Serotonin- producing neurons profusely innervate brain regions via long-range projections.

Narcolepsy is a chronic sleep disorder linked to the loss of orexin- producing neurons in the hypothalamus.

Recently the orexin- producing neurons have been proved to promote arousal and attention through their projections to the BF.

We found that melanin concentrating hormone- producing neurons (MCH neurons) in the hypothalamus actively contribute to forgetting in rapid eye movement (REM) sleep.