ORCID Profile
0000-0001-5073-6954
Current Organisation
La Trobe University
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Ecology | Behavioural Ecology | Ecological Physiology | Animal Neurobiology | Biological Adaptation
Publisher: Wiley
Date: 04-06-2018
DOI: 10.1002/JEZ.2189
Publisher: Elsevier BV
Date: 06-2020
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 10-2007
Publisher: Oxford University Press (OUP)
Date: 07-03-2022
Abstract: Sleep is a prominent behavioral and biochemical state observed in all animals studied, including platyhelminth flatworms. Investigations into the biochemical mechanisms associated with sleep—and wakefulness—are important for understanding how these states are regulated and how that regulation changed with the evolution of new types of animals. Unfortunately, beyond a handful of vertebrates, such studies on invertebrates are rare. We investigated the effect of seven neurotransmitters, and one pharmacological compound, that modulate either sleep or wakefulness in mammals, on flatworms (Girardia tigrina). Flatworms were exposed via ingestion and diffusion to four neurotransmitters that promote wakefulness in vertebrates (acetylcholine, dopamine, glutamate, histamine), and three that induce sleep (adenosine, GABA, serotonin) along with the H1 histamine receptor antagonist pyrilamine. Compounds were administered over concentrations spanning three to five orders of magnitude. Flatworms were then transferred to fresh water and video recorded for analysis. Dopamine and histamine decreased the time spent inactive and increased distance traveled, consistent with their wake-promoting effect in vertebrates and fruit flies pyrilamine increased restfulness and GABA showed a nonsignificant trend towards promoting restfulness in a dose-dependent manner, in agreement with their sleep-inducing effect in vertebrates, fruit flies, and Hydra. Similar to Hydra, acetylcholine, glutamate, and serotonin, but also adenosine, had no apparent effect on flatworm behavior. These data demonstrate the potential of neurotransmitters to regulate sleep and wakefulness in flatworms and highlight the conserved action of some neurotransmitters across species.
Publisher: SAGE Publications
Date: 24-01-2023
DOI: 10.1177/07487304231158947
Abstract: The ability of flatworms to regenerate entire brain structures, and indeed much of their body from mere fragments of the whole animal, presents the unique opportunity to observe the development of day-night rhythms in adult animals. In many animals, young are arrhythmic, and their species-specific timing of activity develops as the animal matures. In this study, we created two flatworm cohorts, housed in isolation, that were regenerating either (1) the brain in a decapitated animal, or (2) major body structures in a bisected, tailless animal. In this way, we observed how bisection influenced the level of activity and diel rhythmicity, and how these developed as each flatworm regenerated. Here, we demonstrate that intact flatworms were predominantly active at night, with peaks in activity seen in the hours after lights-off and before lights-on. While decapitated and tailless flatworms could still move, both were less active than the original animal, and both segments retained a nocturnal lifestyle. Furthermore, decapitated flatworms, once regenerated, again showed a U-shaped pattern of nocturnal activity reminiscent of the two night-time peaks seen in the original animal. These results could be used to further investigate how regeneration may affect motor control and motor output, or to further investigate the presence of a clock in the flatworm brain.
Publisher: Elsevier
Date: 2009
Publisher: Wiley
Date: 04-11-2005
Publisher: The Royal Society
Date: 05-01-2011
Abstract: The function of the brain activity that defines slow wave sleep (SWS) and rapid eye movement (REM) sleep in mammals is unknown. During SWS, the level of electroencephalogram slow wave activity (SWA or 0.5–4.5 Hz power density) increases and decreases as a function of prior time spent awake and asleep, respectively. Such dynamics occur in response to waking brain use, as SWA increases locally in brain regions used more extensively during prior wakefulness. Thus, SWA is thought to reflect homeostatically regulated processes potentially tied to maintaining optimal brain functioning. Interestingly, birds also engage in SWS and REM sleep, a similarity that arose via convergent evolution, as sleeping reptiles and hibians do not show similar brain activity. Although birds deprived of sleep show global increases in SWA during subsequent sleep, it is unclear whether avian sleep is likewise regulated locally. Here, we provide, to our knowledge, the first electrophysiological evidence for local sleep homeostasis in the avian brain. After staying awake watching David Attenborough's The Life of Birds with only one eye, SWA and the slope of slow waves (a purported marker of synaptic strength) increased only in the hyperpallium—a primary visual processing region—neurologically connected to the stimulated eye. Asymmetries were specific to the hyperpallium, as the non-visual mesopallium showed a symmetric increase in SWA and wave slope. Thus, hypotheses for the function of mammalian SWS that rely on local sleep homeostasis may apply also to birds.
Publisher: S. Karger AG
Date: 2020
DOI: 10.1159/000504123
Abstract: Sleep is widespread across the animal kingdom. However, most comparative sleep data exist for terrestrial vertebrates, with much less known about sleep in hibians, bony fishes, and invertebrates. There is an absence of knowledge on sleep in cartilaginous fishes. Sharks and rays are amongst the earliest vertebrates, and may hold clues to the evolutionary history of sleep and sleep states found in more derived animals, such as mammals and birds. Here, we review the literature concerning activity patterns, sleep behaviour, and electrophysiological evidence for sleep in cartilaginous (and bony) fishes following an exhaustive literature search that found more than 80 relevant studies in laboratory and field environments. Evidence for sleep in sharks and rays that respire without swimming is preliminary evidence for sleep in continuously swimming fishes is currently absent. We discuss ways in which the latter group might sleep concurrent with sustained movement, and conclude with suggestions for future studies in order to provide more comprehensive data on when, how, and why sharks and rays sleep.
Publisher: Springer Science and Business Media LLC
Date: 22-04-2022
DOI: 10.1038/S41598-022-10162-7
Abstract: Sleep maintains optimal brain functioning to facilitate behavioural flexibility while awake. Owing to a historical bias towards research on mammals, we know comparatively little about the role of sleep in facilitating the cognitive abilities of birds. We investigated how sleep deprivation over the full-night (12 h) or half-night (6 h) affects cognitive performance in adult Australian magpies ( Cracticus tibicen ), relative to that after a night of undisturbed sleep. Each condition was preceded and followed by a baseline and recovery night of sleep, respectively. Prior to each treatment, birds were trained on an associative learning task on the day after experimental treatment (recovery day), birds were tested on a reversal learning task. To glean whether sleep loss affected song output, we also conducted impromptu song recordings for three days. Ultimately, sleep-deprived magpies were slower to attempt the reversal learning task, less likely to perform and complete the task, and those that did the test performed worse than better-rested birds. We also found that sleep-deprived magpies sang longer yet fewer songs, shifted crepuscular singing to mid-day, and during the post-recovery day, song frequency bandwidth narrowed. These results collectively indicate that sleep loss impairs motivation and cognitive performance, and alters song output, in a social adult songbird.
