Understanding Tonic Rem Sleep: Brain Activity And Muscle Relaxation

Tonic REM sleep is a parasympathetically driven state with no eye movements, decreased EEG amplitude, and atonia. Tonic REM sleep is one of the two distinguishable microstates of REM sleep, the other being phasic REM sleep. Tonic REM sleep is characterised by muscle activity, which is the strongest predictor of phenoconversion risk to neurodegenerative disease in isolated REM sleep behaviour disorder. Tonic REM sleep exhibits different patterns in young adults and children.

Tonic REM sleep is a parasympathetically driven state

Tonic REM sleep is distinct from phasic REM sleep. Phasic REM sleep is a sympathetically driven state, characterised by rapid eye movements, muscle twitches, cardiorespiratory variability, and middle ear muscle activity. On the other hand, tonic REM sleep is characterised by a lack of eye movements, decreased EEG amplitude, and atonia.

The differentiation between phasic and tonic REM sleep is important for understanding the mechanisms and functions of REM sleep in healthy and pathological conditions. For example, tonic REM sleep muscle activity is the strongest predictor of phenoconversion risk to neurodegenerative disease in patients with isolated REM sleep behaviour disorder.

REM sleep has been found to play a critical role in various functions, from basic physiological mechanisms to complex cognitive processes. It is also associated with dreaming, with the increase in blood flow to the primary visual regions of the cortex potentially explaining the vivid nature of dreams during REM sleep.

It is characterised by no eye movements

Tonic REM sleep is a parasympathetically driven state with no eye movements, decreased EEG amplitude, and atonia. Tonic REM sleep is one of the two distinguishable microstates of REM sleep, the other being the phasic state. Tonic REM sleep is characterised by the absence of eye movements, which differentiates it from the phasic state.

REM sleep, or rapid eye movement sleep, is a neural state that makes up 20-25% of nighttime sleep in healthy human adults. It is characterised by a variety of transient neurophysiological features, including eye movements, muscle twitches, and changes in autonomic activity. However, despite its heterogeneous nature, it is often conceptualised as a homogeneous sleep state.

The differentiation between phasic and tonic REM periods can provide a novel framework to examine the mechanisms and functions of REM sleep. These two states have been shown to be remarkably different neural states with respect to environmental alertness, spontaneous and evoked cortical activity, and information processing. Furthermore, they seem to contribute differently to the dysfunctions of REM sleep in several neurological and psychiatric disorders.

Tonic REM sleep muscle activity has been identified as the strongest predictor of phenoconversion risk to neurodegenerative disease in patients with isolated REM sleep behaviour disorder.

It is associated with decreased EEG amplitude

Tonic REM sleep is a neural state that occupies 20-25% of nighttime sleep in healthy human adults. It is characterised by random rapid movement of the eyes, low muscle tone throughout the body, and vivid dreams. The core body and brain temperatures increase during REM sleep, and skin temperature decreases.

REM sleep is considered a unique phase of sleep due to its physiological similarities to waking states, including rapid, low-voltage desynchronised brain waves. This is where the term paradoxical sleep comes from. During REM sleep, the brain acts as if it is somewhat awake, with cerebral neurons firing with the same overall intensity as in wakefulness.

Electroencephalography (EEG) during REM sleep reveals fast, low-amplitude, desynchronised neural oscillation (brain waves) that resemble the pattern seen during wakefulness. This is in contrast to the slow delta waves pattern of non-REM deep sleep. The low-amplitude brain waves of REM sleep are thus associated with decreased EEG amplitude.

The decreased EEG amplitude observed during REM sleep is characterised by theta rhythms in the brain, with a frequency of 3-10 Hz in the hippocampus. This is in contrast to the high-frequency (15-60 Hz) and low-amplitude activity of the waking state, known as beta activity.

The decrease in EEG amplitude during REM sleep is thought to be related to the abundance of the neurotransmitter acetylcholine, which is higher during waking and REM sleep compared to slow-wave sleep. Injections of acetylcholinesterase inhibitor, which increases acetylcholine levels, have been found to induce REM sleep in humans and other animals.

The microstructure of REM sleep, including its phasic and tonic constituents, is an area of ongoing research. Differentiating and exploring these fine microstates is proposed to provide a novel framework to examine the mechanisms and functions of REM sleep, including its role in various neurological and psychiatric disorders.

It is associated with muscle atonia

REM sleep is a neural state that occupies 20-25% of nighttime sleep in healthy human adults and is characterised by rapid eye movement, muscle twitches, and changes in autonomic activity. During REM sleep, muscle atonia occurs when motoneurons are not generating action potentials. Motoneuron action potentials arise at the initial segment of the cell's axon, close to its soma, and result from a summation of currents that are generated at synapses on the soma and dendrites. If the voltage produced by these currents is above a certain threshold, an action potential is triggered.

The mechanisms causing the atonia of REM sleep are complex, but the relevance of state-dependent motor control justifies the effort that will be required to parse the commentaries and rebuttal. The trigeminal nuclear complex extends from the midbrain to the medulla. The motor nucleus of the trigeminal nerve is located in the pontine brainstem, and the trigeminal motor nerve activates muscles of the mandible and 7 additional muscles. Lateral to the motor nucleus is the sensory trigeminal nucleus that receives proprioceptive, nociceptive, and tactile afferent input from the face and mouth. The space separating the sensory and motor trigeminal nuclei is referred to as the intertrigeminal region.

REM sleep behaviour disorder (RBD) occurs when the body maintains relatively increased muscle tone during REM sleep, allowing the sleeper to move and act out their dreams. Movements may be as minor as leg twitches, but can result in very complex behaviour that may cause serious injury to the individual or their bed partner. RBD is more common with age and has been associated with certain neurological disorders.

Tonic REM sleep muscle activity can be a predictor of neurodegenerative disease

Tonic REM sleep is a parasympathetically driven state with no eye movements, decreased EEG amplitude, and atonia. Tonic REM sleep is one of two distinguishable microstates of rapid eye movement (REM) sleep, the other being phasic REM sleep. REM sleep occupies 20-25% of nighttime sleep in healthy human adults and is characterised by eye movements, muscle twitches, and changes in autonomic activity.

Tonic REM sleep muscle activity has been identified as the strongest predictor of phenoconversion risk to neurodegenerative disease in patients with isolated REM sleep behaviour disorder. A study by Ankur Singh et al. (2023) found that patients with higher amounts of tonic REM sleep muscle activity at the time of diagnosis were more likely to develop neurodegenerative diseases. The study analysed tonic, phasic, and mixed REM sleep activity in patients with isolated REM sleep behaviour disorder, some of whom developed neurodegenerative diseases during the follow-up period. The results showed that those who developed neurodegenerative diseases had significantly higher amounts of tonic REM sleep muscle activity at diagnosis compared to those who did not develop these diseases.

The findings suggest that monitoring tonic REM sleep muscle activity in patients with isolated REM sleep behaviour disorder could help predict their risk of developing neurodegenerative diseases. This information could be valuable for early intervention and disease prevention. Further research is needed to understand the underlying mechanisms and how they contribute to the development of neurodegenerative diseases.

In conclusion, tonic REM sleep muscle activity is a significant predictor of neurodegenerative disease in patients with isolated REM sleep behaviour disorder. The study by Singh et al. highlights the potential of using tonic REM sleep muscle activity as a biomarker for disease risk and the need for further investigation into the role of REM sleep in neurological disorders.

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