National Geographic Tales of the Weird

by David Braun

  “You say that love is nonsense … I tell you it is no such thing. For weeks and months it is a steady physical pain, an ache about the heart, never leaving one, by night or by day; a long strain on one’s nerves like toothache or rheumatism, not intolerable at any one instant, but exhausting by its steady drain on the strength.”

  Henry Brooks Adams

  American writer

  Breaking Up Is Hard to Do

  The study isn’t a “true perfect experiment—we couldn’t control who had the rejection experience and who didn’t,” Smith noted. “This is true of any study that takes advantage of an activity that happened outside of the laboratory,” he said.

  “There’s always the possibility that there’s [some unknown element] about these people who were rejected that was causing the special pattern of what we’re seeing.”

  Yet the results are striking, Smith said, especially because the team analyzed 150 other brain-scan experiments on negative emotions—fear, anxiety, anger, sadness—and found that none of these emotionally painful experiences activate the brain’s physical sensory areas in the same way as an undesired breakup. “There may be something special about rejection.”

  INSTINCTUAL CRAVINGS

  Cocaine Addiction

  Uses Same Brain Paths as Salt Cravings

  In your brain, the harmless craving for potato chips or salty pretzels, scientists have found, may share pathways with dangerous addictions to drugs.

  Drugs such as heroin and cocaine may owe some of their addictive powers to an ancient instinct—our appetite for salt. In a new study of mouse brains, scientists show that the patterns of gene regulation stimulated by salt cravings are the same gene patterns regulated by drug addiction.

  A Million-Year-Old Habit

  Salt appetite is a craving millions of years in the making, with likely roots in the salty seas where life on Earth began. “Land dwellers face a problem in that sodium is a trace element, so they have to have a strategy to ingest sodium, and salt craving or sodium appetite is evolution’s answer to that,” said study co-author Wolfgang Liedtke, an assistant professor of medicine and neurobiology at Duke University.

  Salt appetite can be so strong that animals short on sodium will put life and limb at risk to satisfy the hunger. Mountain goats, for instance, are known to cling to sheer cliffs to access a salt lick, even when a misstep means certain death.

  The new finding suggests that drug addictions may be so hard to overcome in part because cocaine and opiates—both derived from plants—exploit the brain mechanisms critical for salt appetite.

  “Cocaine can usurp the ancient [neural] systems that have made animals better survivors,” Liedtke said. The research offers some of the first evidence for addiction processes previously theorized by other experts, added study co-author Derek Denton of the University of Melbourne and the Florey Neuroscience Institute.

  Rapid Brain Change

  Denton, Liedtke, and colleagues used several techniques (such as withholding salt from test mice or increasing their salt needs by giving them the stress hormone ACTH) to figure out which genes in mammal brains were activated by salt cravings.

  The team noticed that, almost as soon as the salt-depleted mice started drinking salt water, the patterns of gene regulation triggered by the need began to reverse. The rapid response is a surprise because it means brain changes in the mice occurred before significant amounts of salt had moved from the stomach to the bloodstream.

  TRUTH:

  PEOPLE HAVE TASTE RECEPTORS IN THEIR LUNGS.

  “It was stunning and perplexing to see that just ten minutes of drinking salty water led to a complete change of the whole sophisticated and elaborate genetic program,” Duke’s Liedtke said.

  Addiction Drivers Still Unknown

  It’s possible that the research may lead to new treatments for drug addiction that don’t rely on “cold turkey” abstinence, which is less likely to be successful against such strong, instinctual cravings.

  Overall, though, Liedtke cautions that the new study doesn’t fully explain the neural drivers of drug addiction. “Sodium appetite is a healthy instinct. Heroin addiction is a disease that can kill a human,” he said. “To go from a healthy instinct to a malady—other things must be happening in the brain.”

  SECRETS OF SMELL

  Different Nose Parts for Stinky, Sweet

  Tiny hot spots in our noses tell our brains what smells good and what smells yucky.

  Millions of receptors in the nose’s smelling organ aren’t scattered at random. Instead, the receptors congregate in small regions that help the brain discern good smells from bad ones, among other potential functions.

  Up Your Nose

  The evidence was gathered by sticking electronic probes up people’s noses and measuring the chatter of nasal neurons as subjects were exposed to scents. The findings imply that the pleasantness of a smell is hardwired within our heads, calling into question the impact of life experience on how people perceive smells.

  “It’s both exciting and disturbing,” said Don Wilson of the New York University School of Medicine, a neurobiologist who was not involved in the work. “It doesn’t fit in with what I think or a lot of other researchers think about smell.” Instead of the brain processing all scent information, for instance, it seems nasal neurons preprocess some of it—almost as if the nose has its own small brain.

  TRUTH:

  HUMANS CAN RECOGNIZE ABOUT 10,000 DIFFERENT SMELLS.

