July 10, 2018 | Categories: Sleep
Pet owners may have watched their dogs or cats snooze and wonder whether they were dreaming, and possibly if their sleep patterns were at all like humans. The science community is working hard at conducting research to see what we can learn about sleep from animals.
Dogs Can Suffer from Sleep Disorders, Too
The Stanford Center for Sleep Sciences and Medicine has been studying canine narcolepsy for years now to learn how genetics play into this brain-sleep condition. According to an article on the Stanford Medicine website, a narcoleptic Chihuahua named Watson was being used in a clinic by Emmanuel Mignot, M.D., PhD, professor of psychiatry and behavioral sciences, to help explain narcolepsy to children at the clinic who suffer from severe conditions. (Get tips on how to keep your dog safe during the summer.)
Other animals that researchers continue to study the sleep behaviors of are mice, some mammals, and birds.
Ducks Can Explain Why It’s Hard to Fall Asleep in Hotels
Prior to conducting sleep research on animals in Europe, Niels C. Rattenborg, Ph.D., Group Leader, Max Planck Institute for Ornithology in Germany, worked for 10 years as technician in human sleep laboratories in St. Louis, Mo. While there, he developed an interest in birds as well as evolution and ecology, so he decided to go back to graduate school and combine those interests with his knowledge about sleep. His focus is studying animals that have to sleep in challenging situations, like birds that get by on very little sleep and how they sleep while flying.
For Rattenborg’s doctorate degree, he studied sleep in birds, particularly how ducks look out for their flock. “I focused on the phenomena called unihemispheric sleep,” he said. “That’s the ability to sleep with one half of the brain at a time. In my dissertation work, we showed that birds can actually switch from sleeping with both halves of the brain to sleeping with only one half, and they do that when they’re sleeping in more dangerous situations.” Simply put, in unihemispheric sleep, one cerebral hemisphere sleeps while the other is awake.
For the actual experiment, Rattenborg’s team put groups of ducks together in the laboratory and found that the ones at the edge of the group spent more time sleeping with one eye open, with the open eye directed away from the other birds, as if watching for approaching predators, he explained. “They’re able to switch on this half-sleep when needed,” Rattenborg said.
This 1999 study published in the journal, Behavior in Brain Research, inspired researchers to try to understand why humans sleep poorly when they’re in a new environment. “It’s called the ‘first night effect,’ which is basically you don’t sleep as well in a new hotel or away from home,” said Rattenborg. “Quite remarkably, they found that when people sleep in a new environment, they still sleep with both halves of the brain, but one half doesn’t sleep as deeply as it does once they’re used to that environment,” he said. “They found that out by measuring both the intensity of sleep by looking at the brain waves, but also by presenting little sounds to each ear,” he said.
During the participants’ first napping session in the sleep lab, when a sound was presented to the half of the brain that wasn’t sleeping as deeply, people were more likely to wake up. These findings, published in Current Biology last year, suggest that the left hemisphere is more vigilant and easily aroused when sleeping in a new environment, according to the study. On the second napping session in that environment, participants didn’t hear the sounds, which suggests that the two halves of the brain slept symmetrically. The authors concluded that the shallower sleep, increased vigilance, and increased responsiveness of the left hemisphere serves to protect the sleeper in a potentially dangerous environment.
“I was quite excited about [these findings] because people might question, ‘That’s nice what ducks do, but how does that help us understand human sleep?’ That study caused people to think differently about a phenomenon that humans experience and to investigate that in a different way and led to a greater understanding of how our brain sleeps under different circumstances,” Rattenborg said.
“The only other mammals where unihemispheric sleep is known based on research are dolphins, eared seals and manatees,” said Rattenborg. “There, it seems to be an adaptation in the dolphins that allows them to keep surfacing to breathe while obtaining some sleep in one half of the brain at a time.”
Rattenborg also studies whether birds sleep in flight (yes) and looks for similarities and differences between birds’ sleeping brains and human brains.
“In general terms, more traditional biomedical research aimed at understanding human sleep that focuses on standard laboratory animals like mice and rats and dogs in some cases, can greatly enhance our understanding of sleep and lead to treatments for certain sleep disorders,” says Rattenborg.
Some Animals Use REM Sleep
“Birds, just like mammals, have two types of sleep,” says Rattenborg of the Max Planck Institute for Ornithology in Germany. “They have REM (rapid eye movement) sleep and non-REM sleep. The brain waves are remarkably similar to humans.” But those periods of sleep differ greatly – maybe (brain) size does matter. : )
“Episodes of REM sleep in birds are very short, typically less than 10 seconds at a time, whereas in mice it would be tens of seconds or one minute, and in humans it could be up to 45 minutes toward the end of the night,” says Rattenborg.
This article was created for Sleep Number’s blog.
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