Neuroanatomy of Sleep

The major areas of the brain that promote sleep include:

· Ventrolateral Preoptic Area (VLPO)

· Basal forebrain

· Thalamus

· Reticular Nucleus of the Thalamus (RNT)

· Brainstem Raphe nuclei

· Solitary Tract Nucleus (in the medulla)

Ventrolateral Preoptic Area (VLPO)

· Uses GABA, Galanin

· Diffuse projections to inhibit activating areas

· Anterior hypothalamus

o Has projections to the Solitary Tract Nucleus (STN) and pontine parabrachial nuclei

· Orbitofrontal cortex

o Projects to the STN, VLPO, anterior hypothalamus and parabrachial nuclei

· Reticular Nucleus of the Thalamus (RTN) produces sleep spindles 12-14 Hz

· Fatal Familial Insomnia is related to degeneration of selective thalamic nuclei

· Dorsal Raphe Nuclei (DRN) in the brainstem contains serotonin

· Has complex interactions and appears to modulate both wakefulness and sleep

· Located in the medulla

· Receives sensory input from 9th & 10th cranial nerves

o Baroreceptors and chemoreceptors from the thoracic and abdominal viscera

· Neurotransmitter is unknown

· STN and dorsal medullary reticular formation Project to parabrachial nuclei in the rostral pons and midbrain

o Parabrachial nuclei Project to thalamus, hypothalamus, preoptic area, amygdala, orbitfrontal cortex

o STN also projects directly to all of these areas except the orbitofrontal cortex

References:

Kryger, Principles and Practice of Sleep Medicine, Elsevier 2005

Sleep Neurobiology for the Clinician. Espana and Scammell. Sleep 2004;27:811. (excellent review)

Hypocretins (orexins) and sleep-wake disorders. Lancet Neuro 2005; 4:673.