Publisher: Springer Science and Business Media LLC
Date: 28-04-2023
DOI: 10.1007/S00265-023-03326-6
Abstract: The string-pulling paradigm is an approach commonly used in the study of animal cognition to investigate problem-solving abilities. This test involves an out-of-reach reward that can only be acquired through pulling a string. Australian magpies ( Gymnorhina tibicen tyrannica ) can solve cognitive tasks requiring associative and reversal learning, spatial memory, and inhibitory control. Nonetheless, whether magpies can pass a test of means-end understanding—the string-pull test—is unclear. We tested wild magpies on a string-pulling task with five configurations, including a long loose string that required several pulls to obtain food, a short string that only required a single pull to complete, and two short strings—one intact and connected to the food reward the other broken and unable to yield food when pulled. Of the 11 magpies tested, none solved the long string task at first presentation. Two naïve birds and three, subsequently trained, birds succeeded at the short string. Once proficient at the short string, four of these five birds then solved the long string task in addition, three learned to choose a functional, intact string over a non-functional, broken string. Overall, these observations provide evidence that Australian magpies have the ability to solve string-pulling tasks but it remains unclear whether they do so by trial-and-error or if they possess means-end understanding. We found, for the first time, that wild, free-ranging Australian magpies can learn to solve different versions of a string-pulling task a version with a short string, a long string, and two strings next to each other where one of them was broken and non-functional (broken string task). Some magpies spontaneously solved the task with the short string, where other magpies required training, and magpies only managed to solve the task with the long string after they had succeeded on the short string task. Furthermore, some of the magpies solved the broken string task but required a high number of trials to do so. Overall, our findings show that Australian magpies have the ability to solve string-pulling tasks but it remains unclear whether they do so by trial-and-error or if they understand causal relations between objects.
Publisher: Elsevier BV
Date: 12-2020
Publisher: Oxford University Press (OUP)
Date: 24-05-2018
DOI: 10.1093/SLEEP/ZSY105
Abstract: The changes in electroencephalogram (EEG) activity that characterize sleep and its sub-states-slow-wave sleep (SWS) and rapid eye movement (REM) sleep-are similar in mammals and birds. SWS is characterized by EEG slow waves resulting from the synchronous alternation of neuronal membrane potentials between hyperpolarized down-states with neuronal quiescence and depolarized up-states associated with action potentials. By contrast, studies of non-avian reptiles report the presence of high-voltage sharp waves (HShW) during sleep. How HShW relate to EEG phenomena occurring during mammalian and avian sleep is unclear. We investigated the spatiotemporal patterns of electrophysiological phenomena in Nile crocodiles (Crocodylus niloticus) anesthetized with isoflurane to determine whether they share similar spatiotemporal patterns to mammalian and avian slow waves. Recordings of anesthetized crocodiles were made using 64-channel penetrating arrays with electrodes arranged in an 8 × 8 equally spaced grid. The arrays were placed in the dorsal ventricular ridge (DVR), a region implicated in the genesis of HShW. Various aspects of the spatiotemporal distribution of recorded signals were investigated. Recorded signals revealed the presence of HShW resembling those reported in earlier studies of naturally sleeping reptiles. HShW propagated in complex and variable patterns across the DVR. We demonstrate that HShW within the DVR propagate in complex patterns similar to those observed for avian slow waves recorded from homologous brain regions. Consequently, sleep with HShW may represent an ancestral form of SWS, characterized by up-states occurring less often and for a shorter duration than in mammals and birds.
Publisher: The Company of Biologists
Date: 10-05-0010
DOI: 10.1242/BIO.012179
Abstract: What is the most humane way to kill hibians and small reptiles that are used in research? Historically, such animals were often killed by cooling followed by freezing, but this method was outlawed by ethics committees because of concerns that ice-crystals may form in peripheral tissues while the animal is still conscious, putatively causing intense pain. This argument relies on assumptions about the capacity of such animals to feel pain, the thermal thresholds for tissue freezing, the temperature-dependence of nerve-impulse transmission and brain activity, and the magnitude of thermal differentials within the bodies of rapidly-cooling animals. A review of published studies casts doubt on those assumptions, and our laboratory experiments on cane toads (Rhinella marina) show that brain activity declines smoothly during freezing, with no indication of pain perception. Thus, cooling followed by freezing can offer a humane method of killing cane toads, and may be widely applicable to other ectotherms (especially, small species that are rarely active at low body temperatures). More generally, many animal-ethics regulations have little empirical basis, and research on this topic is urgently required in order to reduce animal suffering.
Publisher: Frontiers Media SA
Date: 27-11-2018
Publisher: SAGE Publications
Date: 09-05-2012
Abstract: In most animals, sleep is considered a global brain and behavioral state. However, recent intracortical recordings have shown that aspects of non–rapid eye movement (NREM) sleep and wakefulness can occur simultaneously in different parts of the cortex in mammals, including humans. Paradoxically, however, NREM sleep still manifests as a global behavioral shutdown. In this review, the authors examine this paradox from an evolutionary perspective. On the basis of strategic modeling, they suggest that in animals with brains composed of heavily interconnected and functionally interdependent units, a global regulator of sleep maintains the behavioral shutdown that defines sleep and thereby ensures that local use-dependent functions are performed in a safe and efficient manner. This novel perspective has implications for understanding deficits in human cognitive performance resulting from sleep deprivation, sleep disorders such as sleepwalking, changes in consciousness that occur during sleep, and the function of sleep itself.
