3.5.2 Sleep
The Neural Circuits Involved in Sleep, Arousal, Effects of Sleep Deprivation, Primary Sleep Disorders, and the Role of Sleep in Other Psychiatric Disorders
Sleep:
The neural circuits involved in sleep are complex and involve multiple brain regions and pathways. Some of the key brain regions involved in sleep include the hypothalamus, the thalamus, and the brainstem.
The hypothalamus is a region of the brain that plays a key role in the regulation of sleep. It contains several nuclei that are involved in the control of sleep, including the suprachiasmatic nucleus (SCN) and the ventrolateral preoptic nucleus (VLPO). The SCN is responsible for the generation of the sleep-wake cycle, while the VLPO is involved in the promotion of sleep.
The thalamus is a brain region that serves as a hub for information processing and communication between different brain regions. It plays a key role in the regulation of sleep by inhibiting arousal-promoting pathways and promoting sleep-promoting pathways.
The brainstem is the lower part of the brain that connects to the spinal cord. It contains several nuclei that are involved in the control of sleep, including the raphe nuclei and the locus coeruleus. These nuclei produce neurotransmitters that are involved in the promotion of sleep, such as serotonin and norepinephrine.
Overall, the neural circuits involved in sleep are complex and involve the interaction of multiple brain regions and pathways. Disruptions in these circuits can lead to sleep disorders such as insomnia (Saper, 2005).
Arousal:
Arousal is the state of being awake and alert, and it is regulated by several neural circuits in the brain. Some of the key brain regions involved in the regulation of arousal include the prefrontal cortex, the amygdala, and the brainstem.
Orexin is a neurotransmitter that is involved in the regulation of sleep and wakefulness. It is produced by a small group of neurons located in the lateral hypothalamus called the orexin neurons. Orexin plays a key role in the regulation of sleep by promoting wakefulness and inhibiting sleep. When orexin neurons are activated, they release orexin into the brain and stimulate arousal-promoting pathways, such as those that involve the neurotransmitter histamine. This results in increased alertness and wakefulness.
Conversely, when orexin neurons are inactive or inhibited, sleep-promoting pathways are activated, and sleep is more likely to occur. Orexin levels in the brain are highest during wakefulness and lowest during sleep, and this pattern is thought to be regulated by the sleep-wake cycle.
Overall, orexin is an important component of the neural circuits involved in sleep and wakefulness, and disruptions in its production or signalling have been linked to sleep disorders such as narcolepsy (Posner, 1990).
Effects of sleep deprivation:
Sleep deprivation can have a number of effects on neural circuits in the brain. Some of the key effects of sleep deprivation on neural circuits include:
| Effect of sleep deprivation: | Summary: |
| Impaired cognition and memory | Sleep deprivation can impair cognitive function, including attention, concentration, and decision-making. It can also disrupt the consolidation of memories and lead to difficulty in learning new information. These effects may be due to disruptions in neural circuits in the prefrontal cortex and hippocampus, which are important for these functions. |
| Altered emotional processing | Sleep deprivation can alter the way the brain processes emotions, leading to changes in mood and emotional reactivity. This may be due to disruptions in neural circuits in the amygdala and prefrontal cortex, which are involved in the regulation of emotions. |
| Decreased neuroplasticity | Sleep deprivation can impair neuroplasticity, which is the ability of the brain to reorganize and adapt in response to experience. This may be due to disruptions in neural circuits involved in learning and memory, such as those in the hippocampus and neocortex. |
| Increased inflammation | Sleep deprivation has been linked to increased inflammation in the brain, which may contribute to a range of negative health outcomes. This may be due to disruptions in neural circuits involved in the regulation of inflammation, such as those in the hypothalamus. |
(Banks, 2007)
Overall, sleep deprivation can have significant effects on neural circuits in the brain, leading to impairments in cognitive and emotional function and increasing the risk of negative health outcomes.
Primary sleep disorders:
Primary sleep disorders are a group of conditions that are characterized by disturbances in sleep patterns and quality. These conditions are thought to be due to disruptions in neural circuits in the brain that are involved in the regulation of sleep.
Some of the key neural circuits involved in primary sleep disorders include those in the hypothalamus, the thalamus, and the brainstem.
| Primary sleep disorder category: | Diagnosis: |
| Insomnia | Idiopathic insomnia Paradoxical insomnia |
| Parasomnias | Confusional arousals REM behaviour disorder Sleepwalking |
| Primary hypersomnias | Idiopathic hypersomnia Narcolepsy with cataplexy Narcolepsy without cataplexy Recurrent hypersomnia |
| Sleep-related breathing disorders | Cheyne-stokes respirations Central sleep apnea Obstructive sleep apnea Sleep-related hypoventilation |
| Sleep-related movement disorders | Periodic limb movement disorder Restless legs syndrome |
Role of sleep in other psychiatric disorders:
Sleep disturbances are common in many psychiatric disorders, and they can often be an important symptom of these conditions. Moreover, sleep disturbances can also have a negative impact on the course and outcome of psychiatric disorders.
For example, sleep disturbances have been linked to a range of negative outcomes in individuals with mood disorders, such as depression and bipolar disorder. Sleep disturbances can also exacerbate symptoms of anxiety disorders, such as generalized anxiety disorder and post-traumatic stress disorder (PTSD).
In addition, sleep disturbances may be a risk factor for the development of certain psychiatric disorders. For example, research has shown that individuals with chronic sleep problems are at increased risk for developing depression and anxiety.
Overall, the role of sleep in psychiatric disorders is complex and multifaceted. Further research is needed to fully understand the relationship between sleep and psychiatric disorders and to develop effective treatments for sleep disturbances in these conditions (Ohayon, 2003).
References:
(1) Banks, S., & Dinges, D. F. (2007). Behavioral and physiological consequences of sleep restriction. Journal of Clinical Sleep Medicine, 3(5), 519-528.
(2) Ohayon, M. M., & Roth, T. (2003). Place of chronic insomnia in the course of depressive and anxiety disorders. Journal of Psychiatric Research, 37(3), 9-15.
(3) Posner, M. I., & Petersen, S. E. (1990). The attention system of the human brain. Annual Review of Neuroscience, 13(1), 25-42.
(4) Saper, C. B., Lu, J., & Chou, T. C. (2005). The sleep switch: hypothalamic control of sleep and wakefulness. Nature Reviews Neuroscience, 6(1), 13-24.