We believe this is the first evidence for an animal behaviorally controlling sleep and wakefulness simultaneously in different regions of the brain, the researchers say.
The results provide the best evidence for a long-standing supposition that single-hemisphere sleep evolved as creatures scanned for enemies. The preference for opening an eye on the lookout side could be widespread, he predicts. Hes seen it in a pair of birds dozing side-by-side in the zoo and in a single pet bird sleeping by mirror. The mirror-side eye closed as if the reflection were a companion and the other eye stayed open.
Useful as half-sleeping might be, its only been found in birds and such water mammals(哺乳动物)as dolphins, whales, and seals. Perhaps keeping one side of the brain awake allows a sleeping animal to surface occasionally to avoid drowning.
Studies of birds may offer unique insights into sleep. Jerome M. Siegel of the UGLA says he wonders if birds half-brain sleep is just the tip of the iceberg(冰山). He speculates that more examples may turn up when we take a closer look at other species.
16. Which of the following is evidence that TT is widely practiced?
A) TT has been in existence for decades.
B) Many patients were cured by therapeutic touch.
C) TT therapists are often employed by leading hospitals.
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