Publisher: Springer Science and Business Media LLC
Date: 11-03-2023
DOI: 10.1007/S00360-023-01480-X
Abstract: The behaviors that characterize sleep have been observed across a broad range of different species. While much attention has been placed on vertebrates (mostly mammals and birds), the grand ersity of invertebrates has gone largely unexplored. Here, we introduce the intrigue and special value in the study of sleeping platyhelminth flatworms. Flatworms are closely related to annelids and mollusks, and yet are comparatively simple. They lack a circulatory system, respiratory system, endocrine glands, a coelom, and an anus. They retain a central and peripheral nervous system, various sensory systems, and an ability to learn. Flatworms sleep, like other animals, a state which is regulated by prior sleep/wake history and by the neurotransmitter GABA. Furthermore, they possess a remarkable ability to regenerate from a mere fragment of the original animal. The regenerative capabilities of flatworms make them a unique bilaterally symmetric animal to study a link between sleep and neurodevelopment. Lastly, the recent applications of tools for probing the flatworm genome, metabolism, and brain activity make their entrance into the field of sleep research all the more timely.
Publisher: Frontiers Media SA
Date: 19-05-2020
Publisher: Elsevier BV
Date: 06-2022
Publisher: Elsevier
Date: 2019
Publisher: S. Karger AG
Date: 2017
DOI: 10.1159/000475590
Abstract: The functions of slow wave sleep (SWS) and rapid eye movement (REM) sleep, distinct sleep substates present in both mammals and birds, remain unresolved. One approach to gaining insight into their function is to trace the evolution of these states through examining sleep in as many taxonomic groups as possible. The mammalian and avian clades are each composed of two extant groups, i.e., the monotremes (echidna and platypus) and therian (marsupial and eutherian [or placental]) mammals, and Palaeognaths (cassowaries, emus, kiwi, ostriches, rheas, and tinamous) and Neognaths (all other birds) among birds. Previous electrophysiological studies of monotremes and ostriches have identified a unique “mixed” sleep state combining features of SWS and REM sleep unlike the well-delineated sleep states observed in all therian mammals and Neognath birds. In the platypus this state is characterized by periods of REM sleep-related myoclonic twitching, relaxed skeletal musculature, and rapid eye movements, occurring in conjunction with SWS-related slow waves in the forebrain electroencephalogram (EEG). A similar mixed state was also observed in ostriches although in addition to occurring during periods with EEG slow waves, reduced muscle tone and rapid eye movements also occurred in conjunction with EEG activation, a pattern typical of REM sleep in Neognath birds. Collectively, these studies suggested that REM sleep occurring exclusively as an integrated state with forebrain activation might have evolved independently in the therian and Neognath lineages. To test this hypothesis, we examined sleep in the elegant crested tinamou ( i Eudromia elegans /i ), a small Palaeognath bird that more closely resembles Neognath birds in size and their ability to fly. A 24-h period was scored for sleep state based on electrophysiology and behavior. Unlike ostriches, but like all of the Neognath birds examined, all indicators of REM sleep usually occurred in conjunction with forebrain activation in tinamous. The absence of a mixed REM sleep state in tinamous calls into question the idea that this state is primitive among Palaeognath birds and therefore birds in general.
Publisher: Wiley
Date: 19-03-2008
DOI: 10.1111/J.1365-2869.2008.00636.X
Abstract: Birds provide a unique opportunity to evaluate current theories for the function of sleep. Like mammalian sleep, avian sleep is composed of two states, slow-wave sleep (SWS) and rapid eye-movement (REM) sleep that apparently evolved independently in mammals and birds. Despite this resemblance, however, it has been unclear whether avian SWS shows a compensatory response to sleep loss (i.e., homeostatic regulation), a fundamental aspect of mammalian sleep potentially linked to the function of SWS. Here, we prevented pigeons (Columba livia) from taking their normal naps during the last 8 h of the day. Although time spent in SWS did not change significantly following short-term sleep deprivation, electroencephalogram (EEG) slow-wave activity (SWA i.e., 0.78-2.34 Hz power density) during SWS increased significantly during the first 3 h of the recovery night when compared with the undisturbed night, and progressively declined thereafter in a manner comparable to that observed in similarly sleep-deprived mammals. SWA was also elevated during REM sleep on the recovery night, a response that might reflect increased SWS pressure and the concomitant 'spill-over' of SWS-related EEG activity into short episodes of REM sleep. As in rodents, power density during SWS also increased in higher frequencies (9-25 Hz) in response to short-term sleep deprivation. Finally, time spent in REM sleep increased following sleep deprivation. The mammalian-like increase in EEG spectral power density across both low and high frequencies, and the increase in time spent in REM sleep following sleep deprivation suggest that some aspects of avian and mammalian sleep are regulated in a similar manner.
Publisher: MDPI AG
Date: 28-01-2021
DOI: 10.3390/CLOCKSSLEEP3010008
Abstract: Sleep has a multitude of benefits and is generally considered necessary for optimal performance. Disruption of sleep by extended photoperiods, moonlight and artificial light could therefore impair performance in humans and non-human animals alike. Here, we review the evidence for effects of light on sleep and subsequent performance in birds. There is accumulating evidence that exposure to natural and artificial sources of light regulates and suppresses sleep in diurnal birds. Sleep also benefits avian cognitive performance, including during early development. Nevertheless, multiple studies suggest that light can prolong wakefulness in birds without impairing performance. Although there is still limited research on this topic, these results raise intriguing questions about the adaptive value of sleep. Further research into the links between light, sleep and performance, including the underlying mechanisms and consequences for fitness, could shed new light on sleep evolution and urban ecology.
Publisher: Elsevier BV
Date: 06-2008
DOI: 10.1016/J.SMRV.2007.10.003
Abstract: The correlates of mammalian sleep have been investigated previously in at least eight comparative studies in an effort to illuminate the functions of sleep. However, all of these univariate analyses treated each species, or taxonomic Family, as a statistically independent unit, which is invalid due to the phylogenetic relationships among species. Here, we reassess these influential correlates of mammalian sleep using the formal phylogenetic framework of independent contrasts. After controlling for phylogeny using this procedure, the interpretation of many of the correlates changed. For instance, and contrary to previous studies, we found interspecific support for a neurophysiological role for rapid-eye-movement sleep, such as memory consolidation. Also in contrast to previous studies, we did not find comparative support for an energy conservation function for slow-wave sleep. Thus, the incorporation of a phylogenetic control into comparative analyses of sleep yields meaningful differences that affect our understanding of why we sleep.
