Before the availability of artificial light, moonlight was the only source of light sufficient to... more Before the availability of artificial light, moonlight was the only source of light sufficient to stimulate nighttime activity; still, evidence for the modulation of sleep timing by lunar phases is controversial. Here, we use wrist actimetry to show a clear synchronization of nocturnal sleep timing with the lunar cycle in participants living in environments that range from a rural setting with and without access to electricity in indigenous Toba/Qom communities in Argentina to a highly urbanized postindustrial setting in the United States. Our results show that sleep starts later and is shorter on the nights before the full moon when moonlight is available during the hours following dusk. Our data suggest that moonlight likely stimulated nocturnal activity and inhibited sleep in preindustrial communities and that access to artificial light may emulate the ancestral effect of early-night moonlight.
As humans transitioned from hunter-gatherer to agricultural to highly urbanized post-industrial c... more As humans transitioned from hunter-gatherer to agricultural to highly urbanized post-industrial communities they progressively created environments that isolated sleep from its ancestral regulators, including the natural light-dark cycle. A prominent feature of this isolation is the availability of artificial light during the night, which delays the onset of sleep and shortens its duration. Before artificial light, moonlight was the only source of natural light sufficient to stimulate activity during the night; still, evidence for the modulation of sleep timing by lunar phases under natural conditions is controversial. Here we use data collected with wrist actimeters that measure daily sleep to show a clear synchronization of nocturnal sleep timing with the lunar cycle in participants who live in environments that range from a rural setting without access to electricity to a highly urbanized post-industrial one. The onset of sleep is delayed and sleep duration shortened as much as 1...
The present study attempted to determine differences between children and adults in the resolutio... more The present study attempted to determine differences between children and adults in the resolution of third-party property disputes involving different claims for ownership. Children (n = 110; mean age ± SD = 6.3 ± 1.2) and adults (n = 74; 37.5 ± 12.6) watched videos depicting ownership conflicts between two characters who held opposing claims over an object and were asked to decide who should own it. In the stories, each character based her claim on one of four distinct arguments: Discovery, Creation, Occupation, and Transaction. A key difference between these claims lies on the presence or absence of a “first possession” element: Discovery and Creation imply prior possession of the discovered or created object, whereas Occupation and Transaction necessarily involve a preexisting owner. We found that children assigned ownership to prior possessors in the stories twice as much as adults (Medians = 4 and 2, out of four cases, respectively; p < 0.001), and favored discoverers and c...
We studied locomotor activity rhythms of C57/Bl6 mice under a chronic jet lag (CJL) protocol (Chr... more We studied locomotor activity rhythms of C57/Bl6 mice under a chronic jet lag (CJL) protocol (ChrA(6/2) ), which consisted of 6-hour phase advances of the light-dark schedule (LD) every 2 days. Through periodogram analysis, we found 2 components of the activity rhythm: a short-period component (21.01 ± 0.04 h) that was entrained by the LD schedule and a long-period component (24.68 ± 0.26 h). We developed a mathematical model comprising 2 coupled circadian oscillators that was tested experimentally with different CJL schedules. Our simulations suggested that under CJL, the system behaves as if it were under a zeitgeber with a period determined by (24 - [phase shift size/days between shifts]). Desynchronization within the system arises according to whether this effective zeitgeber is inside or outside the range of entrainment of the oscillators. In this sense, ChrA(6/2) is interpreted as a (24 - 6/2 = 21 h) zeitgeber, and simulations predicted the behavior of mice under other CJL schedules with an effective 21-hour zeitgeber. Animals studied under an asymmetric T = 21 h zeitgeber (carried out by a 3-hour shortening of every dark phase) showed 2 activity components as observed under ChrA(6/2): an entrained short-period (21.01 ± 0.03 h) and a long-period component (23.93 ± 0.31 h). Internal desynchronization was lost when mice were subjected to 9-hour advances every 3 days, a possibility also contemplated by the simulations. Simulations also predicted that desynchronization should be less prevalent under delaying than under advancing CJL. Indeed, most mice subjected to 6-hour delay shifts every 2 days (an effective 27-hour zeitgeber) displayed a single entrained activity component (26.92 ± 0.11 h). Our results demonstrate that the disruption provoked by CJL schedules is not dependent on the phase-shift magnitude or the frequency of the shifts separately but on the combination of both, through its ratio and additionally on their absolute values. In this study, we present a novel model of forced desynchronization in mice under a specific CJL schedule; in addition, our model provides theoretical tools for the evaluation of circadian disruption under CJL conditions that are currently used in circadian research.
Circadian rhythms are endogenous and need to be continuously entrained (synchronized) with the en... more Circadian rhythms are endogenous and need to be continuously entrained (synchronized) with the environment. Entrainment includes both coupling internal oscillators to external periodic changes as well as synchrony between the central clock and peripheral oscillators, which have been shown to exhibit different phases and resynchronization speed. Temporal desynchronization induces diverse physiological alterations that ultimately decrease quality of life and induces pathological situations. Indeed, there is a considerable amount of evidence regarding the deleterious effect of circadian dysfunction on overall health or on disease onset and progression, both in human studies and in animal models. In this review we discuss the general features of circadian entrainment and introduce diverse experimental models of desynchronization. In addition, we focus on metabolic, immune and cognitive alterations under situations of acute or chronic circadian desynchronization, as exemplified by jet-la...
