The Mystery Of Rem Sleep: Are We Unconscious?

Sleep is a state of reduced consciousness, and the sleep-wake cycle is a variation in one's awareness, with phases of wakefulness and sleep. During REM sleep, the brain appears more active than during wakefulness, and almost all muscles of the body are paralysed, except for respiratory muscles and extraocular muscles. While REM sleep is commonly associated with dreams, it is possible to dream during any sleep stage. However, the question remains: how do we know we aren't conscious during REM sleep?

Consciousness during NREM sleep

Consciousness is an individual's awareness of themselves, their surroundings, and their own mind, including their thoughts and dreams. Sleep is a physiological state of reduced consciousness.

During REM sleep, the brain appears more active on an electroencephalogram (EEG) compared to when a person is awake and alert. REM sleep is also characterised by muscle atonia, where almost all of the body's muscles are paralysed, with the exception of the respiratory muscles and extraocular muscles. This phase of sleep is when the brain produces the vivid images and events that we know as dreams.

NREM sleep, on the other hand, is characterised by slow, low-frequency EEG patterns. The body experiences lowered heart rate, respiration rate, and renal function, and increased digestion. While it was previously thought that the brain disconnected during NREM sleep, recent studies have found that the brain remains interconnected during this phase of sleep.

A study published in 'The Journal of Neuroscience' found that not all forms of communication within the cerebral cortex are lost during NREM sleep. Specifically, correlations are preserved between neurons located within individual regions and between some subpopulations of neurons located in different cerebral areas. These findings have made it possible to analyse the scientific basis of consciousness.

Another study, published in 'Scientific Reports', investigated changes in EEG connectivity associated with consciousness during NREM sleep. It found that compared to unconsciousness, conscious experiences during NREM sleep were associated with reduced phase-locking at low frequencies (<4 Hz). Transitivity and clustering coefficient in the delta and theta bands were also significantly lower during consciousness compared to unconsciousness. These findings suggest that alterations in spectral and spatial characteristics of network properties in posterior brain areas, particularly decreased local (segregated) connectivity at low frequencies, may be an indicator of consciousness during sleep.

While the above studies suggest that consciousness may be present during NREM sleep, it is important to note that the concept of consciousness during sleep is a complex topic that is still being actively researched and debated.

Inhibitory neurons and insomnia

Inhibitory neurons play a crucial role in regulating sleep, particularly in the induction of sleep and the control of sleep-wake behaviour. These neurons release inhibitory neurotransmitters, which prevent or reduce neuronal activity in the receiving neuron. One such inhibitory neurotransmitter is gamma-aminobutyric acid (GABA), which is produced by GABAergic neurons.

GABAergic neurons in the Ventral Medial Midbrain/Pons (VMP) area of the brain have been found to suppress dopamine systems, thereby inducing sleep. Studies on mice have shown that the ablation of these GABAergic neurons leads to increased wakefulness, with longer durations of wakeful episodes and fewer episodes overall. This indicates that these neurons play a significant role in promoting sleep and inhibiting wakefulness.

The ventrolateral preoptic nucleus (VLPO), located in the anterior hypothalamus, also contains inhibitory neurons that promote sleep. These neurons release inhibitory neurotransmitters, such as GABA, to suppress the activity of the reticular activating system (RAS), which is responsible for regulating cortical alertness, wakefulness, and attention. This inhibition by the VLPO helps promote sleep and inhibit wakefulness.

Additionally, the orexin system, composed of neurotransmitters that maintain wakefulness, also plays a role in the regulation of sleep-wake behaviour. A loss of orexin-producing neurons can result in narcolepsy, a disorder characterised by excessive daytime sleepiness and sudden transitions into sleep.

The complex interplay between inhibitory and excitatory neurons, as well as various neurotransmitters, contributes to our understanding of insomnia and other sleep disorders. Further research in this field may lead to the development of more effective treatments for insomnia that specifically target these neuronal mechanisms and neurotransmitter systems.

Microsleep and its dangers

Microsleep refers to brief periods of sleep, usually lasting less than 30 seconds, during which the brain rapidly shifts between being asleep and awake. While microsleep can occur in rested individuals, it is most commonly caused by sleep deprivation or underlying sleep disorders. It often happens when a person is performing a monotonous task, such as driving on an empty highway or watching a movie.

