Changes in autonomic nerve activity induced by the brief cognitive test. (a) Log-transformed low-frequency component power (ln LF), (b) high-frequency component power (ln HF) and (c) the LF/HF ratio. EOB, eyes open; ECB, eyes closed before; KPT-DS, dual-task session of the kana pick-out test; KPT-AS, answer session of the kana pick-out test; EOA, eyes open after; ECA, eyes closed after. Values are presented as the mean and standard error of the mean. *p < 0.05, **p < 0.01, ***p < 0.001, significantly different from the corresponding values. #p < 0.1, trend for a difference from the corresponding values.