I may take the time to read this whole thread, sorry for skipping it guys! Let me know if there is anything I say that's already been discussed. Anyway, I saw the thread and figured it'd be a neat discussion to get into.
To start off, I want to address a few things you've stated in your opening post, Sageous. I want to address, most specifically, the idea that delta sleep is "empty" and quiet. There isn't much evidence that much dreaming takes place during this stage of sleep, but given the fact that the structures that are responsible for episodic memory and cognition are typically shut off during this stage, meaning any dream that is occurring may as well not be occurring at all (much like a night where you drank wayyyyy too much). Granted, one of the major structures for cognition being shut off suggests that you be unable to experience anything at all during a typical session of sleep, but children are known to have night terrors during this portion of sleep (apparently stage 3 and 4, so as deep as it gets). Children have vastly different brain functioning, but it is interesting to note regardless. The reason I argue that dreams may still occur at times during these two latest NREM stages is based on more reading I've done about brain activity during sleep. As just a small tidbit of background information, I need to shed some light on how consciousness is constructed. It is a result of self-regulating thalamocortical circuits... feedback loops that filter relevant somatosensory information and prune irrelevant signals by feedback induced inhibition of neuronal excitation. This loop of thalamocortical circuits basically traces the spreading of electrical signals through the brain as it takes in sensory information, associates things and gives them meaning based on past experiences, comes together as a final "big picture", which is then analyzed by higher brain function, i.e. "you".
Time for a new paragraph, phew. The term thalamocortical comes from the sharing of information up from the thalamus and thalamic circuits through the cortical circuits. Thalamic circuits are shut off during deep sleep... they are the circuits that send sensory information to the rest of the brain. Similar things can be said of other known brain structures involved in the actual taking in of sensory information. However, cortical projections always keep running through their circuit, even with a total absence of information from the brainstem and thalamus. This happens no matter the cause of the loss of sensory input, it's how the Ganzfeld experiment and hypnagogic hallucinations work. The difference in these cases is that brain structures paramount to cognition and memory are functioning at the time. This easily explains why NREM sleep is capable of dreams, even though they are typically fragmented and difficult to derive any meaning out of. Now, enough neuronal firing in pertinent areas of the brain may be inhibited that the imagery and sensations generated by the still-projecting cortical loops may be so fragmented and localized that the projections by those circuits aren't able to communicate properly as well, I haven't read enough yet to know. Certainly if acetylcholine is well-inhibited enough in the 3 structures I mentioned at the beginning of the post that are responsible for episodic memory and, to a degree, cognition, it wouldn't count for anything anyway. Sleep-induced amnesia would see to it that all the information is lost on you. However, any interruptions during sleep or other significant function-alterating circumstances like drugs (pharmaceutical and otherwise), diseases, disorders, injuries, lucidity, etc., might allow for a dream to both be remembered and to have occurred in the first place.
I know, it's kind of a silly thing for me to have written all this information about, but I figured someone might be interested. After all, the thread is named Exploring Delta Sleep. Maybe I misinterpreted exploring's meaning in this case, but... well, fuck it who cares, lol.
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