In the noise-tagged task, the α and θ powers and the θ / α ratio in the first runs behaved with similar tendencies as compared to its respective second runs, but showing an insignificant trend of mental load alleviation for α and θ powers (ANOVA testing for linear trend: p = 0.748 for α power; p = 0.472 for θ power), but a significant trend of mental load alleviation for the θ / α ratio (ANOVA testing for linear trend: p = 0.015).
Specifically, for the second runs (i.e., sequence order 6–10; Figure 5 ) of the non-noise BCI task, a trend representing the increase in mental load as the decrease in α power and the increase in θ power, and in the θ / α ratio, seemed to be present among the successive sequences, but did not reach statistical significance ( F (4, 95) = 0.66, p = 0.618 for α power; F (4, 95) = 0.34, p = 0.848 for θ power; F (4, 95) = 1.47, p = 0.217 for θ / α ratio; one-way ANOVA with Bonferroni-corrected post-hoc tests).