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Session Schedule

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0:00:00
Introduction
Markus Schmidt (Switzerland)

0:03:20
A mammalian and Bird’s Eye perspective of sleep diversity
Gianina Ungurean (Germany)

0:24:50
Ecological flexibility in sleep duration
Niels Rattenborg (Germany)

presentation not available: Long-term monitoring of sleep-wake behaviors and the role of ambient ecological conditions
Isabella Capellini (United Kingdom)

0:44:55
Comparative studies of seasonal impacts on sleep expression in birds and mammals
Peter Meerlo (Netherlands)

1:10:40
Strategies of resource optimization through sleep-wake alternation
Markus Schmidt (Switzerland)

Summary

Although sleep appears universal across species, its expression is highly variable and difficult to reconcile when searching for a universal sleep function. To illustrate, prolonged wakefulness during mating or migration, as seen in pectoral sandpipers or frigate birds, illustrates that sleep loss can confer evolutionary advantages without apparent functional deficits. Similarly, ecological conditions, including seasonality and ambient temperature have been shown to have a tremendous impact on sleep expression and its daily structure. Decades of sleep laboratory research have focused on maintaining constant experimental conditions, including light-dark cycle, temperature and food availability. However, evolutionary biology has provided organisms in the wild the ability to dynamically modulate sleep expression and structure as a function of ecological condition. This diversity of sleep expression has created a divide between proximate (physiological) and ultimate (evolutionary) explanations of sleep function, while complicating our understanding of why sleep is essential. Specifically, while physiological studies explain how sleep modulates processes like memory or immune function, such work generally fails to address why sleep is ultimately required.

In spite of recent new advances expanding our understanding of sleep expression from the laboratory to the wild, important questions remain: 1) What does the diversity of sleep expression across species tell us about sleep function? 2) What is the role of ecological context in driving this variation in sleep expression? 3) What are the potential mechanisms promoting the dynamic flexibility in sleep structure? 4) How do we bridge our current understanding of physiological sleep mechanisms and functions with established principles of evolutionary biology and selective pressures driving species diversification?

This symposium brings together established sleep researchers and young and upcoming academics of both sexes to present their exciting work on comparative sleep neurophysiology and evolutionary biology. Gianina Ungurean will briefly introduce the symposium on sleep diversity by presenting her work on the contrasting and opposite patterns of pupillary responses seen in mammals and birds during sleep and wakefulness. Niels Rattenborg will introduce key concepts on the great diversity of sleep expression across avian species, including concepts that challenge our understanding of sleep function. Isabella Capellini will present her new data on long-term monitoring of wild mammals revealing great inter-individual differences and a critical role of ecological conditions in modulating sleep-wake behaviors. Peter Meerlo will present the role of seasonality in driving fundamental shifts in sleep quantity and expression. Markus Schmidt will introduce unifying concepts derived from the energy allocation hypothesis of sleep and the role of sleep-wake alternation as a mechanism for promoting diverse resource optimization strategies, integrating evolutionary principles with neurophysiological insights.

Learning Objectives:

Upon completion of this CME activity, participants will be able to:
• Define pupillary responses and their opposite response patterns as seen in mammals and birds
• Review the great adaptive diversity in sleep duration across species and how these data challenge our understanding of sleep function
• Elucidate the role of ecological ambient conditions on long-term plasticity of sleep expression and using life history theory to understand inter-individual differences
• Describe the role of seasonality in driving fundamental shifts in the expression of sleep in birds and mammals
• Elucidate the role of state-specific metabolic coupling in defining resource optimization strategies as expressed through sleep-wake alternation and structure