Before discussing specific types of sleep disorders, it is necessary to understand the aminergic and cholinergic model of sleep, a model that looks at alterations in levels of neurological activity during different stages of sleep. This model allows us to understand how sleep disorders deviate from normal sleep patterns.

Sleep is regulated by aminergic and cholinergic neurons:

• aminergic: inhibitory function; aminergic neurons are those containing amines such as seratonin, epinephrine, and norepinephrine
• cholinergic: excitatory function; neurons containing acetylcholine

Normal Sleep:

• In NREM (non-REM) sleep, the activity of the two types of neurons fluctuates, but maintains a constant equilibrium (Hobson 1989).
• During normal REM sleep, the activity of excitatory cholinergic receptors exceeds that of the inhibitory aminergic receptors (Hobson 1989).

A model of aminergic and cholinergic activity during different states of consciousness. During wakefulness, levels of amingergic and cholinergic activity are balanced and high. During NREM the levels of both hormones are balanced and low, but during REM sleep, cholinergic activity dominates. Source:http://www.sleephomepage.org/sleepsyllabus/fr-f.html

In Disorders:

• When the activity of aminergic neurons exceeds that of cholinergic, the resulting disorder is insomnia (inability to sleep) (Hobson 1989).
• Conversely, when the activity of cholinergic neurons exceeds aminergic neurons, the resulting disorder is hypersomnia (excessive sleepiness) (Hobson 1989).

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