  Taking One in the Nose

  The human nose contains a postage stamp—size smelling organ, called the olfactory epithelium, at the roof of the nasal cavity. By probing mouse noses to measure the firing of nasal neurons, scientists had previously discovered that scent receptors might be organized into groups, similar to the way the tongue has zones armed to detect specific tastes such as sour, sweet, and salty.

  But a rodent’s nose has more than 1,200 different types of scent receptors, and even a tiny probe could touch tens of thousands of receptors in one reading, making it hard to get a clear signal.

  Humans have roughly 400 different kinds of receptors, however, making the business of sticking probes in noses and plucking out useful information more fruitful.

  How the Nose Knows

  A team led by neuroscientist Noam Sobel, of the Weizmann Institute of Science in Israel, asked more than 80 people to sniff substances with odors known to be either pleasant or unpleasant across many cultures.

  Ordinary smells can be made up of tens to hundreds of compounds, so Sobel and his colleagues puffed only pure chemicals into the noses of their wired subjects, one scent at a time.

  Pooling together 801 neural recordings from people’s noses, the team found that some regions of the epithelium are better at detecting scent than other regions. The researchers also found hot spots that are better at interpreting either pleasantness or unpleasantness.

  “To my surprise, this means something about the epithelium is tuned to pick up certain information” in certain zones, New York University’s Wilson said. “We don’t understand what the purposes of those zones are,” he added, “but that’s exciting.”

  “Only three receptor types facilitate all of color vision … For human smell you have 400 [receptors], so it becomes a very complex system to decode.”

  Joel Mainland

  geneticist, Duke University Medical Center

  SMARTER LIVING THROUGH SLEEPING

  Sleep Cherry-Picks Memories

  Boosts Cleverness

  Your body may be resting during those 40 winks, but your brain is hard at work. The sleeping brain is busy “calculating” what to remember and what to forget, a new study says.

  While people are asleep, the brain is selecting what they remember, resulting in sharper and clearer thinking, a new study suggests. Previous research had shown that sleep helps people consolidate their memories, fixing them in the brain so we can retrieve them later. But the new study—a review based on past research on sleep an
d memory as well as new studies—suggests that sleep also transforms memories in ways that make them somewhat less accurate but more useful in the long run.

  Alaska Inuit teens sleep in a tent in a file picture. (Photo Credit 2.5)

  What to Leave In, What to Leave Out

  For example, sleep-enabled memories may help people produce insights, draw inferences, and foster abstract thought during waking hours. “The sleeping brain isn’t stupid—it doesn’t just consolidate everything you put into it, but calculates what to remember and what to forget,” said study leader Jessica Payne, a cognitive neuroscientist at the University of Notre Dame in Indiana.

  For instance, the memory details that seem to get remembered best are often the most emotional ones, Payne said. Payne and colleagues found that when people are shown a scene with an emotion-laden object in the foreground—such as a wrecked car—they are more likely to remember that object than, say, palm trees in the background, especially if they are tested after a night of slumber.

  Rather than preserving scenes in their entirety, the brain apparently restructures scenes to remember only their most emotional and perhaps most important elements while allowing less emotional details to deteriorate.

  Don’t Sleep on It

  Researchers at the University of Massachusetts—Amherst recently conducted a study whose findings suggest that sleeping after a traumatic event may enhance painful emotional memories. “Today, our findings have significance for people with post-traumatic stress disorder, for example, or those asked to give eyewitness testimony in court cases,” says Rebecca Spencer, one of the neuroscientists who worked on the study. Interestingly enough, most people find it difficult to sleep after experiencing a troubling event—almost as though the brain does not want to sleep on it.

  Picking Memories

  Measurements of brain activity support this notion, revealing that brain regions linked with emotion and memory consolidation are periodically more active during sleep than when awake.

  “It makes sense to selectively remember emotional information—our ancestors would not want to forget a snake was in a particular location or that someone in the tribe was particularly mean and should be avoided,” said Payne, whose study appeared in the journal Current Directions in Psychological Science. “Memories are not so much about remembering the past as being able to anticipate and predict multiple possible futures.”

  But there are dark sides to such selectivity. For instance, the brain can focus on remembering negative experiences at the exclusion of others, which occurs in depression and post-traumatic stress disorder. Future research may shed light on what details are remembered and how they’re remembered, which could help people deal with trauma, Payne noted. “You could also see such work being helpful in coming up with solutions in the classroom or in the business world,” she said.

  TRUTH:

  YOU’LL SPEND ABOUT SIX YEARS OF YOUR LIFE DREAMING.

  Looking Ahead

  Future research may also reveal which components of sleep might be linked with these mental processes. “Does it require the REM sleep associated with dreaming, or deeper slow-wave sleep?” said Robert Stickgold, a cognitive neuroscientist at Harvard Medical School who researches sleep. Overall, “sleep is doing much more complicated stuff than just stabilizing or strengthening memories,” Stickgold added.

  “We’re seeing the sorts of memory processing in sleep that we usually attribute to cleverness.”

