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How REM and non-REM sleep may work together to help us solve problems -- ScienceDaily

Suppose I give you a creativity puzzle where you have all the information you need to solve it, but you can't, because you're stuck," says first author Penny Lewis, a professor at the Cardiff University School of Psychology. "You could think of that as you've got all the memories that you need already, but you need to restructure them -- make links between memories that you weren't linking, integrate things that you weren't integrating." Studies show that this kind of restructuring often happens while we are asleep, so Lewis and her co-authors drew on that literature, as well as physiological and behavioral data, to create a model of what might be happening during each stage. Their model proposes that non-REM sleep helps us organize information into useful categories, whereas REM helps us see beyond those categories to discover unexpected connections.

The Science of Sleep: Dreaming, Depression, and How REM Sleep Regulates Negative Emotions – Brain Pickings

The more severe the depression, the earlier the first REM begins. Sometimes it starts as early as 45 minutes into sleep. That means these sleepers’ first cycle of NREM sleep amounts to about half the usual length of time. This early REM displaces the initial deep sleep, which is not fully recovered later in the night. This displacement of the first deep sleep is accompanied by an absence of the usual large outflow of growth hormone. The timing of the greatest release of human growth hormone (HGH) is in the first deep sleep cycle. The depressed have very little SWS [slow-wave sleep, Stages 3 and 4 of the sleep cycle] and no big pulse of HGH; and in addition to growth, HGH is related to physical repair. If we do not get enough deep sleep, our bodies take longer to heal and grow. The absence of the large spurt of HGH during the first deep sleep continues in many depressed patients even when they are no longer depressed (in remission). The first REM sleep period not only begins too early in the night in people who are clinically depressed, it is also often abnormally long. Instead of the usual 10 minutes or so, this REM may last twice that. The eye movements too are abnormal — either too sparse or too dense. In fact, they are sometimes so frequent that they are called eye movement storms.

The role of sleep in bipolar disorder | NSS

A convergence of evidence suggests that sleep problems in bipolar disorder result from dysregulation across both process C and process S systems. Biomarkers of depressive episodes include heightened fragmentation of rapid eye movement (REM) sleep, reduced REM latency, increased REM density, and a greater percentage of awakenings, while biomarkers of manic episodes include reduced REM latency, greater percentage of stage I sleep, increased REM density, discontinuous sleep patterns, shortened total sleep time, and a greater time awake in bed. These findings highlight the importance of targeting novel treatments for sleep disturbance in bipolar disorder.

REM versus deep sleep

I was just going to comment that there's also evidence that suggest that deeper sleep, that what we call slow-wave sleep, non-REM sleep, might be more involved in sort of strengthening memories in a way that they're for REM. So for example, if you want to remember someone's name or phone number that might be where that non-REM sleep is valuable. And that REM sleep seems to be more involved in memory processing where you're not trying to exactly remember it in the form that you first saw it but rather to extract meaning from it. So to get patterns or to figure out the rules of something or to extract just to get the sort of the executive summary. But that seems to be more of what REM sleep that's about and that would fit in with the emotional piece too because, of course, if something had happens during the day, you don't simply want to remember it better than next morning. You want to understand it.

REM and PTSD

For example, we know in PTSD, which is perhaps one of the quintessential psychiatric conditions of dysfunctional emotional memory processing, there you see profound disruptions of sleep, including REM sleep. And by trying to ameliorate(ph) or restore that REM sleep, recent findings have demonstrated benefits in terms of clinical PTSD outcome.

REM launders emotion

One of the things that's been emerging over the past five or six years in the literature is that REM sleep seems to serve an almost sort of overnight therapy benefit in terms of our emotional well-being and our mental health. And what's interesting is that REM sleep chemically, in terms of the anuric transmitters that swirl around the brain, REM sleep is perhaps the only time during the 24-hour period where a particular stress neurochemical called norepinephrine or noradrenaline is actually suppressed and it's completely shut down from the brain. And it seems to be that REM sleep is a perfect chemical environment, almost like a therapy session, where you can take emotional events from the prior day and perhaps just smooth the sharp edges off those experiences, and almost like an overnight soothing balm, as it were.