Results of two-way repeated measures ANOVA for all questions in “Altered states of consciousness rating scale”.

Results of two-way repeated measures ANOVA for all questions in “Altered states of consciousness rating scale”.</p

Amplitude spectral power for the L and R electrodes (top) in the pre-sauna (pre) and at each rest in the sauna set (post1, post2, post3) for the sauna and control groups.

Amplitude spectral power for the L and R electrodes (top) in the pre-sauna (pre) and at each rest in the sauna set (post1, post2, post3) for the sauna and control groups.</p

Average scores of questions in S-MARE before sauna (pre) and at each rest during the sauna set (post1, post2, post3) in the sauna and control groups.

Average scores of questions in S-MARE before sauna (pre) and at each rest during the sauna set (post1, post2, post3) in the sauna and control groups.</p

Experimental procedure.

Saunas are becoming increasingly popular worldwide, being an activity that promotes relaxation and health. Intense feelings of happiness have been reported shortly after enjoying a hot sauna and cold water, what is known in Japan as the “totonou” state. However, no research has investigated what occurs in the brain during the “totonou” state. In the present study, participants underwent a sauna phase, consisting of three sets of alternating hot sauna, cold water, and rest. We elucidated changes in brain activity and mood in the “totonou” state by measuring and comparing brain activity and emotional scales before and after the sauna phase and during the rest phase in each set. We found significant increases in theta and alpha power during rest and after the sauna phase compared to before the sauna phase. Moreover, in an auditory oddball task, the p300 amplitude decreased significantly and MMN amplitude increased significantly after the sauna phase. The increase in MMN indicates higher activation of the pre-attentional auditory process, leading to a decrease in attention-related brain activity P300. Hence, the brain reaches in a more efficient state. Further, the response time in behavioral tasks decreased significantly. In addition, the participants’ subjective responses to the questionnaire showed significant changes in physical relaxation and other indicators after being in the sauna. Finally, we developed an artificial intelligence classifier, obtaining an average accuracy of brain state classification of 88.34%. The results have potential for future application.</div

Classification accuracy of decoding “totonou” for each participant in, and the average accuracy of the sauna group.

Classification accuracy of decoding “totonou” for each participant in, and the average accuracy of the sauna group.</p

Correlation between neural change and changes in the scores of Q2, Q4 and Q14.

Correlation between neural change and changes in the scores of Q2, Q4 and Q14.</p

Summary of post-hoc tests for pairwise comparisons of sets on each frequency band.

Summary of post-hoc tests for pairwise comparisons of sets on each frequency band.</p

Fig 5 -

RT (A), Average SAA (B), and HR (C) before (pre) and after sauna (post3) in the sauna and control groups. Error bars represent s.e.m.* p < 0.05 and ** p < 0.01.</p

Exosome purification: (a) the quantities of exosomes before and after purification; (b) gel electrophoresis analyses of purified exosomes; (c) gel electrophoresis analyses of disrupted exosomes.

<p>Exosome purification: (a) the quantities of exosomes before and after purification; (b) gel electrophoresis analyses of purified exosomes; (c) gel electrophoresis analyses of disrupted exosomes.</p

S1 Dataset -

Saunas are becoming increasingly popular worldwide, being an activity that promotes relaxation and health. Intense feelings of happiness have been reported shortly after enjoying a hot sauna and cold water, what is known in Japan as the “totonou” state. However, no research has investigated what occurs in the brain during the “totonou” state. In the present study, participants underwent a sauna phase, consisting of three sets of alternating hot sauna, cold water, and rest. We elucidated changes in brain activity and mood in the “totonou” state by measuring and comparing brain activity and emotional scales before and after the sauna phase and during the rest phase in each set. We found significant increases in theta and alpha power during rest and after the sauna phase compared to before the sauna phase. Moreover, in an auditory oddball task, the p300 amplitude decreased significantly and MMN amplitude increased significantly after the sauna phase. The increase in MMN indicates higher activation of the pre-attentional auditory process, leading to a decrease in attention-related brain activity P300. Hence, the brain reaches in a more efficient state. Further, the response time in behavioral tasks decreased significantly. In addition, the participants’ subjective responses to the questionnaire showed significant changes in physical relaxation and other indicators after being in the sauna. Finally, we developed an artificial intelligence classifier, obtaining an average accuracy of brain state classification of 88.34%. The results have potential for future application.</div