Rem Sleep: Brain Regions Activated And Their Functions

The brain is highly active during sleep, and the activity is spatiotemporally organised. The brain's activity during sleep is not just a reflection of sleep states but also plays a role in controlling sleep state switching.

During REM sleep, the brain exhibits distinct global cortical dynamics and is controlled by the occipital cortex. The brain's activity during REM sleep is dominated by the activation of the occipital cortical network, especially the retrosplenial cortex.

REM sleep is characterised by:

- Low-amplitude synchronisation of fast oscillations in the cortical EEG

- Very low muscle tone (atonia) in the EMG

- Singlets and clusters of rapid eye movements (REM) in the EOG

- Myoclonic twitches, most apparent in the facial and distal limb musculature

- Pronounced fluctuations in cardio-respiratory rhythms and core body temperature

- Penile erection and clitoral tumescence

The brainstem, thalamus, basal forebrain, amygdala, and cerebellum are all involved in the regulation of sleep and wakefulness.

The brainstem, thalamus, and hypothalamus are involved in REM sleep

The brainstem, thalamus, and hypothalamus are involved in the regulation of REM sleep. The brainstem, specifically the pons, is responsible for the generation of muscle atonia during REM sleep. The thalamus sends and receives information from the senses to the cerebral cortex and is active during REM sleep. The hypothalamus contains groups of nerve cells that act as control centers affecting sleep and wakefulness.

The pons, medulla, and midbrain control the transitions between wake and sleep

The pons, medulla, and midbrain are all part of the brainstem, which controls the transitions between wake and sleep. The pons, in particular, plays a key role in REM sleep. It contains a substantial population of spinally projecting neurons that function to produce the muscle atonia of REM sleep. These neurons increase firing in anticipation of, and are maximally active in, REM sleep. They produce motor atonia by activating inhibitory interneurons in both the medulla and the spinal cord.

The thalamus and basal forebrain regulate REM sleep and wakefulness

The thalamus and basal forebrain are two of the many brain regions that regulate REM sleep and wakefulness. The thalamus is a peanut-sized structure deep inside the brain that contains groups of nerve cells that act as control centres affecting sleep and wakefulness. The thalamus sends and receives information from the senses to the cerebral cortex, and during most stages of sleep, the thalamus becomes quiet, allowing you to tune out the external world. However, during REM sleep, the thalamus is active, sending the cortex images, sounds, and other sensations that fill our dreams. The basal forebrain, near the front and bottom of the brain, also promotes sleep and wakefulness.

The amygdala is associated with REM sleep and emotional processing

The amygdala is a cluster of nuclei in the temporal lobes and parts of the limbic system. It is widely associated with the processing of affectively laden stimuli and plays an important role in the guidance of behavioural responses to such stimuli.

The amygdala is highly active during REM sleep, and its activity is correlated with autonomic responses to psychosocial stress. REM sleep is thought to serve to reorganise neural representations of emotional experiences by distributed reactivation of these representations in the amygdala, hippocampus, and neocortical structures, driven by synchronised theta oscillations between these regions and increased cholinergic activity. Together with reduced adrenergic neurotransmission during REM sleep, these processes allow for concomitant reductions of the affective arousal associated with the experiences.

The amygdala is also involved in the formation of emotional memories, and its activation during REM sleep has been shown to correlate with autonomic responses to psychosocial stress.

The prefrontal cortex is involved in REM sleep and dreaming

The prefrontal cortex is also involved in the loss of self-conscious awareness in sleep, which is most notable when awakening from a dream. The sudden switch from the self-absorbed awareness of dream reality to an awareness of waking is associated with the deactivation of the prefrontal cortex during REM sleep.

The prefrontal cortex is also implicated in the deficits in self-reflective awareness, orientation and memory during dreaming.

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