Russell G Foster

University of Oxford | OX

Background The natural light environment is far more complex than that experienced by animals under laboratory conditions. As a burrowing species, wild mice are able to self-modulate their light exposure, a concept known as light environment sampling behaviour. By contrast, under laboratory conditions mice have little opportunity to exhibit this be...

Electrophysiological recordings from freely behaving animals are a widespread and powerful mode of investigation in sleep research. These recordings generate large amounts of data that require sleep stage annotation (polysomnography), in which the data is parcellated according to three vigilance states: awake, rapid eye movement (REM) sleep, and no...

Salt-Inducible kinases, which comprise a family of three homologous serine-threonine kinases were first described for their role in sodium sensing, but have since been shown to regulate multiple aspects of physiology. These kinases are activated or deactivated in response to extracellular signals that are cell surface receptor mediated, and go on t...

For nearly a century, we have known that brain photoreceptors regulate avian seasonal biology. Two photopigments, vertebrate ancient opsin (VA) and neuropsin (OPN5), provide possible molecular substrates for these photoreceptor pathways. VA fulfills many criteria for providing light input to the reproductive response, but a functional link has yet...

Circadian entrainment in mice relies primarily on photic cues that trigger the transcription of the core clock genes Period1/2 in the suprachiasmatic nucleus (SCN), thus aligning the phase of the clock with the dawn/dusk cycle. It has been shown previously that this pathway is directly regulated by adenosine signalling and that adenosine A2A/A1 rec...

The field of “circadian medicine” is a recent addition to chronobiology and sleep research efforts. It represents a logical step arising from the increasing insights into the circadian system and its interactions with life in urbanised societies; applying these insights to the health/disease balance at home and in the medical practice (outpatient)...

Mistimed exposure to light has been demonstrated to negatively affect multiple aspects of physiology and behavior. Here we analyzed the effects of chronic exposure to abnormal lighting conditions in mice. We exposed mice for 1 year to either: a standard light/dark cycle, a “light-pollution” condition in which low levels of light were present in the...

Over the last decades remarkable advances have been made in the understanding of the photobiology of circadian rhythms. The identification of a third photoreceptive system in the mammalian eye, in addition to the rods and cones that mediate vision, has transformed our appreciation of the role of light in regulating physiology and behavior. These ph...

Circadian rhythms are essential for the survival of all organisms, enabling them to predict daily changes in the environment and time their behaviour appropriately. The molecular basis of such rhythms is the circadian clock, a self-sustaining molecular oscillator comprising a transcriptional–translational feedback loop. This must be continually rea...

Light is known to exert powerful effects on behavior and physiology, including upon the amount and distribution of activity across the day/night cycle. Here we use home cage activity monitoring to measure the effect of differences in home cage light spectrum and intensity on key circadian activity parameters in mice. Due to the relative positioning...

Significance Our current understanding of how sleep is regulated is based upon the model of sleep homeostasis, which defines a variable called Process S as a measure of sleep need, and a so-called “flip-flop” model of state switching, which builds on a notion of a mutually antagonistic relationship between subcortical sleep-promoting and wake-promo...

Dysfunction of the glutamate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor GluA1 subunit and deficits in synaptic plasticity are implicated in schizophrenia and sleep and circadian rhythm disruption. To investigate the role of GluA1 in circadian and sleep behaviour, we used wheel-running, passive-infrared, and video-based hom...

Absence of dystrophin, an essential sarcolemmal protein required for muscle contraction, leads to the devastating muscle-wasting disease Duchenne muscular dystrophy. Dystrophin has an actin-binding domain, which binds and stabilises filamentous-(F)-actin, an integral component of the RhoA-actin-serum-response-factor-(SRF) pathway. This pathway play...

Significance In modern societies, people are regularly exposed to artificial light (e.g., light-emitting electronic devices). Dim light in the evening (DLE) imposes an artificial extension of the solar day, increasing our alertness before bedtime, delaying melatonin timing and sleep onset, and increasing sleepiness in the next morning. Using labora...

Light plays a critical role in regulating physiology and behavior, including both visual and non-visual responses. In mammals, loss of both eyes abolishes all of these responses, demonstrating that the photoreceptors involved are exclusively ocular. By contrast, many non-mammalian species possess extra-ocular photoreceptors located in the pineal co...

Bipolar disorder is a chronic neuropsychiatric condition associated with mood instability, where patients present significant sleep and circadian rhythm abnormalities. Currently, the pathophysiology of bipolar disorder remains elusive, but treatment with lithium continues as the benchmark pharmacotherapy, functioning as a potent mood stabilizer in...

An introduction to circadian rhythms

Psychotic experiences (PE) are associated with poorer functioning, higher distress and the onset of serious mental illness. Environmental exposures (e.g. childhood abuse) are associated with the development of PE. However, which specific exposures convey risk for each type or dimension of PE has rarely been explored. The Oxford Wellbeing Life and S...

Study objectives Torpor is a regulated and reversible state of metabolic suppression used by many mammalian species to conserve energy. Whereas the relationship between torpor and sleep has been well-studied in seasonal hibernators, less is known about the effects of fasting-induced torpor on states of vigilance and brain activity in laboratory mic...

