Regarding our letter on heart rate alterations in pranayamas (1):
1. Pranayama has been described as voluntary regulation of breathing (more often slowing down) which ultimately achieves a calm state of mind. In Savitri pranayama the subject strives to regulate the ratios (inhale: End-inspiratory Kumbhak: expiration: end-expiratory Kumbhak) as 2:1:2:1. In Mahat Yoga and Vibhaga pranayamas there is virtually no emphasis on the ratios. Breathing is expected to be slow and rhythmic.
We found that the pattern was consistent and there was no attempt to consciously regulate it. In Mahatyoga the mind was allowed to be engaged in thoughts of union of self with the Supreme, whereas in Vibhaga Pranayama the attention was focused on three different (imaginary) sectors of the lungs i.e., upper, middle, and lower.
2. It is possible that in spite of having more than five years' experience, the subject was practising Pranayama with muscular exertion.
3. As mentioned in the first response Vibhaga and Mahat Yoga Pranayamas were not similar to the traditional pranayamas (with ratios 1:2:2 or 1:4:2).
Regarding our letter on heart rate and respiratory changes accompanying single thought and thoughtless states (2) :
1. Studies by Roland and Friberg (3) have reported changes in regional cerebral blood flow with different types of targetted thinking (e.g. mentally tracing a route or repeating silently a meaningless jingle). In the absence of such facilities, other measures such as recording the cerebral evoked potentials would have given only a very gross neural correlate of the state of thinking since the neural generators of middle and long latency evoked potentials are still poorly understood. Hence, in the study reported, we relied wholly on the subjective report of the Yoga practitioner.
2. The comment
"because mainly the expiratory phase of respiratory cycle is seen disturbed, indicating cortical interference in autonomic function" is not entirely logical. Voluntary control can be expected to alter either the inspiratory and or the expiratory phase of respiration. Quite apart from this, it is reasonable to assume that changes in neural activity related to thinking (or a thoughtless state) would influence other parts of the brain, and possibly alter the respiration. It would be very unusual to expect that a
'no thought state' would occur simultaneously with an absence of cerebral activity.
3. It may be pointed out that the graph gave only one representative sample of the respirogram recorded during
'no thought' and 'single thought' states. In contrast, values shown in the Table were mean values ± S.D.
Vivekananda Kendra Yoga Research Foundation,
Telles S., Desiraju T.: Heart rate alterations in different types of pranayamas. Indian J Physiol Pharmacol 1992; 36: 287-288.
Telles S., Desiraju T.: Heart rate and respiratory changes accompanying yogic conditions of single thought and thoughtless states. Indian J Physiol Pharmacol 1992; 36: 293-294.
Roland PH, Friberg L.: Localisation of cortical areas activated by thinking. J Neurophysiol 1985. 53: 1219-1243.