Before the availability of artificial light, moonlight was the only source of light sufficient to... more Before the availability of artificial light, moonlight was the only source of light sufficient to stimulate nighttime activity; still, evidence for the modulation of sleep timing by lunar phases is controversial. Here, we use wrist actimetry to show a clear synchronization of nocturnal sleep timing with the lunar cycle in participants living in environments that range from a rural setting with and without access to electricity in indigenous Toba/Qom communities in Argentina to a highly urbanized postindustrial setting in the United States. Our results show that sleep starts later and is shorter on the nights before the full moon when moonlight is available during the hours following dusk. Our data suggest that moonlight likely stimulated nocturnal activity and inhibited sleep in preindustrial communities and that access to artificial light may emulate the ancestral effect of early-night moonlight.
As humans transitioned from hunter-gatherer to agricultural to highly urbanized post-industrial c... more As humans transitioned from hunter-gatherer to agricultural to highly urbanized post-industrial communities they progressively created environments that isolated sleep from its ancestral regulators, including the natural light-dark cycle. A prominent feature of this isolation is the availability of artificial light during the night, which delays the onset of sleep and shortens its duration. Before artificial light, moonlight was the only source of natural light sufficient to stimulate activity during the night; still, evidence for the modulation of sleep timing by lunar phases under natural conditions is controversial. Here we use data collected with wrist actimeters that measure daily sleep to show a clear synchronization of nocturnal sleep timing with the lunar cycle in participants who live in environments that range from a rural setting without access to electricity to a highly urbanized post-industrial one. The onset of sleep is delayed and sleep duration shortened as much as 1...
The present study attempted to determine differences between children and adults in the resolutio... more The present study attempted to determine differences between children and adults in the resolution of third-party property disputes involving different claims for ownership. Children (n = 110; mean age ± SD = 6.3 ± 1.2) and adults (n = 74; 37.5 ± 12.6) watched videos depicting ownership conflicts between two characters who held opposing claims over an object and were asked to decide who should own it. In the stories, each character based her claim on one of four distinct arguments: Discovery, Creation, Occupation, and Transaction. A key difference between these claims lies on the presence or absence of a “first possession” element: Discovery and Creation imply prior possession of the discovered or created object, whereas Occupation and Transaction necessarily involve a preexisting owner. We found that children assigned ownership to prior possessors in the stories twice as much as adults (Medians = 4 and 2, out of four cases, respectively; p < 0.001), and favored discoverers and c...
We studied locomotor activity rhythms of C57/Bl6 mice under a chronic jet lag (CJL) protocol (Chr... more We studied locomotor activity rhythms of C57/Bl6 mice under a chronic jet lag (CJL) protocol (ChrA(6/2) ), which consisted of 6-hour phase advances of the light-dark schedule (LD) every 2 days. Through periodogram analysis, we found 2 components of the activity rhythm: a short-period component (21.01 ± 0.04 h) that was entrained by the LD schedule and a long-period component (24.68 ± 0.26 h). We developed a mathematical model comprising 2 coupled circadian oscillators that was tested experimentally with different CJL schedules. Our simulations suggested that under CJL, the system behaves as if it were under a zeitgeber with a period determined by (24 - [phase shift size/days between shifts]). Desynchronization within the system arises according to whether this effective zeitgeber is inside or outside the range of entrainment of the oscillators. In this sense, ChrA(6/2) is interpreted as a (24 - 6/2 = 21 h) zeitgeber, and simulations predicted the behavior of mice under other CJL schedules with an effective 21-hour zeitgeber. Animals studied under an asymmetric T = 21 h zeitgeber (carried out by a 3-hour shortening of every dark phase) showed 2 activity components as observed under ChrA(6/2): an entrained short-period (21.01 ± 0.03 h) and a long-period component (23.93 ± 0.31 h). Internal desynchronization was lost when mice were subjected to 9-hour advances every 3 days, a possibility also contemplated by the simulations. Simulations also predicted that desynchronization should be less prevalent under delaying than under advancing CJL. Indeed, most mice subjected to 6-hour delay shifts every 2 days (an effective 27-hour zeitgeber) displayed a single entrained activity component (26.92 ± 0.11 h). Our results demonstrate that the disruption provoked by CJL schedules is not dependent on the phase-shift magnitude or the frequency of the shifts separately but on the combination of both, through its ratio and additionally on their absolute values. In this study, we present a novel model of forced desynchronization in mice under a specific CJL schedule; in addition, our model provides theoretical tools for the evaluation of circadian disruption under CJL conditions that are currently used in circadian research.
Circadian rhythms are endogenous and need to be continuously entrained (synchronized) with the en... more Circadian rhythms are endogenous and need to be continuously entrained (synchronized) with the environment. Entrainment includes both coupling internal oscillators to external periodic changes as well as synchrony between the central clock and peripheral oscillators, which have been shown to exhibit different phases and resynchronization speed. Temporal desynchronization induces diverse physiological alterations that ultimately decrease quality of life and induces pathological situations. Indeed, there is a considerable amount of evidence regarding the deleterious effect of circadian dysfunction on overall health or on disease onset and progression, both in human studies and in animal models. In this review we discuss the general features of circadian entrainment and introduce diverse experimental models of desynchronization. In addition, we focus on metabolic, immune and cognitive alterations under situations of acute or chronic circadian desynchronization, as exemplified by jet-la...
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Papers by Leandro Casiraghi