> Garbage collection tasks are postposed to when we're asleep, but they can only be put off for so long and there's a capacity for "stuff to consolidate later" that fills up
Do we have a strong reason to believe that? I know brain and sleep mechanisms are tricky topics with lots of unknowns, but I thought I had read research that showed sleeping brains likely perform a chemical analogue to "garbage collection".
Indeed, it's called the glymphatic system. We evolved to have a circadian system that drains brain waste products during sleep. There are probably other unknown neurological consequences of sleep that remain to be detailed.
In addition to the chemical ones others discussed, there is informational "garbage collection" as well. There are a bunch of motor tasks that only show certain types improvement after sleep - not time, sleep. There are also rodent studies where you can do a learning task and then "clear" part of their hippocampus using optogenetics. If you clear it before sleep, they forget what they "learned" if you clear it after sleep they still remember it. Again, multiple clever conditions to control for time and separate it from sleep.
It's unlikely for sleep to only do one thing. At a minimum it reduces caloric expenditures and accumulation of damage or risk through activity. It also allows time to heal injuries without the need for inflammation to immobilize the area.
Really lack of movement is probably useful and harmful for all kinds of things. REM sleep probably has some brain benefits but moving the eyes may relate to circulating fluid within the eye etc etc.
Do we have a strong reason to believe that? I know brain and sleep mechanisms are tricky topics with lots of unknowns, but I thought I had read research that showed sleeping brains likely perform a chemical analogue to "garbage collection".