Selective Hemispheric Stimulation by Unilateral Forced Nostril Breathing
Authors: D. A. Werntz, R. G. Bickford, D. Shannahoff-Khalsa
DOI / Source: https://pubmed.ncbi.nlm.nih.gov/3449485/
Date: 1987
Reading level: Intermediate
Why This Matters for Freedivers
Freediving performance is often limited by stress, “busy brain,” and breathing rhythm—not just lung size. This study suggests that deliberately breathing through one nostril can measurably shift brain activity patterns, which may be useful as a simple, non-tech tool for pre-dive calming, focus, and mental state control (especially for divers who get anxious or overstimulated before a dive).
Synopsis
Most freedivers have heard some version of “nasal breathing calms you down,” and many have heard of yogic techniques like alternating nostril breathing. This paper takes that idea into a lab setting and asks a more specific question: if you force airflow through only one nostril for a period of time, does it reliably change brain activity between the left and right hemispheres?
The authors build on earlier work showing a natural “nasal cycle,” where congestion alternates between nostrils over time. They suggest that this nasal cycle is linked with a rhythm of alternating dominance in brain activity between hemispheres. The proposed mechanism is not mystical: the nasal mucosa is controlled by the autonomic nervous system, and changes in airflow/congestion may track changes in sympathetic/parasympathetic tone. If nasal airflow is part of a broader left–right autonomic pattern, then deliberately shifting airflow to one nostril might shift brain activity too.
To test it, they recorded EEG while subjects did periods of unilateral forced nostril breathing (closing one nostril and breathing only through the other). They focused on integrated EEG amplitude—a way of summarizing overall EEG “power” over time—then compared the balance between hemispheres. The key prediction was simple: forced breathing through one nostril would increase EEG amplitude in the contralateral hemisphere (right nostril → left hemisphere, left nostril → right hemisphere).
The results mostly matched that prediction. Across multiple attempts and subjects, unilateral nostril breathing tended to push the EEG balance in the expected direction, and the effect often appeared fairly quickly (commonly within a couple of minutes, though timing varied). They also ran control conditions suggesting it wasn’t just the hand/arm position used to block the nostril; the airflow change itself seemed to be the critical ingredient.
The authors interpret this as evidence that nasal airflow is not just “air supply,” but part of a coupled rhythm between breathing pathways, autonomic tone, and brain activity. They also point toward potential practical applications: if certain psychological states (or performance states) are linked with unhelpful lateralization patterns, unilateral nostril breathing might be a non-invasive way to nudge the system back toward a more useful balance. For freedivers, the most interesting takeaway is that how you breathe—down to which nostril is dominant—may influence arousal, attention, and internal mental processing in measurable ways.
Abstract
This study examined whether unilateral forced nostril breathing alters cerebral hemispheric activity. EEG recordings were used to measure integrated EEG amplitude and hemispheric dominance while subjects breathed through only one nostril for set periods. Forced breathing through one nostril tended to produce a relative increase in EEG amplitude in the contralateral hemisphere, consistent with a coupling between the nasal cycle, autonomic regulation of nasal airflow, and alternating hemispheric activity. The findings suggest unilateral nostril breathing can non-invasively shift hemispheric EEG dominance and may have potential applications where altered cerebral lateralization is relevant.