Hypocretin (Hcrt) neurons are found in the lateral hypothalamus and were first linked to sleep function due to a significant loss of Hcrt neurons in the brains of patients with narcolepsy [20,21] and low levels of Hcrt-1 in the cerebrospinal fluid (CSF) of narcoleptic patients [105]. Here, HCRT is linked to narcolepsy.