Travis, F.T., Tecce, J.J., Guttman, J., (2001). Cortical Plasticity, Contingent Negative Variation, and Transcendent Experiences during Practice of the Transcendental Meditation Technique. Biological Psychology, 55, 41-55.

Abstract
This study investigated effects of transcendent experiences on CNV amplitude, CNV rebound, and distraction effects. Three groups of age-matched subjects with few (< once/yr), more frequent (10-20/year), or daily self-reported transcendent experiences received 31 simple RT trials (flash [S1] / tone [S2] / button press) followed by 31 divided-attention trials-randomly intermixed trials with or without a three-letter memory task in the S1-S2 interval). Late CNV amplitudes in the simple trials were smallest in the group with fewest, and largest in the group with most frequent transcendent experiences. Conversely, CNV distraction effects were largest in the group with fewest and smallest in the group with most frequent transcendent experiences. (The second group's values were in the middle in each case.) These data suggest culminative affects of transcendent experiences on cortical preparatory response (heightened late CNV amplitude in simple trials) and executive functioning (diminished distraction effects in letter trials).