Publisher: Elsevier BV
Date: 06-2022
DOI: 10.1016/J.CUB.2022.04.004
Abstract: Energy derived from food is a precious resource to animals. Those finite calories are often well-earned through exhaustive foraging effort, which can dominate waking hours, to support physiological processes (e.g. body maintenance and growth) and ecological necessities (e.g. predator avoidance and courting) that are pertinent to the production of progeny. So, it is unsurprising to find that animals have evolved strategies to guard against the gratuitous waste of hard-won caloric energy. Yet, it remains surprising to find such ersity, and elegant creativity, in those solutions. Brief ex les of energy-saving innovation could include the very shape of animals and how they move, from streamlined swimming sharks to skyward-soaring seabirds or the evolutionary appearance of various states of dormancy, such as endothermic animals sacrificing high body temperature through modest (torpor) or severe (hibernation) curtailments to metabolic heat production. Another reversibly dormant state with energetic benefits is sleep.
Publisher: Elsevier
Date: 2009
Publisher: Elsevier BV
Date: 06-2008
DOI: 10.1016/J.BBR.2008.01.006
Abstract: Sleep is a prominent behaviour in the lives of animals, but the unresponsiveness that characterizes sleep makes it dangerous. Mammalian sleep is composed of two neurophysiological states: slow wave sleep (SWS) and rapid-eye-movement (REM) sleep. Given that the intensity of stimuli required to induce an arousal to wakefulness is highest during deep SWS or REM sleep, mammals may be most vulnerable during these states. If true, then animals should selectively reduce deep SWS and REM sleep following an increase in the risk of predation. To test this prediction, we simulated a predatory encounter with 10 wild-caught Norway rats (Rattus norvegicus), which are perhaps more likely to exhibit natural anti-predator responses than laboratory strains. Immediately following the encounter, rats spent more time awake and less time in SWS and REM sleep. The reduction of SWS was due to the shorter duration of SWS episodes, whereas the reduction of REM sleep was due to a lower number of REM sleep episodes. The onset of SWS and REM sleep was delayed post-encounter by about 20 and 100 min, respectively. The reduction of REM sleep was disproportionately large during the first quarter of the sleep phase, and slow wave activity (SWA) (0.5-4.5 Hz power density) was lower during the first 10 min of SWS post-encounter. An increase in SWA and REM sleep was observed later in the sleep phase, which may reflect sleep homeostasis. These results suggest that aspects of sleep architecture can be adjusted to the prevailing risk of predation.
Publisher: The Company of Biologists
Date: 10-2015
DOI: 10.1242/JEB.127605
Abstract: Reduced vigilance is the conspicuous cost of sleep in most animals. To mitigate against this cost, some birds and aquatic mammals have evolved the ability to sleep with one-half of their brain at a time, a phenomenon known as unihemispheric sleep. During unihemispheric sleep the eye neurologically connected to the ‘awake’ hemisphere remains open while the other eye is closed. Such unilateral eye closure (UEC) has been observed across avian and non-avian reptiles, but has received little attention in the latter. Here, we explored the use of UEC in juvenile saltwater crocodiles (1) under baseline conditions, and in the presence of (2) other young crocodiles and (3) a human. Crocodiles increased the amount of UEC in response to the human, and preferentially oriented their open eye towards both stimuli. These results are consistent with observations on unihemispherically sleeping cetaceans and birds, and could have implications for our understanding of the evolution of unihemispheric sleep.
Publisher: Wiley
Date: 14-02-2006
Publisher: Oxford University Press (OUP)
Date: 2022
DOI: 10.1093/SLEEPADVANCES/ZPAC036
Abstract: Sleep serves many important functions. And yet, emerging studies over the last decade indicate that some species routinely sleep little, or can temporarily restrict their sleep to low levels, seemingly without cost. Taken together, these systems challenge the prevalent view of sleep as an essential state on which waking performance depends. Here, we review erse case-studies, including elephant matriarchs, post-partum cetaceans, seawater sleeping fur seals, soaring seabirds, birds breeding in the high Arctic, captive cavefish, and sexually aroused fruit flies. We evaluate the likelihood of mechanisms that might allow more sleep than is presently appreciated. But even then, it appears these species are indeed performing well on little sleep. The costs, if any, remain unclear. Either these species have evolved a (yet undescribed) ability to supplant sleep needs, or they endure a (yet undescribed) cost. In both cases, there is urgent need for the study of non-traditional species so we can fully appreciate the extent, causes, and consequences of ecological sleep loss.
Publisher: Wiley
Date: 17-11-2006
DOI: 10.1111/J.1365-2869.2006.00559.X
Abstract: Quantitative comparative studies of sleep have focused exclusively on mammals. Such studies have repeatedly found strong relationships between the time spent in various sleep states and constitutive variables related to morphology, physiology, and life history. These studies influenced the development of several prominent hypotheses for the functions of sleep, but the applicability of these patterns and hypotheses to non-mammalian taxa is unclear. Here, we present the first quantitative analysis of sleep in a non-mammalian taxon (birds), focusing on the daily amount of time spent in slow-wave sleep (SWS) and rapid-eye movement (REM) sleep as determined by electrophysiological methods. We examined the relationships between constitutive and sleep variables in 23 avian species following earlier studies in mammals, but also considered an index of exposure to predators while asleep and controlled for shared evolutionary history among taxa. Overall, our results were very different from those obtained for mammals. Most remarkably, the relationships between both SWS time and REM sleep time and all constitutive variables were very weak and markedly non-significant, even though we had adequate power to detect correlations typical of the mammalian data. Only an index of exposure to predation during sleep was significantly related to sleep time, which is the only result common to both birds and mammals. Our results suggest that further insight into the function(s) of sleep across the animal kingdom may require an expansion of sleep research beyond the current mammalian paradigm.
Publisher: Elsevier BV
Date: 03-2009
DOI: 10.1016/J.NEUBIOREV.2008.08.010
Abstract: Birds are the only taxonomic group other than mammals that exhibit high- litude slow-waves in the electroencephalogram (EEG) during sleep. This defining feature of slow-wave sleep (SWS) apparently evolved independently in mammals and birds, as reptiles do not exhibit similar EEG activity during sleep. In mammals, the level of slow-wave activity (SWA) (low-frequency spectral power density) during SWS increases and decreases as a function of prior time spent awake and asleep, respectively, and therefore reflects homeostatically regulated sleep processes potentially tied to the function of SWS. Although birds also exhibit SWS, previous sleep deprivation studies in birds did not detect a compensatory increase in SWS-related SWA during recovery, as observed in similarly sleep-deprived mammals. This suggested that, unlike mammalian SWS, avian SWS is not homeostatically regulated, and therefore might serve a different function. However, we recently demonstrated that SWA during SWS increases in pigeons following short-term sleep deprivation. Herein we summarize research on avian sleep homeostasis, and cast our evidence for this phenomenon within the context of theories for the function of SWS in mammals. We propose that the convergent evolution of homeostatically regulated SWS in mammals and birds was directly linked to the convergent evolution of large, heavily interconnected brains capable of performing complex cognitive processes in each group. Specifically, as has been proposed for mammals, the interconnectivity that forms the basis of complex cognition in birds may also instantiate slow, synchronous network oscillations during SWS that in turn maintain interconnectivity and cognition at an optimal level.
Publisher: Public Library of Science (PLoS)
Date: 24-08-2011
Publisher: SAGE Publications
Date: 27-04-2022
DOI: 10.1177/02698811221089039
Abstract: The BALB/c mouse has been proposed as a model of human psychiatric disorders characterised by elevated anxiety and altered sociability. Juvenile BALB/c mice show decreased social exploratory behaviour, increased anxiety, and reduced brain serotonin synthesis compared to other strains including C57BL/6J mice. To determine whether supplementation of brain serotonin synthesis alters social behaviour and activation of serotonergic neurons across subregions of the dorsal raphe nucleus (DR) in BALB/c mice. Juvenile male BALB/c mice were assigned to one of four treatment conditions: vehicle/vehicle, carbidopa (25 mg/kg)/vehicle, vehicle/5-HTP (10 mg/kg), carbidopa (25 mg/kg)/5-HTP (10 mg/kg). Social behaviour was measured using the three-chamber social approach test, followed by immunohistochemical staining for TPH2 and c-Fos to measure activation of serotonergic neurons across subregions of the DR. Mice treated with carbidopa/5-HTP spent more time in the social cage zone and covered more distance in the social approach test compared to other treatment groups. There was no difference between treatment groups in the activation of serotonergic neurons across subregions of the DR. However, the DRD was associated with increased social approach behaviour in carbidopa/5-HTP treated animals. Supplementation of serotonin synthesis can increase social approach behaviour in juvenile BALB/c mice. An increase in locomotor behaviour was also observed suggesting that increasing central serotonin synthesis may have led to a reduction in state anxiety, manifesting in increased exploratory behaviour. As no effect on serotonergic activation within the DR was found, alternative mechanisms are likely important for the effects of 5-HTP on social behaviour.
Publisher: Oxford University Press (OUP)
Date: 14-05-2022
Abstract: In this study, we (1) describe sleep behavior and architecture, and (2) explore how sleep is regulated in dusky antechinus (Antechinus swainsonii), a small insectivorous marsupial. Our aim is to provide the first investigation into sleep homeostasis in a marsupial. Wild-caught male dusky antechinus (n = 4) were in idually housed in large indoor cages under a natural photoperiod of 10.5 h light/13.5 h dark. Continuous recordings of EEG, EMG, and tri-axial accelerometry were performed under baseline conditions and following 4-h of extended wakefulness. Antechinus engage in SWS and REM sleep. Some aspects of these states are mammal-like, including a high amount (23%) of REM sleep, but other features are reminiscent of birds, notably, hundreds of short sleep episodes (SWS mean: 34 s REM sleep: 10 s). Antechinus are cathemeral and sleep equally during the night and day. Immediately after the sleep deprivation ended, the animals engaged in more SWS, longer SWS episodes, and greater SWS SWA. The animals did not recover lost REM sleep. Sleep architecture in dusky antechinus was broadly similar to that observed in eutherian and marsupial mammals, but with interesting peculiarities. We also provided the first evidence of SWS homeostasis in a marsupial mammal.
Publisher: The Royal Society
Date: 12-09-2012
Abstract: Signal plasticity is considered an important step in the evolution of animal communication. In acoustic communication, signal transmission is often constrained by background noise. One adaptation to evade acoustic signal masking is the Lombard effect, in which an animal increases its vocal litude in response to an increase in background noise. This form of signal plasticity has been found in mammals, including humans, and some birds, but not frogs. However, the evolution of the Lombard effect is still unclear. Here we demonstrate for the first time the Lombard effect in a phylogentically basal bird species, the tinamou Eudromia elegans . By doing so, we take a step towards reconstructing the evolutionary history of noise-dependent vocal plasticity in birds. Similar to humans, the tinamous also raised their vocal pitch in noise, irrespective of any release from signal masking. The occurrence of the Lombard effect in a basal bird group suggests that this form of vocal plasticity was present in the common ancestor of all living birds and thus evolved at least as early as 119 Ma.
Publisher: SAGE Publications
Date: 10-05-2019
Abstract: Sharks are an interesting group of vertebrates, as many species swim continuously to “ram” oxygen-rich seawater over their gills (ram ventilators), whereas other species “pump” seawater over their gills by manipulating buccal cavity volume while remaining motionless (buccal pumpers). This difference in respiratory physiology raises the question: What are the implications of these differences in lifestyle for circadian rhythms? We investigated the diel activity patterns of 5 species of sharks, including 3 ram ventilating species: the school shark ( Galeorhinus galeus), the spotted estuary smooth-hound ( Mustelus lenticulatus), and the spiny dogfish ( Squalus acanthias) and 2 buccal pumping species: the Port Jackson ( Heterodontus portusjacksoni) and draughtsboard ( Cephaloscyllium isabellum) sharks. We measured the amount, duration, and distance traveled while swimming over multiple days under a 12:12 light:dark light regime for all species and used modified light regimes for species with a clear diel rhythm in activity. We identified a surprising ersity of activity rhythms. The school shark and smooth-hound swam continuously however, whereas the school shark swam at the same speed and covered the same distance during the day and night, the smooth-hound swam slower at night and traversed a shorter distance. A similar pattern was observed in the spiny dogfish, although this shark swam less overall. Both the Port Jackson and draughtsboard sharks showed a marked nocturnal preference for swimming. This pattern was muted and disrupted during constant light and constant dark regimes, although circadian organization of this pattern was maintained under certain conditions. The consequences of these patterns for other biological processes, such as sleep, remain unclear. Nonetheless, these 5 species demonstrate remarkable ersity within the activity rhythms of sharks.
