Frederick Travis, (2001), Autonomic and EEG Patterns Distinguish Transcending from other Experiences during Transcendental Meditation Practice. International Journal of Psychophysiology, 42, 1-9.

Abstact: This study compared EEG and autonomic patterns during transcending to "other" experiences during Transcendental Meditation (TM) practice. To correlate specific meditation experiences with physiological measures, the experimenter rang a bell three times during the TM session. Subjects categorized their experiences around each bell ring. Transcending, in comparison to "other" experiences during TM practice, was marked by: (1) significantly lower breath rates, (2) higher respiratory sinus arrhythmia amplitudes, and (3) higher EEG alpha amplitude and (4) alpha coherence. In addition, skin conductance responses to the experimenter-initiated bell rings were larger during transcending. These findings suggest that monitoring patterns of physiological variables may index dynamically changing inner-experiences during meditation practice. This could allow a more precise investigation into the nature of meditation experiences and a more accurate comparison of meditation states with other eyes-closed conditions.