So, like I said, I've been trying to consider all of the different ways that the brain could maximize its ability to record memories. The first thing that comes to mind for this is disinhibition, or inhibiting the basic inhibitory mechanisms which are always running to some degree in our brain. The easiest way I can describe this is that each part of our brain is wired to be able to work at an extremely high level of activity, but because of the way they all interact with and inhibit each other they're normally operating at a much lower capacity than this. This is a very good thing, because having all of your brain be completely active at once would be called having a massive seizure. However, because of this it is possible for different areas of the brain to work at a much higher than normal capacity, such as the limbic areas involved in memory during dreams.
The major inhibitory neurotransmitter throughout the brain is GABA. This is the chemical that alcohol and benzodiazepines work around, among other drugs. However, alcohol has several non-GABA effects as well and it wouldn't be entirely right to use it to relate to in this particular situation, so for now I'm going to stick to the benzodiazepines. Most people who know much about basic drugs don't think of GABA as anything more than something that lowers activity, and the benzos are largely to blame. Under normal conditions in the adult brain, GABA inhibits memory storage, and a very significant site of action for this is the hippocampus. The thing is though that because GABA does normally exist to some degree throughout the day, what would be considered inhibition from the standpoint of versus no GABA at all could to us just be called a "normal" amount of memory encoding, until those functions are pushed even further than what they're normally at. This is why some drugs, such as ginkgo biloba, are able to enhance memory by blocking some of the activity of GABA, but I'll get to that shortly. The way benzos work is different from most drugs used either medicinally or recreationally, in that they don't actually alter levels of the neurotransmitter they focus on, GABA, but increase its ability to bind to GABA(A) receptors in various areas of the brain. They do this by binding to a range of different GABA(A) subunits, which are differentially distributed in the brain. For example, the subunit alpha-1 is thought to play a particularly important role in GABA's effects on memory, and therefore under normal conditions an alpha-1 subunit agonist such as many benzos will enhance the memory loss induced by GABA without necessarily changing the intensity of its other effects. Bilobalide, one of the chemicals in ginkgo biloba, does the opposite of this. It is an alpha-1 antagonist, lowering GABA's amnesiac effects, and it's thought that this is largely how the plant enhances memory.
So that's all well and good, but what a lot of people don't realize is that GABA's effects are actually much more flexible than just inhibitory action, and GABA(A) receptors can cause excitatory effects as well. I mentioned this recently in another thread, as part of a different theory, which I now could expand a bit further on because I know even more about it. The way it works revolves around the fact that GABA receptors' activity depends on the local concentration of chloride ions, with low levels causing inhibitory effects and high levels causing excitatory effects. When the brain is still young, GABA actually normally functions as an excitatory neurotransmitter, and this is mostly due to different levels of chloride transporters that occur colocalized with GABA receptors in the developing compared to the mature brain. The transporters are known as KCC2 and NKCC1, the former of which lowers chloride ion levels and the latter of which raises them, so the brain starts out with low levels of KCC2 and high levels of NKCC1 and these reverse as it grows. However, these aren't the only factors involved here. Another big one seems to be the activity of the carbonic anhydrase CAVII, which is an enzyme that catalyzes carbon dioxide. This enzyme significantly increases in numbers shortly after the developmental switch of GABA from excitatory to inhibitory, and because of downstream activity it causes due to altering the levels and activity respectively of bicarbonate and potassium, it can result in the same kind of changes as having a low KCC2 / high NKCC1 setup. The difference is that this activity doesn't become significant until it is either activated by an outside mechanism or by heavy stimulation of GABA receptors themselves. Knowing this, it adds a whole new layer to how this system must be considered.
I've actually known for a long time that certain GABAergic drugs can cause so-called "paradoxical" effects, such as stimulation and hallucinations, as opposed to the sedation and lowering of psychotomimetic activity that would normally be expected. This is a very rare effect for some people in certain benzodiazepines, and is a more common occurrence particularly in a class of drugs known as non-benzodiazepines which work on these same subunits. Furthermore, it is well known that muscimol, a drug which works by directly activating the core GABA(A) receptors, can cause hallucinations and an overall blend of psychedelic and dissociative effects, though still unique as well. In fact, many people compare the hallucinations caused by GABAergic drugs to a waking lucid dream state, though there still are some disruptions in normal conscious function do to widespread activity throughout the brain. With muscimol this is easy enough to understand, since taking it in a large amount would logically heavily stimulate those receptors in the same way as GABA itself and could cause the switch back from inhibitory to excitatory effects. I think the effects of the drugs working on the subunits can be explained in a similar way, but with some clear differences. Since the way they change GABA activity varies quite a bit from one place to the next, it makes sense that only those drugs which significantly effected the receptors specifically involved in enhancing the activity of CAVII would be able to recreate this effect, and this could account for why most GABAergics tend to only cause inhibitory effects by focusing on the other properties of GABA, but also why some of them are able to slip through the cracks every now and then.
Where this lands us next is at something called theta rhythm. This is a brainwave pattern that, in the hippocampus, is associated with motor behavior, alertness, spatial learning, and REM sleep. That last one should have caught your attention! It is known that acetylcholine receptors, specifically muscarinic ones, are able to promote the generation of theta waves, but it's thought that because of how they work there must be a central mechanism which they are mainly promoting rather than being the main source of activity themselves. And what's really cool is that this source of activity seems to lie with GABA receptors. What I'm super psyched about right now is that I read a study earlier today that claimed that this generation of theta waves from cholinergic receptors could be reversed by a GABA(A) antagonist, and it went on to suggest methods by which acetylcholine release could facilitate the activity of CAVII and cause the inhibitory to excitatory GABA switch. The most convincing of these seems to be by causing an increase in the cellular levels of calcium, which is known to enhance spatial learning, among other things. In fact, both acetylcholine and glutamate receptors which are known to increase dream clarity and vividness raise levels of calcium. But what really matters to me is just the fact that acetylcholine was shown to be involved, and that those muscarinic receptors can cause these effects.
