Posts tagged with "Current Biology"

Into the light: Babies in the womb may see more than we thought

November 26, 2019

The transitions that mark the beginning and end of human life are marked by the same phenomenon: light. In fact, a new study conducted at the University of California-Berkeley has found that, eve by the second trimester—long before a baby’s eyes can see images—they can detect light.

Previously, the light-sensitive cells in the developing retina— the thin sheet of brain-like tissue at the back of the eye— were assumed to be simple” on-off switches,” presumably there to set up the 24-hour, day-night rhythms parents hope their baby will follow.

Now, with funding from the National Institutes of Health, researchers have discovered evidence that these simple cells actually talk to one another as part of an interconnected network that gives the retina more light sensitivity than once thought, and that may enhance the influence of light on behavior and brain development in unsuspected ways.

In the developing eye, perhaps 3% of ganglion cell—the cells in the retina that send messages through the optic nerve into the brain—are sensitive to light and, to date, researchers have found about six different subtypes that communicate with various places in the brain. Some talk to the suprachiasmatic nucleus to tune our internal clock to the day-night cycle. Others send signals to the area that makes our pupils constrict in bright light.

But others connect to surprising areas: the perihabenula, which regulates mood, and the amygdala, which deals with emotions.

In mice and monkeys, recent evidence suggests that these ganglion cells also talk with one another through electrical connections called gap junctions, implying much more complexity in immature rodent and primate eyes than imagined.

“Given the variety of these ganglion cells and that they project to many different parts of the brain, it makes me wonder whether they play a role in how the retina connects up to the brain,” said Marla Feller, a UC Berkeley professor of molecular and cell biology and senior author of a paper that appeared this month in the journal Current Biology. “Maybe not for visual circuits, but for non-vision behaviors. Not only the pupillary light reflex and circadian rhythms, but possibly explaining problems like light-induced migraines, or why light therapy works for depression.”

The cells, called intrinsically photosensitive retinal ganglion cells (ipRGCs), were discovered only ten years ago, surprising those such as Feller, who had been studying the developing retina for nearly 20 years. She played a major role, along with her mentor, Carla Shatz of Stanford University, in showing that spontaneous electrical activity in the eye during development— so-called retinal waves —is critical for setting up the correct brain networks to process images later on.

“We thought they (mouse pups and the human fetus) were blind at this point in development,” said Feller. “We thought that the ganglion cells were there in the developing eye, that they are connected to the brain, but that they were not really connected to much of the rest of the retina, at that point. Now, it turns out they are connected to each other, which was a surprising thing.”

UC Berkeley graduate student Franklin Caval-Holme combined two-photon calcium imaging, whole-cell electrical recording, pharmacology, and anatomical techniques to show that the six types of ipRGCs in the newborn mouse retina link up electrically, via gap junctions, to form a retinal network that the researchers found not only detects light, but responds to the intensity of the light, which can vary nearly a billionfold.

Gap junction circuits were critical for light sensitivity in some ipRGC subtypes, but not others, providing a potential avenue to determine which ipRGC subtypes provide the signal for specific non-visual behaviors that light evokes.

“Aversion to light, which pups develop very early, is intensity-dependent,” suggesting that these neural circuits could be involved in light-aversion behavior, Caval-Holme said. “We don’t know which of these ipRGC subtypes in the neonatal retina actually contributes to the behavior, so it will be very interesting to see what role all these different subtypes have.”

The researchers also found evidence that the circuit tunes itself in a way that could adapt to the intensity of light, which probably has an important role in development, Feller said.

“In the past, people demonstrated that these light-sensitive cells are important for things like the development of the blood vessels in the retina and light entrainment of circadian rhythms, but those were kind of a light on/light off response, where you need some light or no light,” she said. “This seems to argue that they are actually trying to code for many different intensities of light, encoding much more information than people had previously thought.”

Research contact: @EurekaAlert

So you think he can dance?

July 11, 2019

Can’t stop those toes from tapping? Just want to boogie down? You have company: A Harvard study of YouTube sensation Snowball, the dancing cockatoo, spotlights the surprising variety and creativity of his moves and suggests that he, and some other vocal-learning animals, may be capable of some of the kind of sophisticated brain function thought to be exclusively human.

The white bird with the yellow-crested head became an Internet sensation in 2009 when videos of him grooving in perfect time to Another One Bites the Dust” by the British rock band Queen went viral. To date, 7.3 million people have clicked on the three-and-a-half-minute clip and millions more have watched videos of the bird bouncing and bobbing to chart-toppers by Michael Jackson and the Back Street Boys.

But was he really dancing in time to the beat of the music, or just imitating his owner? Or did someone edit in music over his moves to make it look like he could dance? The questions fascinated Ani Patel, a cognitivie neuroscientist..