  TURNING BACK THE CLOCK

  Drug Could Make Aging Brains More Youthful?

  Senior moments and mind fogs might be a thing of the past as a recent study in monkeys hints that declining neural activity can be revved up in older brains.

  You can’t teach an old brain new tricks—but you can restore its ability to remember the old ones, a new study in monkeys suggests. Chemicals given to rhesus macaques blocked a brain molecule that slows the firing of the brain’s nerve cells, or neurons, as we age—prompting those nerve cells to act young again.

  “It’s our first glimpse of what’s going on physiologically that’s causing age-related cognitive decline,” said study leader Amy Arnsten, a neurobiologist at Yale University. “We all assumed, given there’s a lot of architectural changes in aged brains … that we were stuck with it,” Arnsten said. But with the new results, “the hopeful thing is that the neurochemical environment still makes a big difference, and we might be able to remediate some of these things.”

  Stress Less!

  Intense stress has been shown to have the same effect as aging on the nerve cells in the prefrontal cortex that are responsible for the formation and retention of memories. While the changes caused by stress are reversible, it remains possible that continued exposure to stress increases the decline of memory with age.

  The Importance of Working Memory

  As the brain gets older, the prefrontal cortex begins to decline quickly. This part of the brain is responsible for many high-order functions, including maintaining working memories—the ability to keep things on a “mental sketch pad” in the absence of stimuli from an action-based task. Researchers previously found that in young brains, nerve cells in the prefrontal cortex excite each other to keep working memories on the brain’s slate. “Those connections depend on the neurochemical environment, [which] has to be just right, like Goldilocks,” she said.

  But when people reach their 40s and 50s, that part of the brain begins to accumulate too much of a signaling molecule called cAMP, which can stop the cells from firing as efficiently—leading to forgetfulness and distractedness. The number of seniors in the United States will likely double by 2050, and many of them will struggle to cope with the frenetic information age, according to the study.

  Super Rat

  When a lab rat named Hobbie-J was just an embryo, a team of scientists injected her with genetic material that caused an overexpression of the gene NR2B, which helps control the rate at which brain cells communicate. The change allowed Hobbie-J’s brain cells to communicate a little bit longer than those of her average counterparts, resulting in higher intelligence. These findings suggest that using drugs to target this gene in humans may help alleviate disorders like dementia and Alzheimer’s disease. However, the researchers caution against enhancing memories in healthy people. “There is a reason we forget,” says Guosong Liu, a neuroscientist. “We are supposed to leave our bad experiences behind, so they do not haunt us.”

  Monkey See, Monkey Remember

  For their study, Arnsten and her colleagues spent years training six rhesus macaques of various ages how to play simple video games that require the use of working memory. “The youngsters do it great for a long time—they’re just like humans,” she said. Once the monkeys had mastered the task, the team made recordings of single neurons firing using a tiny fiber inserted painlessly into the brain—a first in any elderly living animal. Not surprisingly, the team found that the younger animals’ neurons fired often during periods when there were no stimuli. Neurons in the older animals tended to be less active during the same periods, according to the study, which was published in the journal Nature.

  But when the team administered certain drugs to the older animals via the fibers—including a chemical called guanfacine—the chemicals blocked the cAMP pathways and revved up neural activity.

  Brain Boosters in the Future?

  Guanfacine is currently an ingredient in a drug used to treat high-blood pressure in adults. The chemical is also in separate clinical trials to see if it improves working memory in the elderly. Arnsten added that she and her team had led previous studies showing that the drug improved working memory in monkeys, and those results have been repeated by other groups in both monkeys and humans. (It is worth noting that Arnsten does receive royalties from the sale of extended-release guanfacine, called Intuniv, for the treatment of attention deficit hyperactivity disorder in children and adolescents. She does not receive royalties for the generic form of guanfacine being used in the clinical trial
.)

  Arnsten cautions that even if the drug is approved as a brain booster, it’s too early to say how much memory improvement a person could expect. “We can’t say it [would] bring you back to being a 30-year-old,” she said.

  Meanwhile, neuroscientist James L. McGaugh, who was not part of the study team, says that the previous studies “did not, as I understand it, provide evidence that the enhanced performance was directly associated with ‘restored firing’ of the neurons. That was an implication.”

  Drug trials tested the effects on rhesus macaques’ working memory. (Photo Credit 2.6)

  An Open Question

  Importantly, the evidence of enhanced working memory from the previous studies comes from different methods for administering the drugs than those used in the new study, said McGaugh, a fellow at the Center for the Neurobiology of Learning and Memory at the University of California, Irvine.

  And for the new experiment, in which the drugs were delivered directly to the brain, the team didn’t show conclusively whether monkeys’ working memory got better after treatment—though past studies have shown a link.

  Thus, it’s still an “open question” whether more nerve cell activity actually caused memory improvements, McGaugh said. “This is not to question the importance of the findings—just the missing piece of information as I understand their experiments.”