I'll try to keep this part brief, but to explain how I feel about the next point I think I should explain what I think imagination is. The part of the brain known as the amygdala is critically involved in motivation and thought, and it is located right next to the hippocampus. Stimulation of the amygdala is known to stimulate the hippocampus as well, and in fact has been linked to generation of out-of-body experiences and dreams. I personally believe that this is because the hippocampus contains a mental map of our environment, and that would be how our perceptions are created by our memories being written in, as it is all encoded into place by the data contained in the hippocampus. As an extension of this, I believe that our imagination is actually just a lower form of dreaming, and that our ability to visualize things while awake is the result of "map" data being written into the hippocampus from the amygdala at a level that doesn't cause those internally-generated sensations to replace the ones we have pulled in externally, but it does allow us to "see", "hear", "feel", or what have you sort of in the background of our mind. Therefore, a dream environment would be the result of having those external perceptions removed and replaced by internal ones pumped up to the level of what we would normally use to encode the waking world. This corresponds to the fact that the amygdala, like the hippocampus, is hyperactive during dreams. It also goes great lengths to explain why, when we're in our right (lucid) minds during a dream, we have essentially total control over what happens to us, because it's just like controlling your imagination. And I don't think I really need to convince anyone here that our imaginations and dream environments are intimately linked.
Now, something that is very-well known is that acetylcholine has a positive effect on visualization and dreams. Supplements that raise levels of it, such as galantamine, have the ability to enhance both. I've always thought that this must somehow relate to a potentiation of dopamine activity, which I feel is at the core of hallucinations, but I could never really say how for sure. I've had different theories, but none of them have gotten me as excited (hahahaha... yeah, nerdy joke) as this one. The inhibition that GABA produces at normal resting states lowers the activity of dopaminergic neurons, which means things that release them will do less so (compared to lower than normal GABA levels). However, when the GABA activity switches from inhibitory to excitatory, it will actually cause that dopamine to be released more efficiently. So what that basically means is that if acetylcholine causes this GABA switch, it should directly facilitate dopaminergic activity and increase the stability of hallucinations, visualizations, and dreams, just as it does. What really ties this all together though is that REM sleep is associated with the highest levels of acetylcholine in the hippocampus you'll ever normally have. This means that this GABA switch should also be running at its strongest at this point. Given that the amygdala is also hyperactive, it would mean that your motivation to move and explore would also be very high, and I believe that this lies at the core of dreaming. If you become lucid and decide to just sit down and do nothing then the dream will end, right? Given that, could it not be that it's this incredibly high amount of stimulation/motivation that is beginning this entire process which leads to higher acetylcholine, enhanced CAVII, excitatory GABA, theta waves, and facilitated dopamine? And therefore, would it not make sense that once you consciously decided to stop actively participating, this process would be inhibited just as it would if you returned to a resting state while awake and the GABA would return to normal, therefore plummeting dopamine levels and causing the dream to fall apart? In other words, if this was all true, couldn't GABA logically be at the heart of the dream world?
I feel that this is supported by the way GABAergic hallucinogens are described, but I think it goes even further than that. The psychedelic 5-HT2A receptors actually induce the release of acetylcholine, GABA, and dopamine in the hippocampus as well, and psychedelics are said to cause REM sleep-like patterns of activity in the brain. So if they can cause this same kind of effect to happen, it would make sense to me that it could contribute to the massive amount of processing power involved in powerful psychedelic experiences. On the other hand, dissociatives cause GABA and acetylcholine levels to lower. But, while still causing a release in dopamine. This means that even though they don't cause excitatory behavior from GABA, they still significantly inhibit its regular inhibitory behavior and facilitate dopaminergic effects. And when you consider that the amount of sensory stimulation between the psychedelic and dissociative experiences differs so much like I mentioned before, I would imagine that this could pick up a good amount of the slack. But what it really makes me think about is the question: if psychedelics actually cause more potential for expansion of power than dissociatives but are somewhat hindered by the massive amount of information they need to store, then what does that imply for dreams? If dreams do work the way I speculated here, then that would put their GABA effects in line with psychedelics rather than dissociatives. But as I mentioned before too, the amount of information that needs to be stored in a dream would be closer to between waking world and dissociative levels of stimulation than that of psychedelics, so would that mean that the memory encoding powers of dreams are a bit further increased beyond what I already postulated before?
So basically, what it would come down to is that our brains would be in a constant state of active learning and memory encoding in dreams that actually resulted from not only a form of disinhibition but one taken all the way to excitation, and to an extreme, and that could cause some time dilation as well if what I said before is true. I honestly think this is an awesome thought for many reasons stretching beyond time dilation too, but that is what got me here, and I've been trying to figure this sort of stuff out for a while now so I'm pretty happy to have arrived here just because I happened to be working on this issue as well!
I apologize for typing up such an incredibly long post again, but I really did just want to get my whole thought process out there. And like before, I've covered so much that I worry I might have missed some stuff... so that's it for now.
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