Time-Varying Light Exposure in Chronobiology and Sleep Research Experiments
TL;DR: In this paper, the authors introduce basic concepts in time-varying stimuli, and provide a checklist-based set of recommendations for documenting time varying light exposure based on current best practices and standards.
Abstract: Light exposure profoundly affects human physiology and behavior through circadian and neuroendocrine photoreception primarily through the melanopsin-containing intrinsically photosensitive retinal ganglion cells. Recent research has explored the possibility of using temporally patterned stimuli to manipulate circadian and neuroendocrine responses to light. This mini-review, geared to chronobiologists, sleep researchers, and scientists in adjacent disciplines, has two objectives: (1) introduce basic concepts in time-varying stimuli and (2) provide a checklist-based set of recommendations for documenting time-varying light exposures based on current best practices and standards.
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TL;DR: In this article , the most common setups that scientists use for generating light stimulation, from lab-made approaches to commercially available technologies, are described, and a set of characterization and calibration principles that researchers should consider when carrying out experiments with the described optical stimulators are discussed.
Abstract: This chapter describes the most common setups that scientists use for generating light stimulation, from lab-made approaches to commercially available technologies. The studied optical stimulation systems are divided into nonimage-forming and image-forming arrangements. Two classical systems widely used are among the first: the Maxwellian view system and the Ganzfeld stimulator. Between the image-forming arrangements, the focus is on approaches that consider off-the-shelf devices and the recent appearance of multi-primary displays, which allow the inclusion of more primaries and the generation of stimulation for independent and combined photoreceptor and postreceptoral excitations. Some of the several limitations that can have important implications in research practice are also examined, such as those related to color gamut, sampling frequency, light range, and spatial resolution. Since experimentation on how optical radiation is processed by the human neural system requires the reliability of the parameters and variables under study to be assured, the characterization and consequent calibration of experimental devices are essential. Therefore the chapter discusses a set of characterization and calibration principles that researchers should consider when carrying out experiments with the described optical stimulators. Outstanding characteristics are stimulator response curve, primaries' spectral power distribution, additivity, modulation transfer function, and temporal stability. Finally, some possible sources of artifacts that researchers should consider when these stimulators are used are presented. Throughout this last section, data based on different optical stimulator measurements is provided.
4 citations
TL;DR: In this paper , the authors present the treatment of totally blind patients suffering from non-24-hour sleep-wake rhythm disorder, which is associated with mood disorders and loss of appetite and gastrointestinal disturbances due to disrupted circadian hormone regulation.
Abstract: Various physiological systems and behaviors such as the sleep-wake cycle, vigilance, body temperature, and the secretion of certain hormones are governed by a 24-hour cycle called the circadian system. While there are many external stimuli involved the regulation of circadian rhythm, the most powerful environmental stimulus is the daily light-dark cycle. Blind individuals with no light perception develop circadian desynchrony. This leads to non-24-hour sleep-wake rhythm disorder, which is associated with sleep-wake disorders, as well as mood disorders and loss of appetite and gastrointestinal disturbances due to disrupted circadian hormone regulation. As the diagnosis is often delayed because of under-recognition in clinical practice, patients must cope with varying degrees of social and academic dysfunction. Most blind individuals report that non-24-hour sleep-wake rhythm disorder affects them more than blindness. In the treatment of totally blind patients suffering from non-24-hour sleep-wake rhythm disorder, the first-line management is behavioral approaches. Drug therapy includes melatonin and the melatonin agonist tasimelteon. Diagnosing blind individuals’ sleep disorders is also relevant to treatment because they can be improved with the use of melatonin and its analogues or by phototherapy if they have residual vision. Therefore, assessing sleep problems and planning treatment accordingly for individuals presenting with blindness is an important issue for ophthalmologists to keep in mind.
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TL;DR: In this article , the authors provide a framework for the characterization, calibration, and reporting of digital sensors, based on verification, analytic validation, and clinical validation (V3) as a state-of-the-art approach for tools and standards in digital medicine to light dosimetry.
Abstract: Background Light exposure is an important driver and modulator of human physiology, behavior and overall health, including the biological clock, sleep-wake cycles, mood and alertness. Light can also be used as a directed intervention, e.g., in the form of light therapy in seasonal affective disorder (SAD), jetlag prevention and treatment, or to treat circadian disorders. Recently, a system of quantities and units related to the physiological effects of light was standardized by the International Commission on Illumination (CIE S 026/E:2018). At the same time, biometric monitoring technologies (BioMeTs) to capture personalized light exposure were developed. However, because there are currently no standard approaches to evaluate the digital dosimeters, the need to provide a firm framework for the characterization, calibration, and reporting for these digital sensors is urgent. Objective This article provides such a framework by applying the principles of verification, analytic validation and clinical validation (V3) as a state-of-the-art approach for tools and standards in digital medicine to light dosimetry. Results This article describes opportunities for the use of digital dosimeters for basic research, for monitoring light exposure, and for measuring adherence in both clinical and non-clinical populations to light-based interventions in clinical trials.
1 citations
TL;DR: In this paper, the effect of different illumination levels on three indicators (heart rate, electrodermal activity, and respiration) was investigated in coal mine lighting simulation experiment system.
Abstract: Low-light environment affects human physiology, psychology, and behavior. It causes errors in work and increases accidents. In this study, we built a coal mine lighting simulation experiment system. The system not only includes an experimental environment simulation system and a physiological indicator test system, but also adds a miners’ working simulation system. We aim to study the effect of different illumination levels (0lx, 10lx, 50lx, 100lx, and 200lx) on three indicators: heart rate, electrodermal activity, and respiration. The results show illuminance has a significant negative correlation with all the above three indicators. Heart rate seems to be most significantly affected by illuminance, and it changes significantly from the normal level (200lx) at 50lx. By contrast, the respiratory rate and electrodermal activity change significantly at 10lx. When the illuminance is 50~100lx, all the three indicators return to the normal level. The results suggest that coal mine illumination should be around 50~100lx. When the minimum illumination is less than 10lx, accidents tend to increase.
