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Human brain cells don’t continue to grow into adulthood, according to a new study
Research with other species lends weight to these findings.
We used to think neurogenesis—the growth of new brain cells, occurred throughout one’s lifetime. A shocking new study out of UC-San Francisco finds that instead, no more memory cells grow in the hippocampus after childhood. That's staggering, as this area of the brain associated with really important things such as learning, memory, and emotion. One of the largest studies of its kind to date, the scientists examined 59 human brain specimens, all of varying ages, and found no new neuron formation past age 13.
Neuroscientists have been debating since the late 1920s whether or not neurogenesis occurs into adulthood. From the ‘80s on, the prevailing view was that neurogenesis takes place throughout our lives. That’s because lots of studies confirmed the phenomenon occurring past the juvenile stage in the brains of other species, including birds, mice, rats, and nonhuman primates. In rats, for instance, new neurons are constantly formed around the olfactory bulb, which is associated with the sense of smell.
Arturo Alvarez-Buylla was the senior author of the study. He told Medical News Today, "We find that if neurogenesis occurs in the adult hippocampus in humans, it is an extremely rare phenomenon, raising questions about its contribution to brain repair or normal brain function." Lead researcher Shawn Sorrells, said they couldn’t find any new neurons in the adult samples they examined. The study’s findings were published in the journal Nature.
Model of the brain. By CNX OpenStax, Wikimedia Commons.
According to this research, our brain creates loads and loads of new neurons during the prenatal and neonatal stages. In early childhood, dramatic bursts of neurogenesis occur in the frontal lobe—the very front part of the brain, responsible for executive functions such as decision-making, learning, and planning. After that, neurogenesis drops off and becomes exceptionally rare, according to this study.
To conduct it, researchers collected hippocampus samples ranging from the fetal stage to age 77. These came from the US, China, and Spain. Some samples were from cadavers, while others were excess tissue removed during brain surgery, to help relieve severe epilepsy.
With each sample, the researchers examined a particular part of the hippocampus called the dentate gyrus, an area crucial to memory formation. They sliced up this region and applied antibodies which would congregate at new neurons or any newly formed cell. While this occurred often in samples from fetuses and young children, after age 1 it was rare, and after age 13, researchers found no new neuron formation.
The idea is bound to be controversial as certain diets, exercises programs, and even antidepressants, rest on the idea that they instigate the growth of fresh neurons. Among neuroscientists, there’s a variety of beliefs, ranging from the notion that the human brain generates many neurons each day, to the conjecture that neurogenesis is actually quite rare.
Neuronal formation isn’t a simple process. It begins with progenitor cells, which turn into stem cells before becoming neurons. "It requires the birth of the cell,” Alvarez-Buylla told CNN, “the migration or the movement of the cell to the right place, which is not an easy task in the very dense structure of the brain -- and then that cell has to make space to grow and connect to other cells and then contribute in a functional way to that circuit." The brains of infants and young children are primed for this, while with adult brains, researchers aren’t sure.
Neurons in an adult mouse's hippocampus. Credit: Wikipedia.
Another study that supports this one states that whales and dolphins don’t experience neurogenesis as adults. Yale neuroscientist Pasko Ravic has worked with monkeys and finds that they go through little neurogenesis during adulthood, as opposed to rodents. The reason might be, neural networks within adult primate brains are complex, and the growth of such cells could disrupt normal operations.
This study, although provocative, gives us a snapshot of only one region of the brain. More research will have to be done to confirm these results and see whether the same is true in other parts. Many neuroscientists say, even if adults do experience neurogenesis, there’s still no proof that it rejuvenates the brain. Instead, making new connections might be what’s really worthwhile. In another sense, this study could aid us in the search for a cure to Alzheimer’s, as neurogenesis was one avenue researchers were exploring.
Want to learn more about neurogenesis in the adult brain? Click here.
Geologists discover a rhythm to major geologic events.
- It appears that Earth has a geologic "pulse," with clusters of major events occurring every 27.5 million years.
- Working with the most accurate dating methods available, the authors of the study constructed a new history of the last 260 million years.
- Exactly why these cycles occur remains unknown, but there are some interesting theories.
Our hearts beat at a resting rate of 60 to 100 beats per minute. Lots of other things pulse, too. The colors we see and the pitches we hear, for example, are due to the different wave frequencies ("pulses") of light and sound waves.
Now, a study in the journal Geoscience Frontiers finds that Earth itself has a pulse, with one "beat" every 27.5 million years. That's the rate at which major geological events have been occurring as far back as geologists can tell.