It was unbelievable when I first saw that video,” said Patel, the William and Flora Hewlett Foundation Fellow at the Radcliffe Institute for Advanced Study at Harvard University. He is is working on a book about the evolution of music cognition based in part on his cross-species research. “I still remember it. I was staring at the screen and my jaw just hit the floor. I thought, ‘Is this real? Could this actually be happening?’ Within minutes I’d written Snowball’s owner.”

To test his theory, Patel and a team of researchers filmed Snowball while they alternately slowed down or sped up some of the bird’s favorite dance tracks. They watched as the parrot repeatedly synchronized his steps to the varied tempos.

“He predicted the timing of the beat, and he did this spontaneously without having been trained,” said Patel, whose 2009 findings were similar to those reported by Harvard researchers that same year involving the African grey parrot Alex and his ability to match his movements to the beats of novel songs.

Now, thanks to Patel’s new paper, “Spontaneity and diversity of movement to music are not uniquely human,” Snowball’s legion of fans have another video gem, a compilation piece featuring the parrot’s 14 different dance moves, some of which Patel and his collaborators suspect the bird came up with on his own.

In the paper, Patel and his team list the five traits they believe are required for an animal to be able to spontaneously dance to music: vocal learning; the ability to imitate; a propensity to form long-term social bonds; the ability to learn a complex sequence of movement; and an attentiveness to communicative movements. Humans and parrots share all five.

“We think these five together in an animal brain lay the foundation for an impulse to dance to music with diverse movements,” said Patel, who noted other animals can do some of the five things but not others. Monkeys, for example, can imitate movements but have very limited vocal learning capacity, he said, and thus can’t move rhythmically to music. “It’s unusual for all five things to come together, and when they do it means a brain is primed to develop dancing behavior if it’s given exposure to music with rhythm and beat.”

The study, published in Current Biology, lists the more than a dozen separate movements Snowball liked to break out back in 2009 when dancing to Cyndi Lauper’s Girls Just Want to Have Fun and the 1980 Queen hit.

The researchers filmed Snowball dancing to the songs, then coded his individual movements. In order to qualify as a distinct move, the parrot had to repeat it at least two times at different points in the study.

The report’s lead author, R. Joanne Jao Keehn, a cognitive neuroscientist and a trained dancer, analyzed the videos frame by frame and labeled Snowball’s different motions. She found that among the bird’s favorite steps are the “Vogue,” the movement of his head from one side of his lifted foot to another; the “Headbang with Lifted Foot,” when he lifts his foot and bangs his head simultaneously; and the “Head-Foot Sync,” during which he moves his head and foot in unison.

In addition to being wildly entertaining, the bird’s variety of movements point to a type of cerebral flexibility that suggests his creative choreography is not simply “a brainstem reflex to sound,” said Patel. “It’s actually a complex cognitive act that involves choosing among different types of possible movement options. It’s exactly how we think of human dancing.”

Research contact: @Harvard

Don’t ‘sleep in’ on Saturday or Sunday

March 1, 2019

Wake up, America! A study conducted at the University of Colorado–Boulder has found that trying to catch up on shut-eye over the weekend may not be such a good idea—for either your waistline or your health, CNN reported on February 28.

“Weekend catch-up sleep is not protective,” Dr. Vsevolod Polotsky, director of Sleep Research at the Johns Hopkins University School of Medicine, told the cable news network, adding, “The bottom line of this study is that even if you sleep longer on weekends, if you continue to sleep poorly, you will still eat too much, and you will still gain weight.”

Study author Kenneth Wright, Jr., who directs the Sleep Lab at the UC-Boulder, agrees. “Sleeping in on weekend doesn’t correct the body’s inability to regulate blood sugar, if that weekend is followed by a workweek or [a]school week full of insufficient sleep,” he told CNN.

The study by Wright and his colleagues—published in the journal Current Biology—assigned 36 healthy young men and women to three groups that prescribed different sleep requirements over a total of 10 days. None of the participants had newborns in the home or any health impairments that would affect the quality of their sleep.

The first group had the opportunity to sleep for nine hours each night for the 10 days. The second group was restricted to only five hours of sleep a night for the same duration, while the third was restricted to five hours Monday through Friday but allowed to sleep as long as they wanted on the weekend and go to bed as early as they liked on Sunday night. Come Monday, that third group was put back on the deprived sleep schedule of only five hours a night.

Both of the sleep-deprived groups snacked more after dinner and gained weight during the study—men, much more than women, CNN reports. The sleep-deprived men showed an overall 2.8% increase in their weight, while women’s body size went up by only 1.1%. By comparison, men who slept in on the weekend showed a 3% increase in weight, while women’s body size went up 0.05%

Gaining weight while sleep-deprived isn’t surprising, Wright said. “One of the things we and others have found in the past is that when people don’t sleep enough, they tend to eat more, partly because their body is burning more calories. But what happens is that people eat more than they need and therefore gain weight.

