Transcendental Consciousness experiences are marked by 1) slow inhalation called "apneustic breathing" from 10–60 sec in duration or marked reduction in breath volume (40%), 2) increase of frequency of peak power in the EEG, and 3) skin conductance orienting at the onset of these experiences.
This figure shows a forty-second tracing of breath rate (BR: exhale is down), heart rate (HR), skin conductance (EDA: down is increasing sympathetic activity) and heart rate variability (HRV: up is increasing heart rate). Notice the 16-second period of apneustic breathing in the middle of the figure. It begins with an exhale and ends with an exhale, suggesting a slow inhalation throughout. The breath rate tracing is flat, because the thermistor can not pick up slow inhalation. Also, notice the EDA and HR response at the onset of the apneustic breathing period.
Maharishi predicted in 1963, that changes in breathing would be a major marker of the experience of Transcendental Consciousness. He predicted:
If the breathing could be brought to a state where it was neither active nor passive, that state of extremely delicate breath where the breath could be said to be flowing and yet not flowing, the metabolism would be established in a state of suspension between activity and no-activity on the level of Being. This would harmonize the body with Being. Life would be sustained, but its expression would be silent in the relative existence. This is the state of the nervous system which would keep the mind awake in itself, and, with reference to this state of self-awareness of the mind, the whole body would be sustained in itself. (Science of Being and Art of Living, p. 197).
Breath suspensions from 10–60 seconds long were the first published marker of Transcendental Consciousness in 1982. Recent research has clarified that the breath is not actually "suspended" during so-called respiratory "suspensions." Kesterson and Clinch, using a spyrometer, discovered that slow inhalation occurs throughout these periods, called apneustic breathing. This type of breathing is supported by different respiratory drive centers in the brain stem than breathing seen during waking. This finding supports the argument that Transcendental Consciousness is a state of consciousness distinct from waking, sleeping, or dreaming.