Budgerigars have complex sleep structure similar to that of mammals.

Birds and mammals share specialized forms of sleep including slow wave sleep (SWS) and rapid eye movement sleep (REM), raising the question of why and how specialized sleep evolved. Extensive prior studies concluded that avian sleep lacked many features characteristic of mammalian sleep, and therefore that specialized sleep must have evolved independently in birds and mammals. This has been challenged by evidence of more complex sleep in multiple songbird species. To extend this analysis beyond songbirds, we examined a species of parrot, the sister taxon to songbirds. We implanted adult budgerigars (Melopsittacus undulatus) with electroencephalogram (EEG) and electrooculogram (EOG) electrodes to evaluate sleep architecture, and video monitored birds during sleep. Sleep was scored with manual and automated techniques, including automated detection of slow waves and eye movements. This can help define a new standard for how to score sleep in birds. Budgerigars exhibited consolidated sleep, a pattern also observed in songbirds, and many mammalian species, including humans. We found that REM constituted 26.5% of total sleep, comparable to humans and an order of magnitude greater than previously reported. Although we observed no spindles, we found a clear state of intermediate sleep (IS) similar to non-REM (NREM) stage 2. Across the night, SWS decreased and REM increased, as observed in mammals and songbirds. Slow wave activity (SWA) fluctuated with a 29-min ultradian rhythm, indicating a tendency to move systematically through sleep states as observed in other species with consolidated sleep. These results are at variance with numerous older sleep studies, including for budgerigars. Here, we demonstrated that lighting conditions used in the prior budgerigar study-and commonly used in older bird studies-dramatically disrupted budgerigar sleep structure, explaining the prior results. Thus, it is likely that more complex sleep has been overlooked in a broad range of bird species. The similarities in sleep architecture observed in mammals, songbirds, and now budgerigars, alongside recent work in reptiles and basal birds, provide support for the hypothesis that a common amniote ancestor possessed the precursors that gave rise to REM and SWS at one or more loci in the parallel evolution of sleep in higher vertebrates. We discuss this hypothesis in terms of the common plan of forebrain organization shared by reptiles, birds, and mammals.

State-related changes in breathing. Are we missing sleep-disordered breathing syndromes in veterinary patients?

In recent decades, treatment of sleep disorders has developed rapidly. Prevalent and severe sleep disorders affecting respiration have been discovered in clinical sleep disorders centers. Although sleep studies are not currently, and may never become, a clinical tool for veterinarians, evidence from investigative work shows that dogs, at least, can suffer from "sleep-disordered breathing" syndromes similar to those affecting humans. The physiology and pathophysiology of sleep and breathing are strikingly similar in dogs and humans.

Macular disease in related rhesus monkeys.

During (January) 1986-(May) 1988, we examined 272 eyes in 136 rhesus monkeys in the closed Cayo Santiago colony of the Caribbean Primate Research Center of the University of Puerto Rico. Seventy-eight eyes were less than 10 years of age. One hundred and ninety-four were aged 10-28 years. The fundi were examined and photographed. Fluorescein angiography was performed in some eyes. Selected cases were evaluated for 'acuity' loss by recording of pattern-evoked retinal and cortical signals. Light and electron microscopy were used to evaluate the pigment epithelium of some animals. Thirty-eight percent of all eyes had posterior pole drusen. Incidence was highly age-related. When late-stage lesions were found, we did not see neovascularization, but late hyperfluorescence was consistent with degenerative scarring and atrophy. Electrophysiology demonstrated moderately reduced acuity in the presence of numerous macular drusen. Electrooculograms were low normal. Histopathology showed changes identical to those reported in human age-related macular degeneration. No eyes less than 10 years of age had confluent drusen or disciform-like lesions. The incidence of drusen in samples of some social groups was much higher than others.

New findings on sleep stage organization in squirrel monkeys.

The EEGs of 11 squirrel monkeys were studied during nocturnal sleep under conditions maintaining relative freedom of movement and minimal social intercourse. For the amount and partition of the different sleep stages, the present findings markedly differ from previous observations in experimental restrained conditions. Six sleep stages were defined by both EEG and spectral analysis criteria. Wakefulness, which occurred during the first period of the night, was more abundant (45%) and deep sleep (SIII) and REM sleep were less abundant (SIII: 5.1%; REM: 3.1%) in unrestrained squirrel monkeys. With predominant light sleep (85%), less abundant deep sleep and a REM sleep organization in short episodes, the sleep pattern in this New World monkey appeared fragmented and close to African monkey sleep.

Sleep pattern in the rook, Corvus frugilegus.

In the rook, Corvus frugilegus, electrographic and behavioural correlates of sleep and wakefulness have been determined under natural lighting conditions. Slow wave sleep (SWS) was characterized by high amplitude slow EEG activity, low neck EMG, and behavioural inactivity. Paradoxical sleep (PS) was characterized by low amplitude fast EEG activity and inconsistent decrease in EMG. PS episodes always commenced with head downward. Several eye movements occurred activity were present. The rook spent in sleep 31.8% of the 24-h period. PS however, eye movements, high tonic neck EMG activity, and behavioural activity were present. The rook spent in sleep 31.8% of the 24-h period. PS constituted 1.8% of total sleep, while the rest of total sleep was occupied by SWS. On the average, episodes of SWS and PS lasted 10.8 min and 24 s respectively. The daily percentage of SWS was highly correlated with the mean episode duration. PS amount was better correlated with the number of episodes than with their mean duration. Our data suggest that over-short period of recovery from surgery and adaptation with implanted electrodes could lead to underestimation of sleep duration in rook.

An electrophysiological and behavioral study of sleep in emperor penguins under natural ambient conditions.

In two pairs of emperor penguins surgically implanted for chronic recordings of EEG, EOG and EMG, four arousal stages were characterized on the basis of behavioral and electrophysiological criteria: wakefulness (W), drowsiness (D), slow-wave sleep (SWS) and paradoxical sleep (PS). The general patterns of electrographic correlates observed for each arousal stage resemble those reported in other birds. Sleep patterns were examined with these two pairs placed under natural ambient conditions of light and air temperature, the first pair being exposed to moderate cold under alternate conditions of day and night, and the second studied when daylight was total at thermoneutrality. The time spent in sleep (TST) by each group was 41.3% and 45.1% of the 24 hr period respectively, the difference not being significant. As in other birds, PS occurred in very brief episodes lasting, on average, 8 to 10 seconds and occupying only 5 to 6% of the 24 hr period. Whatever the external conditions, the PS to TST ratio appeared to remain unchanged (12 to 14%). Its relatively high value is discussed in relation to predation susceptibility.