“Marijuana, Dreaming, Memory…
– Marijuana (cannabis) and its compounds reduce the amount of a neurotransmitter called acetylcholine that is accessible in the brain
– Memory is also affected because of the reduction of acetylcholine…
…marijuana reduces the amount of acetylcholine that is available in the brain, it reduces the ability for individuals to create new memories…
…Acetylcholine promotes awareness. When you are most awake in your life, you have a lower level of acetylcholine being transmitted in your brain and a higher level of serotonin… – Taileaters – Lee Adams – taileater.com/2017/10/11/marijuana-dreaming-memory-alzheimers/
Acetylcholine Pathway
“This Is Why Your Dreams Are So Intense When You Stop Smoking Weed…
…According to Dr Hamburger, this resurgence of dreams happens because weed suppresses your REM 
sleep. When you put your rolling papers, pipe or vapourisers away for a while, your REM sleep suddenly recovers the free reign it had before you became a blacked out stoner…
…We don’t remember the things that happen while we are sleeping, because we’re in a lowered state of consciousness. That has something to do with the fact that when you’re asleep, you’re processing the memories of things that happened during the day and essentially filing them away in your brain.” – Vice – Twan Stoffels – March 4 2015 – https://www.vice.com/en_us/article/7b7gn4/why-are-your-dreams-suddenly-so-intense-when-you-stop-smoking-weed-876
“Does marijuana affect dreaming?…”
…Yes, smoking marijuana does affect your quality of sleep, namely it hinders your body’s ability to produce REM sleep..
...Administration of THC significantly reduced eye movement activity during sleep with rapid eye movements (REM) and, to a lesser extent, the duration of REM itself. .
…Smoking marijuana may alter short-term memory… Even if you can pull of a lucid dream while stoned, you may not remember it the next day…” – B November 30 2009 – Lucid Guide – http://lucidguide.com/dream-articles/does-marijuana-affect-dreaming
“Marijuana, REM Sleep, and Dreams…
…..In fact, studies show that marijuana lengthens the time the brain spends in deep sleep, which leads 
to less REM sleep..
…Regular users of cannabis experience an abnormal increase in REM sleep when use is stopped. This is called the REM rebound effect, which leads to longer and denser periods of REM sleep. The REM rebound explains why cannabis users often experience highly vivid dreaming when trying to quit…. – leaf science – Health – Sep 13, 2014 – https://www.leafscience.com/2014/09/13/marijuana-rem-sleep-dreams/