TY - JOUR
T1 - Facultative control of avian unihemispheric sleep under the risk of predation
AU - Rattenborg, Niels C.
AU - Lima, Steven L.
AU - Amlaner, Charles J.
N1 - Funding Information:
We thank D. Hews, K. Hopper, and two anonymous reviewers for their constructive comments on the manuscript, and A. Boysen, C. Mathews, D. Sparks, P. Zollner, R. Hawkins and L. Rattenborg for their assistance with the mallards. This research was funded in part by NIMH grants RO1 MH37160 and RO1 MH42032 awarded to CJA, and NSF grant IBN-9723437 to SLL.
PY - 1999/11/15
Y1 - 1999/11/15
N2 - Birds and aquatic mammals are the only taxonomic groups known to exhibit unihemispheric slow-wave sleep (USWS). In aquatic mammals, USWS permits sleep and breathing to occur concurrently in water. However, the function of avian USWS has been unclear. Our study is based on the premise that avian USWS serves a predator detection function, since the eye contralateral to the awake hemisphere remains open during USWS. If USWS functions as a form of predator detection, then birds should be able to control both the proportion of slow-wave sleep composed of USWS and the orientation of the open eye in response to changes in predation risk. To test these predictions we recorded eye state and the EEG of mallard ducks (Anas platyrhynchos) sleeping in groups of four birds arranged in a row. Birds at the ends of the row were more exposed than those in the central positions, who were flanked on both sides by other birds, and thus should perceive a greater risk of predation. Consistent with a predator detection function, when compared to birds in the group's center, birds at the exposed ends of the row showed a 150% increase in USWS and a preference for directing the open eye away from the group, the direction from which a predator is most likely to approach. Furthermore, during USWS mallards responded rapidly to threatening visual stimuli presented to the open eye. This ability to facultatively control sleep and wakefulness simultaneously in different regions of the brain probably involves the neuroanatomical interhemispheric separation responsible for independent hemispheric functioning during wakefulness in birds.
AB - Birds and aquatic mammals are the only taxonomic groups known to exhibit unihemispheric slow-wave sleep (USWS). In aquatic mammals, USWS permits sleep and breathing to occur concurrently in water. However, the function of avian USWS has been unclear. Our study is based on the premise that avian USWS serves a predator detection function, since the eye contralateral to the awake hemisphere remains open during USWS. If USWS functions as a form of predator detection, then birds should be able to control both the proportion of slow-wave sleep composed of USWS and the orientation of the open eye in response to changes in predation risk. To test these predictions we recorded eye state and the EEG of mallard ducks (Anas platyrhynchos) sleeping in groups of four birds arranged in a row. Birds at the ends of the row were more exposed than those in the central positions, who were flanked on both sides by other birds, and thus should perceive a greater risk of predation. Consistent with a predator detection function, when compared to birds in the group's center, birds at the exposed ends of the row showed a 150% increase in USWS and a preference for directing the open eye away from the group, the direction from which a predator is most likely to approach. Furthermore, during USWS mallards responded rapidly to threatening visual stimuli presented to the open eye. This ability to facultatively control sleep and wakefulness simultaneously in different regions of the brain probably involves the neuroanatomical interhemispheric separation responsible for independent hemispheric functioning during wakefulness in birds.
KW - Birds
KW - Evolution
KW - Eye state
KW - Slow-wave sleep
KW - Unihemispheric
KW - Vigilance
KW - Vision
UR - http://www.scopus.com/inward/record.url?scp=0032888355&partnerID=8YFLogxK
U2 - 10.1016/S0166-4328(99)00070-4
DO - 10.1016/S0166-4328(99)00070-4
M3 - Article
C2 - 10563490
AN - SCOPUS:0032888355
SN - 0166-4328
VL - 105
SP - 163
EP - 172
JO - Behavioural Brain Research
JF - Behavioural Brain Research
IS - 2
ER -