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7 Things We Can Turn Off and On in the Brain

Original image
iStock / Rebecca O'Connell

As much as we’d like to think we’re always in control of our own actions, a lot of human behavior, mood, and habit can be traced to involuntary reactions in the brain. As researchers learn more about what’s going on inside our heads, they’re finding the light switches that control some of our most basic functions—many of which can be turned off. 

1. Thirst

Researchers know the control center for thirst is somewhere in the hypothalamus, an almond-sized section of the human brain that regulates a number of our basic functions (hunger, sex drive, temperature). But recently, neuroscientists at Columbia University identified two specific populations of neurons in the hypothalamus of mice that control the impulse to hydrate, and they wanted to know what happens when they’re activated. By using a process called optogenetics, they manipulated these cells to make them sensitive to certain wavelengths of light. Then, fiber-optic cables were implanted in the brains of mice that when illuminated, turned the corresponding neurons on or off.

They found that one group of thirst neurons “evokes intense drinking behavior” when activated. How intense? Mice drank up to eight percent of their body weight in water when these neurons were switched on. That’s the equivalent of a human drinking a gallon and a half of water in 10 minutes.

The second group of neurons reduces the desire to drink, even when the animal is deprived of water. You can see video of some very thirsty mice from this study here.

2. Hunger

Using the same optogenetics technique, scientists at Johns Hopkins University have pinpointed the brain cells that control our impulse to eat. When these cells are activated in mice, the rodents are compelled to stuff themselves well beyond the point of being full. But when they’re shut down, the mice ignore food, even when they should be hungry. Researchers think this information could potentially help treat eating disorders in humans.

3. Consciousness

We consider consciousness and self-awareness to be defining characteristics of human life. So it may surprise you to know that such sacred traits can be turned off and on like a light switch in a lab setting. At George Washington University, Mohamad Koubeissi and his team accidentally flipped the switch while using electrodes to stimulate different parts of the brain in an epileptic woman.

When they stimulated a section called the claustrum, the patient lost consciousness, but she didn’t pass out. Instead she sat motionless with a blank stare and showed no response to cues around her. She snapped out of her trance when the stimulation stopped, and had no memory of the lapse. "Ultimately, if we know how consciousness is created and which parts of the brain are involved then we can understand who has it and who doesn't," says Christof Koch at the Allen Institute for Brain Science in Seattle. "Do robots have it? Do fetuses? Does a cat or dog or worm?” The caveat: because of her epilepsy, this woman had part of her hippocampus removed, so her brain is far from that of a “normal” person.

Other studies have shown the human brain may switch off self-awareness when we’re stressed, without any help from researchers. In 2006, neurobiologists from the Weizmann Institute of Science in Rehovot, Israel observed that when humans are forced to focus on a difficult task (particularly under a strict deadline), the area of our brains associated with introspection, the cortex, becomes quiet, and we go into a sort of robotic mode until the task is done. This ability could have evolved for purposes of self-defense. "If there is a sudden danger, such as the appearance of a snake, it is not helpful to stand around wondering how one feels about the situation," researcher Ilan Goldberg told New Scientist.

4. Pain

We can already ease pain with certain drugs, but many treatments come with side effects like dependency and tolerance. Saint Louis University researcher Daniela Salvemini and her team think they’ve found a way to treat chronic pain caused by nerve damage, including the physical agony caused by chemotherapy and bone cancer. By turning on the “A3 adenosine receptor” in the brain and spinal cord, Salvemini and her team were able to block pain caused by nerve damage in rodents, without any of the side effects associated with drug treatments.

5. Violence

What if we could reduce the human urge to fight? Dayu Lin from New York University zoomed in on the hypothalamus, the previously-mentioned hub of bodily functions, to look at the specific neurons that fire during acts of physical violence. By stimulating those neurons using optogenetics, Lin was able to turn male mice into vicious fighters that attacked anything in their vicinity—including inanimate objects, and both male and female mice. She could also calm them, quelling their violent urges by silencing these neurons. Could this strategy one day be used on people? "I think there's every reason to think that this would be true in humans," says Newton Canteras, a neuroscientist at the University of São Paulo in Brazil, and a co-author of this study.

