Dreaming Beyond Rem Sleep: What Does It Mean?

Dreaming is a series of thoughts, images, or emotions occurring during sleep. While it was previously believed that dreaming only happened during REM sleep, we now know that it can occur during non-REM sleep as well. Dreams tend to be more vivid during REM sleep, but they can also occur during the early, non-REM stages of sleep. In fact, a 2020 study found that participants who were woken up during non-REM sleep were able to describe their dreams, which tended to be more abstract than those that occurred during REM sleep.

Dreaming occurs in both REM and non-REM sleep

During REM sleep, the eyes move rapidly, and brain activity is similar to how it is when a person is awake. The body is temporarily paralysed during this stage, which prevents sleepers from acting out their dreams. Dreams during REM sleep are usually more vivid, emotional, and physically engaging than dreams during non-REM sleep.

Non-REM sleep, on the other hand, is characterised by slower brain waves, slower breathing, and a slower heart rate. The deeper stages of non-REM sleep are when the body repairs and regenerates tissues, builds bone and muscle, and strengthens the immune system. Dreams during non-REM sleep tend to be more abstract and less vivid than those during REM sleep.

The stages of sleep alternate throughout the night, with non-REM sleep occurring first, followed by a shorter period of REM sleep, and then the cycle starts over again. Each cycle lasts between 90 and 120 minutes, and as the night progresses, the amount of time spent in REM sleep increases.

REM sleep is characterised by quick eye movement, irregular breathing, and increased brain activity

REM sleep, or rapid eye movement sleep, is the fourth of four stages of sleep. It is characterised by quick eye movement, irregular breathing, elevated heart rate, and increased brain activity. During REM sleep, the eyes move rapidly in different directions, and the brain is highly active. The brain activity during REM sleep is similar to its activity when a person is awake.

REM sleep is also associated with dreaming. Dreams typically happen during this stage of sleep, and they tend to be more vivid than those that occur during non-REM sleep. Dreaming is thought to be linked to the brain's process of emotional processing. The amygdala, the part of the brain responsible for processing emotions, is activated during REM sleep.

In addition to dreaming and emotional processing, REM sleep plays a role in memory consolidation, brain development, and wakefulness preparation. During this stage, the brain processes new learnings and motor skills from the day, committing some to memory and deciding which ones to delete. Researchers also hypothesise that REM sleep promotes brain development, as newborns spend most of their sleep time in this stage.

The first cycle of REM sleep typically occurs about 60 to 90 minutes after falling asleep. As a full night's sleep progresses, the cycles shift towards a higher proportion of REM sleep. The first period of REM sleep is usually the shortest, lasting about 10 minutes, while later REM stages get longer, with the final one lasting up to an hour.

Non-REM sleep is when the body repairs and regrows tissues

Sleep is divided into two main types: Non-Rapid Eye Movement (NREM) sleep and Rapid Eye Movement (REM) sleep. NREM sleep is further divided into three stages, each with its own characteristics and functions in body repair.

Stage 3 of NREM sleep, also known as slow-wave sleep or deep sleep, is when much of the body's repair work takes place. During this stage, the body increases its production of growth hormone, which is essential for tissue repair and growth. This stage is crucial for physical restoration, including muscle repair, bone growth, and immune system strengthening.

In addition to tissue repair and growth, NREM sleep also plays a role in memory consolidation and learning. During Stage 2 of NREM sleep, the body temperature drops, and the heart rate slows, creating an environment conducive to repair and regeneration. The brain's activity during this stage is characterised by slow brain waves with occasional bursts of rapid brain activity known as sleep spindles. These bursts are believed to be the brain organising memories and information from wakeful hours.

NREM sleep is important for the body to repair and regrow tissues as it is during this time that the body produces growth hormone, which is crucial for tissue repair and growth. Deprivation of NREM sleep can have adverse effects on the body, including weakened immune function, increased risk of cardiovascular disease, impaired cognitive function, and even accelerated ageing.

While the function of REM sleep remains a matter of debate, it is known to play a role in dreaming, memory, emotional processing, and healthy brain development. Dreams that occur during REM sleep tend to be more vivid and emotionally charged compared to those that occur during NREM sleep.

Dreaming during REM sleep is associated with more vivid and emotional dreams

The occurrence of dreams during REM sleep can be tested by waking volunteers during either non-REM or REM sleep and asking them if they were dreaming. Subjects awakened from REM sleep recall elaborate, vivid, hallucinogenic, and emotional dreams, whereas subjects awakened during non-REM sleep report fewer dreams, which are more conceptual, less vivid, and less emotion-laden.

REM sleep is the fourth and final stage of sleep. During REM sleep, the eyes move rapidly, the heart rate increases, breathing becomes irregular, and the body experiences temporary muscle tone loss. Most adults need about two hours of REM sleep each night.

Dreaming is important for learning and memory

Research has found that dreaming allows the brain to make connections between new information and past experiences, aiding in memory consolidation. For example, a study at Harvard Medical School found that participants who dreamed about navigating a virtual maze performed better on the task than those who stayed awake and rehearsed it. The dreamers made connections between the maze and other aspects of their lives, cementing the shape of the maze into their memory.

Additionally, dreaming has been linked to improved emotional processing. During REM sleep, the brain reactivates key emotional and memory-related structures while being free of the anxiety-triggering molecule noradrenaline. This allows for the reprocessing of upsetting memories in a calmer and safer environment, leading to a reduction in emotional reactivity when awake.

Furthermore, dreaming may also influence long-term moods and physiological states. For instance, a study found that dreaming about drinking water reduced feelings of thirst upon waking. Dreaming has also been linked to enhanced creativity, with studies showing that participants who were awakened during REM sleep displayed increased creativity and problem-solving abilities.

Overall, dreaming plays a crucial role in learning and memory consolidation, emotional processing, and creative thinking. By making connections between new information and past experiences, reducing the emotional impact of traumatic events, and influencing long-term moods and physiological states, dreaming contributes significantly to cognitive performance and well-being.

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