The accumulation of adenosine is strongly correlated with the need for sleep and the detection of sleep pressure is antagonised by caffeine. Caffeine also affects the circadian timing system directly and independently of sleep physiology, but how caffeine mediates these effects upon the circadian clock is unclear. Here we identify an adenosine-base...

The aim of this study was to compare the pattern of changes in brain structure resulting from congenital and acquired bilateral anophthalmia. Brain structure was investigated using 3T magnetic resonance imaging (MRI) in Oxford (congenital) or Manchester (acquired). T1-weighted structural and diffusion-weighted scans were acquired from people with a...

Polyphasic sleep is the practice of distributing multiple short sleep episodes across the 24-hour day rather than having one major and possibly a minor (“nap”) sleep episode each day. While the prevalence of polyphasic sleep is unknown, anecdotal reports suggest attempts to follow this practice are common, particularly among young adults. Polyphasi...

Primary insomnia is often considered a disorder of 24‐hr hyperarousal. Numerous attempts have been made to investigate nocturnal heart rate (HR) and its variability (HRV) as potential pathophysiological hallmarks of altered arousal levels in insomnia, with mixed results. We have aimed to overcome some of the pitfalls of previous studies by using a...

Acute exposure to light exerts widespread effects on physiology, in addition to its key role in photoentrainment. Although the modulatory effect of light on physiological arousal is well demonstrated in mice, its effect on memory performance is inconclusive, as the direction of the effect depends on the nature of the behavioural task employed and/o...

Circadian rhythms are 24-h cycles in physiology and behavior that occur in virtually all organisms. These processes are not simply driven by changes in the external environment as they persist under constant conditions, providing evidence for an internal biological clock. In mammals, this clock is located in the hypothalamic suprachiasmatic nuclei...

Light around twilight provides the primary entrainment signal for circadian rhythms. Here we review the mechanisms and responses of the mouse and human circadian systems to light. Both utilize a network of photosensitive retinal ganglion cells (pRGCs) expressing the photopigment melanopsin (OPN4). In both species action spectra and functional expre...

Sleep and wakefulness are not simple homogenous all-or-none states, but instead are characterized by rich dynamics of brain activity across many temporal and spatial scales. Rapid global state transitions between waking and sleeping are believed to be controlled by hypothalamic circuits, but the contribution of the hypothalamus to within-state chan...

Torpor is a regulated reversible state of metabolic suppression used by many mammalian species to conserve energy. Although torpor has been studied extensively in terms of general physiology, metabolism and neuroendocrinology, the effects of hypometabolism and associated hypothermia on brain activity and states of vigilance have received little att...

Experimental evidence suggests that perinatal light imprinting of circadian clocks and systems may affect downstream physiology and cancer risk in later life. For humans, the predominant circadian stimulus is the daily light-dark cycle. Herein, we explore associations between perinatal photoperiod characteristics (photoperiod: duration of daylight...

Circadian rhythms are endogenous 24-hour oscillations in physiology and behaviour that enable organisms to predict and adapt to the rhythmic changes of the day/night cycle. While the rhythm of activity and rest is perhaps the most familiar, changes in body temperature, heart rate, hormone production, and even cognitive function also occur. By contr...

Meal timing and composition are frequently reported in the literature as zeitgebers (that is, time cues) for the circadian system of humans and animal models, albeit secondary to light. Although widely assumed to be true, evidence for food zeitgeber effects specific to humans is notably scarce. Fostering zeitgeber hygiene in the general population...

Our visual perception of the world - seeing form and colour or navigating the environment - depends on the interaction of light and matter in the environment. Light also has a more fundamental role in regulating rhythms in physiology and behaviour, as well as in the acute secretion of hormones such as melatonin and changes in alertness, where light...

Purpose: Light input, via the eyes, is essential for regulating circadian rhythms. Eye diseases can cause disruption of vital biological rhythms. Of totally blind people, 87% report sleep problems. There are no UK guidelines for visual disturbance-related circadian rhythm disruption. Our objective was to systematically review the literature to det...

Purpose: Diabetic retinopathy (DR) is associated with retinal neuronal and vascular damage. DR has previously been shown to affect the photosensitive retinal ganglion cells (pRGCs). PRGCs are essential for the entrainment of circadian rhythms; thus, DR progression could lead to worsening sleep quality and mood. We investigate the relationship betw...

Our visual perception of the world – seeing form and colour or navigating the environment – depends on the interaction of light and matter in the environment. Light also has a more fundamental role in regulating rhythms in physiology and behaviour, as well as in the acute secretion of hormones like melatonin and changes in alertness, where light ex...

Sleep enhances the consolidation of memory; however, this property of sleep may be detrimental in situations where memories of an event can lead to psychopathology, such as following a traumatic event. Intrusive memories of trauma are emotional memories that spring to mind involuntarily and are a core feature of post-traumatic stress disorder. Tota...

The reasons why we sleep have been debated endlessly and the arguments have tended to focus upon one key biological function that applies to the human species. Such explanations cannot account for the ubiquity of sleep across all animal life. This Opinion Paper explores the logic which enables all animal sleep to be defined as follows: Sleep is a p...