Interestingly, Lin and her team found violence-inducing neurons overlap and compete with neurons associated with sex. In fact, the act of sex temporarily suppresses the violent urges in mice.

6. Bad habits

Can’t stop biting your nails? Plagued by an urge to crack your knuckles? Neuroscientists have found the brain cells responsible for habit formation, at least in rats. By turning these neurons on or off, they are able to eliminate or encourage the formation of new habits. To test this, they gave lab rats a new habit. With a little help from a tasty reward, scientists trained the rodents to navigate a maze until it became so habitual that they’d do it even after the reward was replaced by punishment. But when the neurons were inhibited in the lab, the habit disappeared.

Right now, this kind of procedure would be too invasive to try on humans, says Professor Ann Graybiel, a member of the McGovern Institute for Brain Research at MIT. But it does pave the way for similar, more advanced treatments in the future.

7. Parkinson’s, depression—and maybe Alzheimer’s

Using electrodes embedded in the brain, a neurosurgeon from the University of Toronto named Andres Lozano is harnessing electricity to treat some of humanity’s most vexing ailments. For example, Lozano knows which neurons in the brain are misfiring to cause the severe shaking associated with Parkinson’s disease. In his TED Talk, he explains, “we use electricity to dictate how they fire, and we try to block their misbehavior using electricity. So in this case, we are suppressing the activity of abnormal neurons.” As a result of this suppression, tremors can be dramatically reduced.

Lozano has done similar work with areas in the brain that cause severe depression and is “seeing very striking results in these patients,” he says. Can this approach work for memory? In 2014, he launched a clinical trial to treat 50 people with mild Alzheimer’s with electrical stimulation “to get these areas of the brain that were not using glucose to use glucose once again.” We’ll know in April if the treatment worked.

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Weather Watch
Will the Solar Eclipse Have an Impact on the Weather?

The United States will have a front-row seat to one of the most spectacular solar eclipses to sweep across the country in our lifetimes. Millions of lucky observers from coast to coast will have the chance to watch the Moon scoot in front of the Sun on the afternoon of August 21, 2017, briefly plunging cities like Salem, Oregon, Hopkinsville, Kentucky, and Columbia, South Carolina, into night-like darkness during the day. Read our field guide to the solar eclipse for tips on how to make the most of this spectacular event.

While a solar eclipse can be amazing to behold, the phenomenon has little impact on Earth. It may, however, have a small but noticeable effect on weather in the areas that experience a total eclipse.

The entire country will be able to see the Moon cover the Sun in some form, but the best viewing areas will be along a northwest-to-southeast path across the middle of the country. According to NASA, a location needs at least 90 percent coverage to notice any darkening at all, and even 99 percent coverage of the Sun only provides the same level of darkness you'd see at twilight. Areas totally covered by the Moon's relatively narrow shadow will experience conditions akin to dusk, prompting street lights to turn on and even tricking birds and bugs into thinking that the day is drawing to an end. Studies have shown that the total eclipse could also have an effect on temperatures and even winds.

Researchers who studied an eclipse across Europe in 1999 found that the event lowered air temperatures by as much as 5°F across the path of totality. This brief dip in air temperatures also affected local wind speed and direction—not by much, but it was enough for both people and instruments to take notice of the so-called "eclipse wind." The effect on the atmosphere in Europe wasn't a fluke. A weather station in Zambia recorded a temperature drop of nearly 15°F during a solar eclipse in June 2001, and there are reports through history of observers noticing a distinct cooling effect in the midst of a lunar shadow.

