Meditation The Relaxation Response And Physiological Changes

Benson and his colleagues were among the first to use Western experimental standards to study the physiology of meditation and its potential clinical benefits. In experiments involving Transcendental Meditation conducted at the Harvard Medical School and at the University of California at Irvine, physiological parameters were monitored in subjects in both meditative and nonmeditative states. Measures of blood pressure, heart rate, rectal temperature, and skin resistance as well as electroencephalographic (EEG) events were recorded at 20-minute intervals. During the meditative states oxygen consumption, carbon dioxide elimina

Meditation and the Relaxation Response tion, respiratory rates, minute ventilation (the amount of air inhaled and exhaled in a 1-minute period), and arterial blood lactate levels (an indication of anaerobic metabolism) were reduced. These acute changes are all compatible with reduced SNS activity and were not evident when the subjects simply sat quietly. Since these initial demonstrations, others have documented that elicitation of the relaxation response results in important physiological changes that are mediated by reduced SNS activity.

In addition to the SNS effects of the relaxation response, its central nervous system effects have been dramatically illustrated in a controlled study of frontal EEG beta-wave activity. Novice subjects listened to either a tape designed to elicit the relaxation response or a control tape that provided a discussion of the relaxation response and its benefits. Using topographic EEG

mapping, researchers found that elicitation of the relaxation response appeared to reduce cortical activation in anterior regions of the brain (see Fig. 1).

Another study has also provided evidence of the effect of the relaxation response on CNS indices of arousal. Jacobs, Benson, and Friedman examined the efficacy of a multifactor behavioral intervention for chronic sleep-onset insomnia. The interventions included education about sleep (e.g., sleep states, sleep architecture) and sleep hygiene (e.g., abstaining from alcohol, caffeine, and nicotine use in the evening), sleep scheduling, and modified stimulus control (restricting use of the bed to sleeping). The subjects were taught relaxation-response techniques and were instructed to practice them at bedtime. Those insomniacs exposed to the intervention exhibited significant reductions in sleep-onset latency and were indistinguishable from

Fronta! Frontal

Fronta! Frontal

Occipital Occipital

Figure 1 Beta relative power for control and relaxation response (RR) conditions. Vertical color bar indicates beta relative power (white highest, black lowest). Topographic maps are displayed in relative spectral power for greater resolution. Note: At RR end (lower right), beta relative power is significantly (p < .0164) decreased in frontal areas.

Occipital Occipital

Figure 1 Beta relative power for control and relaxation response (RR) conditions. Vertical color bar indicates beta relative power (white highest, black lowest). Topographic maps are displayed in relative spectral power for greater resolution. Note: At RR end (lower right), beta relative power is significantly (p < .0164) decreased in frontal areas.

Meditation and the Relaxation Response normal sleepers. More importantly, the insomniacs showed a marked reduction in cortical arousal, as assessed EEG power spectra analyses; specifically, the percentages of beta total power decreased from pre- to posttreatment.

The relaxation response training most likely mediated these reductions in cortical arousal and were therefore probably responsible for the dramatic decrease in sleep-onset latency. These findings in insomniacs support the contention that regular elicitation of the relaxation response leads to physiological changes opposite to those seen during the fight-or-flight response (i.e., decreased vs increased cortical arousal, respectively).

Since the physiological changes and therapeutic effects of the regular elicitation of the relaxation response lead to significant beneficial physiological changes and these effects appear to be the same as those associated with rest and sleep, what extra benefits does this practice offer above and beyond those derived from sleeping? Actually, the two activities are quite different. Although oxygen consumption plummets within the first few minutes of eliciting the relaxation response (in this example through meditation), oxygen consumption during sleep decreases appreciably only after several hours (see Fig. 2). The concentration of carbon dioxide in the blood increases significantly during sleep, whereas during meditation it decreases. The electrical conductivity of the skin tends to increase during sleep, indicating reduced sympathetic activity. However, the rate and magnitude of sleep-related increases in skin conductivity are much smaller than those observed during meditation and other relaxation-response techniques. Researchers have demon-

strated that CNS effects of the relaxation response also differ from those observed during sleep.

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