Stefania Piscopo

Lab. of Animal Physiology and Evolution, Stazione Zoologica Anton Dohrn,80121 Napoli, Italy

TABLE OF CONTENTS

1. Abstract

2. Introduction

3. Main features of sleep

4. General ideas about the phylogeny of sleep

5. Possible functions of sleep

6. Sleep and synaptic plasticity

7. Cnidarians

8. Nematodes

9. Molluscs

10. Arthropods

11.Discussion & Conclusion

11.1. Towards a general hypothesis

12. Acknowledgements

13.References

1. ABSTRACT

A fascinating but still partly unsolved scientific question is to understand the function/s of sleep. Many hypotheses have been proposed, and in this review I focus on the idea that sleep has a role in supporting brain plasticity, learning and memory. Although the majority of sleep research is concentrated on vertebrates, especially humans and mammals, sleep-like behaviour is also evident in some invertebrates. Though surprisingly there are very few studies that have directly tested if there is a mechanistic link between sleep and plasticity. I argue that a phylogenetic approach gives potential insight into the mechanisms and roles of sleep, by allowing an analysis by comparison of the evolution of sleep and rest/activity cycles in organisms showing radically different lifestyles and brain plans. This review attempts to set the scene for a much more profound analysis of these issues using phylogenetic tools.