The duration of the eclipse and the amount of moisture in the air will determine how much the Moon's shadow will lower temperatures. Moist air has a higher heat capacity than drier air, so when it's muggy outside it takes longer for the air to warm up and cool down. This is why daily temperatures fluctuate less in Miami, Florida, than they do in Phoenix, Arizona. Communities that lie among the drier, cooler Rocky Mountains are more likely to witness a noteworthy dip in temperatures compared to states like Tennessee or South Carolina, which are typically locked in the humid doldrums of summer at the end of August.

If you're lucky enough to witness this spectacular astronomical phenomenon, make sure you bring your eclipse glasses—and a thermometer.

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Space
7 Eye-Opening Facts About Venus

For all the efforts to find another inhabitable planet orbiting a distant star, it might surprise you to learn that a very real Earth 2.0 exists in this solar system—just one planet over. Not Mars (which actually isn't much like Earth at all), but rather, our other neighbor: Venus. Mental Floss spoke to geophysicist Bob Grimm, a program director at the Southwest Research Institute and chair of NASA's Venus Exploration Analysis Group. Here are a few things we learned about Earth's twin sister.

1. BY THE NUMBERS, VENUS LOOKS A LOT LIKE EARTH.

Venus has a radius of 3760 miles. Earth's is 3963. Its mass and gravity are 82 percent and 91 percent of Earth's, respectively—pretty similar as planets go. Venus is composed of a mostly basalt crust, silicate mantle, and iron core. Earth is the same. The two planets likely share common origins somewhere around 4.5 billion years ago.

In fact, by all accounts, we should be able to land our flying saucers on Venus, saddle up a dinosaur, and start building tract housing. It's perfect for colonization, but for a few minor differences. Its year is shorter, at 224.7 days. (And its days are much longer, at 243 Earth days per Venus day.) The Sun would rise in the west and set in the east because of the planet's retrograde orbit (which, by the way, is the most circular of any planet in the solar system). And then there's another small problem …

2. IT'S HOT. VERY, VERY HOT.

Venus is hotter than Mercury, despite being 30 million miles farther from the Sun. How hot? Hot enough, on average, to melt a block of lead the way a block of ice would melt on Earth. Venus suffers from a runaway greenhouse effect. Sunlight penetrates the dense clouds surrounding Venus, heating the landscape. The ground in turn blasts out heat, which rises and tries to escape the atmosphere. But carbon dioxide, which makes up 96 percent of its atmosphere, traps the heat, keeping things nice and toasty, around 900°F. And those clouds aren't the white, fluffy variety. They're made of droplets of sulfuric acid, which makes its lightning storms especially harrowing.

3. VENUS HOLDS THE KEY TO UNDERSTANDING EXOPLANETS.

"'Does Earth-size mean Earth-like?' is a basic problem of planetology," says Grimm. "Understanding how Earth and Venus diverged is essential to understanding comparative planetology, and potentially exoplanets—these worlds orbiting distant stars that are being discovered telescopically."

Knowing more about Venus would help scientists better distinguish potentially habitable worlds out there, and better understand how a good world can go bad, from a sustaining-life perspective. "Geology and meteorology are intimately related to the evolution of the Earth and the evolution of life on Earth," Grimm notes. "Even though we may not be looking for life on Venus, it's important to understanding Earth's place in the solar system and in the universe."

4. IT DIDN'T HAVE DINOSAURS. (PROBABLY.)

You might have run across old illustrations of Venus with conditions similar to the Carboniferous Period on Earth. Astronomers have known for just under a hundred years that Venus's atmosphere is devoid of oxygen, without which you can't have water. But even a modest backyard telescope can see the clouds enveloping our neighbor, and as Carl Sagan explained, from there you're only a couple of erroneous jumps from assuming a brontosaurus. (Thick clouds mean more water than land. More water than land means swamps. Dinosaurs lived in swamps. Dinosaurs live on Venus. QED.) Said Sagan: "Observation: There was absolutely nothing to see on Venus. Conclusion: It must be covered with life."

