Nasal cycle

The nasal cycle is the rhythmic, alternating side-to-side fluctuation in nasal airflow. It is known to be regulated by the autonomic nervous system probably from the centres located in brainstem.

Nasal Cycle is the name given by western medicine for the readily noticeable yet regularly missed  pattern in human breathing - we do not breath equally (50:50) using both nostrils. At any given time, either the left or the right nostril is more actively breathing. Further, this one-sidedness reverses on a periodic basis. Much research has been done on the duration of nasal cycle.

Although readily noticeable, for some reason, this phenomenon has received very little attention under Western Medicine. The phenomenon was first noted - on record - by Kayser, a German rhinologist in Breslau, 1895.

On the other hand, this alternate-nostril-breathing is central to various breathing practices such as Pranayama, in Yoga and also in various systems of Alternative medicines. As per these systems, breathing pattern is directly linked to the working of our minds. Balancing the left and right sides of the mind is ultimately desired.

In the field of Neurosciences, researchers can measure 'how active' each cerebral hemisphere is, at baseline and while performing specific tasks. It has been known for a long time that an ultradian rhythm of alternating cerebral hemispheric activity exists in humans and animals. At any given time, either the left OR the right hemisphere of the brain is 'more active' than the other and this hemispherical dominance changes periodically. Recent findings in neuroscience have revealed that the nasal cycle is intricately linked to the ultradian rhythm of alternating cerebral hemispheric activity. Whenever the nasal cycle switches sides, the hemispheric dominance also seems to change. Although a clear association between the two has been established, causality is still arguable - whether the nostril-change causes the change in hemispherical-predominance or vice-versa.