We explored changes of behaviors and brain functions accompanying cognitive load by examining task accuracy, reaction time, and time series EEG power of the alpha band during n-back tasks. Dominant variability of reaction time and increase of fluctuation of the alpha power at 0.01 Hz were shown in a high cognitive task (3-back) compared to a low cognitive task (0-back). Furthermore, enhancement of the alpha power fluctuation at the very low frequency related to higher task performance, suggesting ability of the brain to flexibly adjust behaviors to cognitive load by environmental demands.
