Q: Is delta meditation really that important? Isn’t gamma more important? Why do some people focus on delta meditation when there is virtually no scientific evidence for it?
A: The reason I tend to focus on delta meditation is in part because of its significance in the major meditative traditions. Vedanta, for example, speaks of the profundity of the “sleep self,” which correlates with deep, dreamless sleep and the delta brainwave pattern. The great Jnana yogi Ramana Maharshi also emphasized the importance of remaining conscious while in the state of deep, dreamless sleep in which the sense of self dissolves entirely. Again, in the Yogic traditions this is the state of nirvikalpa samadhi, a profound state of meditative absorption in which the self-identified witness (the sense of “I”) utterly vanishes. Likewise, Mahayana Buddhist texts refer to deep sleep states (delta) as a means of tasting the body of the Buddha.
Interestingly, of all the major brainwave patterns, Delta is arguably the one brainwave pattern that humans could never live without, as it drives all of the unconscious processes in the autonomic nervous system. It is during the delta state of deep sleep in which the contracted self-sense completely disappears. It is this nightly connection with the Self that allows us to awaken in the morning feeling renewed and ready for the day. To go indefinitely without making this connection results in death, because this deep sleep self is what supports the life of the body.
Fast wave patterns like gamma, on the other hand, disappear when people are put under anesthesia, yet delta activity remains under anesthesia. Many cases have been documented in which individuals exhibiting delta brainwaves and absolutely no gamma activity during surgery, have later perfectly recalled everything that was said by the surgeons while under anesthesia. This evidence again supports the idea that delta activity is correlated with the ever-present, ever-conscious and transcendent aspect of human beings. This is the field of consciousness and infinite potentiality that supports and gives rise to all sentient beings.
As to the claim that there are no studies showing the significance of delta activity in the brain during meditation, this simply is not the case. In fact, here are just a few examples of the presence of delta activity during uncommonly deep states of meditation:
High amplitude delta was observed during the peak experience of an experienced Transcendental Meditation teacher:
Another TM-related study found simultaneous delta and alpha in long-term TM practitioners who reported spontaneous “witnessing” states of profound meditation during deep dreamless sleep: http://psycnet.apa.org/psycinfo/1994-44323-001
The Menninger Foundation studied Swami Rama, who would enter a samadhic state of “yogic sleep” in which he could perfectly recall words and sounds that were sounded off in his proximity, even as his brain exhibited nothing but pure delta activity: http://www.sciencedirect.com/science/article/pii/S0079612308621597
It’s also important to to point out the research findings of neurofeedback pioneer Dr. James V. Hardt, who has correlated delta activity with the awakening of the kundalini spiritual energy spoken of in yogic texts.
Let us also not forget that the amygdala and hippocampus, which play primary roles in coding the emotional memories that so deeply influence the identity of the small self, themselves operate primarily in the delta and theta frequencies. Firstly, this fact may explain why theta and delta meditations can feel so relaxing, as they are very likely soothing to the overly-stimulated amygdala and hippocampus by literally vibrating them at their own resonant frequencies. I am convinced that this resonating of the amygdala and hippocampus at their resonant frequencies (at fairly low amplitude) is the reason why we see so much spontaneous emotional release and emergence of long-forgotten memories in deep theta and delta meditation.
Secondly, by matching the resonant frequencies of the amygdala and hippocampus through theta and delta meditation, and by consistently increasing the amplitude with which they are delivered, the scientific principle of resonance is set into play by resonating the limbic system, of which they are a part, at its own resonant frequency. All systems, including the limbic system, have a resonant frequency at which they tend to vibrate with very high amplitude. The Tacoma Narrows Bridge in the 1940’s, for example, collapsed due to a steady wind that vibrated the bridge at its resonant frequency, until it began to sway so violently that it eventually came apart.
I am convinced that the same thing happens when the limbic system is resonated at its own resonant frequency: the separate-self identity, which is so deeply tied to the emotional energy of the limbic system, literally is resonated until it comes apart, until all of its hidden aversions, attachments and habituations are resonated so deeply that they eventually detach from the realm of the unconscious and float up into the field of conscious awareness to be dissolved.
Dr. Jeffrey Thompson has also conducted extensive research in which he observed deep delta and sub-delta brainwave patterns in highly seasoned yogis during profound, ecstatic meditation. While he also observed fast activity (like gamma, hyper-gamma and lambda patterns) within many of these same yogis, he nevertheless concluded that these faster gamma-related patterns rode on (i.e., were literally carried and facilitated by) delta and sub-delta (which he refers to as “epsilon”) carrier waves. Again, his conclusion after years of research was that these delta-related states somehow mediate the transcendent reality out of which the other patterns emerge and to which they eventually return. In other words, his research agrees with other wisdom traditions, which claim that states correlated with delta activity are facilitated by the ever-present field of consciousness out which all things emerge and are sustained.