Thanks Margaret.
One thing I know for sure is that comatose patients in hospitals display predominantly Delta brainwaves even deeper than a healthy person's Delta during sleep. It's paradoxical for me to try to relate this to my own experiences entraining Delta, because in this state I usually feel mentally optimum.
Without wanting to discourage anyone, and you didn't need to hear it here first, Delta accesses levels so deep and primitive that these may be pre-language parts of the brain. This may explain why some researchers say subliminals simply don't work while one is in a Delta state -- as the parts of the brain accessed are so basic that words are simply noises and devoid of meaning. Like how the words would sound to a one-year-old infant long before language is learned. Paradoxically, my own experience is that subliminals do work in Delta, and the same researchers that say they don't work in Delta say they work especially well in Alpha and Theta, which one must pass through before reaching Delta.
I think it's safe to say that everybody's "Delta" is a little different than everyone else's. And I'm aware of cases where comatose patients have heard conversations, and after having gotten out of the coma, recalling the conversation.
I don't know. But it's interesting to think about.
