CHANGES IN P300 FOLLOWING TWO YOGA-BASED RELAXATION TECHNIQUES
S. P. Sarang & Shirley Telles

 

Cyclic meditation (CM) is a technique that combines “stimulating” and “calming” practices, based on a statement in ancient yoga texts suggesting that such a
combination may be especially helpful to reach a state of mental equilibrium. The changes in the peak latency and peak amplitude of P300 auditory event–related potentials were studied before and after the practice of cyclic meditation compared to an equal duration of supine rest in 42 volunteers (group mean age ± SD, 27 ± 6.3 years), from Fz, Cz, and Pz electrode sites referenced to linked earlobes. The sessions were one day apart and the order was alternated. There was reduction in the peak latencies of P300 after cyclic meditation at Fz, Cz, and Pz compared to the “pre” values. A similar trend of reduction in P300 peak latencies at Fz, Cz, and Pz was also observed after supine rest, compared to the respective “pre” values, although themagnitude of change in each casewas less after supine rest compared to after cyclic meditation. The P300 peak amplitudes after CM were higher at Fz, Cz, and Pz sites compared to the “pre” values. In contrast, no significant changes were observed in the P300 peak amplitudes at Fz, Cz, and Pz after supine rest compared to the respective “pre” state. The present results support the idea that “cyclic” meditation enhances cognitive processes underlying the generation of the P300.

INTRODUCTION

Meditation has been described as a training in awareness that, over long periods, produces definite changes in perception, attention, and cognition (Brown,
1977). Most of the early reports on the effects of meditation have dealt with Transcendental Meditation (TM). TM was adapted from ancient Indian texts by Maharishi Mahesh Yogi.While practicing TM, subjects sit in a comfortable posture and mentally repeat a given mantra, returning their attention to it whenever attention wanders (Woolfolk, 1975). The practice of TM was reported to cause reductions in heart rate, respiratory rate, and oxygen consumption, and to increase the level or stability of the electrodermal response as well as the alpha in the EEG (Wallace, 1970; Wallace et al., 1971). These changes were the basis for describing the physiological state induced byTMas “wakeful and hypometabolic.” It was also considered interesting to investigate whether TM would improve meditators’ overall performance while producing a state of reduced physiological arousal (Bloomfield et al., 1975). A study was conducted to compare three different measures of attention in 20 people who had been practicing TM for 3 months and a matched control group whowere not practicing TM. The rationale for the studywas that all types of meditations are supposed to increase the ability to concentrate on external tasks and objects (Pelletier, 1972). Meditators performed better on a test for: (i) auto-kinetic effect suggesting a better ability to concentrate, (ii) in a rod and frame test that suggested that they were more in tune with internal cues, and (iii) in an embedded figure test that suggested a better ability to concentrate without being distracted by surrounding factors.
More recently the effects of transcendent experiences, described to occur during the practice of TM, were studied on the contingent negative variation (CNV) amplitude, rebound, and distraction effects in 41 healthy volunteers (Travis et al., 2002). CNV is an event-related potential occurring between a warning stimulus and an imperative stimulus requiring a response (Walter et al., 1964). Late CNV amplitudes were largest in meditators who had transcendent experiences daily. Because late CNV reflects proactive preparatory processes including mobilization of motor, perceptual, cognitive, and attentional resources, the data were taken to suggest that transcendent experiences enhance cortical responses and executive functioning. Another meditation technique, called “cyclic meditation” (CM) that also has its origin in ancient Yoga texts was shown to reduce oxygen consumption, breath rate, and increase breath volume more than a comparable period of supine rest (SR) in 40 male volunteers aged between 20 and 47 years. The magnitude of change in these three measures was greater after CM: (i) oxygen consumption decreased by 32.1 % after CM compared with 10.1% after SR; (ii) breath rate decreased by 18.0% after CM and 15.2 % after SR; and (iii) breath volume increased by 28.8% after CM and 15.9% after SR (Telles et al., 2000).
The present studywas planned to determine whether cyclic meditation (like TM) would increase the ability to pay attention to a given stimulus in addition to the already described effect of reducing metabolic and respiratory rates (Telles et al., 2000). The P300 component of the event-related brain potentials (ERPs) is considered as a “cognitive” neuro-electric phenomenon because it is generated in psychological tasks when subjects attend to and discriminate stimuli that differ from one another on some dimension. Such discrimination produces a relatively large, positivewaveform with amodal latency of about 300 ms when elicited with auditory stimuli (Polish & Kok, 1995). The P300 eventrelated brain potentials (ERP) reflect fundamental cognitive events requiring attentional and immediate memory–processes (Polich, 1999). Hence, in the present study the P300 was recorded before and after (i) cyclic meditation and (ii) a comparable period of supine rest.