CLOSE
iStock / Rebecca O'Connell
iStock / Rebecca O'Connell

7 Things We Can Turn Off and On in the Brain

iStock / Rebecca O'Connell
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.

nextArticle.image_alt|e
The American Museum of Natural History
arrow
Lists
10 Surprising Ways Senses Shape Perception
The American Museum of Natural History
The American Museum of Natural History

Every bit of information we know about the world we gathered with one of our five senses. But even with perfect pitch or 20/20 vision, our perceptions don’t always reflect an accurate picture of our surroundings. Our brain is constantly filling in gaps and taking shortcuts, which can result in some pretty wild illusions.

That’s the subject of “Our Senses: An Immersive Experience,” a new exhibition at the American Museum of Natural History in New York City. Mental Floss recently took a tour of the sensory funhouse to learn more about how the brain and the senses interact.

1. LIGHTING REVEALS HIDDEN IMAGES.

Woman and child looking at pictures on a wall

Under normal lighting, the walls of the first room of “Our Senses” look like abstract art. But when the lights change color, hidden illustrations are revealed. The three lights—blue, red, and green—used in the room activate the three cone cells in our eyes, and each color highlights a different set of animal illustrations, giving the viewers the impression of switching between three separate rooms while standing still.

2. CERTAIN SOUNDS TAKE PRIORITY ...

We can “hear” many different sounds at once, but we can only listen to a couple at a time. The AMNH exhibit demonstrates this with an audio collage of competing recordings. Our ears automatically pick out noises we’re conditioned to react to, like an ambulance siren or a baby’s cry. Other sounds, like individual voices and musical instruments, require more effort to detect.

3. ... AS DO CERTAIN IMAGES.

When looking at a painting, most people’s eyes are drawn to the same spots. The first things we look for in an image are human faces. So after staring at an artwork for five seconds, you may be able to say how many people are in it and what they look like, but would likely come up short when asked to list the inanimate object in the scene.

4. PAST IMAGES AFFECT PRESENT PERCEPTION.

Our senses often are more suggestible than we would like. Check out the video above. After seeing the first sequence of animal drawings, do you see a rat or a man’s face in the last image? The answer is likely a rat. Now watch the next round—after being shown pictures of faces, you might see a man’s face instead even though the final image hasn’t changed.

5. COLOR INFLUENCES TASTE ...

Every cooking show you’ve watched is right—presentation really is important. One look at something can dictate your expectations for how it should taste. Researchers have found that we perceive red food and drinks to taste sweeter and green food and drinks to taste less sweet regardless of chemical composition. Even the color of the cup we drink from can influence our perception of taste.

6. ... AND SO DOES SOUND

Sight isn’t the only sense that plays a part in how we taste. According to one study, listening to crunching noises while snacking on chips makes them taste fresher. Remember that trick before tossing out a bag of stale junk food.

7. BEING HYPER-FOCUSED HAS DRAWBACKS.

Have you ever been so focused on something that the world around you seemed to disappear? If you can’t recall the feeling, watch the video above. The instructions say to keep track of every time a ball is passed. If you’re totally absorbed, you may not notice anything peculiar, but watch it a second time without paying attention to anything in particular and you’ll see a person in a gorilla suit walk into the middle of the screen. The phenomenon that allows us to tune out big details like this is called selective attention. If you devote all your mental energy to one task, your brain puts up blinders that block out irrelevant information without you realizing it.

8. THINGS GET WEIRD WHEN SENSES CONTRADICT EACH OTHER.

Girl standing in optical illusion room.

The most mind-bending room in the "Our Senses" exhibit is practically empty. The illusion comes from the black grid pattern painted onto the white wall in such a way that straight planes appear to curve. The shapes tell our eyes we’re walking on uneven ground while our inner ear tells us the floor is stable. It’s like getting seasick in reverse: This conflicting sensory information can make us feel dizzy and even nauseous.

9. WE SEE SHADOWS THAT AREN’T THERE.

If our brains didn’t know how to adjust for lighting, we’d see every shadow as part of the object it falls on. But we can recognize that the half of a street that’s covered in shade isn’t actually darker in color than the half that sits in the sun. It’s a pretty useful adaptation—except when it’s hijacked for optical illusions. Look at the image above: The squares marked A and B are actually the same shade of gray. Because the pillar appears to cast a shadow over square B, our brain assumes it’s really lighter in color than what we’re shown.