Publisher: Springer Science and Business Media LLC
Date: 28-02-2014
Publisher: American Association for the Advancement of Science (AAAS)
Date: 28-09-2012
Abstract: Sleep serves restorative and memory functions, but it does not always operate analogously across species. Deferral of sleep may be possible when selection strongly favors the awake. Lesku et al. (p. 1654 see the Perspective by Siegel ) show that sleep may be deferred without cost or impairment in pectoral sandpipers. These birds breed collectively in the high Arctic, and male competition is intense. Competing for, and displaying to, females are both physically and cognitively demanding, yet birds who slept the least showed no decrease in their ability to perform these activities. Indeed, those males who slept the least obtained the most matings and sired the most offspring.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 24-10-2008
Publisher: Springer Science and Business Media LLC
Date: 13-02-2019
DOI: 10.1038/S41598-019-38780-8
Abstract: Many ideas have been put forward for the adaptive value of the cassowary casque and yet, its purpose remains speculative. Homeothermic animals elevate body temperature through metabolic heat production. Heat gain must be offset by heat loss to maintain internal temperatures within a range for optimal performance. Living in a tropical climate, cassowaries, being large bodied, dark feathered birds, are under thermal pressure to offload heat. We tested the original hypothesis that the casque acts as a thermal window. With infrared thermographic analyses of living cassowaries over an expansive range of ambient temperatures, we provide evidence that the casque acts as a thermal radiator, offloading heat at high temperatures and restricting heat loss at low temperatures. Interestingly, at intermediate temperatures, the casque appears thermally heterogeneous, with the posterior of the casque heating up before the front half. These findings might have implications for the function of similar structures in avian and non-avian dinosaurs.
Publisher: Oxford University Press (OUP)
Date: 25-08-2021
Abstract: We explore non-rapid eye movement (NREM) and rapid eye movement (REM) sleep homeostasis in Australian magpies (Cracticus tibicen tyrannica). We predicted that magpies would recover lost sleep by spending more time in NREM and REM sleep, and by engaging in more intense NREM sleep as indicated by increased slow-wave activity (SWA). Continuous 72-h recordings of EEG, EMG, and tri-axial accelerometry, along with EEG spectral analyses, were performed on wild-caught Australian magpies housed in indoor aviaries. Australian magpies were subjected to two protocols of night-time sleep deprivation: full 12-h night (n = 8) and first 6-h half of the night (n = 5), which were preceded by a 36-h baseline recording and followed by a 24-h recovery period. Australian magpies recovered from lost NREM sleep by sleeping more, with increased NREM sleep consolidation, and increased SWA during recovery sleep. Following 12-h of night-time sleep loss, magpies also showed reduced SWA the following night after napping more during the recovery day. Surprisingly, the magpies did not recover any lost REM sleep. Only NREM sleep is homeostatically regulated in Australian magpies with the level of SWA reflecting prior sleep/wake history. The significance of emerging patterns on the apparent absence of REM sleep homeostasis, now observed in multiple species, remains unclear.
Publisher: Cambridge University Press
Date: 14-07-2011
Publisher: The Royal Society
Date: 09-10-2017
Abstract: Despite being a prominent aspect of animal life, sleep and its functions remain poorly understood. As with any biological process, the functions of sleep can only be fully understood when examined in the ecological context in which they evolved. Owing to technological constraints, until recently, sleep has primarily been examined in the artificial laboratory environment. However, new tools are enabling researchers to study sleep behaviour and neurophysiology in the wild. Here, we summarize the various methods that have enabled sleep researchers to go wild, their strengths and weaknesses, and the discoveries resulting from these first steps outside the laboratory. The initial studies to ‘go wild’ have revealed a wealth of interin idual variation in sleep, and shown that sleep duration is not even fixed within an in idual, but instead varies in response to an assortment of ecological demands. Determining the costs and benefits of this inter- and intrain idual variation in sleep may reveal clues to the functions of sleep. Perhaps the greatest surprise from these initial studies is that the reduction in neurobehavioural performance resulting from sleep loss demonstrated in the laboratory is not an obligatory outcome of reduced sleep in the wild. This article is part of the themed issue ‘Wild clocks: integrating chronobiology and ecology to understand timekeeping in free-living animals’.
Publisher: Frontiers Media SA
Date: 05-06-2209
Publisher: Elsevier BV
Date: 07-2009
DOI: 10.1016/J.NEUBIOREV.2009.04.002
Abstract: The comparative methods of evolutionary biology are a useful tool for investigating the functions of sleep. These techniques can help determine whether experimental results, derived from a single or few species, apply broadly across a specified group of animals. In this way, comparative analysis is a powerful complement to experimentation. The variation in the time mammalian species spend asleep has been most amenable for use with this approach, given the large number of mammals for which sleep data exist. Here, it is assumed that interspecific variation in the time spent asleep reflects underlying differences in the need for sleep. If true, then significant predictors of sleep times should provide insight into the function of sleep. Many such analyses have sought the evolutionary determinants of mammalian sleep by relating the time spent in the two basic states of sleep, rapid eye movement (REM) and non-REM sleep, to constitutive variables thought to be functionally related to sleep. However, the early analyses had several methodological problems, and recent re-analyses have overturned some widely accepted relationships, such as the idea that species with higher metabolic rates engage in more sleep. These more recent studies also provide evolutionarily broad support for a neurophysiological role for REM sleep. Furthermore, results from comparative analyses suggest that animals are particularly vulnerable to predation during REM sleep, a finding that lends further support to the notion that REM sleep must serve an important function. Here, we review the methodology and results of quantitative comparative studies of sleep. We highlight important developments in our understanding of the evolutionary determinants of sleep and emphasize relationships that address prevailing hypotheses for the functions of sleep. Lastly, we outline a possible future for comparative analyses, focusing on work in non-mammalian groups, the use of more physiologically meaningful variables, and electrophysiological sleep studies conducted in the wild.
