Rem Sleep: Gateway To The Dream World

Dreaming can occur in both rapid eye movement (REM) and non-REM (NREM) sleep. However, dreams that are vivid and emotional mostly happen during REM sleep.

REM sleep is distinguishable from NREM sleep by the different brain wave patterns and eye movements that characterise each type of sleep. REM sleep is marked by the suspension of homeostasis, rapid eye movements, and increased brain activity. NREM sleep includes three distinct stages characterised by gradually slowed brain waves.

During REM sleep, the muscles that prevent body movements become active, leading to temporary paralysis. This is a normal function of REM sleep and prevents sleepers from physically acting out their dreams.

Dreams mostly occur about 90 minutes after falling asleep, during the REM stage of sleep. However, dreams can also occur during any of the stages of sleep.

Dreaming occurs in both REM and non-REM sleep

REM Sleep and Dreaming

During REM sleep, the brain becomes highly active and functions at levels similar to when a person is awake. Dreams that occur during this stage are often vivid, elaborate, hallucinogenic, and emotional. REM sleep is also associated with increased brain activity, breathing, heart rate, and blood pressure.

Non-REM Sleep and Dreaming

Non-REM sleep, on the other hand, is characterised by slower brain wave activity and decreased body movements. Dreams that occur during this stage tend to be more conceptual, abstract, and less vivid. However, it is important to note that dreams can still occur during non-REM sleep and aren't just a recollection of REM dreams.

Factors Affecting Dream Recall

Whether or not a person recalls their dreams upon waking depends on various factors. For example, dreams that are particularly memorable, emotional, or triggered by external stimuli are more likely to be remembered. Additionally, being woken up during REM sleep can increase the likelihood of dream recall.

REM sleep is characterised by muscle relaxation, eye movement, faster respiration, and increased brain activity

During REM sleep, the body and brain undergo several changes. The body experiences muscle relaxation, with a temporary loss of muscle tone, except for the eyes, which move rapidly. The brain, on the other hand, exhibits heightened activity, with brain waves similar to those during wakefulness.

REM sleep is also known as paradoxical sleep due to its similarities to the waking state. While the body is in a state of paralysis, the brain remains active, with cerebral neurons firing at an intensity comparable to that of wakefulness. This heightened brain activity is believed to be responsible for the vivid dreams often associated with REM sleep.

In addition to muscle relaxation and eye movement, REM sleep is characterised by faster respiration and increased heart rate, with respiration and cardiac function becoming irregular. There is also an increase in blood pressure and oxygen consumption by the brain. The body temperature decreases during REM sleep, and twitching of the face and limbs may occur.

REM sleep typically occurs about 60 to 90 minutes after falling asleep and recurs in cycles of about 90 minutes. Each cycle includes a larger proportion of REM sleep, with most REM sleep occurring in the second half of the night. The first REM episode is characterised by theta rhythms in the brain, while subsequent episodes are punctuated by ponto-geniculo-occipital (PGO) waves, which cause the rapid eye movements characteristic of this sleep stage.

The transition to REM sleep brings about marked physical changes. The body abruptly loses muscle tone, a state known as REM atonia, which may serve as a protective measure to prevent individuals from acting out their dreams. However, this hypothesis has been challenged by the discovery that dreams can also occur during non-REM sleep stages.

The brainstem plays a crucial role in regulating REM sleep, with electrical and chemical activity originating in this region. The brainstem gives rise to PGO waves, which manifest as electrical bursts during the transition from deep sleep to REM sleep. These waves are responsible for the rapid eye movements and may also contribute to the visual aspects of dreams.

While REM sleep is associated with dreaming, it is important to note that dreams can also occur during non-REM sleep stages. Dreaming during REM sleep may be more common and is often characterised by narrative structure, convincingness, and the incorporation of instinctual themes. However, both REM and non-REM sleep play essential roles in memory consolidation and emotional processing.

Non-REM sleep has three stages, the first being the shortest and lightest, and the third being the deepest

Sleep is divided into two main types: rapid eye movement (REM) sleep and non-REM (NREM) sleep. NREM sleep is further divided into three stages, the first being the shortest and lightest, and the third being the deepest.

