TY - JOUR
T1 - History and future of comparative analyses in sleep research
AU - Lesku, John A.
AU - Roth, Timothy C.
AU - Rattenborg, Niels C.
AU - Amlaner, Charles J.
AU - Lima, Steven L.
N1 - Funding Information:
This work was supported by the Max Planck Society, University of Nevada, and Indiana State University.
PY - 2009/7
Y1 - 2009/7
N2 - The comparative methods of evolutionary biology are a useful tool for investigating the functions of sleep. These techniques can help determine whether experimental results, derived from a single or few species, apply broadly across a specified group of animals. In this way, comparative analysis is a powerful complement to experimentation. The variation in the time mammalian species spend asleep has been most amenable for use with this approach, given the large number of mammals for which sleep data exist. Here, it is assumed that interspecific variation in the time spent asleep reflects underlying differences in the need for sleep. If true, then significant predictors of sleep times should provide insight into the function of sleep. Many such analyses have sought the evolutionary determinants of mammalian sleep by relating the time spent in the two basic states of sleep, rapid eye movement (REM) and non-REM sleep, to constitutive variables thought to be functionally related to sleep. However, the early analyses had several methodological problems, and recent re-analyses have overturned some widely accepted relationships, such as the idea that species with higher metabolic rates engage in more sleep. These more recent studies also provide evolutionarily broad support for a neurophysiological role for REM sleep. Furthermore, results from comparative analyses suggest that animals are particularly vulnerable to predation during REM sleep, a finding that lends further support to the notion that REM sleep must serve an important function. Here, we review the methodology and results of quantitative comparative studies of sleep. We highlight important developments in our understanding of the evolutionary determinants of sleep and emphasize relationships that address prevailing hypotheses for the functions of sleep. Lastly, we outline a possible future for comparative analyses, focusing on work in non-mammalian groups, the use of more physiologically meaningful variables, and electrophysiological sleep studies conducted in the wild.
AB - The comparative methods of evolutionary biology are a useful tool for investigating the functions of sleep. These techniques can help determine whether experimental results, derived from a single or few species, apply broadly across a specified group of animals. In this way, comparative analysis is a powerful complement to experimentation. The variation in the time mammalian species spend asleep has been most amenable for use with this approach, given the large number of mammals for which sleep data exist. Here, it is assumed that interspecific variation in the time spent asleep reflects underlying differences in the need for sleep. If true, then significant predictors of sleep times should provide insight into the function of sleep. Many such analyses have sought the evolutionary determinants of mammalian sleep by relating the time spent in the two basic states of sleep, rapid eye movement (REM) and non-REM sleep, to constitutive variables thought to be functionally related to sleep. However, the early analyses had several methodological problems, and recent re-analyses have overturned some widely accepted relationships, such as the idea that species with higher metabolic rates engage in more sleep. These more recent studies also provide evolutionarily broad support for a neurophysiological role for REM sleep. Furthermore, results from comparative analyses suggest that animals are particularly vulnerable to predation during REM sleep, a finding that lends further support to the notion that REM sleep must serve an important function. Here, we review the methodology and results of quantitative comparative studies of sleep. We highlight important developments in our understanding of the evolutionary determinants of sleep and emphasize relationships that address prevailing hypotheses for the functions of sleep. Lastly, we outline a possible future for comparative analyses, focusing on work in non-mammalian groups, the use of more physiologically meaningful variables, and electrophysiological sleep studies conducted in the wild.
KW - Bird
KW - Energy conservation
KW - Function
KW - Human
KW - Independent contrasts
KW - Mammal
KW - Memory consolidation
KW - Phylogeny
KW - REM sleep
KW - Slow wave activity
UR - http://www.scopus.com/inward/record.url?scp=67649476126&partnerID=8YFLogxK
U2 - 10.1016/j.neubiorev.2009.04.002
DO - 10.1016/j.neubiorev.2009.04.002
M3 - Review article
C2 - 19443034
AN - SCOPUS:67649476126
SN - 0149-7634
VL - 33
SP - 1024
EP - 1036
JO - Neuroscience and Biobehavioral Reviews
JF - Neuroscience and Biobehavioral Reviews
IS - 7
ER -