Publisher: Elsevier BV
Date: 06-2023
Publisher: Frontiers Media SA
Date: 18-03-2019
Publisher: Brill
Date: 13-09-2022
DOI: 10.1163/1568539X-BJA10183
Abstract: We investigated tool use in twelve wild-caught Australian magpies. When presented with a tool use apparatus consisting of two transparent walls with a food reward placed in-between, seven magpies pulled the stick out of the apparatus acquiring the food within. On one occasion, one magpie manipulated the removed stick, carried it back to the apparatus, dropped it between the two walls and proceeded to rake out the food within reach of its beak. We believe this observation is important for the field of comparative cognition as it (1) is the first study to report stick tool use in Australian magpies, and (2) shows a novel behaviour in a ground foraging bird that, as far as we know, do not naturally use tools for food extraction. This study provides preliminary evidence that Australian magpies may be added to the list of bird species that can use tools.
Publisher: Elsevier BV
Date: 08-2019
DOI: 10.1016/J.CUB.2019.07.024
Abstract: Trade-offs shape animal behaviour. For decades, the study of trade-offs has provided insight into how animals make decisions, but they have rarely been explored in relation to sleep. A new study reveals a role for sleep in saving energy in garden warblers on a stopover during a northward migration, but with ecological costs.
Publisher: Elsevier BV
Date: 10-2017
DOI: 10.1016/J.CUB.2017.08.024
Abstract: What is the 'simplest' animal that sleeps? When did sleep first evolve? Do all animals sleep? Tantalizing hints to answers come from new research showing that jellyfish, one of the earliest evolving groups of animals, have a sleep-like restful state.
Publisher: The Royal Society
Date: 07-10-2015
Abstract: Change in day length is an important cue for reproductive activation in seasonally breeding animals to ensure that the timing of greatest maternal investment (e.g. lactation in mammals) coincides with favourable environmental conditions (e.g. peak productivity). However, artificial light at night has the potential to interfere with the perception of such natural cues. Following a 5-year study on two populations of wild marsupial mammals exposed to different night-time levels of anthropogenic light, we show that light pollution in urban environments masks seasonal changes in ambient light cues, suppressing melatonin levels and delaying births in the tammar wallaby. These results highlight a previously unappreciated relationship linking artificial light at night with induced changes in mammalian reproductive physiology, and the potential for larger-scale impacts at the population level.
Publisher: American Veterinary Medical Association (AVMA)
Date: 07-2019
Publisher: Springer Science and Business Media LLC
Date: 29-01-2022
DOI: 10.1007/S00455-021-10389-Y
Abstract: Dysphagia occurs commonly in the intensive care unit (ICU). Despite the clinical relevance, there is little worldwide research on prevention, assessment, evaluation, and/or treatment of dysphagia for ICU patients. We aimed to gain insight into this international knowledge gap. We conducted a multi-center, international online cross-sectional survey of adult ICUs. Local survey distribution ch ions were recruited through professional and personal networks. The survey was administered from November 2017 to June 2019 with three emails and a final telephone reminder. Responses were received from 746 ICUs (26 countries). In patients intubated > 48 h, 17% expected a > 50% chance that dysphagia would develop. This proportion increased to 43% in patients intubated > 7 days, and to 52% in tracheotomized patients. Speech-language pathologist (SLP) consultation was available in 66% of ICUs, only 4% reported a dedicated SLP. Although 66% considered a routine post-extubation dysphagia protocol important, most (67%) did not have a protocol. Few ICUs routinely assessed for dysphagia after 48 h of intubation (30%) or tracheostomy (41%). A large proportion (46%) used water swallow screening tests to determine aspiration, few (8%) used instrumental assessments (i.e., flexible endoscopic evaluation of swallowing). Swallowing exercises were used for dysphagia management by 30% of ICUs. There seems to be limited awareness among ICU practitioners that patients are at risk of dysphagia, particularly as ventilation persists, protocols, routine assessment, and instrumental assessments are generally not used. We recommend the development of a research agenda to increase the quality of evidence and ameliorate the implementation of evidence-based dysphagia protocols by dedicated SLPs.
Publisher: The Company of Biologists
Date: 10-2018
DOI: 10.1242/JEB.182634
Abstract: Sleep in birds is composed of two distinct sub-states, remarkably similar to mammalian slow-wave sleep (SWS) and rapid eye movement (REM) sleep. However, it is unclear whether all aspects of mammalian sleep are present in birds. We examined whether birds suppress REM sleep in response to changes in sleeping conditions that presumably evoke an increase in perceived predation risk, as observed previously in rodents. Although pigeons sometimes sleep on the ground, they prefer to sleep on elevated perches at night, probably to avoid nocturnal mammalian ground predators. Few studies to date have investigated how roosting sites affect sleep architecture. We compared sleep in captive pigeons on days with and without access to high perches. On the first (baseline) day, low and high perches were available on the second day, the high perches were removed and on the third (recovery) day, the high perches were returned. The total time spent sleeping did not vary significantly between conditions however, the time spent in REM sleep declined on the low-perch night and increased above baseline when the pigeons slept on the high perch during the recovery night. Although the amount of SWS did not vary significantly between conditions, SWS intensity was lower on the low-perch night, particularly early in the night. The similarity of these responses between birds and mammals suggests that REM sleep is influenced by at least some ecological factors in a similar manner in both groups of animals.
