Anuloma Viloma Timer
Pranayama practitioners have spent two and a half thousand years making a specific claim. That the right and left nostrils are not interchangeable. That breathing through one rather than the other puts the body and the mind into different states. That alternating between the two, in a specific count and a specific order, produces a third state that neither nostril produces alone.
For most of the past century, the response to this from people outside the tradition has been polite skepticism. The plumbing of the nose is symmetric. The lungs do not know which nostril delivered the air. Whatever the practitioners are noticing must be happening somewhere else.
In April 2025, a research group led by Joel Frohlich published a paper in PLOS ONE titled “Neuronal oscillations and functional connectivity of paced nostril breathing: A high-density EEG study.” It is the first study to record the brain at high density during paced single-nostril and alternate-nostril breathing and to ask, directly, whether the two nostrils produce different signals.
They do.
What the study measured
Twenty-three adults wore 128-channel EEG caps and performed three paced breathing conditions: left-nostril only, right-nostril only, and alternating between the two (anuloma viloma, sometimes spelled anulom vilom). Each condition lasted several minutes at a controlled rate. The researchers looked at two things in the EEG signal: oscillation power in standard frequency bands, and functional connectivity between brain regions.
The first finding is the cleanest. Both single-nostril conditions suppressed alpha and mu oscillations over central and parietal areas of the cortex. Alpha and mu are inhibitory rhythms. Their suppression is associated with the cortex being more active and more responsive. The suppression was stronger over the ipsilateral hemisphere, meaning the same side as the breathing nostril. Left nostril breathing pulled the alpha down over the left brain regions. Right nostril breathing pulled it down over the right.
The second finding is the one practitioners will recognise. Alternate nostril breathing suppressed those same inhibitory rhythms more strongly than either single-nostril condition alone. Switching back and forth did not split the effect. It amplified it.
The researchers also reported an increase in frontal midline theta during paced breathing across all conditions. Frontal midline theta is associated with focused attention, working memory engagement, and the feeling of effortful internal control. This part of the result tracks what every breathwork tradition reports about deliberate breath pacing, regardless of which nostril does the work.
Why this is the first direct confirmation
There have been previous studies. EEG during pranayama has been recorded since the 1970s. Functional MRI has looked at nostril breathing. Heart rate variability and skin conductance have been measured during alternate nostril practice for decades. None of them are this clean.
Older EEG studies typically used twenty or thirty channels and could not resolve the spatial source of the signal well enough to say which hemisphere was doing what. fMRI studies could resolve the spatial source but had to deal with the noise of the participant breathing inside the scanner. Studies of autonomic markers like heart rate variability told you the practice did something to the nervous system without telling you where.
A 128-channel cap is a different instrument. It can attribute signal to specific cortical regions with a confidence the older studies did not have. The Frohlich group used that instrument to ask the question pranayama practitioners have been asking for centuries, and they got a quantitative answer.
What the alternating part of the practice does
The traditional instruction for nadi shodhana is to inhale through the left nostril, exhale through the right, inhale through the right, and exhale through the left, repeating that cycle. There is a pause (kumbhaka) between the inhale and the exhale in many lineages.
If left and right nostril breathing each suppress inhibitory rhythms over their own side of the brain, the alternating instruction has a specific shape. It is repeatedly switching which hemisphere has its inhibition lowered. Over a few minutes the practice has, in effect, modulated both hemispheres in turn. The Frohlich result shows that this alternation does more than the sum of two single-nostril sessions. The suppression is stronger.
What the EEG cannot tell you directly is what the strengthened effect feels like, or what it does for daily life. That part is still the practitioner’s report. But the brain signal is now on the record.
What to do with this
If you already practice alternate nostril breathing, the study is a quiet vindication. The thing you have been doing has now been confirmed at the cortical level by an instrument that could not have been built in 1975.
If you have not, the recommended starting point is the same as it has been: ten minutes a day for a few weeks, slow nasal pace, alternate sides on a count you can hold without strain. A separate 2025 RCT published in the Annals of Neurosciences by Mittal and colleagues used exactly this protocol (ten minutes daily, six weeks) in hypertensive patients and reported significant reductions in both systolic and diastolic blood pressure, with HRV parameters confirming improved parasympathetic tone. The Frohlich study tells you where, in the brain, the practice is acting. The Mittal study tells you what changes in the body when it does.
A timer is the simplest tool that makes the practice repeatable. Pick one that counts each phase separately, that includes a pause (kumbhaka) phase if you want it, and that does not lock the technique behind a subscription. The technique itself is older than the App Store. The price should match.
Anuloma Viloma Timer is free on the App Store. No subscription necessary.