A planetary calendar has 10 dates in red
Credit: Jagoush / Adobe Stock
According to lead author and geologist Michael Rampino of New York University's Department of Biology, "Many geologists believe that geological events are random over time. But our study provides statistical evidence for a common cycle, suggesting that these geologic events are correlated and not random."
The new study is not the first time that there's been a suggestion of a planetary geologic cycle, but it's only with recent refinements in radioisotopic dating techniques that there's evidence supporting the theory. The authors of the study collected the latest, best dating for 89 known geologic events over the last 260 million years:
- 29 sea level fluctuations
- 12 marine extinctions
- 9 land-based extinctions
- 10 periods of low ocean oxygenation
- 13 gigantic flood basalt volcanic eruptions
- 8 changes in the rate of seafloor spread
- 8 times there were global pulsations in interplate magmatism
The dates provided the scientists a new timetable of Earth's geologic history.
Tick, tick, boom
Credit: New York University
Putting all the events together, the scientists performed a series of statistical analyses that revealed that events tend to cluster around 10 different dates, with peak activity occurring every 27.5 million years. Between the ten busy periods, the number of events dropped sharply, approaching zero.
Perhaps the most fascinating question that remains unanswered for now is exactly why this is happening. The authors of the study suggest two possibilities:
"The correlations and cyclicity seen in the geologic episodes may be entirely a function of global internal Earth dynamics affecting global tectonics and climate, but similar cycles in the Earth's orbit in the Solar System and in the Galaxy might be pacing these events. Whatever the origins of these cyclical episodes, their occurrences support the case for a largely periodic, coordinated, and intermittently catastrophic geologic record, which is quite different from the views held by most geologists."
Assuming the researchers' calculations are at least roughly correct — the authors note that different statistical formulas may result in further refinement of their conclusions — there's no need to worry that we're about to be thumped by another planetary heartbeat. The last occurred some seven million years ago, meaning the next won't happen for about another 20 million years.
A new episode of "Your Brain on Money" illuminates the strange world of consumer behavior and explores how brands can wreak havoc on our ability to make rational decisions.
- Effective branding can not only change how you feel about a company, it can actually change how your brain is wired.
- Our new series "Your Brain on Money," created in partnership with Million Stories, recently explored the surprising ways brands can affect our behavior.
- Brands aren't going away. But you can make smarter decisions by slowing down and asking yourself why you're making a particular purchase.
How Apple and Nike have branded your brain | Your Brain on Money | Big Think youtu.be
Brands can manipulate our brains in surprisingly profound ways. They can change how we conceptualize ourselves and how we broadcast our identities out to the social world. They can make us feel emotions that have nothing to do with the functions of their products. And they can even sort us into tribes.
To grasp the power of brands, look to Apple. In the 1990s, the company was struggling to compete with Microsoft over the personal computer market. Despite flirting with bankruptcy in the mid-1990s, Apple turned itself around to eventually become the most valuable company in the world.
That early-stage success wasn't due to superior products.
"People talk about technology, but Apple was a marketing company," John Sculley, a former Apple marketing executive, told The Guardian in 1997. "It was the marketing company of the decade."
So, how exactly does branding make people willing to wait hours in line to buy a $1,000 smartphone, or pay exorbitant prices for a pair of sneakers?
Branding and the brain
For more than a century, brands have capitalized on the fact that effective marketing is much more than simply touting the merits of a product. Some ads have nothing to do with the product at all. In 1871, for example, Pearl Tobacco started advertising their cigarettes through branded posters and trading cards that featured exposed women, a trend that continues to this day.
It's crude, sure. But research shows that it's also remarkably effective, even on monkeys. Why? The answer seems to center on how our brains pay special attention to information from the social world.
"In theory, ads that associate sex or status with specific brands or products activate the brain mechanisms that prioritize social information, and turning on this switch may bias us toward the product," wrote neuroscience professor Michael Platt for Scientific American.
Brands can burrow themselves deep into our subconscious. Through ad campaigns, brands can form a web of associations and memories in our brains. When these connections are robust and positive, it can change our behavior, nudging us to make "no-brainer" purchases when we encounter the brand at the store.
It's a marketing principle that's related to the work of Daniel Kahneman, a psychologist and economist who won the 2002 Nobel Memorial Prize in Economic Sciences. In his book "Thinking Fast and Slow", Kahneman separates thinking into two broad categories, or systems:
- System 1 is fast and automatic, requiring little effort or voluntary control.
