Coherence, reflects quantitatively the degree of coincidence of paired EEG signals, was also conducted by the Brain Vision Analyzer software (Brain Products, GmbH). Firstly, FFT converted signal of time domain to frequency domain of EEG data. Then, coherence analysis was computed for eight long‐distance electrode pairs with more than 10–12 cm (F3‐O1, F4‐O2, F7‐F8, F3‐F4, T7‐T8, P7‐P8, C3‐C4, P3‐P4) and eight short‐distance electrode pairs with <10 cm (Fp1‐F3, Fp2‐F4, Fp1‐Fp2, C3‐P3, C4‐P4,T8‐P8, T7‐P7, O1‐O2). The distribution of brain electrodes was shown in Figure 1.
