3, Pz, P4, P8; “oc” includes the occipital electrodes POz, O1, O2.