An Analysis of the REM Sleep-Memory Consolidation Hypothesis

An Analysis of the REM Sleep-Memory Consolidation Hypothesis

Have you found that you remember something more strongly if you get more sleep? If so, then you may have confirmed the REM Sleep-Memory Consolidation Hypothesis. What this hy-pothesis states is that the more REM sleep you get, the more you are to remember, whether in the form of an increase in memory because of more of it or a decrease in memory because of a de-privation. Research by several scientists states that this phenomenon can come about due to “the replay of neuronal activity seen during prior learning episodes” (Siegel). Others believe that this replay may be a result of genetically programmed neuronal development that may be a factor in the “extinction of memory traces” or have no function in neuronal plasticity.

Numerous experiments have been devoted to wondering if there is a positive correlation between REM sleep and memory. In 2000, Dave and Margoliash studied the motor cortex of ze-bra finches and found that their “neural activity patterns in sleep” were similar to their singing when they were awake, suggesting that sleep plays a role in the consolidation of procedural memory. This hypothesis is also supported by the fact that infants and babies sleep for a consi-derably long time. Other findings have focused more on the macro-level interaction by saying the hippocampus plays a role in memory consolidation during REM sleep. Work on the hippocampus has shown that memories are recorded better when impulses arrive at the high points of the theta rhythm while those that arrive at the low points of the rhythm “can undo the facilitation” of a memory. In 2000, Stickgold and his colleagues studied dreams and found that 10% of dreams were those of a task just learned. Other dreamers reported that their dreams were those of a learned task that occurred after that task was consolidated. Many of the dreams were also linked to the place where the learning had occurred or were matched with the emotions of the learning experience.

Other findings have considered whether the deprivation of REM sleep can prevent mem-ory. A 1962 finding by Jouvet stated that with REM sleep deprivation, the animal subject had a total loss of muscle tone, suggesting that REM sleep is necessary for proper memory functioning of muscles. The study has been extended by Vimont-Vicary and colleagues in 1966 to show that if animals, specifically rats, are restricted to a small area surrounded by water, they will fall into the water if “they assume the maximally relaxed recumbent posture required for REM sleep.” In addition, Quervain in 1998 showed that without REM sleep, the animal experiences more stress which can combine with loss of REM sleep to produce a synergistic effect of memory consolida-tion impediment.

Despite these claims that there is a positive correlation between REM sleep and memory, numerous findings seem to disprove this belief. Louie and Wilson in 2001 found that the replay of events occurred in the latter REM stages rather than the first ones after the process, suggesting that there are more factors in memory consolidation than just REM sleep. In addition, a majority of dreams do not have any particular relationships to events we have just learned. In Jouvet’s same study, the findings reported that “some non-REM sleep can occur without complete relaxa-tion” of the muscles, which were previously viewed as a reason for the necessity of REM sleep. As for the surrounded by water test, several studies reported no difference in memory consolida-tion while some stated that there was an increase in it. In 1982, van Hulzen devised an experi-ment where the rat was rocked gently back in forth so that there would be less stress on the ani-mal. The findings showed that there was no learning deficit, suggesting that stress caused the memory loss. Numerous drugs such as monoamine oxidase (MAO) inhibitors are able to suppress REM sleep without any learning deficit.

Regardless of the actual verdict on the positive correlation between REM sleep and memory correlation, it can be said that any experiments that improve the conditions of human beings are beneficially. Even if the hypotheses are wrong, they do bring in new data that can possibly be attributed to other hypotheses. With the help of advanced scientific tools like MRI machines, we can delve deeper into the human mind. Continued research is needed to determine if we ourselves should sleep longer or whether our children should do so also. Further studies should control for unwanted variables such as stress and that the sample sets are large enough and varied enough to draw a valid conclusion from.  

Works Cited

Siegel, Jerome M. "The REM Sleep-Memory Consolidation Hypothesis. " Science 294.5544 (2001): 1058-1063. Research Library Core, ProQuest. Web. 6 Aug. 2009.