Subjects
18 healthy male volunteers participated in this study They were between 20 and 52 years (mean ± S.D. was 34.1 ± 8.1 years), and they had 5-25 years experience of the meditation procedure (mean ± S.D. was 10.1 ± 6.2 years). The study was explained to the subjects and their signed informed consent was taken, according to the ethics laid down by the Indian Council of Medical Research New Delhi.

Meditation
The Brahmakumaris Raja (= Raj) yoga meditation (BK) has spread from the organisation"s headquarters at Mount Abu (Rajasthan, India) throughout India, and to other countries as well. During meditation, subjects sit in a comfortable posture with their eyes open, and with gaze fixed on a meaningful symbol (a light). At the same time they actively think positive thoughts about a Universal force pervading all over, as light and peace (Easy Raj Yoga, 1981).

Test sessions
Each subject was assessed in two types of session involving either a meditation period (with targeted thinking) or a non-meditation period (with random thinking). Each type of session was repeated thrice on different days, but at the same time of day.

During the recording session the subject sat in a comfortable chair in a dimly-lit, air conditioned and sound-attenuated cabin. Subjects were observed throughout on a closed-circuit television. Each session was of 36 min duration, of which 24 min was spent in meditation (with eyes open) preceded and followed by 6-min periods of relaxation, also with eyes open. These meditation sessions were repeated thrice by each subject on different days. In addition, there were also three non-meditation ("control") sessions, which were similar in design, except that the period corresponding to the 24 min of meditation was spent sitting relaxed, without targeted thinking.

Data acquisition and analysis
Recordings were made on Grass model 78D polygraph. EKG was recorded using a standard limb lead II configuration. Skin resistance (SR) was recorded with AgCl disc electrodes placed approx. 4 cm apart on the palmar surface of the right hand. Electrode gel CSR (Technocarta, Hyderabad, India) was used, and a constant current of 10 µA was passed. Finger plethysmogram amplitude was recorded with a photo-cell transducer kept at the base of the right thumb nail. Respiration was recorded via a rubber stethograph connected through a pressure transducer.

In addition, the EEG was recorded from electrodes placed at F3, F4, 01 and 02, referenced to the contralateral earlobe. Also, EOG and chin EMG were recorded as is usual for sleep-stage scoring (Rechtschaffen and Kales, 1968). This allowed any sleep episodes to he detected and excluded from the analysed data.

The SR values were sampled at 20s intervals from the continuously acquired record. The heart rate was obtained by counting the number of QRS complexes occurring in successive epochs of 40s periods analysed throughout. The respiratory rate was calculated from the record by counting the breath cycles in successive 40s epochs continuously. 20s or its multiple (i.e., 40 s) time epochs were used while calculating SR, heart rate and respiratory rate to make it feasible to correlate these data with that of EEG acquired simultaneously and subjected to computerized power spectral analysis in 20s epochs. For the present group of meditators the EEG data have been presented elsewhere (Kulkarni et al., 1988), and have not been reiterated here as no interesting correlations emerged between autonomic and EEG changes. The finger plethysmogram amplitude was calculated from measurement on 20 plethysmogram waves picked up randomly in each 6-min period.

Data analysis was done in two ways. viz., (1). For the group as a whole two statistical tests were used. (a), A two-factor (Factor A, meditation vs. non-meditation and Factor B, pre vs. during) ANOVA was carried out to assess the effects of both factors, as well as the interaction of

Table -1 : Heart rate in different conditions of the meditation and non-meditation sessions of the 18 subjects M, meditation period; pre-M, period preceding Meditation; NM, non-meditation period; n, number of values averaged per subject; pre-NM, period preceding Non-meditation; n.s., non significant.
 

all four variables listed above (Snedecor and Cochran, 1967; Zar, 1984). (b), A paired t-test (two-tailed) was performed on the averaged data. The values of each variable obtained in the three meditation sessions of a subject were averaged for: (a), the-24 min period of meditation; (b), the corresponding 24 min period of a non-meditation session; (c), the baseline state of the 6- min period in the eyes open state preceding the meditation, or the non- meditation period in the corresponding type of sessions and (d), the post-meditation (or post- non-meditation period). The averaged data of each of the 18 meditators were subjected to the paired t-test (two-tailed) to assess at the group level whether the following comparisons were significantly different: (a), meditation period and its preceding (eyes open) baseline period; (b), non- meditation period and its preceding (eyes open) baseline period; (c), meditation period and non- meditation period and (d), post-meditation period and premeditation period.

(II), On an individual basis data were also examined and changes which met the following criteria were noted: (a), changes during meditation (compared to the preceding period) should exceed those during post-meditation or non- meditation periods (also compared to the initial baseline period); (b), changes should occur in one direction, consistently during the three repeat sessions of a subject and (c), in order to quantify the change, arbitrary cut-off points were selected for each variable as follows: changes in heart rate should be equal to/more than 2 beats / 40 s, similarly for respiration, a change equal to/more than one breath per 40 s, for SR a change equal to more than 10 kΩ and for finger plethysmogram amplitude a change equal to or more than 0.40 cm.