- System 2 is slow and requires subjective deliberation and logic.
Brands that tap into "system 1" are likely to dominate the competition. After all, it's far easier for us as consumers to automatically reach for a familiar brand than it is to analyze all of the available information and make an informed choice. Still, the most successful brands can have an even deeper impact on our psychology, one that causes us to conceptualize them as something like a family member.
A peculiar relationship with brands
Apple has one of the most loyal customer bases in the world, with its brand loyalty hitting an all-time high earlier this year, according to a SellCell survey of more than 5,000 U.S.-based smartphone users.
Qualitatively, how does that loyalty compare to Samsung users? To find out, Platt and his team conducted a study in which functional magnetic resonance imaging scanned the brains of Samsung and Apple users as they viewed positive, negative, and neutral news about each company. The results revealed stark differences between the two groups, as Platt wrote in "The Leader's Brain":
"Apple users showed empathy for their own brand: The reward-related areas of the brain were activated by good news about Apple, and the pain and negative feeling parts of the brain were activated by bad news. They were neutral about any kind of Samsung news. This is exactly what we see when people empathize with other people—particularly their family and friends—but don't feel the joy and pain of people they don't know."
Meanwhile, Samsung users didn't show any significant pain- or pleasure-related brain activity when they saw good or bad news about the company.
"Interestingly, though, the pain areas were activated by good news about Apple, and the reward areas were activated by bad news about the rival company—some serious schadenfreude, or "reverse empathy," Platt wrote.
The results suggest a fundamental difference between the brands: Apple has formed strong emotional and social connections with consumers, Samsung has not.
Brands and the self
Does having a strong connection with a brand justify paying higher prices for their products? Maybe. You could have a strong connection with Apple or Nike and simultaneously think the quality of their products justifies the price.
But beyond product quality lies identity. People have long used objects and clothing to express themselves and signal their affiliation with groups. From prehistoric seashell jewelry to Air Jordans, the things people wear and associate with signal a lot of information about how they conceptualize themselves.
Since the 1950s, researchers have examined the relationship between self-image and brand preferences. This body of research has generally found that consumers tend to prefer brands whose products fit well with their self-image, a concept known as self-image congruity.
By choosing brands that don't disrupt their self-image, consumers are able not only to express themselves personally, but also broadcast a specific version of themselves into the social world. That might sound self-involved. But on the other hand, humans are social creatures who use information from the social world to make decisions, so it's virtually impossible for us not to make inferences about people based on how they present themselves.
Americus Reed II, a marketing professor at the University of Pennsylvania, told Big Think:
"When I make choices about different brands, I'm choosing to create an identity. When I put that shirt on, when I put that shirt on — those jeans, that hat — someone is going to form an impression about what I'm about. So, if I'm choosing Nike over Under Armour, I'm choosing a kind of different way to express affiliation with sport. The Nike thing is about performance. The Under Armour thing is about the underdog. I have to choose which of these different conceptual pathways is most consistent with where I am in my life."
Making smarter decisions
Brands may have some power over us when we're facing a purchasing decision. So, considering brands aren't going away, what can we do to make better choices? The best strategy might be to slow down and try to avoid making "automatic" purchasing decisions that are characteristic of Kahneman's fast "system 1" mode of thinking.
"I think it's important to always pause and think a little bit about, "Okay, why am I buying this product?" Platt said.
As for getting out of the brand game altogether? Good luck.
"I've heard lots of people push back and say, "I'm not into brands,"" Reed II said. "I take a very different view. In some senses, they're not doing anything different than what someone who affiliates with a brand is doing. They have a brand. It's just an anti-brand brand."
Powerful branding can not only change how you feel about a company, it can actually change how your brain is wired.
- Powerful branding can not only change how you feel about a company, it can actually change how your brain is wired.
- "We love to think of ourselves as rational. That's not how it works," says UPenn professor Americus Reed II about our habits (both conscious and subconscious) of paying more for items based primarily on the brand name. Effective marketing causes the consumer to link brands like Apple and Nike with their own identity, and that strong attachment goes deeper than receipts.
- Using MRI, professor and neuroscientist Michael Platt and his team were able to see this at play. When reacting to good or bad news about the brand, Samsung users didn't have positive or negative brain responses, yet they did have "reverse empathy" for bad news about Apple. Meanwhile, Apple users showed a "brain empathy response for Apple that was exactly what you'd see in the way you would respond to somebody in your family."