During microsleep, a person may appear awake with their eyes open, but their brain is not processing external information as it normally would. They may experience lapses in attention, slowed eye movements, and partial or full eye closure. While microsleep can be harmless in certain situations, it can pose serious dangers in others.

Dangers of Microsleep

Microsleep is particularly dangerous when it occurs during activities that require constant attention and quick reaction times, such as driving, operating heavy machinery, or performing surgery. Even a few seconds of microsleep can lead to fatal accidents. According to the National Highway Traffic Safety Administration, up to 6,000 fatal crashes each year may be linked to drowsy drivers experiencing microsleep.

Microsleep can also be a concern for certain professionals, including air traffic controllers, process workers in plants or refineries, and medical workers on night shifts or extended hours. Sleep deprivation among medical workers has been associated with an increased risk of needlesticks, injuries with sharp instruments, and other medical errors.

Preventing Microsleep

To reduce the risk of microsleep, it is important to address sleep deprivation and underlying sleep disorders. Here are some strategies to prevent microsleep:

• Take short, 20-minute power naps to improve alertness.
• Take breaks and refrain from risky activities when feeling tired.
• Engage in conversation, which stimulates brain cells and increases oxygen intake.
• Consume caffeine in moderation, allowing 30 minutes for it to take effect.
• Improve sleep habits by maintaining a consistent sleep schedule, exercising during the day, and limiting screen time before bed.

Dreaming during REM sleep

During REM sleep, the eyes move around rapidly in different directions, and the brain is active. Dreams typically happen during this stage, and they can be intense as the brain is more active. REM sleep is important for learning and memory, and it helps with concentration and regulating mood. It stimulates areas of the brain that help with learning and memory and also helps the brain to repair itself and process emotional experiences.

However, it is important to note that dreaming also occurs during non-rapid eye movement (NREM) sleep. While dreams during REM sleep are typically more vivid and fantastical, dreams during NREM sleep tend to be more coherent and grounded in thoughts or memories.

The default view is that there is conscious experience in sleep only when we dream. Since dreams usually occur during REM sleep, it is generally assumed that there is no sleep consciousness outside of this stage. However, some argue that there is a variety of sleep experiences, and insisting that dreams are the only form of sleep consciousness may cause us to miss out on understanding the variety of sleep experiences.

Lucid dreaming techniques

It is generally assumed that there is no sleep consciousness outside of REM sleep. During REM sleep, the brain appears more active on an electroencephalogram (EEG) compared to alertness. However, during this sleep phase, almost all muscles of the body are paralysed, except for the respiratory muscles and extraocular muscles.

Lucid dreaming is when you're conscious during a dream, and it typically happens during REM sleep. During a lucid dream, you're aware of your consciousness, and you can often control what happens in your dream. Some people report that lucid dreams feel very vivid and real, while others say they feel hazier.

• Wake-initiated lucid dreaming (WILD): This is when you directly enter a dream from a waking state. You need to relax until you experience a hypnagogic hallucination, which occurs when you're about to fall asleep.
• Reality testing: This is a form of mental training that increases your metacognition by training your mind to notice your own awareness. You can do reality tests while you're awake, such as asking yourself, "Am I dreaming?", checking your environment, and noticing your own consciousness and how you're engaging with your surroundings.
• Wake back to bed (WBTB): This technique involves entering REM sleep while you're still conscious. Set an alarm for 5 hours after your bedtime, stay up for 30 minutes, then go back to sleep. You'll be more likely to lucid dream when you go back to sleep.
• Mnemonic induction of lucid dreams (MILD): Created by Dr. Stephen LaBerge, this technique is based on a behaviour called prospective memory, which involves setting an intention to do something later. You make the intention to remember that you're dreaming. As you fall asleep, think of a recent dream, identify a "dream sign", and tell yourself that you will remember that you're dreaming the next time it happens.
• Keeping a dream journal: Writing down your dreams helps you remember them and recognise dream signs. It's also said to enhance awareness of your dreams.

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