The sopite syndrome (/soʊˈpaɪt/; Latin: sopire, "to lay to rest, to put to sleep") is a neurological disorder that relates symptoms of fatigue, drowsiness, and mood changes to prolonged periods of motion. The sopite syndrome has been attributed to motion-induced drowsiness such as that experienced by a baby when rocked. Researchers Graybiel and Knepton first used the term "the sopite syndrome", in 1976, to refer to the sometimes sole manifestation of motion sickness, though other researchers have referred to it as "Sopite syndrome."