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Publié par | ludwig-maximilians-universitat_munchen |
Publié le | 01 janvier 2011 |
Nombre de lectures | 36 |
Poids de l'ouvrage | 7 Mo |
Extrait
Avian Sleep Homeostasis:
Electrophysiological, Molecular and Evolutionary Approaches
John A. Lesku
Dissertation
an der Fakultät für Biologie
der Ludwig‐Maximilians‐Universität München
angefertigt am
Max‐Planck‐Institut für Ornithologie in Seewiesen
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Erstgutachter: Prof. Dr. Manfred Gahr
Zweitgutachter: Prof. Dr. Christian Leibold
Mündlichen Prüfung am 27 April 2011 3
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Summary ......................................................................................................................................... 5
General Introduction ...................................................................................................................... 6
Chapter 1 – Sleep and Sleep States: Evolution and Ontogeny ..................................................... 24
Chapter 2 – Ostriches Sleep Like Platypuses ................................................................................ 53
Chapter 3 – Increased EEG Spectral Power Density during Sleep Following
Short‐term Sleep Deprivation in Pigeons (Columba livia):
Evidence for Avian Sleep Homeostasis ..................................................................... 78
Chapter 4 – Local Sleep Homeostasis in the Avian Brain:
Convergence of Sleep Function in Mammals and Birds? ........................................ 111
Chapter 5 – Molecular Correlates of Local Sleep in the Pigeon (Columba livia) ........................ 144
General Discussion ...................................................................................................................... 159
General Acknowledgements ....................................................................................................... 177
Addresses of Co‐authors ............................................................................................................. 178
Author Contributions .................................................................................................................. 179
Curriculum Vitae ......................................................................................................................... 181
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SSuummmmaarryy
The function of slow wave sleep (SWS) and rapid eye movement (REM) sleep in mammals is an
unanswered question in neuroscience. Aside from mammals, only birds engage in these states.
Because birds independently evolved SWS and REM sleep, the study of sleeping birds may help
identify shared traits related to the function of these states. Throughout this dissertation, we
apply such a bird’s perspective to the sleeping brain. We begin with a review on knowledge
gained through the study of sleep in animals (Chapter 1). Next, we present results from the
first electrophysiological study of sleep in the most basal group of living birds by studying
ostriches (Chapter 2). Although ostriches engage in unequivocal SWS, their REM sleep
electrophysiology is unique and resembles features of REM sleep present only in basal
mammals. Thus, the evolution REM sleep may have followed a recurring sequence of steps in
mammals and birds. The remaining chapters deal with the regulation of sleep (or sleep
homeostasis). Sleep homeostasis refers to an increase in the intensity of sleep (typically
quantified as slow wave activity, SWA) following an extended period of wakefulness. Although
such a response has long been known to occur in mammals, it has been unclear whether birds
are capable of similar changes in SWA following sleep loss. We provide the first experimental
evidence for a mammalian‐like increase in SWA following enforced wakefulness in birds
(Chapter 3). In mammals, SWA increases locally in brain regions used more during prior
wakefulness. To see if SWS is regulated locally in birds, we stimulated one part of the pigeon
brain during enforced wakefulness and observed a local increase in SWA during subsequent
sleep (Chapter 4). Brain regions not stimulated asymmetrically during wakefulness showed a
symmetric increase in SWA. These patterns of a/symmetry may reflect changes in the strength
of synapses, as they do in mammals, because they are mirrored by changes in the slope of slow
waves during SWS – a purported marker of synaptic strength. Lastly, we investigate whether
local increases in SWA in birds are mediated by similar molecular mechanisms to those of
mammals (Chapter 5). Surprisingly, mRNA levels of such proteins did not respond to unilateral
visual stimulation during enforced wakefulness in the manner predicted based on work derived
from mammals, but further study is needed to resolve the meaning of this difference. Overall,
this dissertation presents several novel findings on the evolution and regulation of avian sleep. 6
GGeenneerraall IInnttrroodduuccttiioonn
The function of sleep is unknown, but not for lack of study (Stickgold 2005, Tononi and Cirelli
2006, Krueger et al. 2008, Rector et al. 2009, Diekelmann and Born 2010). Most research aimed
at answering this question focuses on mammals, and has yielded a wealth of information on
changes in brain act