John A. Lesku's research while affiliated with La Trobe University and other places
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Publications (118)
A new study shows that bearded dragons have a peculiar way to coordinate sleep state changes between brain hemispheres. The hemisphere that acts first imposes its activity on the other during their REM sleep-like state.
Exposure of wildlife to anthropogenic noise is associated with an array of disruptive effects. Research on this topic has focused on the behavioural and physiological responses of animals to noise, with little work investigating potential links to cognitive function. To fill this gap in our understanding, we explored how environmentally relevant ur...
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, spa...
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....
Pharmaceutical pollution is a major driver of global change, with the capacity to alter key behavioural and physiological traits in exposed animals. Antidepressants are among the most commonly detected pharmaceuticals in the environment. Despite well-documented pharmacological effects of antidepressants on sleep in humans and other vertebrates, ver...
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 diversity of invertebrates has gone largely unexplored. Here, we introduce the intrigue and special value in the study of sleeping platyhelminth flatworms. Flat...
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 costs. Taken together, these systems challenge the prevalent view of sleep as an essential state on which waking performance depends. Here,...
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 apparat...
City-living animals are exposed to pervasive human-generated noise from traffic and industry. There is growing evidence that this exposure may have deleterious physiological and behavioural effects. Cognitive processes could be particularly sensitive to the disruptive effects of noise, but little is known about the potential effects of noise on cog...
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 p...
Study Objectives
In this study, we (1) describe sleep behaviour 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.
Methods
Wild-caught male dusky antechinus (n = 4) were individual...
Background:
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.
Aim:
To determine whether...
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 cogni...
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 s...
Study Objectives
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 t...
Study Objectives
We explore NREM and 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).
Methods
Continuous 72-h recordings of EEG, EMG...
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...
Birds share many traits in common with mammals, including homeothermy and large brains capable of performing complex cognitive processes. Interestingly, birds also exhibit two sleep states in many, but not all, respects similar to mammalian NREM and REM sleep. Recent EEG-based studies of birds in the wild revealed novel adaptations such as the abil...
Urban areas are inherently noisy, and this noise can disrupt biological processes as diverse as communication, migration, and reproduction. We investigated how exposure to urban noise affects sleep, a process critical to optimal biological functioning, in Australian magpies (Cracticus tibicen). Eight magpies experimentally exposed to noise in capti...
Artificial light at night can disrupt sleep in humans [1, 2, 3, 4] and other animals [5, 6, 7, 8, 9, 10]. A key mechanism for light to affect sleep is via non-visual photoreceptors that are most sensitive to short-wavelength (blue) light [11]. To minimize effects of artificial light on sleep, many electronic devices shift from white (blue-rich) to...
Sleep is known to occur in most, if not all, animals studied thus far. Recent studies demonstrate the presence of sleep in flatworms and jellyfish, suggesting that this behaviour evolved early in the evolution of animals. Sharks are the earliest known extant, jawed vertebrates and may play an important role in understanding the evolutionary history...
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: Wh...
Artificial light at night could have widespread and detrimental impacts on sleep. To reduce disruptive effects of artificial light on sleep in humans, most smartphones and computers now have software that reduces blue light emissions at night. Little is known about whether reducing blue light emissions from city lights could also benefit urban wild...
For many decades, sleep researchers have sought to determine which species 'have' rapid eye movement (REM) sleep. In doing so, they relied predominantly on a template derived from the expression of REM sleep in the adults of a small number of mammalian species. Here, we argue for a different approach that focuses less on a binary decision about hav...
Sleep is a highly conserved state across the animal kingdom. However, sleep duration, behavior and associated neural activity show great diversity across taxonomic groups, and sometimes even within the same species. Understanding sleep functions depends on understanding when sleep emerged, which of its characteristics have persisted throughout evol...
Sleep is widespread across the animal kingdom. However, most comparative sleep data exist for terrestrial vertebrates, with much less known about sleep in amphibians, 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 evol...
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.
Birds exhibit two types of sleep that are in many respects similar to mammalian rapid eye movement (REM) and non-REM (NREM) sleep. As in mammals, several aspects of avian sleep can occur in a local manner within the brain. Electrophysiological evidence of NREM sleep occurring more deeply in one hemisphere, or only in one hemisphere - the latter bei...
Manual scoring of polysomnography data is labor-intensive and time-consuming, and most existing software does not account for subjective differences and user variability. Therefore, we evaluated a supervised machine learning algorithm, SomnivoreTM, for automated wake–sleep stage classification. We designed an algorithm that extracts features from v...