10. WE SEE FACES EVERYWHERE.

The human brain is really good at recognizing human faces—so good it can make us see things that aren’t there. This is apparent in the Einstein hollow head illusion. When looking at the mold of Albert Einstein’s face straight on, the features appear to pop out rather than sink in. Our brain knows we’re looking at something similar to a human face, and it knows what human faces are shaped like, so it automatically corrects the image that it’s given.

All images courtesy of the American Museum of Natural History unless otherwise noted.

nextArticle.image_alt|e
NASA/JPL-Caltech
arrow
Space
More Details Emerge About 'Oumuamua, Earth's First-Recorded Interstellar Visitor
 NASA/JPL-Caltech
NASA/JPL-Caltech

In October, scientists using the University of Hawaii's Pan-STARRS 1 telescope sighted something extraordinary: Earth's first confirmed interstellar visitor. Originally called A/2017 U1, the once-mysterious object has a new name—'Oumuamua, according to Scientific American—and researchers continue to learn more about its physical properties. Now, a team from the University of Hawaii's Institute of Astronomy has published a detailed report of what they know so far in Nature.

Fittingly, "'Oumuamua" is Hawaiian for "a messenger from afar arriving first." 'Oumuamua's astronomical designation is 1I/2017 U1. The "I" in 1I/2017 stands for "interstellar." Until now, objects similar to 'Oumuamua were always given "C" and "A" names, which stand for either comet or asteroid. New observations have researchers concluding that 'Oumuamua is unusual for more than its far-flung origins.

It's a cigar-shaped object 10 times longer than it is wide, stretching to a half-mile long. It's also reddish in color, and is similar in some ways to some asteroids in our solar system, the BBC reports. But it's much faster, zipping through our system, and has a totally different orbit from any of those objects.

After initial indecision about whether the object was a comet or an asteroid, the researchers now believe it's an asteroid. Long ago, it might have hurtled from an unknown star system into our own.

'Oumuamua may provide astronomers with new insights into how stars and planets form. The 750,000 asteroids we know of are leftovers from the formation of our solar system, trapped by the Sun's gravity. But what if, billions of years ago, other objects escaped? 'Oumuamua shows us that it's possible; perhaps there are bits and pieces from the early years of our solar system currently visiting other stars.

The researchers say it's surprising that 'Oumuamua is an asteroid instead of a comet, given that in the Oort Cloud—an icy bubble of debris thought to surround our solar system—comets are predicted to outnumber asteroids 200 to 1 and perhaps even as high as 10,000 to 1. If our own solar system is any indication, it's more likely that a comet would take off before an asteroid would.

So where did 'Oumuamua come from? That's still unknown. It's possible it could've been bumped into our realm by a close encounter with a planet—either a smaller, nearby one, or a larger, farther one. If that's the case, the planet remains to be discovered. They believe it's more likely that 'Oumuamua was ejected from a young stellar system, location unknown. And yet, they write, "the possibility that 'Oumuamua has been orbiting the galaxy for billions of years cannot be ruled out."

As for where it's headed, The Atlantic's Marina Koren notes, "It will pass the orbit of Jupiter next May, then Neptune in 2022, and Pluto in 2024. By 2025, it will coast beyond the outer edge of the Kuiper Belt, a field of icy and rocky objects."

Last month, University of Wisconsin–Madison astronomer Ralf Kotulla and scientists from UCLA and the National Optical Astronomy Observatory (NOAO) used the WIYN Telescope on Kitt Peak, Arizona, to take some of the first pictures of 'Oumuamua. You can check them out below.

Images of an interloper from beyond the solar system — an asteroid or a comet — were captured on Oct. 27 by the 3.5-meter WIYN Telescope on Kitt Peak, Ariz.
Images of 'Oumuamua—an asteroid or a comet—were captured on October 27.
WIYN OBSERVATORY/RALF KOTULLA

U1 spotted whizzing through the Solar System in images taken with the WIYN telescope. The faint streaks are background stars. The green circles highlight the position of U1 in each image. In these images U1 is about 10 million times fainter than the faint
The green circles highlight the position of U1 in each image against faint streaks of background stars. In these images, U1 is about 10 million times fainter than the faintest visible stars.
R. Kotulla (University of Wisconsin) & WIYN/NOAO/AURA/NSF

Color image of U1, compiled from observations taken through filters centered at 4750A, 6250A, and 7500A.
Color image of U1.
R. Kotulla (University of Wisconsin) & WIYN/NOAO/AURA/NSF

Editor's note: This story has been updated.

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios