It comes from yoga, alternate nostril breathing. There is no scientific basis for the regulation claim afaik and the idea here is that both nostrils are linked

It comes from yoga, alternate nostril breathing. There is no scientific basis for the regulation claim afaik and the idea here is that both nostrils are linked to nadis, energy channels. While the nasal cycle does seem brain connected, Ive seen no proof it actually works upon the nervous system (as claimed) apart from the fact the practice is relaxing.