DISCUSSION

The present results revealed that practice of ujjayi on bhastrika type of pranayama resulted in a significant increase in peaking amplitudes of Na wave (by 108% over PEC value), and a significant decrease (9% of ECC value) in its latency. No such alterations of Na wave were produced in untrained on the involuntarily on-going tidal breathing.

There were no alterations in the peaking amplitudes or latencies of the Pa wave. However, since it is well-known that the peaking of MLRs varies considerably (the later the wave type, the more of its variation, in general), it can not be ruled out that the Pa wave alterations may also attain statistical significance when a much larger number of subjects is examined.

The results support the view that the conscious pranayamic practice could lead to a generalized modulation of processing of signals, i.e., even in neural systems not involved in breathing regulation, and also that such a modulation could operate at the primary thalamo-cortical state. It has been postulated that the Na wave may be due to activity at the mesencephalic or diencephalic level and Pa wave to auditory cortex (Deiber et al., 1988). Also, experiencing pranayama exercise over the period of about 21 months did not seem to change the processing of signals at other times (non-pranayama periods) in the subjects, since there was no significant difference in the baseline values (PEC) of the Na wave, obtained before and after about the 21 months of pranayama practice. Hence, no permanent functional changes seem to have occurred in the auditory pathway at the level of generators of the Na wave, but the change occurred only during the periods of pranayama practice. Enhancement of Na wave under ordinary circumstances is interpretted to indicate a facilitation occurring in the processes of sensory signal transmission.
 

Fig. 2. Typical examples of AEP - MLRs recorded in a subject in a test session conducted before he was initialed into yogic practice, and again after having been initiated into yogic practiced for 23 months. In each test session, AEP-MLRs were recorded four times, i.e., before (PEC), after (ECP) and during the pranayamic practice period (PR). In the sessions conduted before initiatiation into yogic training also. AEP-MLRs were recorded in the same sequence of time period, the ECC corresponding to that of PR

Since pranayama is entirely a voluntarily-controlled exercise, and since the comparison has been made between the AEP-MLRs of unattended involuntary (tidal) breathing period and of the consciously generated pranayamic breathing in the same subjects, the difference in the waves has been considered to be due to the conscious mental exercise and attention underlying the con- trolled pranayamic breathing, which may be exerted through corticofugal influences. Also, during the period of normal type of attention held on on-going breathing by an untrained group of subjects, no indication of such a change in the auditory signal processing (Na wave) was observed. Hence, the changes in the Na wave could possibly be related to the process of acquisition of specialised skills through training in pranayama to be able to hold the attention and generate

Table III

Statistical analysts of peakings of Na and Pa waves of MLRs
These were recorded during the condition of eyes closed control sitting periods with random thoughts (ECC) in test sessions conducted before the subjects were initiated and trained in pranayarna, and recorded again after practising pranayama for about 21 months, in test sessions containing pre-pranayama baseline periods of eyes closed state with random thoughts (PEC), and during periods of the pranayama (Ujjayi or Bbastrika) exercise with attention kept on the voluntarily regulated breathing and experiencing in eyes closed state the flow of breath (PR). Comparison is also made (in ANOVA-IV) with data of MLRs of an additional group of subjects uninitiated in pranayama, recorded in test periods of sitting in eyes closed state with random thoughts (PEC’), and during attention concentrated on the on-going tidal involuntary respiration and flow of breath through the nose in eyes closed state (ECC-concn.). For the ANOVA-1 and ll: df for F is 1,16; and P(I). n.s., not significant (P > 0.10). Other abbreviations are as in Table 1.
 

consciously the sensorimotor signals that produce the specific breathing rhythm and associated thoughts of sensation proficiently without letting in distractions or breaks. It should be recalled here that the original goal of yoga is not merely an attention-holding process, but is to ultimately acquire ability to control ‘mindstuff from taking various forms’ (Vivekananda, 1973). It has been also stated that through pranayama “we begin by controlling the breath, as the easiest way of getting control of the prana”. “Thence arises supreme control of the organs” (Vivekananda, 1973).

It should also be mentioned here that in a separate study (unpublished) we have noted that the Na-wave changes were absent during pranayama in subjects of long-standing practice (more than 60 months experience of pranayama). The absence of the Na-wave change may be due to their practising pranayama for so long, by which time the practice would have become so automatic, like a reflexive automation, without needing much of a close attention and mental activity. In one subject (SKT), of the present group as well, a follow-up repeat study done after 30 months of pranayamic experience revealed that the Na-wave changes were no longer occurring during the pranayama session. This is consistent with what has been reported (Seitz et al., 1990) in voluntary motor learning, that alterations in activity (as seen through blood flow changes) or certain areas of the cerebral cortex ‘vanished’ after accomplishing the learning to perform a task automatically. When the discrete ‘forms’ of thoughts of sensation of the pranayamic exercise give place in automatic performance to a relatively uniform state of mind with some stilling of thoughts perhaps through other neural mechanisms, the general control over the primary thalamo cortical processes of information transmission may no longer be required. At the present time, little is known about neural structures and processes that generate transcendental and abstract states of conscious experiencing, in contrast to some knowledge available on the ordinary perceptions of self-conscious states. The types of association cortical neural mechanisms, in particular of the prefrontal system with its limbic interactions (Desiraju, 1979; 1981) that are usually supposed to play roles in determining the nature of contents and states of human mind have yet to be identified. Moreover, advancement in understanding the fundamental source of consciousness and its relation to brain will ultimately determine the extent to which the above can be understood (Desiraju, 1984). The Na-wave changes observed in auditory pathway during attention and conscious regulation of respiratory cycles in pranayama may reflect some generalized process of a dynamic change induced in neural activity at the mesencephalic or diencephalic level.

Oxygen consumption values (Telles and Desiraju, 1991) determined during the period of practice of ujjayi of the type comparable to the variety used in the present study indicated a reduction in metabolism by 19%, and no signs of hypo- or hyperventilation effects. Further, transient changes in systemic circulation do not effect cerebral metabolism due to auto-regulation of blood flow in brain. Hence, the increase in Na-wave amplitude (while the Pa wave remains unchanged) as observed in the present study can not be supposed to be due to any changes in levels of cerebral 02 or C02 as they are most unlikely to be caused.

ACKNOWLEDGEMENT
This study was conducted under financial support of the Indian Council of Medical Research, New Delhi.