But seeing is believing, and the Mariner and Venera series of probes disabused us of the romantic notion of a swampy neighbor to the left. Still, we should probably send robots there to check. Just to be sure.

5. WE HAVEN'T BEEN TO ITS SURFACE SINCE THE 1980S.

Venus was the first planet we visited, with Mariner 2 achieving the first successful planetary encounter in 1962. Four years later, Venera 3 on Venus became the first spacecraft to touch the surface of another planet. (Communications were lost long before impact, but unless a dinosaur ate it, the spacecraft probably touched the ground.) Our first graceful landing on another planet? Venera 7 on Venus. Our efforts to reach its surface go back much further than that, though. The transit of Venus in 1761 practically invented the notion of an international science community. But we abandoned the surface of Venus in 1984, and NASA hasn't launched an orbiter to Venus since Magellan in 1989. 

Since then, the Venus-science community has been trying to get another mission to the launch pad. Presently, U.S. planetary scientists have submitted proposals to NASA for a sub-$1 billion New Frontiers–class mission. They are also working with their colleagues in Russia to launch a joint mission called Venera-D. "We need better radar views of the surface," says Grimm, "and that has to happen at some point to understand the geology. We need deep probes into the atmosphere to understand it better, and we need a new generation of landers."

6. A NEW MISSION COULD HELP SOLVE OUR BIGGEST QUESTIONS.

"There is evidence in the deuterium-to-hydrogen ratio that Venus once had water, maybe hundreds of meters deep, more like a global sea than an ocean," says Grimm. A theoretical paper published last year posed a climate model for Venus suggesting that water could have existed on its surface as recently as 1 billion years ago. Clouds could form in a certain way, shielding the surface from the Sun and allowing stable water at the surface. Furthermore, near-infrared observations support the argument for a watery Venusian past. ESA's Venus Express orbiter in 2012 found evidence of granite-like rocks on some parts of the planet. Granite requires a multiple melting process in the presence of water. A mission to Venus could confirm this.

Meanwhile, one of the most significant revelations from Magellan is that there are only around 1000 craters on the surface with no differences in density, and it is hard to find craters that are obviously in a state of being wiped out by lava, or being faulted. Venus does not have plate tectonics, one of the central mechanisms that organizes all geology on the Earth. So what happened to the surface of Venus? Where is the evidence of the Late Heavy Bombardment seen on other terrestrial planets and moons? One hypothesis is that all of Venus was resurfaced at once. There may have been a global catastrophe on Venus, perhaps as recently 750 million years ago, that quickly "reset" its surface. Other models suggest a subtler resurfacing at work in which craters might be erased over billions of years.

"So this whole idea of the surface age of Venus is a pivotal question for how planets evolve geologically," says Grimm. "But what was Venus like before that? Was there a single catastrophe, or have there been many? Was there just one catastrophe and Venus was watery before that, or has Venus operated in a steady state going back to the first billion years? There is more consensus that in the first several hundred million years to billion years, there could have been water." Further landings on Venus could help us solve the mystery of when Venus's surface was formed, if there was ever water there, and why, if it existed, it went away.

7. VENUS IS KIND OF A YELLOW, EXTREME VERSION OF HAWAII.

If Matt Damon were to get stranded on Venus in a sequel to The Martian, he would need to be resourceful indeed to survive the heat and the corrosive air. But what he would find wouldn't be wholly alien. The winds at the surface of Venus are very gentle, around a meter or so per second. The vistas would consist of hills and ridges, with dark lava rocks of various types, mostly basalt. The atmospheric pressure is 90 times greater than Earth at sea level, so walking there would feel a lot like swimming here.

"I don't think [Venus] would look wavy and hot-hazy, because the atmosphere is pretty stable and uniform right at the surface," says Grimm. "It would be harder to walk through the dense atmosphere, but not as hard as walking through water. We know from landings that it's kind of yellow because of the sulfur in the atmosphere. So with the abundance of lavas in many places on Venus, it sort of looks like a yellowish Hawaii."

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