FA=high-fat, ab libitum (eat-at-will) diet, FT=high-fat, time-restricted diet, NA=normal ab libitum (eat-at-will) diet, NT=normal diet, time-restricted
Diets tell you what you eat, but a new study suggests when you eat matters too. Of two groups of mice who were fed the same high-fat diet, the mice who could eat around the clock were much heavier than those who had food restricted to eight hours per day, in a new study published in Cell Metabolism.
Researchers in the study gave the mice a special high-fat chow, 61% of whose calories come from fat (compared to just 13% in normal feed). The mice who chowed down all day and night became, unsurprisingly, obese, but the ones who ate the same amount of hi-fat food in only eight hours per day did not. Their body weight was comparable to mice fed an equivalent amount of calories on normal feed.
You go to sleep at night, you wake up in the morning—the definition of sleep doesn’t seem so complicated. But start asking questions and things start getting thorny: Are dolphins that never stop swimming sleeping? Are migrating birds that “shut down” half their brains sleeping? Is someone under general anesthesia sleeping? And what about babies in the womb?
Unborn human babies in the womb are pretty difficult to monitor 24/7, so the researchers interested in that last question got ahold of unhatched chicken eggs. In a new Current Biology paper, they report that chicks show higher-brain activity patterns similar to sleep, and the cries of a hen could “wake up” the chick even when other loud but not chicken-salient sounds could not. These higher-brain activity patterns only appear in the last stage of incubation, presumably after their brains become well developed.
To monitor brain activity in the chicks, the scientists carefully made a small hole in the top of the egg and injected radioactive sugars onto the egg’s inner membrane. The developing embryo absorbed these sugars, which the team could then track with a PET scan. Active neurons need energy, which they get from sugar, so mapping the radioactivity in the brain shows what parts of the brain are active.
Remnants of a Cryptocarya woodii leaf, which researchers
say was part of the oldest bedding ever found
In a South African cave, researchers have uncovered traces of the oldest known human bedding, 77,000-year-old mats made of grasses, leaves, and other plant material. While it’s not especially surprising that early humans would have found a way to improve the cold, generally unpleasant experience of sleeping on a cave floor, archaeologists know little about our ancestors’ sleeping habits and habitats.
Researchers at the University of Alaska, Fairbanks have discovered a way to induce hibernation in arctic ground squirrels—by administering a substance that stimulates the brain receptors of adenosine, a molecule involved in slowing nerve cell activity. Induced hibernation could someday be used to preserve the brain functions of human stroke victims, though that’s still a ways off as the current technique only works on the arctic ground squirrels during hibernation season.
Image: Flickr/Threat to Democracy
What’s the News: Smart clothes might soon be coming into bed with you. A company is developing shirts endowed with a chip that senses the changes in breathing that accompany shifts in sleep phase, to help people track how variables like exercise, coffee intake, and stress affect their sleep.
What’s the News: By videotaping sleepwalkers as they got some shut-eye (with their permission, of course), French and Swiss researchers caught on tape what other studies have deduced through brain recordings and memory tasks: As we sleep, our brains seem to replay what we learned during the day. See an example of a a sleepwalker’s re-enactments here:
How the Heck:
What’s the Context:
Not So Fast:
Reference: “Evidence for the Re-Enactment of a Recently Learned Behavior during Sleepwalking” Delphine Oudiette et al. doi:10.1371/journal.pone.0018056
Image: WikimediaCommons / Chad Fitz
The first study of sleep in bees, published this week in the Proceedings of the National Academy of Sciences, found that the tired bees lag just like sleep-deprived humans do. Too bad bees don’t have coffee. Says lead researcher Barrett Klein:
“When deprived of sleep, humans typically experience a diminished ability to perform a variety of tasks, including communicating as clearly or as precisely. We found that sleep-deprived honey bees also experienced communication problems. They advertised the direction to a food site less precisely to their fellow bees.” [Daily Mail]
So how do you keep bees awake when they don’t need to cram for a calculus final? You make them magnetic. Klein attached a piece of either steel or non-magnetic metal to the bees’ backs. Then all through the night, the researchers swung a magnet over the hive three times a minute–a device they call the “insominator.” This jostled the bees with the magnetic steel on their backs and kept them from sleeping.
The problem: Scientists want to study our circadian rhythms, our bodies’ internal clocks, and they can do so on the genetic level by examining how gene expression changes throughout the day. But ordinarily that would require sampling a person’s blood or skin multiple times a day, an ordeal few of us would want to endure.
The solution: hair.
Makoto Akashi’s team reports today in the Proceedings of the National Academy of Sciences that hairs, be they from the beard or head, contain the telltale signature of RNA activity that shows when we humans are at our peak activity level for the day.
How can some sleepers doze through anything from the rattle of a jackhammer to the blast of a jet engine? According to a new study, an extra helping of brain activity in the thalamus–a region tied to the senses–may give some people a better chance at blocking sleep-disturbing sounds.
“I hear complaints a lot as a sleep doctor that noises are interrupting people’s sleep all the time,’’ said Dr. Jeffrey M. Ellenbogen, chief of the division of sleep medicine at Harvard Medical School [and co-author of the study]. “What is it in the brain that makes it have less response to noise at night, and how can we enhance that natural occurring brain-based process to help people sleep?” he said. [The New York Times]
Researchers at the Harvard Medical School asked twelve healthy volunteers to spend three nights in a sleep lab. The first night the researchers let them sleep soundly, but monitored their brain activity. The following two nights, they used four speakers aimed at the sleepers’ heads to play sounds of air and car traffic, ringing telephones, and “hospital-based mechanical sounds,” among other things. They found that those people whose thalami produced more high-frequency signals called “sleep spindles” lasted the longest when barraged with noises: the more sleep spindles, apparently, the better the sleep. The study appears today in Current Biology.
Don’t be deceived by the peaceful look of a newborn baby asleep in a crib–that little tyke may actually be hard at work, soaking up information about the world. A new study has found that newborns are capable of a rudimentary form of learning while they’re asleep, which may be an important process, considering that infants spend between 16 to 18 hours a day in the land of Nod.
Researchers recruited one- and two-day-old infants for the study, published in the Proceedings of the National Academy of Sciences. With each sleeping baby, the researchers played a musical tone and followed that by a puff of air to the eyes, a mild annoyance that caused the infant to automatically scrunch up its eyes. As this sequence of events was repeated, the sleeping babies learned to associate the air puff with the tone, and soon began to to tighten their eyelids as soon as they heard the musical note, even if the air puff didn’t follow. Electrodes stuck to their scalps also showed activity in the prefrontal cortex, which is involved in memory.