REM sleep and slow-wave sleep Avian sleep has two similarities shared with that of mammals ; REM (rapid-eye movement ) sleep and slow-wave sleep (SWS). REM sleep is believed to have an important effect on integral motor functions and storing memories . EEGs show high-amplitude and low-frequencies for REM sleep; SWS tends to show lower-amplitude and higher frequencies during EEG recordings and is believed to be a form of deep sleep. During SWS, membrane potentials in the neurons of the neocortex are undergoing slow oscillations, which explains the typical SWS results of the EEG . Numerous avian species have been shown to exhibit unihemispheric SWS; or the ability to rest one half of the brain in SWS  while the other half appears to show wakefulness . This type of sleep has  been seen in mammals like dolphins and whales. The organism is typically able to keep one of their eyes open during this process, which allows for added vigilance in areas where predation is higher .Rattenborg, Niels C.; Lima, Steven L. & Amlaner, Charles J. (1999). "Facultative control of avian unihemispheric sleep under the risk of predation". Behavioural Brain Research. 105 (2): 163-172. The evolution of this trait for both birds and aquatic mammals is of interest to researchers simply because of the pressures involved. Unihemispheric SWS is thought to have evolved in aquatic mammals since they must return to the surface for oxygen , while this phenomenon is believed to help birds avoid predation, thus creating a homoplasy between the two groups.
REM and slow-wave sleep Avian sleep shares two similarities with that of mammals : rapid eye movement (REM) and slow-wave sleep (SWS). REM sleep is believed to have an important effect on motor functions and memory storage . EEGs show high-amplitude and low-frequency waves during REM sleep; SWS tends toward lower-amplitude , higher-frequency waves, and is believed to be a form of deep sleep. During SWS, membrane potentials in the neurons of the neocortex oscillate slowly . A number of avian species exhibit unihemispheric slow-wave sleep: the ability to rest one half of the brain in SWS , while the other half appears to be awake . This type of sleep has also been seen in dolphins and whales. The organism is typically able to keep one eye open during this process, which allows added vigilance in high-predation environments .Rattenborg, Niels C.; Lima, Steven L. & Amlaner, Charles J. (1999). "Facultative control of avian unihemispheric sleep under the risk of predation". Behavioural Brain Research. 105 (2): 163-172. The evolution of this trait in birds and aquatic mammals is of interest to researchers because of the pressures involved. Unihemispheric SWS is thought to have evolved in aquatic mammals because they must return to the surface for oxygen ; it is believed to help birds avoid predation, demonstrating homoplasy in the two groups.
D
sleep
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has two similarities shared
shares two similarities
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; REM (rapid-eye movement ) sleep
: rapid eye movement (REM)
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integral
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storing memories
memory storage
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low-frequencies for
low-frequency waves during
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to show
toward
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and higher frequencies during EEG recordings and
, higher-frequency waves, and
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are undergoing slow oscillations, which explains the typical SWS results of the EEG
oscillate slowly
R
Numerous avian species have been shown to exhibit unihemispheric SWS; or
A number of avian species exhibit unihemispheric slow-wave sleep:
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,
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show wakefulness
be awake
A
also
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mammals like
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of their eyes
eye
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for
R
areas where predation is higher
high-predation environments
R
for both
in
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simply
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since
because
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, while this phenomenon
; it
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thus creating a homoplasy between
demonstrating homoplasy in