highly significantp < 0.01
As shown in Figure 2B , the β-wave mutual information was statistically different between all age groups in stage N2 ( p < 0.05), especially more significant in the young and elderly groups ( p < 0.001); it was a significant difference between the young and middle-aged groups in stages W, N1, N3, and R ( p < 0.05); and it was even a highly significant difference between the young and elderly groups in stage N3 ( p < 0.01); however, in stages W, N1, N3, and R, both the middle-aged group and the elderly group differences were not statistically significant.