P. Raghuraj • S. Telles

Abstract: A previous report described selective electrical activity of the cerebral hemispheres with uninostril breathing. In the present study, middle latency auditory evoked potentials (MLAEPs) were recorded from symmetrical scalp sites during the practice of uninostril yoga breathing. There were two sessions (40 min each) of right nostril yoga breathing (RNB) and of breath awareness (BAW), with (i) ‘before’, (ii) test (either RNB or BAW) and (iii) ‘after’ periods. The participants were 14 male volunteers aged between 18 and 33 years, and the setting was a yoga centre. MLAEPs were recorded from symmetrical scalp sites (C4 and C3). During RNB, the peak amplitudes of two negative components (viz. Na wave and Nb wave) were significantly increased on the right side. Increased peak amplitudes of Na and Nb waves suggested that RNB increased the number of neurons recruited on the right side, suggesting a possible application of RNB in certain psychiatric disorders with cerebral hemispheric imbalance.

Introduction

The nasal cycle is an ultradian rhythm with alternating patency of the left and right nostrils, occurring every one to eight hours. In awake humans, these spontaneous shifts in nos- tril dominance have been correlated with changes in the activity of the two cerebral hemispheres, based on electroencephalographic (EEG) studies, performance in hemi- sphere-specific tasks and studies of cerebral blood flow. In addition to spontaneous shifts the EEG changes with forced uninostril breathing were also studied, and a higher amplitude was reported over the hemisphere contralateral to the nostril kept patent. Previous experiments studying the effect of hyperventilation through the nose on EEG activity in the cortex suggest that the activity is produced by a neural reflex mechanism in the superior nasal meatus. There are specific yoga breathing practices (pranayamas) that involve breathing selectively through a particular nostril. These techniques can be practiced effortlessly for prolonged periods and allow the effects of unilateral nostril breathing to be evaluated. Uninostril yoga breathing may be exclusively through the right or left nostril. For the present study, the effects of right uninostril yoga breathing were evaluated. Left uninostril yoga breathing was not studied as traditional yoga texts mention that this practice can make a person “lethargic and lead to an introverted state of mind” and hence should not be practiced unless specifically advised by a teacher (guru). However, unpublished data comparing left nostril yoga breathing and breath awareness (BAW) are detailed in the Discussion, in which no specific effect was observed when breathing through the left nostril. With this background this study was designed to compare the middle latency auditory evoked potentials (MLAEPs), recorded from symmetrical scalp sites over left and right cerebral hemispheres, during a right nostril yoga breathing (RNB) practice as compared to BAW. MLAEPs were chosen to be studied, as the MLAEP com- ponents are known to have similar latency and amplitude characteristics on the right and left side, in normal persons [8]. This evaluation of the effects of uninostril yoga breathing on MLAEPs was expected to add to the understanding of possible lateralised changes in MLAEPs and therapeutic implications in certain psychiatric disorders known to be lateralised, such as schizophrenia. In summary, the present study aimed at testing the scientific hypothesis that uninostril yoga breathing influenced the electrical activity of the two cerebral hemispheres, selectively producing detectable alterations in MLAEPs.