Publisher: Elsevier BV
Date: 2022
DOI: 10.2139/SSRN.4255603
Publisher: Oxford University Press (OUP)
Date: 19-01-2018
Publisher: Wiley
Date: 16-07-2020
DOI: 10.1111/JSR.13139
Publisher: Oxford University Press (OUP)
Date: 24-08-2017
DOI: 10.1093/SLEEP/ZSX124
Abstract: Sleep either appeared once early in the evolution of animals, or at multiple instances over evolutionary time. Understanding whether sleep is a diagnostic trait for members of the kingdom Animalia has important implications for our understanding of the evolution of sleep and sleep functions. Unfortunately, knowledge on the phylogenetic breadth of sleep is restricted to vertebrates, a few arthropods and molluscs, and one species of nematode. There is a dearth of information on the other 30 or so animal phyla. Here, we provide original data on a previously unstudied group of animals with respect to sleep: platyhelminth flatworms. These free-living animals are relatively simple, with a rudimentary central nervous system and absence of many other specialized physiological systems. Despite this simplicity, inactive flatworms appeared to be sleeping. Specifically, quiescence was organized in a circadian manner, occurring largely during the daytime. This basic rhythm persisted under constant darkness, suggesting that it was endogenously generated. Active flatworms responded more readily to stimulation, and flatworms recovered lost sleep by sleeping longer after a 3-hour period of inactivity deprivation. We were also able to increase inactivity in a dose-dependent manner with exposure to melatonin, a hormone that increases sleep in diurnal animals. Taken together, these data expand our understanding of the phylogenetic extent of sleep and reinforce the idea that sleep evolved early in the evolutionary history of animals. However, additional studies on other types of animals are required for a comprehensive understanding of the origin(s) and evolution of sleep.
Publisher: Elsevier BV
Date: 07-2023
Publisher: University of Chicago Press
Date: 10-2006
DOI: 10.1086/506973
Abstract: Among mammalian species, the time spent in the two main "architectural" states of sleep--slow-wave sleep (SWS) and rapid-eye-movement (REM) sleep--varies greatly. Previous comparative studies of sleep architecture found that larger mammals, those with bigger brains, and those with higher absolute basal metabolic rates (BMR) tended to engage in less SWS and REM sleep. Species experiencing a greater risk of predation also exhibited less SWS and REM sleep. In all cases, however, these studies lacked a formal phylogenetic and theoretical framework and used mainly correlational analyses. Using independent contrasts and an updated data set, we extended existing approaches with path analysis to examine the integrated influence of anatomy, physiology, and ecology on sleep architecture. Path model structure was determined by nonmutually exclusive hypotheses for the function of sleep. We found that species with higher relative BMRs engage in less SWS, whereas species with larger relative brain masses engage in more REM sleep. REM sleep was the only sleep variable strongly influenced by predation risk mammals sleeping in riskier environments engage in less REM sleep. Overall, we found support for some hypotheses for the function of sleep, such as facilitating memory consolidation or learning, but not others, such as energy conservation.
Publisher: Elsevier BV
Date: 08-2016
DOI: 10.1016/J.TREE.2016.05.004
Abstract: Here, we propose an original approach to explain one of the great unresolved questions in animal biology: what is the function of sleep? Existing ecological and neurological approaches to this question have become roadblocks to an answer. Ecologists typically treat sleep as a simple behavior, instead of a heterogeneous neurophysiological state, while neuroscientists generally fail to appreciate the critical insights offered by the consideration of ecology and evolutionary history. Redressing these shortfalls requires cross-disciplinary integration. By bringing together aspects of behavioral ecology, evolution, and conservation with neurophysiology, we can achieve a more comprehensive understanding of sleep, including its implications for adaptive waking behavior and fitness.
Publisher: Elsevier BV
Date: 02-2019
DOI: 10.1016/J.BBR.2018.06.019
Abstract: Autism spectrum disorder (ASD) is a heterogeneous and highly heritable condition with multiple aetiologies. Although the biological mechanisms underlying ASD are not fully understood, evidence suggests that dysregulation of serotonergic systems play an important role in ASD psychopathology. Preclinical models using mice with altered serotonergic neurotransmission may provide insight into the role of serotonin in behaviours relevant to clinical features of ASD. For ex le, BALB/c mice carry a loss-of-function single nucleotide polymorphism (SNP C1473 G) in tryptophan hydroxylase 2 (Tph2), which encodes the brain-specific isoform of the rate-limiting enzyme for serotonin synthesis, and these mice frequently have been used to model symptoms of ASD. In this study, juvenile male BALB/c (G/G loss-of-function variant) and C57BL/6 J (C/C wild type variant) mice, were exposed to the three-chamber sociability test, and one week later to the elevated plus-maze (EPM). Tryptophan hydroxylase 2 (TPH2) activity was measured following injection of the aromatic amino acid decarboxylase (AADC)-inhibitor, NSD-1015, and subsequent HPLC detection of 5-hydroxytryptophan (5-HTP) within subregions of the dorsal raphe nucleus (DR) and median raphe nucleus (MnR). The BALB/c mice showed reduced social behaviour and increased anxious behaviour, as well as decreased 5-HTP accumulation in the rostral and mid-rostrocaudal DR. In the full cohort of mice, TPH2 activity in the mid-rostrocaudal DR was correlated with anxious behaviour in the EPM, however these correlations were not statistically significant within each strain, suggesting that TPH2 activity was not directly associated with either anxiety or sociability. Further research is therefore required to more fully understand how serotonergic systems are involved in mouse behaviours that resemble some of the clinical features of ASD.
Publisher: The Royal Society
Date: 03-2022
Abstract: Sharks represent the earliest group of jawed vertebrates and as such, they may provide original insight for understanding the evolution of sleep in more derived animals. Unfortunately, beyond a single behavioural investigation, very little is known about sleep in these ancient predators. As such, recordings of physiological indicators of sleep in sharks have never been reported. Reduced energy expenditure arising from sustained restfulness and lowered metabolic rate during sleep have given rise to the hypothesis that sleep plays an important role for energy conservation. To determine whether this idea applies also to sharks, we compared metabolic rates of draughtsboard sharks ( Cephaloscyllium isabellum ) during periods ostensibly thought to be sleep, along with restful and actively swimming sharks across a 24 h period. We also investigated behaviours that often characterize sleep in other animals, including eye closure and postural recumbency, to establish relationships between physiology and behaviour. Overall, lower metabolic rate and a flat body posture reflect sleep in draughtsboard sharks, whereas eye closure is a poorer indication of sleep. Our results support the idea for the conservation of energy as a function of sleep in these basal vertebrates.
Publisher: Elsevier BV
Date: 06-2028
Start Date: 2017
End Date: 2022
Funder: Australian Research Council
View Funded ActivityStart Date: 2024
End Date: 2027
Funder: Marsden Fund
View Funded ActivityStart Date: 2017
End Date: 12-2022
Amount: $138,074.00
Funder: Australian Research Council
View Funded ActivityStart Date: 02-2014
End Date: 12-2017
Amount: $374,837.00
Funder: Australian Research Council
View Funded Activity