Does anyone know if one can fall asleep into a dream while in the process of mindful insight practice and still maintain mindfulness and concentration? This would be different than establishing mindfulness while dreaming.
Before I became Buddhist I did a lot of random "spiritual" practices, including "astral travel". The later is when you try to retain "waking" consciousness as you fall asleep.
I only had mixed success with the various techniques for achieving that, but the one that worked more or less well was to relax the body and completely refrain from any movement until you lose all bodily sensations. So effectively you let the body "fall asleep" while keeping the mind awaken.
The major difficulty for me was (to avoid) getting overexcited at the moment the body falls asleep - which (overexcitement) resulted in hyperventilation and loss of control.
Eventually I realized that establishing lucid mind inside the dream was easier for me than carrying it over from the waking state, and so I dropped that frustrating practice.
Another related technique I had better success with was doing the Four Immeasurables type meditation at that same moment of falling asleep. This works better as you don't have to artificially restrict body movements, which seems to go counter to deep meditation in my experience.
When you are in deep sleep your Bhavanga consciousness is active and at this stage you are not mindful. If you are in a dream state there is some metal activity hence there can be some mindfulness and concentration, but this goes in hand with Sloth and Torpor hence the level of mindfulness and concentration would be weak.
I've experienced that several times. It took me around ~45 minutes up to an hour to enter a state of dreaming, while meditating. I did not fall asleep for sure as I was sitting up.
The experience was different from lucid dreaming. I experienced lucid dreaming over hundreds of times, so I am confident I am familiar to know a distinct state.
Just like with lucid dreaming, the very first times it is difficult to stay asleep yet mentally aware of your self. Resulting in either loosing self awareness of waking up from the dream.
With this I found the same, but this balance seems even more delicate to me. I was wakefully present in this dream while meditating, but as soon as I realized I was, it lasted only very short.
These dreams while meditating seem more close to wakeful life experiences in a sense that I have a goal, a mental concern or puzzle to solve. Whereas in dreams while being asleep, this tends to be more and more irrational.
How the two states differ in dynamics (wakeful dreaming while asleep/meditating) is not clear to me yet. With dynamics I mean some sort of mechanistic behavior, like gravity here in this physical reality, but then more mentally related. Like when becoming fearful it is more apparent that I am loosing control of the scenario in a lucid dream than in this physical reality because the whole scenario visually starts to mirror my state of mind. How that is different in these dreams while meditating, I am not sure yet.
Good luck with experimenting!