Zen meditation (ZAZEN) is a spiritual exercise held in the Zen sect of Buddhism. Apart from its religious significance, the training of Zen meditation produces changes not only in the mind but also in the body—these influences are of interest to scientific studies, from the stand point of psychology and physiology.

In the present study the EEG changes accompanied with Zen meditation have been revealed and described in detail. The authors discussed further these electro-graphic changes in relation to the consciousness with its underlying neurophysiological background, comparing with that of the hypnotic trance and sleep.

In our study, 48 priests and disciples of Zen sects of Buddhism were selected as the subjects and their EEGs were continuously recorded before, during and after Zen meditation. The following results were obtained;

  • 1The appearance of alpha waves were observed, without regard to opened eyes, within 50 sec. after the beginning of Zen meditation. These alpha waves continued to appear, and their amplitudes increased. And as Zen meditation progressed, the decrease of the alpha frequency was gradually manifested at the later stage. Further the rhythmical theta train with the amplitude modulated alpha-background was observed in some records of the priests. These EEG changes could be classified into 4 stages; the appearance of alpha waves (stage I), an increase of alpha amplitude (stage II), a decrease of alpha frequency (stage III) and the appearance of rhythmical theta train (stage IV).
  • 2These 4 stages of EEG changes were parallel with the disciples' mental states, which were evaluated by a Zen master, and disciples' years spent in Zen training.
  • 3These electrographic changes were also compared with that of the hypnotic trance and sleep. From the electroencephalographic point of view, the changes of stages I, II and III could not be clearly differentiated from those seen in hypnagogic state or the hypnotic sleep, though the changes during Zen meditation were more persistent and did not turn into deeper sleep pattern. The rhythmical theta train is suppressed by click stimulation and turns into a desynchronized pattern, whereas the drowsy pattern turns into alpha waves (the alpha arousal reaction).
  • 4The alpha blocking to the repeated click stimuli with regular intervals was also examined in Zen meditation with opened eyes and the ordinary conditions of control subjects with closed eyes. The former showed a fairly constant blocking time (3–5 sec.) to every stimuli repeated 20 times and the habituation was not recognized. On the other hand, in control subjects the habituation of alpha waves occurred very quickly. This alpha blocking, which is less susceptible to habituation, is of importance to consider the neurophysiological basis of the mental state during Zen meditation.

These electroencephalographic findings lead to the following conclusions; In Zen meditation, the slowing of EEG pattern is confirmed on the one hand, and the dehabituation of the alpha blocking on the other. These indicate the specific change of consciousness. The authors further discussed the state of mind during Zen meditation from the psychophysiological point of view.