Abstract Circadian rhythms and sleep-wake history determine sleep duration and intensity, and influence subsequent waking. Previous studies have shown that T cycles - light-dark (LD) cycles differing from 24 h - lead to acute changes in the daily amount and distribution of waking and sleep. However, little is known about the long-term effects of T...

Introduction: Mood disorders are among the most prevalent and serious mental disorders and rank high among to the leading global burdens of disease. The developmental psychopathology framework can offer a life course perspective on them thus providing a basis for early prevention and intervention. Sleep disturbances, are considered risk factors fo...

Sleep EEG spindles have been implicated in attention, sensory processing, synaptic plasticity and memory consolidation. In humans, deficits in sleep spindles have been reported in a wide range of neurological and psychiatric disorders, including schizophrenia. Genome-wide association studies have suggested a link between schizophrenia and genes ass...

In humans and most other species, changes in the intensity and duration of light provide a critical set of signals for the synchronisation of the circadian system to the astronomical day. The timing of activity within the 24 h day defines an individual’s chronotype, i.e. morning, intermediate or evening type. The aim of this study was to investigat...

Sleep-wake history, wake behaviours, lighting conditions and circadian time influence sleep, but neither their relative contribution, nor the underlying mechanisms are fully understood. The dynamics of EEG slow-wave activity (SWA) during sleep can be described using the two-process model, whereby the parameters of homeostatic Process S are estimate...

Example raw electrophysiological signals recorded from a representative EA mouse during NREM sleep. Four channels of LFPs and corresponding MUA (pNeu) are shown; 5 s of recording is shown at any given time, at a playback speed 2× normal. Note the occurrence of synchronous silent (OFF) periods in the MUA, corresponding to slow waves in the LFP.

Example raw electrophysiological signals recorded from a representative OA mouse during NREM sleep. Four channels of LFPs and corresponding MUA (pNeu) are shown; 5 s of recording is shown at any given time, at a playback speed 2× normal. Note the occurrence of synchronous silent (OFF) periods in the MUA, corresponding to slow waves in the LFP, simi...

Healthy aging is associated with marked effects on sleep, including its daily amount and architecture, as well as the specific EEG oscillations. Neither the neurophysiological underpinnings nor the biological significance of these changes are understood, and crucially the question remains whether aging is associated with reduced sleep need or a dim...

Cryptochromes 1 and 2 (CRY1/2) are key components of the negative limb of the mammalian circadian clock. Like many peripheral tissues, Cry1 and -2 are expressed in the retina, where they are thought to play a role in regulating rhythmic physiology. However, studies differ in consensus as to their localization and function, and CRY1 immunostaining h...

Circadian rhythms are 24-h rhythms in physiology and behaviour generated by molecular clocks, which serve to coordinate internal time with the external world. The circadian system is a master regulator of nearly all physiology and its disruption has major consequences on health. Sleep and circadian rhythm disruption (SCRD) is a ubiquitous feature i...

The master circadian pacemaker in mammals is located in the suprachiasmatic nuclei (SCN) which regulate physiology and behaviour, as well as coordinating peripheral clocks throughout the body. Investigating the function of the SCN has often focused on the identification of rhythmically expressed genes. However, not all genes critical for SCN functi...

Background: Sleep difficulties might be a contributory causal factor in the occurrence of mental health problems. If this is true, improving sleep should benefit psychological health. We aimed to determine whether treating insomnia leads to a reduction in paranoia and hallucinations. Methods: We did this single-blind, randomised controlled trial...

Objective: Age-related cognitive impairment and the prevalence of neurodegenerative disease contribute to decreasing quality of life in affected individuals and their families as well as demand considerable societal responsibility. Sleep supports overall brain activity and contributes to both physical and mental health. As a result, sleep is an at...

Light exerts influences on many physiological and behavioural functions in humans. These functions can be described as image-forming (IF) and non-image forming (NIF) visual processes, both originating in the retina of the eye. Image-forming refers to vision; the process of detecting and distinguishing shapes and colour of objects. Non-image forming...

Two-pore domain (K2P) potassium channels perform essential roles in neuronal function. These channels produce background leak type potassium currents that act to regulate resting membrane potential and levels of cellular excitability. 15 different K2P channels have been identified in mammals and these channels perform important roles in a wide numb...

Background: Disruption of rhythms in activity and rest occur in many diseases, and provide an important indicator of healthy physiology and behaviour. However, outside the field of sleep and circadian rhythm research, these rhythmic processes are rarely measured due to the requirement for specialised resources and expertise. Until recently, the pri...

While time of day, interacting with an individual’s chronotype, can have an important impact upon performance and health, severe disruption of the circadian system adds another level of complexity and severity. ‘When timing goes wrong’ considers the effects of flying across multiple time zones, resulting in jet lag, and shift work on human health....

With each season there are changes in day length, wind speed and direction, temperature, and rainfall, which dictate the optimal times for plants and animals to initiate growth, development, and reproduction. Plants are sessile and cannot escape or hide from seasonal change. Getting the timing right so that germination, bud burst, flowering, dorman...