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, cass...
Both mammals and birds exhibit two sleep states, slow wave sleep (SWS) and rapid eye movement (REM) sleep. Studying certain aspects of sleep-related electrophysiology in freely behaving animals can present numerous methodological constraints, particularly when even fine body movements interfere with electrophysiological signals. Interestingly, unde...
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 incre...
ON THE COVER: The cover image is based on the Review Impacts of artificial light at night on sleep: A review and prospectus by Anne E. Aulsebrook et al., DOI: https://doi.org/10.1002/jez.2189.
Natural cycles of light and darkness govern the timing of most aspects of animal behavior and physiology. Artificial light at night (ALAN)—a recent and pervasive form of pollution—can mask natural photoperiodic cues and interfere with biological rhythms. One such rhythm vulnerable to perturbation is the sleep–wake cycle. ALAN may greatly influence...
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 ne...
Study Objectives
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...
Sarcoptic mange, caused by the parasitic mite Sarcoptes scabiei, causes a substantive burden of disease to humans, domestic animals, and wildlife, globally. There are many effects of S. scabiei infection, culminating in the disease which hosts suffer. However, major knowledge gaps remain on the pathogenic impacts of this infection. Here, we focus o...
Colorful plumage ornaments may evolve because they play a role in mate choice or in intrasexual competition, acting as signals of species identity or of individual quality. The zebra finch (Taeniopygia guttata) is a model organism for the study of mate choice and its colorful plumage ornaments are thought to be used in both of these contexts. Numer...
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...
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. What is the ‘simplest’ animal that sleeps? When did sleep first evolve? Do all animals sleep? Tanta...
Introduction
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...
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 ea...
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, whi...
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 wh...
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 o...
What is the most humane way to kill amphibians 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 inte...
In mammals, the slow-oscillations of neuronal membrane potentials (reflected in the electroencephalogram as high-amplitude, slow-waves), which occur during non-rapid eye movement sleep and anesthesia, propagate across the neocortex largely as two-dimensional traveling waves. However, it remains unknown if the traveling nature of slow-waves is uniqu...
This article was originally published in the Encyclopedia of Sleep published by Elsevier, and the attached copy is provided by Elsevier for the author's benefit and for the benefit of the author's institution, for non-commercial research and educational use including without limitation use in instruction at your institution, sending it to specific...
You Snooze, You Lose
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 bi...
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 amplitude in response to an increase in background noise. T...
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 behav...
Mammals and birds engage in two distinct states of sleep, slow wave sleep (SWS) and rapid eye movement (REM) sleep. SWS is characterized by slow, high amplitude brain waves, while REM sleep is characterized by fast, low amplitude waves, known as activation, occurring with rapid eye movements and reduced muscle tone. However, monotremes (platypuses...
Video showing the behavioral correlates of slow wave sleep (SWS) and rapid eye movement (REM) sleep in the ostrich. SWS is characterized by open eyes and a vertically-held head; REM sleep is characterized by bilateral eye closure and a drooping head.
(MP4)
(A–H) Electroencephalogram (EEG) of the left and right hyperpallia, electrooculogram (EOG) of the left and right eye, the three axes (heave, sway and surge) of the head-mounted accelerometer (ACC), and electromyogram (EMG) of the nuchal muscle showing slow wave sleep (SWS, blue bar), rapid eye movement (REM) sleep (red bar) and wakefulness (green b...
The three 2-dimensional plots that constitute the 3-dimensional Figure 3 in the main article. (reprinted here in the bottom left corner). These plots illustrate the distinctiveness of wakefulness (green), slow wave sleep (SWS, blue) and rapid eye movement (REM) sleep (red) based on differences in eye movements (measured via electrooculogram, EOG),...
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 t...
In most mammals, sleep is composed of two distinct states, rapid eye movement (REM) sleep and slow-wave sleep (SWS). The differentiated nature of mammalian sleep suggests that each state performs a different function, or perhaps different, but complementary components of a unified function. Despite extensive research, the function(s) provided by sl...
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 t...
The functions of sleep remain elusive. Here, we review the current understanding of the evolution and ontogeny of sleep and demonstrate how comparative sleep research has contributed to our greater understanding of why we sleep. For instance, the occurrence of slow-wave sleep and rapid eye movement sleep exclusively in mammals and birds may be rela...