That could be in part, Polotsky told the news outlet, because hunger hormones are affected by a chronic lack of sleep. “The hormone leptin decreases appetite, while the hormone ghrelin increases appetite,” explained Polotsky, who was not involved in the study. “We know from previous research that sleep deprivation causes leptin to drop and ghrelin to rise, so you’re hungry.”

What was surprising to the researchers is what happened to the group who slept in on the weekends. “Even though people slept as much as they could, it was insufficient,” Wright said. “As soon as they went back to the short sleep schedules on Monday, their ability of their body to regulate blood sugar was impaired.”

Why? One of the reasons the weekend group may have been more affected is because their circadian rhythm, or biological clock, had been altered, depriving the body of certain hormones.

“If you catch up during weekends, you habitually eat later, because the circadian clock is shifting,” Polotsky said. “Add in after-dinner snacks; the sleep-deprived eat much more after dinner, as well.”

Not only that, but the weekend recovery group showed increased sensitivity to insulin in both their muscles and their livers, a result not found in the second group on restricted sleep. That’s important, Wright explained to CNN, because the muscle and liver are two of the most important tissues that take up blood sugar after eating.

“That helps us understand why is it that when we don’t get enough sleep, we have an increased risk for things like diabetes,” he added, because “short, insufficient sleep schedules will lead to an inability to regulate blood sugar and increases the risk of metabolic disease in the long term.”

Metabolic syndrome is an array of symptoms such as fat around the waist, abnormal cholesterol, high blood sugar, and high blood pressure—all of which can raise the risk of heart disease, stroke and diabetes.

“And when we go back to getting too little sleep again,” Wright told CNN, “we’re doing things that could be negative for our health long-term.”

The American Academy of Sleep Medicine recommends at least seven hours of sleep each night for adults and much more for children.

Research contact: kenneth.wright@colorado.edu

You won’t be a hit with mosquitoes, if you swat back

July 6, 2018

Do you ever feel as if you have been singled out in a crowd—the only one to return home from outdoor activities with itchy, red welts rising all over your body? Well, we hate to say so, but it’s true: Mosquitos remember the taste and smell of human blood, according to researchers at the Frain Life Science Institute at Virginia Tech, and they often pick on people whose blood tastes the sweetest to them.

That’s the bad news. The good news, based on a recent study, is that, if you swat determinedly at the mosquitoes around you, they will remember the unpleasant sensation—and stay away from you in the future.

Indeed, the Virginia Tech study—published last January in the journal Current Biology—found that the pesky insects have much larger and longer memories than we could have imagined. The researchers found that mosquitoes can learn rapidly and remember the smells of the tastiest hosts. Dopamine is a key mediator of this process. Mosquitoes use this information and incorporate it with other stimuli to develop preferences for a particular vertebrate host species, and, within that population, certain individuals

However, the study also proved that even if an individual is deemed delicious-smelling, a mosquito’s preference can shift if that person’s smell is associated with an unpleasant sensation. Hosts who swat at mosquitoes or perform other defensive behaviors may be abandoned, no matter how sweet.

Clément Vinauger, an assistant professor of Biochemistry in the College of Agriculture and Life Sciences; and Chloé Lahondère, a research assistant professor in the Department of Biochemistry, demonstrated that mosquitoes exhibit a trait known as aversive learning by training female Aedes aegypti mosquitoes to associate odors (including human body odors) with unpleasant shocks and vibrations.

Twenty-four hours later, the same mosquitoes were assessed in a Y-maze olfactometer in which they had to fly upwind and choose between the once-preferred human body odor and a control odor. The mosquitoes avoided the human body odor—suggesting that they had been successfully trained.

By taking a multidisciplinary approach and using cutting-edge techniques, including CRISPR gene editing and RNA interference (RNAi), the scientists also were able to identify that dopamine is a key mediator of aversive learning in mosquitoes.

They targeted specific parts of the brain involved in olfactory integration by fitting mosquitoes with helmets that allowed for brain activity recordings and observations. By placing mosquitoes in an insect flight simulator and exposing the mosquitoes to various smells, including human body odors, the scientists observed how the insects, trained or not, reacted. What they saw is that the neural activity in the brain region where olfactory information is processed was modulated by dopamine in such a way that odors were easier to discriminate, and potentially learn, by the mosquitoes.

“Unfortunately, there is no way of knowing exactly what attracts a mosquito to a particular human. Individuals are made up of unique molecular cocktails that include combinations of more than 400 chemicals,” said Lahondère.  “However, we now know that mosquitoes are able to learn odors emitted by their host and avoid those that were more defensive.”

“Understanding these mechanisms of mosquito learning and preferences may provide new tools for mosquito control,” said Vinauger. “For example, we could target mosquitoes’ ability to learn and either impair it or exploit it to our advantage.”

Research contact: vinauger@vt.edu