1. Controlled Focus: Concentration techniques involve the most mental effort or cognitive control. Meditations such as Zen, Compassion, Qigong, Kundalini Yoga and Vipassana involve concentration and control of the mind. The brain wave pattern characteristic of such “externally” focused practices is called gamma (20-50 Hz). Indeed, gamma waves are seen whenever we focus our attention, even outside of meditation.
2. Open Monitoring: Meditations such as Mindfulness-type practice and Kriya Yoga involve less cognitive control and observation of the breath, body states, thoughts or emotions. The brain wave pattern of internal focusing, theta (5-8 Hz), is seen during these meditations. Theta is observed in the brain any time we monitor or observe internal mental processes.
3. Automatic Transcendence: Meditations such as TM involve no cognitive control and going beyond or transcending the thinking process, leading to a state of pure consciousness. During this state we see the brain wave pattern of maximum alertness or mental clarity, alpha1 (8-10 Hz).