A new study is shedding more light on the relationship between sleep and memory.
The entorhinal cortex, which connects the neocortex brain region and the hippocampus brain region, and is vital to working memory (the memory that we use when we do things like remember a phone number), is persistently active even while we sleep, according to the research in mice from the University of California, Los Angeles. In other words, this part of the brain works like it's remembering something even during sleep.
"The big surprise here is that this kind of persistent activity is happening during sleep, pretty much all the time," study researcher Mayank R. Mehta, neurophysics professor at UCLA, said in a statement. "These results are entirely novel and surprising. In fact, this working memory–like persistent activity occurred in the entorhinal cortex even under anesthesia."
The findings, published in the journal Nature Neuroscience, are important because they provide a new understanding of how the brain is working during sleep -- one that shows how integral the entorhinal cortex is in how memory is consolidated.
LiveScience explained how the new findings differ from the prior understanding of memory and sleep:
Previous research suggested that this critical memory-making process depends on the hippocampus, sometimes called the old brain, communicating with the neocortex during sleep. But a new study shows the main interface between those two regions —- the entorhinal cortex —- also plays an important role in memory formation.
"These results provide, to the best of our knowledge, the first direct evidence for persistent activity in MECIII [medial entorhinal cortex layer III] neurons in vivo and reveal its contribution to cortico-hippocampal interaction that could be involved in working memory and learning of long behavioral sequences during behavior, and memory consolidation during sleep," the researchers wrote in the study.