The loss of hypocretin (orexin) neurons is responsible for narcolepsy (see the top left box on the home page). Because the loss of these neurons causes narcolepsy, it has been assumed that they are active whenever animals are awake. This is incorrect. They are relatively inactive during sleep, but in waking they are not continuously active and are not simply related to EEG arousal. Rather they are maximally active during eating, exploration and grooming, i.e. pleasant states. They are inactive when the rat is recoiling from the first piece of chicken he has ever seen, but when he decides to eat the chicken the neuron becomes very active. This pleasure related activation is consistent with our work showing that the activity of these neurons is linked to opioid addiction (left side of home page (work by Thannickal et al., 2018 and MacGregor et al., 2023 in the lab, and others). In Blouin et al., 2013, also in the left column on the home page, we show that hypocretin release in humans is maximal during pleasure, including positive social interactions, but is minimal in pain, even if the pain is highly arousing, consistent with our neuronal recordings of hypocretin neurons in rats, release of hypocretin in dogs and humans and with the relation of these neurons to addiction.
Video and Audio
The platypus and short nosed echidna are monotremes, egg-laying mammals that have many characteristics of the reptilian predecessors of the mammals. Although originally thought to lack REM sleep, both species have aspects of this state, with the platypus actually having more REM sleep than any other mammal.
Video shows orca mother and calf at 4 weeks postpartum, at which point some sleep behavior has just begun to return in the mother. The neonate, circling and vocalizing, remains more active than the mother during this recording, as it does throughout development.
Informational piece about sleep research on marine mammals (cetaceans). Video produced by ScienCentral, supported by the National Science Foundation.
Video of untreated and of immunosuppressed narcoleptic dogs during food elicited cataplexy tests (FECTs) and the play behavior of the treated dogs.The first segment shows the administration of the FECT to three untreated narcoleptic littermate dogs, age 2.5 months. Dogs are labeled by shaved bands on their backs. Cataplexy is visible as a loss of muscle tone in the hind or fore limbs, drooping tail, sagging posture, wide stance, swaying, drooping eyelids, or interruption of eating caused by jaw hypotonia. The second segment shows the same test administered on the same day to the treated littermates of the dogs shown in the first segment. Little or no cataplexy is seen. Finally, the play segment, also filmed on the same day, shows that the lack of cataplexy in the treated animals is not accompanied by a behavioral depression. Play behavior is vigorous and normal.
see "Human sleep deprivation for 17 days: the Science Fair project of Randy Gardner" (right hand side of this page).