1 citations
TL;DR: In this paper , a method to approximately compute the circadian light reaching the retina based on photopic illuminance reaching the corneal plane and considering the optical density of an aging crystalline lens was proposed.
Abstract: Lighting studies that take into account the age of the inhabitants of an area and are related to circadian light are difficult to find. This study aims to simplify a method to approximately compute the circadian light reaching the retina based on photopic illuminance reaching the corneal plane and considering the optical density of an aging crystalline lens. As an example of this proposed method, calculations were performed with both the D65 and A standard illuminants, showing how the spectral power distribution is modified by the optical density of the crystalline lens, mainly at short wavelengths. Due to these selective wavelength absorptions of the aged lens, a significant variation in the level of daylight equivalent melanopic illuminance (EDI) is present in the retina. With levels of 200 lux at the corneal plane, these variations ranged from 204 EDI lux to 178 EDI lux for the D65 standard illuminant, and from 99 EDI lux to 101 EDI lux for the A standard illuminant for observers aged 10 and 90, respectively. In this work, we aimed to simplify the greatest possible level of calculation of melanopic light, while describing simple protocols that are easy to translate into practice. Our results will allow researchers to carry out optimized lighting designs from both the photometric and circadian perspectives considering the optical density of an aging lens.
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TL;DR: Current studies of fixational eye movements have focused on determining how visible perception is encoded by neurons in various visual areas of the brain to elucidate how the brain makes the authors' environment visible.
Abstract: Our eyes continually move even while we fix our gaze on an object. Although these fixational eye movements have a magnitude that should make them visible to us, we are unaware of them. If fixational eye movements are counteracted, our visual perception fades completely as a result of neural adaptation. So, our visual system has a built-in paradox — we must fix our gaze to inspect the minute details of our world, but if we were to fixate perfectly, the entire world would fade from view. Owing to their role in counteracting adaptation, fixational eye movements have been studied to elucidate how the brain makes our environment visible. Moreover, because we are not aware of these eye movements, they have been studied to understand the underpinnings of visual awareness. Recent studies of fixational eye movements have focused on determining how visible perception is encoded by neurons in various visual areas of the brain.
1,148 citations
TL;DR: It is demonstrated that humans are highly responsive to the phase‐delaying effects of light during the early biological night and that both the phase resetting response to light and the acute suppressive effect of light on plasma melatonin follow a logistic dose‐response curve, as do many circadian responses to light in mammals.
Abstract: Ocular exposure to early morning room light can significantly advance the timing of the human circadian pacemaker. The resetting response to such light has a non-linear relationship to illuminance. The dose-response relationship of the human circadian pacemaker to late evening light of dim to moderate intensity has not been well established. Twenty-three healthy young male and female volunteers took part in a 9 day protocol in which a single experimental light exposure6.5 h in duration was given in the early biological night. The effects of the light exposure on the endogenous circadian phase of the melatonin rhythm and the acute effects of the light exposure on plasma melatonin concentration were calculated. We demonstrate that humans are highly responsive to the phase-delaying effects of light during the early biological night and that both the phase resetting response to light and the acute suppressive effects of light on plasma melatonin follow a logistic dose-response curve, as do many circadian responses to light in mammals. Contrary to expectations, we found that half of the maximal phase-delaying response achieved in response to a single episode of evening bright light ( approximately 9000 lux (lx)) can be obtained with just over 1 % of this light (dim room light of approximately 100 lx). The same held true for the acute suppressive effects of light on plasma melatonin concentrations. This indicates that even small changes in ordinary light exposure during the late evening hours can significantly affect both plasma melatonin concentrations and the entrained phase of the human circadian pacemaker.
1,052 citations
TL;DR: Although the actions of tea-making are ‘automated’ and proceed with little conscious involvement, the eyes closely monitor every step of the process, suggesting that this type of unconscious attention must be a common phenomenon in everyday life.
Abstract: The aim of this study was to determine the pattern of fixations during the performance of a well-learned task in a natural setting (making tea), and to classify the types of monitoring action that the eyes perform. We used a head-mounted eye-movement video camera, which provided a continuous view of the scene ahead, with a dot indicating foveal direction with an accuracy of about 1 deg. A second video camera recorded the subject's activities from across the room. The videos were linked and analysed frame by frame. Foveal direction was always close to the object being manipulated, and very few fixations were irrelevant to the task. The first object-related fixation typically led the first indication of manipulation by 0.56 s, and vision moved to the next object about 0.61 s before manipulation of the previous object was complete. Each object-related act that did not involve a waiting period lasted an average of 3.3 s and involved about 7 fixations. Roughly a third of all fixations on objects could be definitely identified with one of four monitoring functions: locating objects used later in the process, directing the hand or object in the hand to a new location, guiding the approach of one object to another (e.g. kettle and lid), and checking the state of some variable (e.g. water level). We conclude that although the actions of tea-making are 'automated' and proceed with little conscious involvement, the eyes closely monitor every step of the process. This type of unconscious attention must be a common phenomenon in everyday life.
997 citations
960 citations
TL;DR: It is argued that, at the beginning of each action, the oculomotor system is supplied with the identity of the required object, information about its location, and instructions about the nature of the monitoring required during the action.
876 citations