The first stage of NREM sleep is the transition from wakefulness to sleep and generally lasts only a few minutes. During this stage, the eyes are closed, but it is easy to wake the sleeper up. The heart rate and breathing slow down, and the muscles begin to relax.

The second stage of NREM sleep is a light sleep, but deeper than the first stage. The heart rate and breathing slow down further, and the body temperature drops. The brain also exhibits distinct features called sleep spindles and K-complexes. This stage makes up the largest percentage of total sleep time.

The third and final stage of NREM sleep is the deepest sleep stage. It is known as slow-wave, or delta, sleep. The sleeper is very difficult to wake up during this stage, and if they are woken up, they will feel disoriented for a few minutes. The heart rate and breathing are slower, and the body is fully relaxed. The brain produces delta brain waves, which are slower brain waves that indicate healing and restorative sleep. The body performs a variety of health-promoting functions during this stage, including tissue repair and growth, cell regeneration, and strengthening of the immune system.

Dreams that occur during REM sleep are more likely to be remembered

Dreaming occurs in both rapid eye movement (REM) sleep and non-REM (NREM) sleep. However, dreams that occur during REM sleep are more likely to be remembered.

REM sleep is distinguishable from NREM sleep by the different brain wave patterns and eye movements that characterise each type of sleep. REM sleep is marked by the suspension of homeostasis, rapid eye movements, and increased brain activity. NREM sleep includes three distinct stages characterised by gradually slowed brain waves.

Additionally, the body twitches during REM sleep, particularly in the face, arms, and legs. The muscles that prevent body movements become active, leading to temporary paralysis. This is a normal function of REM sleep and prevents sleepers from physically acting out their dreams.

Dreams that occur during REM sleep are also more likely to be remembered because they are more vivid and emotional than dreams that occur during NREM sleep. REM sleep dreams are more elaborate and follow a narrative, whereas NREM sleep dreams are more abstract.

Dreaming may be the brain's way of processing emotions and memories

Dreaming is a universal human behaviour that has been studied across many disciplines, including art, psychology, religion, and politics, yet its function remains poorly understood.

Dreams can occur during both rapid eye movement (REM) sleep and non-REM (NREM) sleep. Dreaming is associated with local decreases in slow-wave activity in posterior brain regions, and the capacity of the brain to generate experiences during sleep is reduced in the presence of neuronal off-states in these regions.

The occurrence of dreams 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, when they occur, are more conceptual, less vivid, and less emotion-laden.

Dreams have been studied in a variety of ways, perhaps most notably within the psychoanalytic framework of revealing unconscious thought processes considered to be at the root of neuroses. Sigmund Freud's *The Interpretation of Dreams*, published in 1900, speaks eloquently to the complex relationship between conscious and unconscious mentation.

Recent studies have provided evidence on the potential interaction between dreaming, sleep alterations, and affective disorders. For example, untreated obstructive sleep apnea may also contribute to fragmented REM sleep as disturbed breathing occurs due to the relaxation of the airway muscles. Sleep apnea may likewise lead to REM sleep deprivation, and effective continuous positive airway pressure (CPAP) therapy may cause a profound rebound of REM sleep.

One way to disentangle the key difference between the active and passive theories of dreaming, i.e., whether dreams support the transformation of emotional reactivity, is to adopt an experimental paradigm from the sleep-dependent memory consolidation field, which investigates how memory performance changes pre-to-post by an intervening sleep period.

The current study investigates whether dreaming plays a passive or active role in memory consolidation and emotion regulation by specifically addressing how the presence and content of dreams affect the prioritisation of emotional memories over neutral memories, as well as changes in valence and arousal ratings to negative stimuli overnight.

Participants completed an emotional picture task before and after a full night of sleep and recorded the presence and content of their dreams upon waking in the morning. The results replicated the emotional memory trade-off (negative images maintained at the cost of neutral memories), but only in those who reported dreaming (Dream-Recallers), and not in Non-Dream-Recallers. Results also replicated sleep-dependent reductions in emotional reactivity, but only in Dream-Recallers, not in Non-Dream-Recallers. Additionally, the more positive the dream report, the more positive the next-day emotional reactivity is compared to the night before. These findings implicate an active role for dreaming in overnight emotional memory processing and suggest a mechanistic framework whereby dreaming may enhance salient emotional experiences via the forgetting of less relevant information.

Frequently asked questions