After spontaneous breathing for 10 minutes, the ninja performed Okinaga for 30 minutes. Okinaga is a very slow breathing, and expiration can require up to 1 minute. Abstract It is well known that amygdala plays a critical role in the development of stress responses and anxiety. It has been reported that nerve cells in the amygdala fire less by prolonged expiration, but clear evidence has not been shown. As a "ninja" technique, there is an extremely prolonged expiratory breathing technique

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... Okinaga, which keeps expiration for one minute. As a pilot study, I examined brain changes by Okinaga with fMRI. One ninja participated. He performed Okinaga for 30 minutes, after spontaneous breathing for 10 minutes. The last 5 minutes of each breathing session were compared by fMRI. A significant decrease in blood flow in the left amygdala and a significant increase in blood flow in the occipital and temporal lobes including the visual cortex and its surrounding area were observed. Although these results are interesting, suggesting that the prolonged expiratory breathing may lead to meditation, I need to investigate further by increasing the number of participants.