We finished the last blog in mid-thought. We were talking about REM sleep and the idea of brain plasticity- the rewiring of our brains that take place when we learn new information.
A recent study in rats showed that 4 days of REM sleep deprivation decreased the amount of new cells in the part of the brain that is associated with long-term memory, in other words they did not make those new circuits.
Another study with rats seems to demonstrate this idea as well. When rats performed a task that required learning, they tended to have an increase in REM sleep afterwards. Also, the more learning involved the quicker they fell into REM sleep. This suggests that the REM sleep was necessary to help consolidate their learning, and the reason why they went into REM so quickly was that the memory could have been lost, had it not been placed into long-term memory banks.
It’s not only rats that seem to need REM- there are similar studies in humans. In one research trial, REM sleep deprivation led to inability to perform well on some memory and logic based tasks.
Is there a difference between the memory consolidation that happens during REM and non-REM sleep?
The theory goes that REM sleep acts as sort of a filter, reviewing and trying to make sense of the images and ideas we process as we live our waking lives. REM sleep allows us to try to order the information and place it in the proper areas of the brain for long term storage. This concept may even explain why our dreams (which virtually always occur during REM) seem so disorganized, because dreaming is just part of the brains sorting process.
It should be noted, that not all experts believe that sleep has anything to do with memory consolidation (though the scale seemed to be slowly tilting towards that side). Some argue that while sleep is obviously a biological need, there is no evidence that the things that the brain does during sleep can’t be done during wake. What about the studies that seem to show that depriving people and animals of sleep seem to worsen their ability to perform? These are explained away as being a response to the stress of sleep deprivation, rather than due to the sleep deprivation itself. To put it simply, imagine how you would feel if someone kept poking you awake every 10 minutes? Probably pretty unhappy, irritated, and irritable.
To sum it all up, to date there is no clear answer to the question that we started this series of blogs with-what is the function of sleep.
I don’t know about you, but I think I’ll sleep on it!
Hopefully, we’ll pick up next time with another (and less esoteric!) topic.